The objective was to determine whether two commonly used ventricular stimulation protocols, one more complex than the other, produced concordant results. If such were the case, the simpler protocol would streamline activities in clinical electrophysiology laboratories.
Background: Two programmed ventricular stimulation protocols were compared. (1) With the tandem method, the first extrastimulus (S2) is moved stepwise to the effective refractory period and then moved out 50 msec; the second extrastimulus (S3) is then decremented until it fails to capture; S2 and S3 are then decremented in a semialternating (tandem) fashion so that both continue to capture. When S2 reaches the refractory period + 10 msec and S3 fails to capture, S3 is then moved out 50 msec, and S4 is decremented as described for S3. (2) With the simple sequential method, the first extrastimulus (S2) is decremented stepwise to the refractory period, and then moved out 10 msec to assure capture; S3 is then similarly decremented to the refractory period and then moved out 10 msec; and S4 is then similarly decremented.
Methods: This was a prospective, randomized, crossover, consecutive series study. Both protocols were tested in each patient on the same day in randomized order.
Results: There were 84 matched studies. Fifty-six patients provided data from baseline electrophysiological studies, and 28 of these provided additional data during drug trials. There was a 93% concordance between the two methods, including the primary outcomes of inducibility of clinical arrhythmias, inducibility of nonclinical arrhythmias, and noninducibility (P < 0.001). Discordances were few and evenly distributed between the two protocols (P = NS). Results were similar for baseline studies and drug trials. The simple sequential method required less time to perform (P < or = 0.01).
Conclusions: Tandem and simple sequential protocols provide concordant results. No advantage could be demonstrated for the more complex tandem method.