PREIMPLANT ATRIAL DEFIBRILLATION TESTING WITH A TEMPORARY CATHETER INSHEEP

Prior to implantation of an atrial defibrillator, its effectiveness sh ould be tested in each patient. A new catheter design for temporary us e with electrodes for atrial defibrillation, electrogram sensing, and pacing was tested in this study. Atrial defibrillation thresholds defi ned using this temporary catheter were compared to the ones defined by catheters intended for chronic use with an implantable atrial defibri llator. Atrial defibrillation threshold was determined in six sheep us ing both types of catheters. Each animal was subjected to studies an 2 consecutive days. On the first day, shocks were applied between two o f the temporary catheters. On the following day, permanent leads were inserted and atrial defibrillation threshold was redetermined. In bath cases, defibrillation electrodes were positioned in the same heart lo cation with one electrode in the distal coronary sinus and the second electrode in the right atrium. Atrial defibrillation threshold was obt ained using 10 V increments or decrements to determine the lowest shoc k intensity needed to defibrillate the atria. Threshold was defined as the shock intensity at which 20 shock percent success was at or betwe en 15% and 85%. Statistical analysis showed no significant difference (P < 0.05) between atrial defibrillation threshold energy (0.53 J vs 0 .55 J), voltage (122 V vs 120 V) or current (2.2 A vs 2.6 A) measured with the temporary catheters and the permanent leads, respectively. Th ese data indicate that temporary catheters can be used for efficacy te sting prior to implant of an atrial defibrillator,and that they predic t atrial defibrillation threshold adequately for chronic leads.