MICROWAVE CATHETER ABLATION USING A CLINICAL PROTOTYPE SYSTEM WITH A LATERAL FIRING ANTENNA DESIGN

Microwave has been considered a potentially more effective and more ve rsatile form of energy than radiofrequency. Its feasibility has been t ested using various prototype systems and catheter designs. This study assessed the safety and efficacy of a clinically-suitable prototype m icrowave power supply and catheter system with a lateral-firing antenn a design for atrioventricular (AV) junction ablation in canines and to correlate with tissue histopathology. The system consisted of a defle ctable catheter with a 6-mm antenna and a thermocouple; and a 2.45-GHz frequency generator with power, time, and temperature controls. AV ju nction ablations were performed using 75 W energy for up to 60 seconds . Effective heating was confirmed by a rise in catheter temperature to 69.3 +/- 8.8 degrees C. Complete AV nodal block was accomplished in a ll canines after an average of 4.1 +/- 2.8 applications at 66.8 +/- 7. 7 degrees C, and persisted after 28 days in all chronic animals. Lesio ns were consistent with thermal necrosis, were hemispherical to semi l inear in shape and have distinct borders. Acute lesions were 3.4 +/- 1 .5 mm wide, 4.8 +/- 2.1 long, and 2.0 +/- 0.9 deep. Chronic lesions sh owed typical healing and were smaller in size. Ablations did not cause any transvalvular, vascular or other cardiac structural damage, and n o coagulum formation was noted on the antenna or catheter tip. Microwa ve AV junction ablation using this clinical prototype system specifica lly designed for it tvas safe and effective. Lesion's depth was limite d to 5 mm with 60-second heating while its shape corresponded to the a ntenna's length. Microwave energy may provide greater versatility for producing discrete or linear ablation.