MICROWAVE ABLATION OF THE ATRIOVENTRICULAR JUNCTION IN OPEN-CHEST DOGS

The use of microwave energy for ablation of the atrioventricular (AV) junction was examined in openchest dogs. Using a specially designed mi crowave catheter and a 2450 MHz generator, microwave energy was delive red to the AV junction according to one of two protocols. In protocol 1, increasing amounts of energy were delivered until irreversible AV b lock occurred. In protocol 2, only two applications of energy were use d, one at low energy and the other at an energy found to be high enoug h to cause irreversible AV block. Each dog received between one and si x applications of microwave energy. The amount of energy delivered per application ranged from 25.6 to 311.4 J. No AV block was seen at 59.4 +/- 28.3 J. Reversible AV block was seen with an energy of 120.6 +/- 58 J. Irreversible AV block was seen at 188.1 +/- 75.9 J. Irreversible AV block could be achieved in each animal. There was no difference in the energy required to cause irreversible AV block between the two pr otocols. The tissue temperature measured near the tip of the microwave catheter was correlated with both the amount of energy delivered and the extent of AV block caused. Histologic examination demonstrated coa gulation necrosis of the conduction system. Microwave energy is a feas ible alternative energy source for myocardial ablation. Since tissue d amage is due exclusively to heating and the resulting rise in temperat ure can be measured, microwave energy may have advantages over current ly existing energy sources in terms of both titrating delivered energy and monitoring the extent of tissue destruction. (C) 1995 Wiley-Liss, Inc.