Prospective evaluation of a sequential pacing and high-energy bidirectional shock algorithm for transvenous cardioversion in patients with ventricular tachycardia.

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Abstract
Rapid ventricular pacing alone or in combination with low- or intermediate-energy shocks has limited efficacy in cardioverting rapid ventricular tachycardia (VT) when delivered through two transvenous catheter electrodes. This prospective study determined the efficacy and safety of an algorithm that used a sequence of rapid ventricular pacing (RVP) and intermediate-energy (5 and 15 J) and high-energy (25J) single, bidirectional shocks delivered by two transvenous catheter electrodes in conjunction with a cutaneous electrode in patients with sustained VT. The bidirectional shock was simultaneously delivered over two electrical vectors via a common right ventricular apical cathode and tow anodes consisting of the superior vena caval catheter electrode and cutaneous patch. The electrical therapy delivered was determined by the cycle length of VT. Slow VT (cycle length greater than 300 msec) was sequentially treated by RVP followed by incremental bidirectional shocks of 5, 15, and 25 J. Rapid VT (cycle length less than 300 msec) was treated with no incremental bidirectional shocks of 15 and 25 J. VT was reinduced to determine reproducibility of the algorithm for episodes that were successfully terminated. For patients in whom the primary algorithm failed, a second algorithm was used that excluded 5 and 15 J shocks and went directly to a 25 J shock. VT was reinduced twice and the secondary algorithm was evaluated. Thus, reproducibility of termination of VT with the primary and secondary algorithm was examined. Fifty episodes of slow VT and 40 episodes of rapid VT were induced in 22 patients (mean left ventricular ejection fraction 31 +/- 14%). Six patients had rapid VT, nine patients had slow VT, and seven patients had both.(ABSTRACT TRUNCATED AT 250 WORDS)