Cellular electrophysiology of fast pathway ablation of rabbit atrioventricular node

Discrete radiofrequency lesion at the atrial insertion site of the tendon o f Todaro in the perfused rabbit preparation lengthens A-H interval, mimicki ng fast pathway input ablation. This study attempts to define the cellular electrophysiology of the ablation region prior to and after the elimination of fast AV node conduction. In six superfused rabbit AV node preparations, the cellular electrophysiology around the region of the atrial insertion t o the tendon of Todaro was recorded using standard microelectrode technique prior to and after ablation. Before ablation, the action potentials record ed in the area of proposed lesion were exclusively from atrial or AN cells. At postablation, the superior margin of the lesion was populated with atri al or AN cells. AN, N, or NH cells bordered the lower part of the lesion. E lectrophysiology of surviving cells at the edges of the lesion showed no si gnificant changes in their V-max, APD(50) or APD(90) and MDP from preablati on values. Fast AV node pathway input ablation in the rabbit heart can be a ccomplished with a singular lesion around the atrial insertion site of the tendon of Todaro, involving atrial or AN cells. The results of the studies imply that inputs to the compact node may act as a substrate for successful ablation of AV node reentry tachycardia.