Catheter Ablation of Canine Ventricular Myocardium Utilizing Radiofrequency Current

Abstract

To determine if catheter‐delivered radiofrequency current (RFC) could safely destroy ventricular myocardium, 6P quadripolar catheters were inserted into the right ventricular and left ventricular endocardium of 11 heparinized, closed‐chest dogs. RFC (continuous wave, 625 kHz) was delivered via a commercially available eiectrosurgical unit for 10–20 sec between the catheter tip and a surface electrode (unipolar configuration). Voltage delivered was 42 ± 8 volts with a current of 0.23 ± 0.07 amperes and an impedance of 182 ± 32 ohms. An average power of 9.8 ± 4.4 watts resulted in a delivered energy of 112 ± 60 joules. The catheters were repositioned in the right and left ventricular apices and RFC was delivered between the two tip electrodes for 10–20 sec (bipolar configuration). Voltage delivered was 44 ± 7 watts with a current of 0.20 ± 0.07 amperes and an impedance of 241 ± 49ohms. An averageof 8.5 ± 4.3 watts of power resulted on delivered energy of 106 ± 29 joules.At necropsy, lesions were identified in 5/11 right and 9/11 left ventricular free‐wall sites and 7/11 right and 11/11 left ventricular apical sites. Lesion size ranged from 4–8 mm in depth and 3–9 mm in diameter and the size did not correlate with energy delivered. The endocardial surface was grossly intact in all. No hemodynamic compromise, electrode pitting, or changes in postshock catheter resistance were noted. However, one dog had spontaneous ventricular fibrillation after a transseptal pulse. Although no large thrombi were noted, a thin layer of endocardial thrombus formation was usually present. We conclude that catheter‐delivered RFC can selectively damage myocardial tissue with minimal complications.