Catheter Ablation of Ventricular Endocardium Using Radiofrequency Energy: Determinants of Lesion Volume and Shape

Radiofrequency energy was delivered at varying powers and durations to excised portions of canine left ventricle that were mounted in a tank of saline at room temperature. A radiofrequenciy generator delivered alternating current in a sine wave pattern at a frequency of 500 kHz, at variable voltage. In each of five excised ventricles, 49 lesions were created, at delivered RMS voltages from 18 to 40 V and durations of ablation from 5 to 180 seconds. Lesion diameter and depth were measured grossly, and lesion volume and shape (ratio of radius/depth) were calculated. Lesion diameter, depth, and volume increased with increasing power and duration of energy delivery, and the relation of delivered energy (joules) to calculated lesion volume (mm³) was linear (r = 0.88, P < 0.001). Shallower lesions were produced by shorter duration of energy delivery at all power levels, and similar volume but deeper, more symmetric lesions by lower power and longer duration of energy delivery. Radiofrequency energy in vitro thus produces reproducible lesions whose volume is proportional to delivered energy, and whose shape can be altered by delivering similar total energies, but varying the power and duration of energy delivery