Comparison of QRS morphologies of spontaneous premature ventricular complexes and ventricular tachycardia induced by programmed stimulation.

We addressed the hypothesis that premature ventricular complexes (PVCs) and sustained ventricular tachycardia (VT) have identical QRS morphologies in 20 patients with recurrent sustained VT. Continuous six-lead ECGs of PVCs and sustained VT induced with programmed stimulation were recorded. A computer program divided the PVCs and VT beats of each patient into distinct morphologic groups and a representative waveform was obtained by averaging the PVC and VT beats of the group members. A correlation coefficient was then derived between the QRS complexes of each PVC and VT morphology. The mean number of PVC morphologies was 12 +/- 8 per patient (range 1 to 26), the mean number of VT morphologies was 2 +/- 1 per patient (range 1 to 5). The correlation coefficient between the dominant PVC morphology and a VT morphology was greater than 0.7 in only three patients. The combined percent contribution of all PVCs with morphologies that were at least possibly identical to those of VT averaged only 13%. Thus PVCs with morphologies identical to those of VT are present in some patients with sustained VT, but these constitute a small proportion of all PVCs.