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[The influence of repetitive delivery of radiofrequency current in catheter ablation].

The single delivery of radiofrequency current to the cardiac tissue can produce discrete small and shallow area of homogeneous coagulation necrosis. Little is known, however, concerning the influence of repetitive deliveries of radiofrequency current to the identical site of the ventricular myocardium. Therefore, in animal experiments using 8 dogs, we investigated the influences of those applications on the ventricular myocardium from the histological and electrocardiographical aspects. The used frequencies of radiofrequency current were 13.56 MHz (RF-50), 520 kHz (Hatt 200 S) and 500 kHz (LL-50). Released power was 25 Watts in current and 20 seconds in duration. The innings of application were 10, 20 and 30 times per one ablation session. The depth of ablated lesion became greater as the applied innings increased in any generator of radiofrequency current. The ablated lesion by the delivery over 20 times reached from the ventricular endocardium to the epicardium. In contrast, surface area produced by repetitive application was determined by the size and length of the tip of electrode catheter. T wave inversion and isolated premature ventricular contraction on electrocardiogram were observed only during repetitive radiofrequency energy application. Thus, since the repetitive delivery of radiofrequency energy to the identical myocardium caused the deep ablated lesion reached to the epicardium, caution should be taken against myocardial perforation in a clinical setting. However, this application could be useful for the ablation of deeper lesion responsible for ventricular tachycardia.