LACK OF BENEFIT OF VERY SHORT BASIC DRIVE TRAIN CYCLE LENGTH OR REPETITION OF EXTRASTIMULUS COUPLING INTERVALS FOR INDUCTION OF VENTRICULAR-TACHYCARDIA

Stimulation Protocol for VT Induction. Introduction: There are conside rable variations of uncertain importance in basic drive train cycle le ngths and degree of repetition of extrastimuli used in programmed vent ricular stimulation protocols in different laboratories. We compare pr ospectively three different stimulation protocols to examine the influ ence of a short basic drive train cycle length and repetition of extra stimuli on induction of ventricular tachycardia.Methods and Results: T hirty consecutive patients who had documented ventricular tachycardia or fibrillation based on underlying coronary artery disease under vr e nt programmed ventricular stimulation with each of the three study pro tocols. Protocol A used a basic drive train cycle length of 400 msec w ith each extrastimulus coupling interval delivered only once. Protocol B used the same basic drive train cycle length, but with each extrast imulus coupling interval repeated three times before decrementing. Pro tocol C used 300 msec as the cycle length of basic drive trains withou t repetition of extrastimuli. Sixty-three percent, 67%, and 63% of the study patients had ventricular tachycardia inducible with protocols A , B, and C, respectively (P = NS). Ventricular fibrillation was induce d in 23% of the 30 patients in all three protocols. There were no sign ificant differences in the mean cycle lengths of induced ventricular t achycardia, the number of extrastimuli used, and the coupling interval of the last extrastimulus inducing ventricular tachycardia among the three protocols. Conclusion: This study showed no clinical benefit for repetition of extrastimuli that have failed to induce a ventricular t achyarrhythmia during programmed ventricular stimulation. A short basi c cycle length of 300 msec was not superior to 400 msec for induction of ventricular tachyarrhythmias. We recommend the use of basic cycle l ength 400 msec with delivery of each extrastimulus interval only once as the initial protocol for programmed ventricular stimulation.