Analysis of ventricular repolarization in context of premature ventricular beats

The aim of this study was to develop an ECG based method to identify changes in repolarization which may presage the appearance of premature ventricular beats (PVBs). Our hypothesis is that these surface repolarization changes may be the manifestation of cellular after depolarizations (ADs). ADs have been shown to be the mechanism of PVBs in the form of triggered automaticity in several settings. Data were collected from 14 patients using XYZ leads, and a digital ambulatory ECG monitor. Beat sequences of 5 sinus beats and a PVB of a single morphology were selected for analysis. A window from the end of the QRS to the next 4 wave or the PVB was chosen for analysis. The pre-PVB T/U wave was compared with all the prior T/U waves using three methods: (1) statistical analysis of 4 T/U wave measurements; (2) residual analysis of signal averaged T/U waves; and (3) power spectrum analysis of a time series of the vector magnitude of the integral of the T/U wave. The statistical analysis was not significant for any of the T/U wave parameters. The power spectrum analysis and residual analysis produced concordant results for 3 of 14 patients showing significant changes in the comparisons of the pre-PVB T/U wave and the prior T/U waves. This study suggests that, in some patients, changes occur in repolarization prior to a PVB. These changes may be evidence of the body surface manifestation of ADs which are large enough to initiate the mechanism of triggered automaticity for the induction of a PVB.