Evaluation of antiarrhythmic drug efficacy using holter electrocardiographic technique.

This study was performed to investigate spontaneous variability in VPC frequency, to determine standards for distinguishing antiarrhythmic efficacy from the spontaneous variability, and to compare the effectiveness of disopyramide, mexiletine, aprindine, propranolol, and diltiazem. Holter ECG techniques were used for this study and the population studied consisted of 182 patients having more than 1000 VPCs/day. Forty patients had ischemic heart disease, 52 had miscellaneous heart disease and 90 were free of heart disease (idiopathic VPCs). Circadian variability of VPCs can be divided into 4 types; Type D (VPCs increasing during waking hours), Type DN (small VPC changes between waking and sleeping hours), Type N (VPCs increasing during sleeping hours) and Type Ir (irregularly occurring VPCs). The incidence of Type D, DN, N and Ir was 45%, 29%, 12% and 14%, respectively. VPC frequency in the first and second recordings at a 7 up to 21 day interval was highly reproducible (r = 0.951). The percent reduction in VPC frequency necessary to distinguish true drug response from spontaneous VPC variability, corresponded to 57% with 95% confidence level, and 67% with 99% confidence level. VPCs were reduced by at least 57% in 19 out of 33 patients (58%) with disopyramide, 9 of 15 (60%) with mexiletine, 11 of 18 (61%) with aprindine, 9 of 24 (38%) with propranolol and 8 of 22 (36%) with diltiazem. Concerning Prop., it is exclusively effective to the Type D VPCs (70%).(ABSTRACT TRUNCATED AT 250 WORDS)