Postextrasystolic changes in the complexity of the QRS complex and T wave.

We tested the hypothesis that ventricular repolarization of the first sinus beat following a ventricular premature beat (VPB) can be modulated in the absence of clearly discernible T-wave changes. We applied principal component analysis (PCA) to assess QRS and T-wave complexity of sinus beats preceding and following VPBs in multiple 10-second resting 12-lead electrocardiograms of two subjects with frequent VPBs and no apparent heart disease. In both subjects, T-wave complexity of the first post-VPB beat was significantly increased compared to the beats preceding the VPB.