Clinical Significance of Vanghan Williams Classification for Treatment of Ventricular Tachycardia. Study of Class IA and IB Antiarrhythmic Agents

Abstract

Ninety-eight cases of ventricular tchycardia (VT) were studied using clinical electrophysiological (EP)-pharmacological assessment to compare the efficacy of class IA (disopyramide-DP, procainamide-PA) and class IB (mexiletine-Mex, Lidocaine-Lid, aprindine-AP) agents available in Japan, and to evaluate the clinical significance of class subdivisions for the treatment of VT. In assessing the efficacy of drugs, we evaluated their ability to prevent and terminate induced sustained VT as well as their ability to suppress spontaneous premature ventricular beats (VPB). I. EP properties: DP significantly extended QTc, ERPRV, and the coupling interval by which VT or repetitive ventricular response (RVR) was induced. On the other hand, Mex and A had no effect. Although no significant extention of QRS width was found, the significant extension of the interval from extrastimulus to the first induced VT or RVR complex by the three drugs indicates that all have suppressive effects on conduction velocity within the reentry circuit. II. Clinical significance: Correspondence of preventive effects was 67% for DP and PA (class IA), 54% for Mex and Lid (class IB), 55% for DP and Mex, 27% for PA and Mex, and 25% for PA and DP. Correspondence of terminating effect was 85% for DP and PA, 80% for DP and PA, 77% for DP and Mex, 75% for Mex and Lid, and 63% for Mex and PA. For suppression of spontaneous VPB's, correspondence rate was 100% for DP and PA, 39% for DP and Mex, 64% for Mex and Lid, 61% for Mex and PA, and 69% for DP and PA. EP properties of class IA and IB drugs, as assessed by ECG and EP studies, agreed with their EP properties in normal isolated cardiac tissue. However, we were unable to discern a clear difference in clinical efficacy between class IA and IB drugs in this study. Our results indicate that IA and IB drugs differ little in prevention and termination of sustained VT, and that PA possesses qualities that set it apart from other IA and IB drugs. Accordingly, limitations of the Vaughan Williams classification system must be kept in mind using it as a reference for drug selection in the clinical treatment of VT. © 1988, The Japanese Circulation Society. All rights reserved.