Methods for documenting antiarrhythmic efficacy

Methods of documenting the efficacy of antiarrhythmic drugs are controversial because of wide inter- and intrasubject variability of the arrhythmias treated. In patients with symptomatic arrhythmias, clinical benefit can be inferred when symptoms are reduced or abolished, but the response cannot be quantitated. Multiple ambulatory monitoring periods before and during treatment permit determination of reductions of arrhythmia to levels of statistical significance but are costly and time-consuming. Programmed electrophysiologic induction study may be helpful in determining efficacy of some antiarrhythmic agents because of its high specificity, but its use is limited because of a low sensitivity. Titrating patients with multiple dosing into accepted plasma level therapeutic ranges may be helpful for individual patient care but does not allow quantitation. Recently, a statistical model based on linear regression analysis with established 95 and 99% confidence intervals has been used to compare efficacy of quinidine and encainide with success. Wider application of this model is suggested for determining antiarrhythmic drug efficacy.