阅读说明：本技术 具有多功能感测元件的治疗设备和使用方法 (Therapeutic device with multifunctional sensing element and method of use ) 是由 B·阿维托尔 于 2018-03-19 设计创作，主要内容包括：一种用于治疗组织区域并评估损伤形成和质量的设备、系统和方法。该系统可以包括医疗设备,该医疗设备在治疗元件上具有多个标测电极,该多个标测电极被配置成在低温流体在治疗元件内的循环之前、期间和之后从组织区域记录单极阻抗测量、双极阻抗测量、局部电活动和起搏阈值测量中的至少一项。这些测量可以被传输到具有处理电路系统的控制单元,该处理电路系统被配置成对治疗前测量、治疗中测量和/或治疗后测量彼此进行比较和/或将治疗前测量、治疗中测量和/或治疗后测量与阈值进行比较,以确定阻塞和/或损伤质量,诸如损伤穿壁性。(A device, system, and method for treating a tissue region and assessing lesion formation and quality. The system may include a medical device having a plurality of mapping electrodes on the treatment element configured to record at least one of unipolar impedance measurements, bipolar impedance measurements, local electrical activity, and pacing threshold measurements from the tissue region before, during, and after circulation of the cryogenic fluid within the treatment element. These measurements may be transmitted to a control unit having processing circuitry configured to compare pre-treatment, in-treatment, and/or post-treatment measurements to one another and/or to thresholds to determine occlusion and/or lesion quality, such as lesion transmurality.)

1. A medical system, the system comprising:

A medical device, the medical device comprising:

A heat transfer region; and

A plurality of mapping electrodes on the heat transport region; and a control unit including:

a cryogenic fluid source in fluid communication with the heat transfer region, the cryogenic fluid source comprising a cryogenic fluid; and

Processing circuitry in electrical communication with the plurality of mapping electrodes and the plurality of sensors, the processing circuitry configured to determine a transmurality of a lesion based on signals received from the plurality of mapping electrodes.

2. The medical system of claim 1, wherein the medical device further comprises a plurality of sensors on the heat transport region, each of the plurality of sensors associated with at least one of the plurality of mapping electrodes.

3. The medical system of claim 2, wherein each of the plurality of mapping electrodes includes a corresponding one of the plurality of temperature sensors.

4. The medical system of any one of claims 1-3, wherein the medical device has a longitudinal axis, and wherein the plurality of mapping electrodes are arranged in a plurality of linear forms, each of the plurality of linear forms being at least substantially parallel to the longitudinal axis.

5. The medical system of any one of claims 1-3, wherein the medical device has a longitudinal axis, the plurality of mapping electrodes being arranged in a plurality of bands, each of the plurality of bands extending at least partially around the longitudinal axis.

6. The medical system of any one of claims 1-3, wherein the plurality of mapping electrodes are arranged in a cluster having two or more mapping electrodes.

7. The medical system of any one of claims 1-3, wherein the plurality of mapping electrodes are randomly arranged on the heat transport region.

8. the medical system of claim 3, wherein each of the plurality of mapping electrodes is configured to record at least one of unipolar impedance measurements, bipolar impedance measurements, local electrical activity, and pacing threshold measurements from a tissue region before, during, and after cycling of the cryogenic fluid within the heat transfer region, and each of the plurality of temperature sensors is configured to record temperature measurements before, during, and after cycling of the cryogenic fluid within the heat transfer region.

9. The medical system of claim 8, wherein the processing circuitry is configured to receive records from the plurality of mapping electrodes and is configured to:

Comparing the unipolar impedance measurements recorded before the cycling of cryogenic fluid in the heat transfer region with unipolar impedance measurements recorded after the cycling of cryogenic fluid in the heat transfer region has ended;

determining a thickness of an ice ball between the heat delivery region and the tissue region based on a comparison of the unipolar impedance measurements; and is

Correlating the thickness of the puck to a damage quality.

10. The medical system of claim 9, wherein the processing circuitry is further programmed to:

Comparing bipolar impedance measurements recorded before the cycling of cryogenic fluid in the heat transfer region with bipolar impedance measurements recorded after the cycling of cryogenic fluid in the heat transfer region has ended;

quantifying ice formation between a pair of heat transfer regions used to record the bipolar impedance measurements based on the comparison of the bipolar impedance measurements; and

Correlating said ice formation with damage quality.

11. The medical system of claim 9, wherein the processing circuitry is further programmed to:

Comparing a pacing threshold measurement recorded before the cycling of cryogenic fluid in the heat transfer region with a pacing threshold measurement recorded after the cycling of cryogenic fluid in the heat transfer region has ended; and

determining whether the tissue region has been ablated based on the comparison.

12. The medical system of claim 11, wherein the processing circuitry is configured to: determining that the tissue region has been ablated when the pacing threshold measurement recorded after the end of the cycling of cryogenic fluid within the heat transfer region is greater than the pacing threshold measurement recorded before the cycling of cryogenic fluid within the heat transfer region by more than a threshold difference.

13. The medical system of claim 8, wherein the processing circuitry is configured to receive records from the plurality of mapping electrodes and to determine, for each of the plurality of mapping electrodes:

At least a portion of the tissue region proximate the mapping electrode has been ablated when the mapping electrode records post-treatment electrogram amplitude values of 0.5mV or less,

The processing circuitry is further configured to determine a lesion surface area based on the post-treatment electrogram amplitudes recorded by each of the plurality of mapping electrodes.

14. The medical system of claim 1, wherein the medical device further comprises:

a first impedance electrode proximate to and distal of the heat transfer region; and

a second impedance electrode proximate and proximal to the heat transfer region, each of the first and second impedance electrodes having a width of about 0.5 mm.

15. The medical system of claim 14, wherein each of the first and second impedance electrodes is configured to record a monopolar impedance measurement and a bipolar impedance measurement, the processing circuitry being further configured to determine a thickness of an iceball between the tissue region and at least the first impedance electrode based on at least one of the monopolar impedance measurement and the bipolar impedance measurement recorded by at least the first impedance electrode.

Technical Field

The present invention relates to methods and systems for treating a tissue region and assessing lesion formation and quality.

Background

cardiac arrhythmias, a group of diseases in which the normal rhythm of the heart is disturbed, affect millions of people. Certain types of cardiac arrhythmias, including ventricular tachycardia and atrial fibrillation, can be treated by ablation (e.g., Radio Frequency (RF) ablation, cryoablation, microwave ablation, etc.) performed on the endocardium or epicardium.

The effectiveness of the ablation procedure (procedure) may depend in large part on the quality of the contact between the treatment element of the medical device and the cardiac tissue. However, proper positioning of the treatment element and achieving good contact between the treatment element and the tissue can be challenging. In addition, the effectiveness of the ablation process may also depend on whether the lesion is transmural (transmural), meaning that it extends all the way through the tissue being treated. However, before a collateral or non-target tissue is affected, it is difficult to determine when the lesion has penetrated the wall and stop the ablation process. Also, it may be difficult to know how long the ablation process must last before sufficient lesions are formed.

Some current methods of assessing or monitoring tissue contact may include directly monitoring tissue using impedance measurements. However, these methods can produce inconclusive results, as these data can be difficult to measure accurately. Further, sensors for these characteristics may not be located on the entire treatment element or even on a substantial portion of the treatment element. Thus, the use of impedance, temperature, pressure, or other such characteristics may not provide a complete indication of tissue contact in relation to the contact status of the treatment element at a sufficient number of locations to give a complete indication of tissue contactuseful information of (a). Such as pressure monitoring through a guidewire lumen, CO₂Still other techniques of monitoring and the like cannot be used to pinpoint (pinpoint) the precise location of insufficient tissue contact in real time.

Additionally, procedures such as Pulmonary Vein Isolation (PVI) are commonly used to treat atrial fibrillation. This procedure typically involves the use of a freezing device, such as a catheter, which is positioned at the ostium of the Pulmonary Vein (PV) such that any blood flow exiting the PV into the Left Atrium (LA) is completely blocked. Once in place, the freezing device may be activated for a sufficient duration to create a desired lesion within the myocardial tissue at the PV-LA junction (such as the PV ostium). If a cryoballoon is used as the therapeutic element of the freezing apparatus, the balloon is typically inflated using a very low temperature liquid gas so that the balloon can create a circumferential lesion around the ostium and/or sinus of the PV in order to interrupt the abnormal electrical signal exiting the PV.

The success of this procedure depends largely on the quality of the lesion(s) created during the procedure and whether the cryoballoon has completely blocked the PV. For example, a complete circumferential lesion is only created when the cryoballoon has completely blocked the PV. Incomplete occlusion allows blood to flow from the PV being treated, through the cryoballoon, and into the left atrium of the heart. This flow of warm blood may prevent the cryoballoon from reaching a temperature low enough to create a permanent lesion in the target tissue. The creation of reversible lesions may not be sufficient to achieve electrical isolation and, as a result, atrial fibrillation may reoccur. Additionally, even if the PV is completely blocked, sub-optimal operation of the cryoablation system may result in a cryoballoon temperature that is not low enough or not applied for a sufficient amount of time to create a permanent lesion in the target tissue.

Current methods of assessing or monitoring PV occlusion include fluorescence imaging of radiopaque contrast agents injected into the PV from the device. Some of the contrast agent may flow from the PV into the left atrium if the device (such as a cryoballoon catheter) has not completely blocked the PV ostium. In that case, the device may be repositioned and more contrast agent injected into the PV. This approach not only requires the use of an auxiliary imaging system, but also exposes the patient to potentially large doses of contrast agent and radiation. Alternatively, a pressure measurement distal to the occlusion site may be used to assess occlusion prior to initiating a cryogen injection. Other methods may involve using a temperature sensor to determine the temperature within the cryoballoon and to correlate the measured temperature with a predicted thickness of ice created in tissue in contact with the cryoballoon. However, it may be difficult to accurately determine ice thickness based solely on balloon temperature, and this latter approach may only be used during injection freezing cycles.

Disclosure of Invention

The present invention advantageously provides methods and systems for treating a tissue region and assessing lesion formation and quality. In one embodiment, a medical system for treating a tissue region includes: a medical device comprising a treatment element and a plurality of mapping (mapping) elements on the treatment element; and a control unit including: a source of cryogenic fluid in fluid communication with the treatment element, circulation of the cryogenic fluid within the treatment element causing an iceball to form between the treatment element and the tissue region; and processing circuitry in electrical communication with the plurality of mapping elements and the plurality of sensors, the processing circuitry configured to determine a wall penetrability of the lesion based on signals received from the plurality of mapping elements.

In one aspect of this embodiment, the medical device further comprises a plurality of sensors on the treatment element, each of the plurality of sensors being associated with at least one of the plurality of mapping elements. In one aspect of this embodiment, each of the plurality of mapping elements includes a corresponding one of a plurality of temperature sensors.

In one aspect of this embodiment, the medical device has a longitudinal axis, and the plurality of mapping elements are arranged in a plurality of linear forms, each of the plurality of linear forms being at least substantially parallel to the longitudinal axis. In one aspect of this embodiment, the treatment element has a distal portion and a proximal portion, each of the plurality of linear forms of mapping elements extending between the distal and proximal portions of the treatment element.

In one aspect of this embodiment, the medical device has a longitudinal axis, and the plurality of mapping elements are arranged in a plurality of bands (bands), each of the plurality of bands extending at least partially around the longitudinal axis.

In one aspect of this embodiment, the plurality of mapping elements are arranged in clusters having two or more mapping elements.

In one aspect of this embodiment, the plurality of mapping elements are randomly arranged on the treatment element.

in one aspect of this embodiment, each of the plurality of mapping elements is configured to record at least one of unipolar impedance measurements, bipolar impedance measurements, local electrical activity, and pacing threshold measurements from the tissue region before, during, and after circulation of the cryogenic fluid within the treatment element, and each of the plurality of temperature sensors is configured to record temperature measurements before, during, and after circulation of the cryogenic fluid within the treatment element. In an aspect of this embodiment, the processing circuitry is configured to receive records from the plurality of mapping elements and is configured to: comparing the unipolar impedance measurements recorded prior to circulation of cryogenic fluid within the treatment element with unipolar impedance measurements recorded after circulation of cryogenic fluid within the treatment element has ended; determining a thickness of the iceball between the treatment element and the tissue region based on a comparison of monopolar impedance measurements; and correlating the thickness of the puck to a damage quality.

in one aspect of this embodiment, the processing circuitry is further programmed to: comparing bipolar impedance measurements recorded before circulation of cryogenic fluid within the treatment element with bipolar impedance measurements recorded after circulation of cryogenic fluid within the treatment element has ended; quantifying ice formation between a pair of therapy elements used to record bipolar impedance measurements based on a comparison of the bipolar impedance measurements; and correlating said ice formation with the quality of the damage.

In one aspect of this embodiment, the processing circuitry is further programmed to: comparing a pacing threshold measurement recorded prior to circulation of cryogenic fluid within the treatment element with a pacing threshold measurement recorded after circulation of cryogenic fluid within the treatment element has ended; and determining whether the tissue region has been ablated based on the comparison.

in one aspect of this embodiment, the processing circuitry is configured to determine that the tissue region has been ablated when the pacing threshold measurement recorded after the circulation of cryogenic fluid within the treatment element has ended is greater than the pacing threshold measurement recorded before the circulation of cryogenic fluid within the treatment element by more than a threshold difference.

In one aspect of this embodiment, the processing circuitry is configured to receive records from the plurality of mapping electrodes and to determine, for each of the plurality of mapping electrodes: when the mapping electrode records a post-treatment electrogram amplitude value of 0.5mV or less, at least a portion of the tissue region proximate the mapping electrode has been ablated, the processing circuitry being further configured to determine a lesion surface area based on the post-treatment electrogram amplitude recorded by each of the plurality of mapping electrodes.

In one aspect of this embodiment, the medical device further comprises: a first impedance electrode positioned proximate and distal to the treatment element, and a second impedance electrode positioned proximate and proximal to the treatment element, each of the first and second impedance electrodes having a width of about 0.5 mm.

In one aspect of this embodiment, each of the first and second impedance electrodes is configured to record a unipolar impedance measurement and a bipolar impedance measurement, the processing circuitry being further configured to determine the thickness of the iceball between the tissue region and at least the first impedance electrode based on at least one of the unipolar and bipolar impedance measurements recorded by at least the first impedance electrode.

In one embodiment, a method of determining lesion transmurality may comprise: positioning a treatment element of a medical device in contact with a tissue region, the treatment device in fluid communication with a source of cryogenic fluid and comprising a cryoballoon and a plurality of mapping elements on the cryoballoon; recording at least one of a pre-treatment (pre-treatment) unipolar impedance measurement, a pre-treatment bipolar impedance measurement, a pre-treatment pacing threshold measurement, and a pre-treatment electrogram (local electrophysiological activity) from the tissue region; transmitting at least one pre-treatment record to a control unit having processing circuitry; circulating the cryogenic fluid within the cryoballoon to reduce the temperature of the cryoballoon to a temperature sufficient to ablate tissue; stopping circulation of the cryogenic fluid within the cryoballoon; recording from the tissue region a corresponding at least one of a post-treatment unipolar impedance measurement, a post-treatment bipolar impedance measurement, a post-treatment pacing threshold measurement, and a post-treatment electrogram amplitude; transmitting at least one post-treatment measurement to the control unit; comparing at least one pre-treatment measurement to the at least one post-treatment measurement; and determining a lesion penetrability in the tissue region based on the comparison.

In an aspect of this embodiment, the method further comprises recording from the tissue region corresponding at least one of an in-treatment unipolar impedance measurement, an in-treatment bipolar impedance measurement, an in-treatment electrogram, and an in-treatment pacing threshold measurement prior to stopping circulation of cryogenic fluid within the cryoballoon. And transmitting at least one in-treatment measurement to the control unit.

in one aspect of this embodiment, the method further comprises comparing the at least one in-treatment measurement to at least one of a corresponding pre-treatment measurement and a corresponding post-treatment measurement. In one aspect of this embodiment, the at least one in-treatment measurement is a monopolar impedance measurement, the at least one of a corresponding pre-treatment measurement and a corresponding post-treatment measurement is a pre-treatment monopolar impedance measurement, comparing the at least one pre-treatment measurement to the at least one in-treatment measurement includes comparing the pre-treatment monopolar impedance measurement to the in-treatment monopolar measurement, the method further comprising: establishing at least one of threshold puck thicknesses; correlating a comparison between the pre-treatment unipolar impedance measurement and the treatment unipolar impedance measurement to an ice hockey thickness; and comparing the associated puck thickness to the threshold puck thickness, determining damage wall-piercing comprising determining that the damage is wall-piercing when the associated puck thickness is at least equal to the threshold puck thickness.

In one aspect of this embodiment, the method further comprises automatically stopping the circulation of cryogenic fluid within the cryoballoon when it is determined that a transmural lesion has been created.

in one embodiment, a medical system for treating a tissue region includes: a medical device, the medical device comprising: a treatment element; a plurality of mapping electrodes on the treatment element, each of the plurality of mapping electrodes configured to record at least one of unipolar impedance measurements, bipolar impedance measurements, local electrical activity, pacing threshold measurements from the tissue region before, during, and after circulation of cryogenic fluid within the treatment element; a plurality of temperature sensors on the treatment element, each of the plurality of temperature sensors associated with at least one of the plurality of mapping elements, each of the plurality of temperature sensors configured to record temperature measurements from the tissue region before, during, and after circulation of the cryogenic fluid within the treatment element; a first impedance electrode proximate to and distal of the treatment element, the first impedance electrode comprising a distal temperature sensor; and a second impedance electrode proximate to and proximal of the treatment element, the second impedance electrode including a distal temperature sensor, each of the first and second impedance electrodes having a width of about 0.5 mm; and a control unit including: a source of cryogenic fluid in fluid communication with the treatment element, circulation of cryogenic fluid within the treatment element causing an iceball to form between the treatment element and the tissue region; and processing circuitry in electrical communication with the plurality of mapping electrodes, the plurality of sensors, the first and second impedance electrodes, and distal and proximal temperature sensors, the processing circuitry configured to determine wall-piercing properties of a lesion based on signals received from the plurality of mapping electrodes by at least one of: comparing the unipolar impedance measurements recorded prior to the circulation of the cryogenic fluid within the treatment element with at least one of unipolar impedance measurements recorded during the circulation of the cryogenic fluid within the treatment element and unipolar impedance measurements recorded after the circulation of the cryogenic fluid within the treatment element has ended; comparing bipolar impedance measurements recorded prior to circulation of cryogenic fluid within the treatment element with at least one of bipolar impedance measurements recorded during circulation of cryogenic fluid within the treatment element and bipolar impedance measurements recorded after circulation of cryogenic fluid within the treatment element has ended; comparing a pacing threshold measurement recorded prior to the circulation of cryogenic fluid within the treatment element with at least one of a pacing threshold measurement recorded during the circulation of cryogenic fluid within the treatment element and a pacing threshold measurement recorded after the circulation of cryogenic fluid within the treatment element has ended; and comparing the electrogram amplitude measurements recorded prior to the circulation of cryogenic fluid within the treatment element with at least one of the electrogram amplitude measurements recorded during the circulation of cryogenic fluid within the treatment element and the electrogram amplitude measurements recorded after the circulation of cryogenic fluid within the treatment element has ended.

Drawings

A more complete understanding of the present invention, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:

FIG. 1 illustrates an exemplary medical system;

Fig. 2 illustrates a close-up view of a distal portion of the medical device shown in fig. 1 having a first configuration of mapping elements;

Fig. 3 illustrates a close-up view of a distal portion of the medical device shown in fig. 1 having a second configuration of mapping elements;

fig. 4 illustrates a close-up view of a distal portion of the medical device shown in fig. 1 having a third configuration of mapping elements;

Fig. 5 illustrates a close-up view of a distal portion of the medical device shown in fig. 1 having a fourth configuration of mapping elements;

Fig. 6 shows a treatment element of a medical device in contact with a target region of tissue;

fig. 7 illustrates an exemplary method of using a medical device having a plurality of mapping elements;

FIG. 8 shows a treatment element of the medical device in contact with the ostium of a pulmonary vein;

FIG. 9 illustrates an exemplary method of determining pulmonary vein occlusion using a medical device; and

Fig. 10 shows a graph of the correlation between temperature, time and impedance during pulmonary vein isolation.

Detailed Description

The devices, systems, and methods described herein can be used to treat tissue and assess the resulting lesions. Before describing in detail exemplary embodiments, it is noted that the system and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

As used herein, relational terms, such as "first" and "second," "top" and "bottom," and the like, may be used solely to distinguish one entity or element from another entity or element without necessarily requiring or implying any physical or logical relationship or order between such entities or elements. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the concepts described herein. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes" and/or "including," when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

In the embodiments described herein, coupling terms such as "in communication with … …" may be used to indicate electrical or data communication, which may be accomplished by, for example, physical contact, induction, electromagnetic radiation, radio signaling, infrared signaling, or optical signaling. Those of ordinary skill in the art will appreciate that various components may interoperate and that modifications and variations are possible in order to achieve both electrical and data communications.

Referring now to the drawings, in which like reference numerals refer to like elements, FIG. 1 shows an embodiment of a medical system, generally designated as "10". The system 10 may generally include a treatment device 12, a control unit 14, and a navigation system 16. The system 10 may optionally include an imaging system 18 for obtaining images of anatomical features within the patient.

The treatment device 12 may be a treatment and mapping device. The apparatus 16 may include an elongate body 22 that may be passed through the vasculature of a patient and/or proximate a tissue region for diagnosis or treatment. For example, the device 12 may be a catheter or a device that may access the pericardial space, which may be delivered to a tissue region via a sheath or intravascular guide (not shown). The elongate body 22 may define a proximal portion 26, a distal portion 28, and a longitudinal axis 30, and may further include one or more lumens disposed within the elongate body 22, thereby providing mechanical, electrical, and/or fluid communication between the elongate body proximal portion 26 and the elongate body distal portion 28.

The device 12 may further include one or more treatment elements 34, the one or more treatment elements 34 being located at the distal portion 28 of the elongate body, coupled to the distal portion 28 of the elongate body, or on the distal portion 28 of the elongate body for energy, therapeutic, and/or research interaction between the medical device 12 and a treatment site or region. In addition to cryotherapy, the treatment region element(s) 34 can also deliver, for example, radio frequency energy, ultrasonic energy, laser energy, or other energy delivery to tissue regions (including cardiac tissue) in the vicinity of the treatment element(s). For example, the treatment element(s) 34 can include a heat delivery region in thermal communication with a coolant or heat source, a heat delivery region in electrical communication with a power source, a body surface treatment element such as a body surface radio frequency electrode, and the like. In addition, the device 12 may include more than one type of treatment element 34. In the exemplary system embodiment shown in fig. 1, the device 12 may include an expandable treatment element 34, such as a cryoballoon that is expanded by circulation of cryogenic fluid within a cryoballoon interior chamber 36. As discussed below, the treatment element 34 may include a plurality of sensing or mapping electrodes 40.

The expandable treatment element 34 shown in fig. 1 may include an inner (or first) freezing balloon 44 and an outer (or second) freezing balloon 46. The treatment element 34 can be coupled to a portion of the distal portion 28 of the elongate body. The treatment element 34 can further include one or more layers of material that provide puncture resistance, radiopacity, and the like. If the apparatus 12 may also include one or more fluid injection elements 48 in fluid communication with a source of cryogenic fluid for delivering cryogenic fluid 52 to the interior chamber 36 of the treatment element 34. The interior chamber 36 may be defined by an interior freezing balloon 44. The inner and outer freezing balloons 44, 46 may define an interstitial space therebetween, which may also optionally be in fluid communication with a source 52 of cryogenic fluid, which source 52 of cryogenic fluid is in or otherwise associated with the control unit 14. To facilitate delivery of cryogenic fluid to the treatment element 34 and recovery (recovery) from the treatment element 34, the apparatus and system may include one or more fluid flow paths between the source 52 of cryogenic fluid and the treatment element 34. For example, the apparatus 12 may include fluid delivery and fluid recovery conduits within the elongate body 22 that are in fluid communication with a source 52 of cryogenic fluid and a cryogenic fluid recovery reservoir 54 or other purging or recovery system.

the treatment element 34 can be coupled to a portion of the distal portion 28 of the elongate body. The apparatus may optionally include a shaft 56 slidably disposed within elongate body 22, and at least a portion of shaft 56 may be located within interior chamber 36 of treatment element 34. The shaft 56 can include or define a distal tip 58 that can protrude beyond the distal end of the treatment element 34. Retraction and extension of the shaft 56 within the elongate body 22 (i.e., longitudinal movement of the shaft 56 within the elongate body 22) may affect the size and shape of the cryoballoons 44, 46. The fluid injection element 48 may be in fluid communication with or defined by a portion of the fluid delivery conduit 60 within the interior chamber 36. By way of non-limiting example, a portion of the fluid delivery conduit 60 may be wrapped around a portion of the shaft 56 within the interior chamber 36. The shaft 56 may further include a guidewire lumen 62 through which a guidewire 64 may extend during a procedure. By way of non-limiting example, the guidewire 64 may extend beyond the distal opening of the guidewire lumen 62 and distally of the treatment element 34 into the pulmonary vein, while the treatment element 34 is used to ablate or map tissue on the left atrial wall. The guidewire 64 may be steerable and may carry one or more sensors and/or mapping electrodes (not shown). In addition, the guidewire lumen 62 can be used to deliver cold saline solution to a location distal to the treatment element for PV occlusion assessment. By way of non-limiting example, the control unit 14 may include a saline reservoir in fluid communication with the guidewire lumen 62 or other portion of the device 12 for delivering cold saline solution to a location distal to the treatment element, such as within the PV. As discussed in more detail below, the cold brine may be used to cause a temperature change detected by the device 12, which may be used to assess ice formation and/or PV occlusion.

The treatment element 34 may include a plurality of mapping elements. As non-limiting examples, the device 12 may include a plurality of mapping electrodes 40, the plurality of mapping electrodes 40 being coupled to, integrated with, or embedded within the material of the outer freezing balloon 46, the material of the outer freezing balloon 46. The plurality of electrodes 40 may be configured for both mapping and delivering therapeutic energy. In addition, the plurality of electrodes 40 may also be configured to record impedance measurements from tissue for lesion assessment, and each electrode may be associated with one or more sensors 42 (such as temperature sensors), as discussed in more detail below. For example, each mapping electrode 40, and optionally a treatment element, in communication with the power source may be a conductive segment for transmitting electrical signals, currents, or voltages to a designated tissue region and/or for measuring, recording, receiving, evaluating, or otherwise using one or more electrical properties or characteristics of surrounding tissue or other electrodes. Further, the mapping electrodes 40 may be in wireless or wired communication with the control unit 14. The electrodes may be configured in a number of different geometric configurations or controllably deployable shapes, and may also vary in number to suit a particular application, target tissue structure, or physiological characteristic.

the device 12 may further include one or more electrodes 66 for measuring impedance signals, and may be referred to herein as impedance electrodes. However, impedance electrode 66 may also be used by navigation system 16 to visualize device 12 on a control unit display and/or a navigation system display. For example, the device 12 may include: a first impedance electrode 66A proximate to and distal of the expandable portion of the treatment element 34, and a second impedance electrode 66B proximate to and proximal of the expandable portion of the treatment element 34. Additionally, each impedance electrode 66 may include or be associated with a thermocouple or other temperature sensor 42 such that impedance and temperature measurements may be recorded at the location of each impedance electrode 66. In one embodiment, the second or proximal impedance electrode 66B includes a temperature sensor 42. In another embodiment, the second or proximal impedance electrode 66B does not include the temperature sensor 42. In addition, the navigation system 16 may receive data from the mapping electrodes 40 to generate a map of at least a portion of the heart (or other treatment location) on which the area of lesion formation and/or device location may be displayed.

As discussed below, the combination of the impedance electrodes 66 and the temperature sensor 42 allows for assessment of occlusion of hollow anatomical features (such as pulmonary veins) by the treatment element 34 without having to use nephrotoxic dyes. For example, the treatment element 34 may be positioned at the PV ostium, such as in a location deemed to occlude the PV. Cold saline may be delivered into the PV distal to the device 12 (e.g., through the guidewire lumen 62), and temperature measurements by thermocouples to other temperature sensors 42 on or associated with the first or distal impedance electrodes 66A may be used to assess ice formation and/or the temperature of blood within the PV (to assess occlusion of the PV). In addition, the impedance electrodes 66 may be sized and positioned to optimize and enhance the accuracy of the impedance recordings. By way of non-limiting example, the first impedance electrode 66A may be immediately distal of the treatment element 34, such as an inflatable or expandable portion 67 of the cryoballoon 44, 46 (as shown in fig. 1). Likewise, the second impedance electrode 66B may be immediately proximal to the treatment element 34 (such as the inflatable or expandable portion 67 of the cryoballoon 44, 46). In practice, each of the first impedance electrode 66A and the second impedance electrode 66B may be in close proximity to the expandable or expandable portion 67 of the treatment element such that they contact at least a portion of the distal face of the treatment element 34 and at least a portion of the proximal face of the treatment element 34, respectively, when the treatment element 34 is expanded or expanded. The proximity of impedance electrodes 66A, 66B to treatment element 34 may minimize or eliminate the opportunity for impedance electrodes 66A, 66B to record non-target or interfering impedance measurements (i.e., impedance measurements unrelated to assessment of ice formation and/or ice thickness).

In addition, the combination of the impedance electrodes 66 and the temperature sensor 42 allows the system 10 to generate an anatomical map(s) of the target treatment location(s), such as the heart, through 3D navigation. This combination also allows system 10 to generate electrophysiological 3D activation and electrogram amplitude map(s) that can then be superimposed on the anatomical map(s).

Although not shown, in addition to monitoring, recording, or otherwise communicating measurements or conditions within the medical device 12 or within the ambient environment at a distal portion of the medical device 12, the system 10 may include one or more sensors to monitor operating parameters throughout the system, including, for example, pressure, temperature, flow rate, volume, power delivery, impedance, and so forth, in the control unit 14 and/or the medical device 12. The sensor(s) may be in communication with control unit 14 for initiating or triggering one or more alarms or therapy delivery modifications during operation of medical device 12. One or more valves, controllers, or the like may be in communication with the sensor(s) to provide controlled dispersion or circulation of fluid through the lumen/fluid path of medical device 12. These valves, controllers, etc. may be located in a portion of medical device 12 and/or in control unit 14.

The medical device 12 may include a handle 68 coupled to the proximal portion 26 of the elongate body. The handle 68 may include circuitry for identifying and/or for controlling the medical device 12 or another component of the system. Additionally, handle 68 may also include a connector that may be mated with control unit 14 to establish communication between medical device 12 and one or more components or portions of control unit 14. The handle 68 may also include one or more actuation or control features that allow a user to control, deflect, steer (steer), or otherwise manipulate a distal portion of the medical device 12 from a proximal portion of the medical device 12. For example, the handle 68 may include one or more components, such as a lever or knob, for manipulating the elongate body 22 and/or additional components of the medical device 12.

as used herein, the term "control unit 14" may include, for simplicity, any system component other than the components of the navigation system 16 and the imaging system 18 (if included), which is not part of the medical device 12 itself, whether physically located inside or outside the control unit 14. Further, navigation system 16 may be a stand-alone system in communication with control unit 14 or may be contained within control unit 14 or integrated with control unit 14, although navigation system 16 is shown in fig. 1 as being physically separate from the control unit. The control unit 14 may include one or more components for delivering one or more forms of energy for use by the system. For example, the control unit 14 may include a source 52 of cryogenic fluid, a venting or purging system for recovering or venting spent fluid for reuse or disposal, which may include a cryogenic fluid recovery reservoir 54 and various control mechanisms. In addition to providing a venting function for the source 52 of cryogenic fluid, the control unit 14 may also include pumps, valves, controllers, and the like to recover and/or recirculate fluid delivered to the handle 68, elongate body 22, and/or fluid passageways of the device 12. Further, the vacuum pump in the control unit 14 may create a low pressure environment in one or more conduits within the medical device 12 such that fluid is drawn into the conduit (s)/lumen(s) of the elongate body 22, away from the distal portion 28 of the elongate body 22 and toward the proximal portion 26 of the elongate body 22. Additionally or alternatively, the control unit 14 may include an energy source 70 as a treatment or diagnostic mechanism in communication with the treatment element(s) 34 of the device 12. By way of non-limiting example, the energy source 70 may be a radiofrequency generator having a plurality of output channels, and may be operable in one or more operating modes (e.g., a monopolar mode and/or a bipolar mode).

The control unit 14 may further include processing circuitry 74, which may include one or more controllers, processors, and/or software modules configured to execute instructions or algorithms to provide for the automated operation and execution of the features, sequences, calculations, or procedures described herein and/or required for a given medical procedure. In one embodiment, the processing circuitry may include a processor and a memory. The memory may be in electrical communication with the processor and have instructions that, when executed by the processor, configure the processor to receive, process, or otherwise use signals from the device 12. Further, the control unit 14 may include one or more user input devices, controls, and a display 76 for collecting and transmitting information from and to a user.

The system 10 may include a navigation system 16, and the navigation system 16 may be any commercially available navigation system suitable for use with the control unit 14, the device 12, and any type of process. By way of non-limiting example, the navigation system 12 may include: a plurality of body surface electrodes 80, a reference electrode (not shown), and processing circuitry 82, the processing circuitry 82 collecting and processing signals from the device mapping electrodes 40, and a display 84 displaying to the user the location of the device 12 within the patient and/or relative to the target anatomical feature, recommended treatment area, tissue thickness, etc. The processing circuitry 82 may include a memory in communication with the processor and having instructions that, when executed by the processor, configure the processor to perform the calculations and determinations discussed herein. The navigation system 12 can also include an energy source (not shown) for delivering energy to the plurality of body surface electrodes 80. Alternatively, the navigation system 12 may be in communication with the control unit energy source 70. For example, the processing circuitry 82 may be configured, programmed, or programmable to perform calculations and make determinations discussed in more detail below to identify anatomical features and/or target locations for the medical device. Further, the processing circuitry 82 may execute software and display a software interface with which a user may interact to select, rotate or mark images, open folders, control the navigation system 12, and so forth. By way of non-limiting example, a user may interact with the software interface using a touch screen, keyboard, mouse, or other input device.

The body surface electrodes 80 can be applied to the skin of a patient 86 and relatively low frequency radio frequency energy can be delivered by the patient toward the surgical site, current device location, or target anatomical feature. Mapping electrodes 40 on device 12 may each record the voltage and impedance from this energy and transmit the data to processing circuitry 82, and processing circuitry 82 may then determine the location of impedance electrode 66 within patient 86, and thus the location of device 86 within patient 86 (in this sense, impedance electrode 66 may function as a navigation electrode). In addition to impedance-based systems, other navigation electrodes may be used, such as magnetic-field-based, hybrid impedance/magnetic-field-based, ultrasound-field-based, and/or radiation-based navigation systems, and/or navigation systems that may be developed in the future. The processing circuitry 82 may perform this calculation multiple times during the procedure, frequently updating the registered locations and displaying this content to the user so that the user can view the location of the device relative to the target anatomical feature and the tissue electrical activity in the target anatomical feature in real-time.

The system 10 may optionally include an imaging system 18, such as an ultrasound system. Imaging system 18 may communicate with and digitally transmit images to navigation system 16 and/or control unit 14 for further processing. Alternatively, the images recorded by imaging system 18 may be recorded by the user and communicated to navigation system 16 and/or control unit 14.

Referring now to fig. 2-5, the distal portion of an exemplary medical device will now be described in more detail. As described above, the device 12 may include one or more treatment elements 34, a plurality of mapping electrodes 40, and one or more impedance electrodes 66. Fig. 1 shows a cross-sectional view of the treatment element 34, and thus the mapping electrode 40 is not shown. Fig. 2 illustrates a distal portion of the medical device 12 of fig. 1 with the mapping electrodes 40 shown. Each mapping electrode 40 and impedance electrode 66 may be constructed of a thermally and/or electrically conductive material, such as a metal, metal alloy, or other suitable biocompatible electrically conductive material. By way of non-limiting example, the conductive material may be incorporated into the external cryoballoon 46 in the area of the mapping electrode 40, implanted in the external cryoballoon 46 in the area of the mapping electrode 40, integrated with the external cryoballoon 46 in the area of the mapping electrode 40, and/or deposited on the external cryoballoon 46 in the area of the mapping electrode 40. As a further non-limiting example, the mapping electrodes 40 may be mechanically coupled to the outer surface of the outer cryoballoon 46, such as by using an adhesive, chemical bonding (bonding), or other suitable attachment means, as may be the case if the mapping electrodes 40 are components such as typical band electrodes. The impedance electrodes 66 and/or the temperature sensor 42 can likewise be attached to the elongate body 22 and/or the treatment element 34.

In the configuration shown in fig. 2, the mapping electrodes 40 may be arranged in a plurality of linear forms extending between the distal end and the proximal end of the outer freezing balloon 46 or between at least the portion of the outer freezing balloon 46 that is not coupled to the shaft 56 or the distal portion 28 of the elongate body. The lines of the mapping electrodes 40 may be at least substantially parallel to the device longitudinal axis 30 (i.e., the lines may be parallel except for subtle or insignificant variations in mapping electrode positioning, such as those that may occur during device manufacturing). While the mapping electrodes 40 are shown in fig. 2 as being neatly arranged, it will be understood that the mapping electrodes 40 may alternatively be located at discrete locations on the cryoballoon 46 in any pattern (e.g., the mapping electrodes 40 may be randomly spaced apart, as shown in fig. 3). Further, the mapping electrodes 40 may be arranged in configurations other than that shown in fig. 2, such as in clusters having two or more mapping electrodes 40 (e.g., as shown in fig. 4), in bands (bands) extending at several locations around the circumference of the cryoballoon 46 (e.g., as shown in fig. 5), or in other patterns. . In the embodiment shown in fig. 5, each band of the mapping electrode 40 may extend at least partially around the longitudinal axis 30, rather than parallel thereto. In other words, the mapping electrodes 40 may be radially arranged about the longitudinal axis at a plurality of locations along the longitudinal axis.

each mapping electrode 40 may include or be associated with one or more sensors 42. Alternatively, each sensor 42 may be associated with one or more mapping electrodes 40. For example, one or more sensors 42 may be coupled to each mapping electrode 40, integrated with each mapping electrode 40, or positioned proximate to each mapping electrode 40. One or more sensors 42 may be configured to record data, such as temperature, pressure, electrograms, or other data.

In one embodiment, the first impedance electrode 66A and its temperature sensor 42 may be immediately distal (as shown in fig. 1) to the treatment element 34, such as the inflatable or expandable portion 67 of the cryoballoon 44, 46. Likewise, the second impedance electrode 66B may be immediately proximal to the treatment element 34 (such as the inflatable or expandable portion 67 of the cryoballoon 44, 46). In practice, each of the first impedance electrode 66A and the second impedance electrode 66B may be in close proximity to the expandable or expandable portion 67 of the treatment element such that they contact at least a portion of the distal face of the treatment element 34 and at least a portion of the proximal face of the treatment element 34, respectively, when the treatment element 34 is expanded or expanded. The proximity of the impedance electrodes 66A, 66B to the treatment element 34 may maximize the sensitivity of the electrodes 66A, 66B to record ice formation on the surface of the treatment element 34.

Additionally, each of the impedance electrodes 66A, 66B may have a width of about 0.5mm (± 0.1mm) or less. Accordingly, the impedance electrodes 66 are relatively small (e.g., compared to the ribbon electrodes used in currently known systems). This size of the impedance electrode 66 and the location of the impedance electrode 66 in close proximity to the treatment element 34 (and in contact with the treatment element 34 in some embodiments) improves impedance measurement accuracy. In addition, each impedance electrode 66A, 66B may also include or be associated with a thermocouple or other sensor 42, such as a pressure sensor, a temperature sensor, or any other suitable sensor for recording a tissue property of interest, 42.

referring now to fig. 6 and 7, embodiments of a medical device located at a target location and methods of using the device are shown. In a first step 110, the distal portion 28 of the device 12 may be navigated to a target treatment location, such as within a chamber of the heart. The treatment site may be accessed through a femoral (femoral), radial (radial), or humeral (brachial) site. In a second step 120, the treatment element 34 may be converted from the at least substantially linear first configuration to the expanded second configuration. For example, cryogenic fluid may be delivered from a source of cryogenic fluid through the fluid delivery conduit 60, the fluid injection element 48, and into the internal chamber 36 to inflate the inner freezing balloon 44 and expand the outer freezing balloon 46 (such expansion of the outer freezing balloon 46 may also be referred to as inflating the outer freezing balloon 46). In a third step 130, the expanded treatment element 34 may be manipulated or positioned such that at least one of the plurality of mapping electrodes 40 is in contact with the target treatment location. The user may use position information from the impedance electrodes 66 and/or the imaging system 18 to assist in the placement of the therapy element 34. For example, the side surface of the treatment element 34 may be used to record data from the tissue with which the treatment element 34 is in contact.

Mapping electrodes 40 may be used for anatomical high resolution chamber definition (such as by collecting a high density of anatomical structures and electrical activity from tissue), high fidelity electrical activation mapping and electrical amplitude determination of heart chambers, pacing and pacing threshold determination, rapid activation maps and electrical activity amplitude maps (such as by recording the electrical activity of the entire heart by moving treatment element 34 relative to the heart tissue), pre-treatment, mid-treatment, and post-treatment tissue impedance determination, ice formation and thickness determination, and post-treatment efficacy to define tissue viability (viatility). Additionally, the treatment element 34 may be used not only for cryoablation, but also for cold mapping.

In a fourth step 140, pre-treatment data may be recorded by the mapping electrode(s) 40 and sensor(s) 42 and transmitted from the mapping electrode(s) 40 and sensor(s) 42 to the control unit processing circuitry 74 for further processing and transmission to the user. The pre-treatment data can provide a baseline or threshold against which the mid-treatment data and post-treatment data can be compared to assess treatment efficacy. For example, the mapping electrodes 40 may be configured to record pre-treatment tissue impedance, pre-treatment local electrical activity, and pre-treatment pacing thresholds. The mapping electrodes 40 may operate as monopolar and bipolar electrode arrays configured to record local electrograms (monopolar and/or bipolar), monopolar pacing thresholds and impedances (monopolar and/or bipolar). Likewise, the sensor 42 may be configured to record pre-treatment temperature measurements.

The pacing threshold is the minimum amount of pulse current (e.g., a pulse having a duration of 0.5 milliseconds) that results in activation of electrical activity in cardiac tissue, such as myocardial tissue. During unipolar pacing energy delivery, pulses may be delivered through designated mapping electrodes 40 (single electrodes) on the treatment elements 34 to body surface electrodes 80 on the patient's skin (e.g., the body surface electrodes may be attached to the patient's legs). The pacing threshold is typically low (such as between 1-2 mA) before the cryogenic fluid circulates within the treatment element (i.e., before treatment or before ablation), while the pacing threshold may be above 20mA after the circulation of the cryogenic fluid within the treatment element has ended (after treatment). This increase indicates that excitable tissue has been destroyed.

Unipolar impedance is a measure of the resistive path between a mapping electrode 40 (a single electrode) in contact with the heart muscle and a reference electrode or body surface electrode on the patient's skin. Monopolar impedance measurements may be used to measure the thickness of the iceball between the treatment element 34 and the tissue. Bipolar impedance, on the other hand, is a measure of the resistive path between two mapping electrode(s) 40, such as two adjacent mapping electrodes 40. The bipolar impedance measurements may be used to determine or quantify how much ice has accumulated between two mapping electrodes 40 and between other pairs of mapping electrodes 40 used to record the bipolar impedance measurements. Typically, this determination is most accurate if the mapping electrodes 40 are within about 5mm of each other.

In a fifth step 150, the treatment element 34 can be activated to ablate the target tissue. For example, the ablation target tissue can be cryogenically cooled by circulating a cryogenic fluid through the treatment element 34 to cool the outer cryoballoon 46 to a temperature sufficient to ablate the tissue with which the outer cryoballoon 46 is in contact. Additionally, if the device 12 includes one or more treatment elements in addition to the cryoballoons 44, 46, the device 12 may also be used to ablate the target tissue by one or more energy modes, such as by delivering radio frequency energy, ultrasonic energy, laser energy, or by other energy delivery to the tissue.

In a sixth step 160, in-treatment data may be collected by the mapping electrode 40 and sensor 42 while the treatment element(s) 34 are activated and the target tissue is ablated, and the data may be transmitted from the mapping electrode(s) 40 and sensor 42 to the control unit processing circuitry 74 for further processing and communication to the user. For example, the mapping electrodes 40 may record high-resolution impedance measurements, and the sensors 42 may record temperature measurements, impedance measurements, electrogram amplitude measurements, and the like from the tissue. These measurements may then be transmitted to the control unit 14 where the processing circuitry 74 may process or use them to determine the size of the tissue lesion created by the treatment (surface area), the area of sufficient lesion formation, and/or the thickness of ice formation at the control unit 14. When the outer cryoballoon 46 is cooled to ablate tissue, ice 90 from the frozen blood around the treatment site may form between the cryoballoon 46 and the tissue and cryoadhere the treatment element 34 to the tissue. The ice 90 may contribute to lesion formation; thus, assessment of the thickness of the ice may provide an indication of the quality of the lesion and the efficacy of the treatment. For example, the processing circuitry may establish a threshold ice thickness indicative of lesion transmurality in a particular region of tissue being treated, such as by using a data table of empirical evidence or historical data for a particular patient. As the ice thickness increases, the mapping electrodes 40 may detect an increase in impedance and the sensors 42 may detect a decrease in temperature.

In a seventh step 170, the circulation of cryogenic fluid within the treatment element 34 may be stopped, either manually or automatically by the system 10, in order to end the ablation of the tissue, allow the ice 90 to melt, and break the cryoadhesion between the treatment element (i.e., the cryoballoon 46) and the tissue. In an eighth step 180, post-treatment data may be transmitted from the mapping electrode(s) 40 and sensors 42 to the control unit processing circuitry 74 for further processing and transmission to the user. Post-treatment data may include, but is not limited to, unipolar pacing threshold, bipolar pacing threshold, unipolar impedance, bipolar impedance, unipolar electrical activity, bipolar electrical activity, and temperature. For example, the processing circuitry 74 may use the pre-treatment, in-treatment, and post-treatment data to determine changes in tissue impedance after ablation (post-treatment) due to ice melting, changes in electrical activity after ablation (post-treatment), and changes in pacing threshold after ablation (post-treatment). The processing circuitry 74 may compare the pre-treatment data to the in-treatment and/or post-treatment data to identify tissue locations where optimal or sufficient lesion formation has occurred and tissue locations where insufficient, incomplete, or insignificant lesion formation has occurred. The processing circuitry 74 may be configured to correlate the thickness of ice between the treatment element and the tissue and/or the amount of ice formation between the mapping electrodes to the quality of lesion formation in the tissue. For example, the processing circuitry may establish a threshold puck thickness (such as an ice thickness between 3mm and 4 mm). If the processing circuitry 74 determines that the thickness of the puck is greater than the threshold thickness, the processing circuitry 74 may determine that a transmural lesion has been formed in the tissue. If the processing circuitry 74 determines that the lesion is transmural, the system may alert the user that no further treatment time is needed.

In a further non-limiting example, processing circuitry 74 may compare the pre-treatment pacing threshold to the post-treatment pacing threshold to determine whether ablation of myocardial tissue has occurred. For example, processing circuitry 74 may establish a threshold difference between the pre-therapy pacing threshold measurement and the post-therapy pacing threshold measurement at which sufficient ablation (lesion formation) is deemed to have occurred. If the post-treatment pacing threshold measurement is greater than the pre-treatment pacing threshold measurement by an amount at least equal to the threshold difference, the processing circuitry may determine that a region of tissue in contact with the treatment element has been ablated. For example, the threshold pacing difference may be an amount about three to five times greater than the pre-treatment pacing threshold amount. In a further non-limiting example, the processing circuitry 74 may compare the pre-treatment unipolar impedance, the post-treatment unipolar impedance, and the post-treatment unipolar impedance to determine a maximum ice thickness and monitor the progress of ice melting after ablation (i.e., once the cycle of cryogenic fluid through the treatment element has ended). In a further non-limiting example, the processing circuitry 74 may compare the pre-treatment bipolar impedance measurement, the in-treatment bipolar impedance measurement, and the post-treatment bipolar impedance measurement to determine the thickness of ice between the mapping electrodes 40. In further non-limiting examples, the processing circuitry 74 may compare the pre-treatment unipolar impedance measurement, the treatment unipolar impedance measurement, and the post-treatment unipolar impedance measurement, and/or compare the pre-treatment bipolar impedance measurement, the in-treatment bipolar impedance measurement, and the post-treatment bipolar impedance measurement to determine lesion formation and thereby determine treatment efficacy. The impedance value(s) that may indicate adequate lesion formation may be based on parameters such as the surface area of the mapping electrode 40 and tissue contact quality.

In a further non-limiting example, the processing circuitry 74 may compare the pre-treatment impedance measurement to the post-treatment impedance measurement between the electrodes to determine the extent of lesion formation, i.e., the surface area of the lesion. The processing circuitry 74 may compare the pre-treatment data and post-treatment data for each mapping electrode 40 to identify which mapping electrodes 40 have recorded an increase in impedance indicating that sufficient lesion formation has occurred. For example, the processing circuitry 74 may use the pre-treatment impedance data to establish or determine a baseline impedance value for each mapping electrode 40. The processing circuitry 74 may then use the in-treatment impedance data to determine electrical activity and/or pacing threshold increases on each of the mapping electrodes 40 in contact with the tissue to define a region that is sufficiently ablated and delineate ablated tissue on the 3D anatomical map. Finally, the mapping circuitry 74 may correlate the location(s) of the mapping electrode 40 deemed to be associated with sufficient lesion formation to create a map or display of the lesion. The processing circuitry 74 and/or the user may then use this data, along with a map or display created therefrom, to automatically or manually determine the surface area (size) of the lesion. In one embodiment, the processing circuitry 74 may be configured to determine, for each mapping electrode 40, that at least a portion of the tissue region proximate to the mapping electrode 40 has been ablated when the mapping electrode 40 records a post-treatment electrogram amplitude value of 0.5mV or less, and the processing circuitry 74 may be further configured to determine the lesion surface area based on the post-treatment electrogram amplitudes recorded by each of the plurality of mapping electrodes 40. In other words, the processing circuitry 40 may be configured to determine whether each mapping electrode 40 is in contact with or proximate to a portion of the tissue region that has been sufficiently ablated. The surface area may then be calculated and a surface area map created by connecting the locations of the mapping electrodes 40 associated with lesion formation.

further, in an optional ninth step 190, the navigation system 16 may receive data from the mapping electrodes 40 and sensors 42 and/or from the control unit 14, and the navigation system processing circuitry 82 may process the data to generate a map of at least a portion of the heart (or other treatment region). The graph may show a treatment site area 94 where optimal or sufficient lesion formation has occurred and a treatment site area 96 where insufficient, incomplete, or insignificant lesion formation has occurred. The map may be displayed to a user who may then use this information to reposition device 12 to ablate or further ablate the area where optimal or sufficient lesion formation has not yet occurred.

although the method illustrated in fig. 7 includes recording pre-treatment data, in-treatment data, and post-treatment data, and comparing the data, it should be understood that in some embodiments the method includes recording and comparing only pre-treatment data with post-treatment data, recording and comparing only pre-treatment data with in-treatment data, or recording and comparing only in-treatment data with post-treatment data. Further, data may be recorded continuously throughout the process. Thus, the pre-treatment data may become in-treatment data and the in-treatment data may become post-treatment data without explicit clarification. Thus, although not explicitly shown in fig. 7, it will be understood that even though a single step is shown, data may be continuously recorded throughout the process. Additionally, it will be understood that in some embodiments, the processing circuitry 74 does not generate or display a map of lesion formation.

Referring now to fig. 8-10, an embodiment of a medical device positioned at and in contact with a pulmonary vein ostium is shown. Fig. 10 shows a graph correlating impedance, time and temperature with pulmonary vein occlusion and ablation (isolation). As used herein, the term "PV tissue" or "pulmonary vein tissue" may include tissue of the PV ostium, the PV sinus, the LA wall tissue, and/or the junction between LA and PV, and is not limited to tissue within PV. In fact, ablation of tissue within the PV may be undesirable. In a first step 210, the distal portion 28 of the device 12 may be navigated to a target treatment location, such as at or near the ostium of a pulmonary vein. The treatment site may be accessed through a femoral, radial, or humeral location. In a second step 220, the treatment element 34 may be converted from the at least substantially linear first configuration to the expanded second configuration. For example, cryogenic fluid may be delivered from a source of cryogenic fluid through the fluid delivery conduit 60, the fluid injection element 48, and into the internal chamber 36 to inflate the inner freezing balloon 44 and expand the outer freezing balloon 46 (such expansion of the outer freezing balloon 46 may also be referred to as inflating the outer freezing balloon 46).

in a third step 330, the expanded treatment element 34 may be manipulated or positioned such that the distal impedance electrode 66A is located within the pulmonary vein. Optionally, the expanded treatment element 34 may also be manipulated such that the at least one mapping electrode 40 is in contact with tissue, such as tissue surrounding the ostium of a pulmonary vein. The user may use position information from the impedance electrodes 66 and/or the imaging system 18 to assist in the placement of the therapy element 34. The expanded treatment element 34 may be positioned at the ostium of a Pulmonary Vein (PV) to occlude the PV, or to block blood flow from the PV into the Left Atrium (LA) of the heart. Occlusion of the PV not only serves to position the treatment element 34 to create a circumferential lesion around the PV ostium, but also prevents warm blood from flowing over the portion of the treatment element 34 that is (or should be) in contact with the target tissue, thereby enhancing the ability of the treatment element 34 to reach sufficiently cold temperatures for creating a permanent and circumferential cryoablation lesion on or in the target tissue. Blood blocked within a PV may be referred to as "stagnant" blood, while blood within an LA may be referred to as "flowing" blood, as blood may still enter the LA from the other three PVs not blocked by catheter 12. The cold saline solution may be delivered from the distal portion of the device 12 into the blood within the PV, such as through a guidewire lumen 62 or other fluid delivery aperture. Impedance and temperature data from the first or distal impedance electrode 66A and the temperature sensor or thermocouple 42 associated with the distal impedance electrode 66A, respectively, may be used to assess PV occlusion by the treatment element 34 and the location of the treatment element 34. The temperature recovery curve may define whether the processing element 34 sufficiently blocks the PV. If the PV is not completely occluded, blood flowing through the treatment element 34 may have the effect of raising the temperature of the treatment element 34. If blood flows through the treatment element 34, the temperature recorded by the temperature sensor 42 associated with the distal impedance electrode 66A will rise faster than if the PV were completely occluded and cold saline solution was delivered into the stagnant blood.

The impedance electrodes 66A, 66B may also be used to assess occlusion of a body lumen (such as a pulmonary vein) by the treatment element 34. In addition, mapping electrodes 40 may be used for anatomical high resolution chamber definition (such as by collecting a high density of anatomical structures and electrical activity from tissue), high fidelity electrical activation mapping and electrical amplitude determination of heart chambers, pacing and pacing threshold determination, fast activation maps (such as by recording the electrical activity of the entire heart by moving treatment element 34 relative to the heart tissue), pre-treatment, in-treatment and post-treatment tissue impedance determination to define tissue viability, effective ablation associated with ice formation and thickness determination, and post-treatment efficacy further defined by local electrogram activity and pacing threshold changes. Additionally, the treatment element 34 may be used not only for cryoablation, but also for cold mapping.

In a fourth step 240, pre-treatment data may be recorded by and transmitted from the impedance electrodes 66A, 66B, mapping electrode(s) 40, and sensor(s) 42 to the control unit processing circuitry 74 for further processing and transmission to the user by the impedance electrodes 66A, 66B, mapping electrode(s) 40, and sensor(s) 42. The pre-treatment data can provide a baseline or threshold against which the mid-treatment data and post-treatment data can be compared to assess treatment efficacy. For example, pre-treatment impedance data from the impedance electrodes 66A, 66B and temperature data from the temperature sensor 42 (particularly data from the first or distal impedance electrode 66A and its associated temperature sensor 42) may be used to determine the quality of the occlusion of the pulmonary vein by the treatment element 34 in a later step by comparison thereof with in-treatment data and/or post-treatment data. As a further example, the mapping electrodes 40 may be configured to record pre-treatment tissue impedance, pre-treatment local electrical activity, and pre-treatment pacing thresholds. The mapping electrodes 40 may operate as monopolar and bipolar electrode arrays configured to record local electrograms (monopolar and/or bipolar), monopolar pacing thresholds and impedances (monopolar and/or bipolar). Likewise, the sensor 42 may be configured to record pre-treatment temperature measurements.

Additionally, as discussed above, temperature data from a temperature sensor or thermocouple 42 associated with distal impedance electrode 66A may be used to assess PV occlusion by treatment element 34 and the location of treatment element 34. For example, as shown in fig. 10, comparing the in-treatment temperature data and/or the post-treatment temperature data to the pre-treatment temperature data may indicate whether the PV is being isolated or has been completely isolated. In a fifth step 250, the pre-treatment may be used to determine if the device 12 is properly positioned at the PV ostium and if not, the device 12 may be repositioned as desired.

In a sixth step 260, the treatment element 34 can be activated to ablate the target tissue. For example, the ablation target tissue can be cryogenically cooled by circulating a cryogenic fluid through the treatment element 34 to cool the outer cryoballoon 46 to a temperature sufficient to ablate the tissue with which the outer cryoballoon 46 is in contact. Additionally, if the device 12 includes one or more treatment elements in addition to the cryoballoons 44, 46, the device 12 may also be used to ablate the target tissue by one or more energy modes, such as by delivering radio frequency energy, ultrasonic energy, laser energy, or by other energy delivery to the tissue.

in a seventh step 270, in-treatment data may be collected by the impedance electrodes 66A, 66B, mapping electrode 40, and/or sensor 42 as the treatment element(s) 34 are activated and the target tissue is ablated, and this data may be transmitted from the impedance electrodes 66A, 66B, mapping electrode(s) 40, and/or sensor 42 to the control unit processing circuitry 74 for further processing and transmission to the user. For example, the impedance electrodes 66A, 66B may record impedance measurements (e.g., high resolution impedance measurements), the mapping electrodes 40 may record impedance measurements (e.g., high resolution impedance measurements), and the sensors 42 may record temperature measurements from the tissue. These measurements may then be transmitted to the control unit 14 where the processing circuitry 74 may process or use them to determine the size of the tissue lesion created by the treatment (surface area), the area of sufficient lesion formation, and/or the thickness of ice formation at the control unit 14. Further, in-treatment impedance measurements from the impedance electrodes 66A, 66B and in-treatment temperature measurements from the sensor(s) 42 may be continuously recorded during the ablation stage and compared to each other to assess occlusion of the PV and thus lesion creation in the tissue surrounding the PV ostium. As discussed above, if the PV is not completely occluded, blood flowing through the treatment element 34 can have the effect of raising the temperature of the treatment element 34, possibly resulting in the formation of reversible lesions on or in the target tissue. Additionally, good blocking of the PV may also be indicated by a significant increase in impedance (e.g., as shown in fig. 10). Ice formation over the first or distal impedance electrode 66A (e.g., as shown in fig. 8) may result in an increased impedance value as measured by the first impedance electrode 66A.

When the outer cryoballoon 46 is cooled to ablate tissue, ice 90 from the frozen blood around the treatment site may form between the cryoballoon 46 and the tissue and cryoadhere the treatment element to the tissue. The ice 90 may aid in lesion formation; thus, assessment of the thickness of the ice may provide an indication of the quality of the lesion and the efficacy of the treatment, and may help prevent damage to non-target tissues, such as the esophagus, lungs, and phrenic nerve. For example, the processing circuitry may establish a threshold ice thickness indicative of adequate circumferential lesion formation in tissue surrounding the pulmonary veins, such as by using a data table of empirical evidence or historical data for a particular patient. As the ice thickness increases, the mapping electrodes 40 may detect the increase in impedance.

In an eighth step 280, the circulation of cryogenic fluid within the treatment element 34 may be stopped, either manually or automatically by the system 10, in order to end the ablation of the tissue, allow the ice 90 to melt, and break the cryoadhesion between the treatment element (i.e., the cryoballoon 46) and the tissue. In a ninth step 290, post-treatment data may be transmitted from the mapping electrode(s) 40 and sensors 42 to the control unit processing circuitry 74 for further processing and transmission to the user. Post-treatment data may include, but is not limited to, unipolar pacing threshold, unipolar impedance, bipolar impedance, and temperature. For example, the processing circuitry 74 may use the pre-treatment data, the in-treatment data, and the post-treatment data to determine post-ablation (post-treatment) ablation efficacy, changes in post-ablation (post-treatment) electrical activity, and changes in post-ablation (post-treatment) pacing thresholds, such as indicated by changes in tissue impedance due to ice melting. The processing circuitry 74 may compare the pre-treatment data to the in-treatment data and/or the post-treatment data to identify tissue locations where optimal or sufficient lesion formation has occurred and tissue locations where insufficient, incomplete, or insignificant lesion formation has occurred. The processing circuitry 74 may be configured to correlate the thickness of ice between the treatment element and the tissue and/or the amount of ice formation between the mapping electrodes to the quality of lesion formation in the tissue. For example, the processing circuitry may establish a threshold puck thickness (such as an ice thickness between 3mm and 4 mm). If the processing circuitry 74 determines that the thickness of the puck is greater than the threshold thickness, the processing circuitry 74 may determine that a transmural lesion has been formed in the tissue. If the processing circuitry 74 determines that the lesion is transmural, the system may alert the user that no further treatment time is needed.

In a further non-limiting example, processing circuitry 74 may compare the pre-treatment pacing threshold to the post-treatment pacing threshold to determine whether ablation of myocardial tissue has occurred. For example, processing circuitry 74 may establish a threshold difference between the pre-therapy pacing threshold measurement and the post-therapy pacing threshold measurement at which sufficient ablation (lesion formation) is deemed to have occurred. If the post-treatment pacing threshold measurement is greater than the pre-treatment pacing threshold measurement by an amount at least equal to the threshold difference, the processing circuitry may determine that a region of tissue in contact with the treatment element has been ablated. For example, the threshold pacing difference may be an amount about three to five times greater than the pre-treatment pacing threshold amount. In a further non-limiting example, the processing circuitry 74 may compare the pre-treatment unipolar impedance, the post-treatment unipolar impedance, and the post-treatment unipolar impedance to determine a maximum ice thickness and monitor the progress of ice melting after ablation (i.e., once the cycle of cryogenic fluid through the treatment element has ended). In a further non-limiting example, the processing circuitry 74 may compare the pre-treatment bipolar impedance measurement, the in-treatment bipolar impedance measurement, and the post-treatment bipolar impedance measurement to determine the thickness of ice between the mapping electrodes. In further non-limiting examples, the processing circuitry 74 may compare the pre-treatment unipolar impedance measurement, the treatment unipolar impedance measurement, and the post-treatment unipolar impedance measurement, and/or compare the pre-treatment bipolar impedance measurement, the in-treatment bipolar impedance measurement, and the post-treatment bipolar impedance measurement to determine lesion formation and thereby determine treatment efficacy. More importantly, the elimination or significant reduction of the post-treatment local electrogram amplitude to a value of about 0.5mV or less, as compared to the pre-treatment local electrogram amplitude, may indicate that sufficient ablation has occurred. For example, a bipolar impedance increase of about 500 ohms (+ -50 ohms) may indicate that sufficient ablation (lesion formation) has occurred.

Further, in an optional tenth step 300, the navigation system 16 may receive data from the mapping electrodes 40 and sensors 42 and/or from the control unit 14, and the navigation system processing circuitry 82 may process the data to generate a map of at least a portion of the heart (or other treatment region). The graph may show a treatment site area 94 where optimal or sufficient lesion formation has occurred and a treatment site area 96 where insufficient, incomplete, or insignificant lesion formation has occurred. The map may be displayed to a user who may then use this information to reposition device 12 to ablate or further ablate the area where optimal or sufficient lesion formation has not yet occurred. By way of non-limiting example, the graph and/or data may be used to determine whether a complete circumferential lesion has been formed around the PV ostium.

Although the method illustrated in fig. 9 includes recording pre-treatment data, in-treatment data, and post-treatment data, and comparing the data, it should be understood that in some embodiments the method includes recording and comparing only pre-treatment data with post-treatment data, recording and comparing only pre-treatment data with in-treatment data, or recording and comparing only in-treatment data with post-treatment data. Further, data may be recorded continuously throughout the process. Thus, the pre-treatment data may become in-treatment data and the in-treatment data may become post-treatment data without explicit clarification. Thus, although not explicitly shown in fig. 9, it will be understood that even though a single step is shown, data may be continuously recorded throughout the process. Additionally, it will be understood that in some embodiments, the processing circuitry 74 does not generate or display a map of lesion formation.

It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Additionally, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. Many modifications and variations are possible in light of the above teaching without departing from the scope and spirit of the invention, which is limited only by the following claims.