Variability of repetitive arrhythmia formation in patients with chronic ventricular arrhythmia

Abstract

The statistical frequency of ventricular couplet formation was determined in 125 long-term electrocardiographic recordings obtained from patients both with and without cllnical cardiovascular disease. The repetition index, defined as the ratio of couplets to isolated premature ventricular complexes, was found to vary widely, from 0 to 333 1,000 , and was not related to the underlying frequency of premature ventricular complexes. The reproducibility of the repetition index was examined and in 19 (83 percent) of 23 patients remained either above or below 10 1,000 premature ventricular complexes on two separate electrocardiographic recordings. In electrocardiograms from patients with known cardiovascular disease, coexistent nonsustained ventricular tachycardia was noted in 8 (15 percent) of 53 with a repetition index of less than 10 1,000 premature ventricular complexes and 34 (62 percent) of 55 with a repetition index value of more than 10 1,000 (p <0.001). In patients without clinical evidence of cardiovascular disease, ventricular tachycardia occurred in 2 (20 percent) of 10 recordings with a repetition index of less than 10 1,000 premature ventricular complexes and in 5 (71 percent) of 7 with a repetition index of more than 10 1,000 (p <0.05). In patients who had two electrocardiograms analyzed, ventricular tachycardia was found at least once in 1 (10 percent) of 10 patients whose repetition index was always less than 10 1,000 premature ventricular complexes and in 11 (85 percent) of 13 patients whose repetition index was 10 or more/1,000 on either or both recordings (p < 0.001). A high repetition index was also found to be predictive of future occurrence of ventricular tachycardia in five of six patients whose index recording showed no tachycardia but a repetition index of at least 10 1,000 premature ventricular complexes. These observations suggest that (1) quantitative approaches to complex ventricular arrhythmia are useful, and (2) the repetition index is a reflection of some aspect of ventricular vulnerability.