LOW-ENERGY SYNCHRONOUS TRANSCATHETER CARDIOVERSION OF ATRIAL-FLUTTER FIBRILLATION IN THE DOG

The feasibility and effectiveness of low energy synchronous transcatheter cardioversion of atrial flutter and fibrillation were examined in dogs with talc-induced pericarditis, A conventional electrode catheter was positioned transvenously in the right atrial appendage. Atrial flutter/ fibrillation was induced by using the train pulse method, and the tachyarrhythmia-inducing threshold was determined. The minimal effective cardioversion energy levels were compared in three different cardioversion methods: method A = delivery of shock between the proximal electrode (cathode) and the backplate (anode), method B = delivery between the proximal electrode (cathode) and the distal electrode (anode) and method C = conventional external cardioversion. In both methods A and B, all 149 cardioversion attempts were successful with shocks of ≤5 J. Shocks of ≤1 J resulted in successful cardioversion in 57 (70%) of 81 attempts, 50 (74%) of 68 attempts and 5 (12%) of 41 attempts with methods A, B and C, respectively. The mean minimal effective cardioversion energy levels were not significantly different between methods A and B (0.62 ± 0.67 versus 0.58 ± 0.71 J). Transcatheter cardioversion decreased the defibrillation threshold 3- to 75-fold (men 6-to 7-fold) from that of transthoracic cardioversion. The defibrillation threshold was not influenced by the inducibility of atrial flutter/fibrillation. There were no complications of heart block, ventricular fibrillation or pathologic evidence of severe shock-induced atrial injury. Thus, low energy synchronous transcatheter cardioversion of atrial flutter/fibrillation is considered feasible and effective. This technique may also be useful in managing the atrial flutter/fibrillation that can occur during electrophysiologic studies. © 1990.