Influence of the cycle length of basic drive on induction of sustained ventricular tachycardia associated with coronary artery disease

The relation between the cycle length of basic drive during programmed ventricular stimulation and the coupling intervals at which sustained monomorphic ventricular tachycardia (VT) was initiated was analyzed in patients with coronary artery disease and documented sustained VT. The study included 28 patients in whom hemodynamically tolerable, monomorphic sustained VT was inducible at different cycle lengths of basic drive during the same electrophysiologic study. The stimulation protocol included single or double premature stimuli during paced ventricular rhythms at different cycle lengths of basic drive. The coupling intervals of premature stimuli for induction of VT (considered the outer margin of the echo zone) during step 1 of the stimulation protocol (basic drive at cycle lengths of 500 or 430 ms) were compared with those during step 2 (basic drive at cycle lengths of 370 or 330 ms). The mean cycle length of induced sustained VT was 370 +/- 79 ms. The mode of induction of VT remained the same in 23 patients (single or double premature stimuli); in 5 patients, fewer premature stimuli were required during step 2 than step 1. By moving from step 1 to step 2, VT could be induced at longer coupling intervals of the premature stimuli in 23 patients (82.1%). The mean increase in the sum of the coupling intervals was 52 +/- 37 ms. In 5 patients, the coupling intervals either did not change from step 1 to step 2 (n = 1) or decreased by an average of -40 +/- 14.1 ms. The results suggest that inducibility of VT is favored by a decrease in the cycle length of basic drive.(ABSTRACT TRUNCATED AT 250 WORDS)