Tissue contact verification system

Abstract

A system for monitoring electrical activity at an ablation site where the system includes an ablation device having an elongate, flexible shaft and a distal treatment section for delivering ablation energy to target tissue, a first electrode mounted on the distal treatment section, a second electrode mounted on the distal treatment section where the second electrode is spaced from the first electrode a distance (D 1 ), a plurality of conducting elements extending along the distal treatment section and being connected to the first electrode and the second electrode, the plurality of conducting elements for connecting the first electrode and the second electrode to an electrophysiological recording system, a processing device programmed to receive the electrical information from the ablation site from the first electrode and the second electrode, and an electrophysiological recording system.

1 . A method for creating a lesion in tissue, the method comprising:
 a) advancing a distal section of cryoablation catheter through the vasculature such that a continuous elongate freeze surface of the distal treatment section of the catheter is located adjacent the tissue to be cooled;   b) evaluating a length of the continuous elongate active surface in direct contact with the tissue to be cooled;   c) cooling the tissue by circulating a cryogenic fluid through the catheter; and   d) confirming cooling of the tissue at the elongate freeze surface without moving the continuous elongate freeze surface.   
     
     
         2 . The method of  claim 1 , wherein at least one of the steps of (b), (d), and (e) are based on monitoring electrical activity of at least one electrode disposed along the continuous elongate active freeze surface. 
     
     
         3 . The method of  claim 2 , wherein monitoring the electrical activity of the at least one electrode comprises monitoring the electrical activity between a plurality of electrodes. 
     
     
         4 . The method of  claim 3 , wherein monitoring the electrical activity comprises monitoring ECG signals. 
     
     
         5 . The method of  claim 4 , wherein each of steps (b), (d), and (e) are based on the monitoring ECG signals. 
     
     
         6 . The method of  claim 2 , wherein monitoring electrical activity further comprises measuring a total impedance corresponding to a current sent through the tissue. 
     
     
         7 . The method of  claim 6 , wherein monitoring electrical activity further comprises measuring a resistance of the current sent through the tissue. 
     
     
         8 . The method of  claim 7 , wherein the step of monitoring electrical activity further comprises measuring a reactance to the current sent through the tissue. 
     
     
         9 . The method of  claim 1 , wherein the length of the continuous elongate freeze surface is at least approximately 4.0 cm. 
     
     
         10 . The method of  claim 1 , wherein the distal section comprises a shape memory alloy. 
     
     
         11 . The method of  claim 1 , wherein the step of circulating the cryogenic fluid forms a ring-shaped continuous lesion in the tissue. 
     
     
         12 . The method of  claim 11 , wherein the ring-shaped continuous lesion encircles the pulmonary veins in the left atrium. 
     
     
         13 . The method of  claim 11 , wherein the tissue is cardiac tissue and the lesion extends through a full thickness of heart wall. 
     
     
         14 . The method of  claim 1 , further comprising displaying a tissue contact value based on the evaluating step. 
     
     
         15 . The method of  claim 1 , further comprising the step of indicating whether the cryoablation catheter is safe to move from the tissue following the step of cooling. 
     
     
         16 . The method of  claim 1 , wherein the advancing step advances the continuous elongate active freeze surface adjacent right or left pulmonary vein antrums, posterior wall of the left atrium or cavo-tricuspid isthmus (CTI). 
     
     
         17 . The method of  claim 1 , wherein confirming tissue necrosis comprises monitoring for the absence of cardiac cell potentials. 
     
     
         18 . The method of  claim 1 , wherein the step of confirming cooling is achieved by confirming ice formation surrounding the continuous elongate freeze surface. 
     
     
         19 .- 52 . (canceled)