Feasibility of a Cryo-Anchoring Catheter for Linear Ablation.

Abstract

Background: Linear ablation lesions are used in multiple ablation strategies including left atrial roof lines, and mitral and tricuspid isthmus lines. A continuous and transmural line is mandatory for effective lesions. A proposed catheter employs cryo-anchoring: the tip initially freezes to adhere to the tissue, permitting the shaft of the catheter to be applied firmly against tissue to create linear lesions.

Methods: Ex vivo tests were performed in a 35°C water bath on turkey skeletal muscle, lamb, and porcine myocardial tissue. The experimental setup allowed the quantification of force exerted from the catheter onto the tissue with bidirectional strain-gauge measurement. Five protocols evaluated: force for tissue or equipment failure during traction, consistency experiments to evaluate the safe level of traction, force for tissue failure in forward pressure, contact force effect on time to transmural lesion, and contact force effect on lesion depth.

Results: Tissue failure in traction occurred at the lowest force of 3.9 kg. This occurred at the ventricular apex of a lamb heart, whereas atrial samples tolerated > 10 kg of force before failure. Correlations between force, lesion thickness, and time to the formation of a transmural lesion were observed. Lesions of 3-4 mm depth occurred at 45 g forward pressure with 60 s lesions. The time required to attain this depth fell to 20 s with forces over 200 g.

Conclusion: There is a broad safety margin between the force required to enhance lesion formation during cryotherapy and the force that can disrupt tissue, both for traction and forward pressure.