INCREASING CATHETER ABLATION LESION SIZE BY SIMULTANEOUS APPLICATION OF RADIOFREQUENCY CURRENT TO 2 ADJACENT SITES

Treatment of ventricular tachycardia by radiofrequency current application can be difficult, partly because of the larger size of the reentry circuit in relation to the lesion generated. Larger lesions than those currently achieved with single radiofrequency applications are desirable. This study evaluated simultaneous radiofrequency application to two adjacent electrodes to determine the effects of interelectrode distance and configuration (bipolar serial vs parallel) on lesion size and tissue temperature. Two 6F electrodes were placed, with the tips facing each other, on bovine myocardium in a saline bath at 37-degrees-C. Radiofrequency current was applied to a single electrode, or simultaneously to two electrodes connected either in series or in parallel. Tissue temperature, power, and lesion size were measured. Lesions produced by simultaneous radiofrequency delivery to both electrodes were more than twice the size of those produced by a single electrode alone (> 100 mm3 vs 33.2 mm3, p < 0.01). Temperatures between electrodes were greater than those temperatures at the same distances from a single electrode (p < 0.001). The size of the lesions increased as interelectrode distance decreased below 3.5 mm (p < 0.030) because of the increasing depth of the lesion between the electrodes. Two electrodes placed in a bipolar as opposed to a parallel configuration were most efficient, as this configuration produced greater lesion sizes for a given level of power delivery (p < 0.0001). The bipolar lesion size decreased by > 50% if one electrode was not in contact with the tissue (p < 0.0004). Thus in this in vitro model, simultaneous application of radiofrequency current to two adjacent sites synergistically increases lesion size more than twice that of a single lesion, in part as a result of an increase in lesion depth between electrodes at areas of overlap. Bipolar radiofrequency ablation using two large, closely spaced electrodes may provide a convenient method to increase lesion size for ablation of ventricular reentry circuits.