QRS morphology-dependent, concordant frequency distribution of single and repetitive forms of ventricular ectopic activity

Abstract

We tested the relationship between the frequency of single premature ventricular complexes (PVCs) of specific QRS morphologies and repetitive forms (RF) of ≥ 2 PVCs. Fourteen patients with multiform PVCs and RFs underwent 8-hour, two-channel continuous electrocardiographic monitoring. After a 2-hour baseline, procainamide was administered intravenously at 25 mg/min until PVC suppression or 1000 mg. Multiple regression analysis was used to relate the frequencies of repetitive forms initiated by PVCs of the most frequent QRS morphology (M 1) and the second most frequent QRS morphology (M 2) to the frequency of M 1 and M 2 single PVCs. Parallel changes in the frequency of M 1 RFs and M 1 PVCs occurred in 9 of 14 patients and parallel changes in the frequency of M 2 RFs and M 2 PVCs occurred in 7 of 14 patients (i.e., the relationships were concordant). In two patients, M 1 RFs related to M 2 PVC frequency; in three patients, M 2 RFs related to M 1 PVC frequency (i.e., the relationships were discordant). Thus concordant frequency distributions were present in 16 or 28 (57%) comparisons, while a discordant relationship occurred in only 5 of 28 (18%) comparisons ( p < 0.005). In conclusion, there is frequent concordance in the frequency distribution of single multiform PVCs and of RFs initiated by PVCs of the same QRS morphology during a pharmacologic intervention. This relationship was demonstrable for PVCs of at least one specific QRS morphology in 13 of the 14 patients studied. Concordance was independent of the absolute frequency of the initiating PVC, suggesting one mechanism whereby RF suppression may become independent of total PVC suppression.