Statistical Distribution of Ventricular Ectopic Beats Assessed by Computer Analysis of Long-Term Electrocardiograms: Problems Related to the Definition of Arrhythmogenesis

The severity and clinical importance of arrhythmogenic effects of antiarrhythmic drugs have been well recognized, but only empirical and naive approaches have been used to define antiarrhythmic and proarrhythmic effects when comparing baseline and on-therapy Holter recordings. This article suggests a new method for the assessment of these effects, based upon comparisons of statistical distributions of ectopic beats recorded on long-term electrocardiograms. Since these distributions are very individual, the Smirov test was used for their comparison. This enables the antiarrhythmic and arrhythmogenic effects to be defined on a precise statistical basis. To demonstrate this method, an analysis is reported of Holter recordings made on six patients suffering from different types of ventricular arrhythmia. In each of these patients, one baseline Holter recording and one recording on each of three different drugs (flecainide, sotalol, and verapamil) were made. The records were digitized using a commercially available system for the analysis of long-term electrocardiograms and random sampling was used to obtain independent samples of arrhythmic episodes that were subsequently statistically analyzed. The results show that the problem of the definition of arrhythmogenesis can be partly addressed in a precise mathematical way and that treatment with an antiarrhythmic preparation may not only have general antiarrhythmic or arrhythmogenic effects, but may also cause a significant change in the character of arrhythmia that can neither be classified as antiarrhythmic nor as arrhythmogenic influence. The clinical implications of this approach are discussed.