[The role of Holter monitoring and electrophysiological studies in the evaluation of ventricular anti-arrhythmia agents].

The roles of Holter monitoring and electrophysiological studies (EPS) in the evaluation of antiarrhythmic drugs for ventricular arrhythmias are to record their effects on ventricular extrasystoles (VES) and ventricular tachycardia (VT), and to search for undesirable rhythmological effects. The usual protocol is to perform baseline studies and then repeat them after a certain period of treatment using a number of modalities, comparison with placebo, control group, in acute or oral administration. Holter monitoring is an economical non-invasive method which carries no risk. Spontaneous arrhythmias of sufficient frequency to be recorded during the monitoring period can be studied. When applied to VES, it provides quantitative rather than qualitative information despite classifications such as Lown's. The results should be analysed taking spontaneous variations of the arrhythmia into consideration. Holter monitoring may also reveal proarrhythmic drug effects (bradycardia, torsades de pointe). However, there are no absolute criteria of efficacy except total suppression of VES, unexplainable by spontaneous variability. Holter antiarrhythmic studies require stable VES which creates a bias in the evaluation of results due to the special selection of patients. Electrophysiological studies are costly, invasive and uncomfortable but they are the only way of assessing paroxysmal VT apart from clinical follow-up. This method is only applicable to inducible VT, which is the commonest form. The investigating protocols are specific and reproducible: a tachycardia which is non-inducible does not recur in 90% of cases, which enables prediction of the antiarrhythmic effect.(ABSTRACT TRUNCATED AT 250 WORDS)