THERMAL ABLATION OF PERFUSED PORCINE LEFT-VENTRICLE INVITRO WITH THE NEODYMIUM-YAG LASER HOT TIP CATHETER SYSTEM

Catheter ablation in the treatment of arrhythmias has been limited by the small lesion size achievable with a radiofrequency energy source. The feasibility of catheter ablation with a neodymium-yttrium-aluminum-garnet [Nd-YAG] laser hot tip catheter was tested because of the capability of achieving a high catheter-tissue contact temperature, which should result in a larger lesion. In a model of isolated perfused pig hearts, 77 endocardial lesions were produced with powers of 1 to 10 watts and peak measured temperatures of 40-degrees to 318-degrees-C. Lesion size correlated with power and temperature, but the correlations were poor. High temperature lesions resulted in significant intramyocardial catheter penetration and only marginal increased lesion width. Catheter ablation with a Nd-YAG laser hot tip catheter is feasible, but carries a risk of perforation at high powers. High temperatures result in tissue dessication with a resultant fall in thermal conductivity that limits the radius of thermal injury and overall lesion size.