ELECTROPHYSIOLOGICAL INVESTIGATION OF VEN TRICULAR-TACHYCARDIA

The ability to induce and terminate ventricular tachycardia reproducib ly by programmed stimulation has led to the development of electrophys iological investigations for the management of patients suffering from spontaneous arrhythmias. The investigation consists in introducing se veral multipolar catheter electrodes under local anaesthesia which are then positioned in contact with the endocardium in several regions of the heart. There is no consensus as to an ideal stimulation protocol for these patients but the basic principle is the introduction of one or several ventricular extrasystoles every 8 beats in sinus rhythm or during a controlled ventricular paced rhythm. At present, the major in dication is rarely diagnostic in the presence of wide QRS complex tach ycardias difficult to analyse by electrocardiography. On the other han d, electrophysiological investigations are highly recommended in cases of unexplained syncope in patients with documented or suspected heart disease, in symptomatic patients with intraventricular conduction def ects in whom ventricular arrhythmias are suspected as the cause of sym ptoms or after cardiac arrest without transmural infarction or, for ma ny teams, after the 48th hour of transmural infarction. Electrophysiol ogical investigations are also justified in patients in whom surgical or catheter ablation of an arrhythmogenic focus is planned because of resistance to antiarrhythmic drug therapy. Evaluation of the efficacy of antiarrhythmic drugs by repeated investigations is common in the Un ited States but is not so widely accepted in Europe. Finally, although greater numbers of arrhythmic events seem to occur in patients in who m sustained monomorphic ventricular tachycardia is inducible in the ea rly post-infarction period, the results of systematic studies are vari able and do not clearly demonstrate the utility of programmed stimulat ion in the routine investigation of these patients.