Relationship between QT interval duration and electrical induction of ventricular tachycardia.

The relation of inducible ventricular tachycardia (VT) to QT interval duration of ventricular paced rhythm has not been evaluated. To clarify this relation we measured corrected QT interval duration (QTc) during sinus rhythm and QT interval duration during ventricular paced rhythm (QT-V) in patients with coronary artery disease without (non-VT group = group B) and with inducible VT (VT group = group A). Duration of QT-V was greater in the VT group (n = 20) compared with non-VT group (n = 20) during ventricular pacing at cycle lengths of 600 ms (424 +/- 26 vs 396 +/- 19 ms, P less than 0.01), of 500 ms (407 +/- 20 vs 383 +/- 21 ms, P less than 0.01), and of 400 ms (390 +/- 21 vs 362 +/- 17 ms, P less than 0.001). During sinus rhythm the mean values of QTc were similar in both groups (408 +/- 25 vs 413 +/- 20 ms, NS). During ventricular stimulation the percentage of patients with values of QT-V exceeding 380 ms was 35% in non-VT group and 95% in VT group (P less than 0.01) at cycle length of 500 ms and 5% versus 60%, respectively, (P less than 0.01), at cycle length of 400 ms. Thus, a trend toward longer QT values of ventricular paced rhythm exists in patients with inducible VT.