Endovascular near critical fluid based cryoablation catheter and related methods

1. A method of performing cryoablation on a heart of a patient, the method comprising:

providing a cryoablation apparatus comprising:

a proximal section, an intermediate section, a distal section, and a distal tip;

a plurality of first tubes extending along the distal section to transport a cryogen along the distal section, wherein each first tube is individually coaxially surrounded by an outer tube, thereby defining a gap between each first tube and each outer tube, and wherein each gap is filled with a thermally conducting fluid;

advancing the cryoablation apparatus through vasculature of the patient and into a space within the heart;

deploying the distal section of the cryoablation apparatus into the space within the heart and against a target area of cardiac tissue; and

applying an application of cryoenergy to the distal section of the cryoablation apparatus to create an elongate continuous lesion in the target area of cardiac tissue.

2. The method of claim 1 , wherein the cryogen is nitrogen.

3. The method of claim 1 , further comprising halting the step of applying after a threshold condition is established.

4. The method of claim 3 wherein the threshold condition is one selected from the group consisting of: length of lesion, thickness of lesion, time elapsed, energy transferred, temperature change, pressure change, flowrate change, and power change.

5. The method of claim 1 , wherein the elongate continuous lesion has a length ranging from 2 to 10 cm.

6. The method of claim 1 , wherein the lesion has a thickness extending an entire thickness of a heart wall in the target area of cardiac tissue for an entire length of the distal treatment section of the catheter in contact with the heart wall in the target area of cardiac tissue.

7. The method of claim 1 , wherein the target area of cardiac tissue is selected from the group of transmural endocardial lesions consisting of: 1) a lesion spanning the atrium over the left and right superior pulmonary vein entries into the atrium, 2) a lesion under the left and right inferior pulmonary vein entries into the atrium, and 3) a vertical lesion on the right of the right superior and inferior vein entries into the atrium.

8. The method of claim 1 , further comprising monitoring at least one of pressure and temperature of the thermally conductive fluid within the gaps.

9. The method of claim 1 , further comprising inserting a guide catheter into the vasculature and advancing the cryoablation apparatus through the guide catheter.

10. The method of claim 1 , wherein the elongate continuous lesion is created by circulating the cryogen through the plurality of first tubes and a plurality of second tubes in the distal section.

11. The method of claim 10 , wherein the cryogen is a near critical fluid.

12. The method of claim 1 , wherein the step of deploying the distal section to contact the target area of cardiac tissue is performed without expanding the distal section.

13. The method of claim 1 , further comprising a conductive media surrounding the outer tubes.

14. The method of claim 13 , further comprising an outer sheath surrounding the conductive media.

15. The method of claim 1 , comprising providing a source of the cryogen, and a console to control the applying step.

16. An endovascular cryoablation-based method for treating arrhythmia of a heart of a patient, the method comprising:

percutaneously inserting a catheter comprising a distal treatment section into the patient's vasculature;

navigating the distal treatment section to the heart, and through an opening in the heart until the distal treatment section is within a space in the heart;

manipulating the distal treatment section of the catheter against a linearly disposed target section of cardiac tissue along an interior wall of the heart,

wherein the step of manipulating is performed without expanding the distal treatment section;

creating an elongate lengthwise-continuous lesion by circulating a cryogen through at least one fluid delivery tube and at least one fluid return tube extending through the distal treatment section;

each said at least one fluid delivery tube being individually surrounded by a protective cover thereby defining a first gap between the protective cover and the at least one fluid delivery tube and

each said at least one fluid return tube being individually surrounded by an outer cover thereby defining a second gap between the outer cover and the at least one fluid return tube, and

filling each of the first gap and the second gap with a thermally conductive fluid prior to performing the step of creating.

17. The method of claim 16 , wherein the thermally conductive fluid is a saline solution.

18. The method of claim 17 , wherein the cryogen is near critical fluid.

19. The method of claim 16 , wherein the arrhythmia is atrial fibrillation.

20. The method of claim 16 , further comprising halting the step of applying after a threshold condition is established.

21. The method of claim 16 , wherein the step of creating is performed by circulating the cryogen through a tube bundle comprising a plurality of the at least one fluid delivery tubes and a plurality of the at least one fluid return tubes.

22. The method of claim 16 , further comprising a conductive media surrounding the outer and protective covers.

23. The method of claim 22 , further comprising an outer sheath surrounding the conductive media.

24. The method of claim 16 , comprising providing a source of the cryogen, and a console to control the circulation of the cryogen.