[High frequency current catheter coagulation using pulsed energy delivery. Results with isolated myocardial tissue]

The feasibility and efficacy of pulsed radiofrequency (RF) current delivery was assessed and compared to results obtained by continuous energy delivery. Energy was delivered to ventricular preparations of isolated porcine hearts (HAT 100, 500 kHz, Osypka, FRG). In the pulsed mode, impulse duration and pause duration were varied between 50 and 500 ms. Total duration of coagulation was 30 s in all cases. The depth of induced lesions was significantly enhanced by a short impulse- and pause duration (50-70 ms) compared to continuous RF energy delivery. At long pause durations (200-500 ms) and short impulse duration, depth and diameter of lesions significantly decreased. The incidence of sudden increases in impedance was markedly attenuated when energy was delivered discontinuously. Thus, pulsed RF energy delivery can be used to enhance the depth of RF lesions. The decreased incidence of sudden rises in impedance during pulsed energy delivery further enhances the feasibility of RF coagulation. An improvement in heat transfer to deeper tissue layers can be considered as the mechanism responsible for these effects.