Detection of beat-to-beat changes in high frequency components of the QRS complex using a free optimal signal averaging system: relationship with ventricular arrhythmias

Abstract

In this study, we evaluated the relationship between beat-to-beat changes in high frequency components of the QRS complex and ventricular arrhythmias by using a newly developed event-related (ER) signal averaging technique. The study involved 82 patients with premature ventricular contractions (PVC), 56 of whom, including 16 with ventricular tachycardia (VT), were enrolled in Analysis I. In Analysis I, averaged sinus beats were classified into three patterns: 1) the sinus beat immediately before PVC (BEF); 2) that immediately after PVC (AFT); and 3) all sinus beats (ALL). Analysis II covered the remaining 26 patients, and involved five modes of event-related signal averaging, using: 1) the second beat preceding PVC (2-B); 2) the beat immediately preceding PVC (1-B); 3) the beat immediately after PVC (1-A); 4) the second beat after PVC (2-A); and 5) the beat isolated (ISO) from PVC. The filtered QRS duration (F-QRS) and the integral voltage of the terminal 40 msec (RMS 40-I) were measured using these averaging patterns. F-QRS in the VT group was longer than that in the non-VT group, but RMS 40-I was shorter. The F-QRS of BEF (1-B) was significantly longer than that of AFT (1-A). The transient difference in the F-QRS was observed in both VT and non-VT groups. This difference was almost eliminated at AFT (1-A) in the non-VT group, but was stable at AFT (1-A) in the VT group. Simultaneousely, RMS 40-I in BEF was significantly shorter than that in AFT. This transient decrease of RMS 40-I was observed in both VT and non-VT groups. Although RMS 40-I after this decrease showed a return almost to the control level at AFT in the non-VT group, it tended to remain even at AFT in the VT group. The sudden prolongation of F-QRS that occurred with the RMS 40-I decrease in BEF was related to the appearance of PVCs. We attributed the fact that these changes in F-QRS and RMS 40-I were observed even at AFT in the VT group to electrophysiologically preferable conditions for reentry.