Catheter systems for cardiac arrhythmia ablation

1. A contact adjusting and tracking system for creating continuous lesions when ablating tissue in an atrial chamber of a heart for treating atrial fibrillation and atrial flutter comprising, in combination:

(a) a guide body sheath having a steerable distal end;

(b) an elongate guidewire having a relatively stiff portion terminating in a relatively soft, flexible distal end portion, said guidewire extending through a lumen of the guide body sheath so as to first exit and then re-enter the distal end portion such that the relatively stiff portion and the relatively soft portion are accessible at a distal end of the guide body sheath, thereby creating a loop of adjustable size proximate the distal end of the guide body sheath;

(c) an ablation catheter having a proximal end and a distal end, said ablation catheter having an expandable ablation element affixed proximate its distal end and a lumen for slidably mounting the ablation catheter over the elongate guidewire; and

(d) a control handle including:

(i) a rotatable member for controlling deflection of the steerable distal end portion of the guide body sheath;

(ii) a slide member joined to the proximal end of the ablation catheter that when manipulated, advances and retracts the ablation balloon element of the ablation catheter about the loop; and

(iii) first and second guidewire locks, the first lock releasably securing the relatively stiff portion and the second lock releasably securing the relatively soft, flexible distal end portion of the guidewire at selected points on the guidewire whereby the size, shape and disposition of the loop can be adjusted and fixed.

2. The contact adjusting and tracking system of claim 1 wherein the expandable ablation element is a cryoablation balloon device.

3. The contact adjusting and tracking system of claim 1 wherein the expandable ablation element includes an energy source for heating targeted tissue sufficient to ablate the tissue.

4. The contact adjusting and tracking system of claim 2 wherein the cryoablation balloon device comprises an inner balloon for containing a cryofluid for creating lesions through freezing of the tissue, the inner balloon being enclosed in an outer balloon containing a body absorbable insulating gas at a predetermined pressure slightly greater than blood pressure within the atrial chamber such that forcefully pressing the cryoablation balloon device against an atrial wall surface displaces the insulating gas to bring the inner balloon into direct contact with the outer balloon at a point of contact with the atrial wall surface.

5. The contact adjusting and tracking system of claim 2 and further including first and second ring electrodes, the first ring electrode located at a surface of a distal margin of the cryoablation balloon device and the second ring electrode located at a proximal end of the cryoablation balloon device for serving as an electrical reference electrode to the first ring electrode, said first and second ring electrodes adapted for measuring an impedance rise during a cryogenic ablation procedure for the pulmonary veins indicative of an extent of circumferential ice formation on an anterior aspect of the cryoablation balloon device that extends to cover the first ring electrode, thereby signaling pulmonary vein occlusion and lesion adequacy and maturation.

6. The contact adjusting and tracking system of claim 4 wherein an outer surface of the outer balloon further comprises a plurality of thermistors and a plurality of electrodes insulated from one another for temperature monitoring and real time electrical activity assessment of lesion maturation.

7. The contact adjusting and tracking system of claim 1 and further including an inflatable anchor at a distal end of the guide body sheath for releasably engaging septal tissue that has been penetrated by the distal end of the guide body sheath during an ablation procedure.

8. The contact adjusting and tracking system of claim 5 wherein said cryoablation balloon device is adapted for placement in a pulmonary vein orifice whereby pulmonary vein ablation adequacy can be assessed by impedance measurements between the second ring electrode and the first ring electrode obtained upon application of a low-power, high-frequency voltage therebetween.