[Demonstration of a major preexcitation syndrome during treatment of auricular flutter using intravenous injection of verapamil].

Electrophysiologic properties of various conduction pathways responsible for preexcitation syndrome are illdefined; they explain the incidence of arrhythmias : supraventricular tachycardia, atrial fibrillation and, in much rarer cases, flutter. The site of Verapamil activity is chiefly the atrioventricular junction, while its action on the refractory period of atrio-ventricular bypass is small and unforeseable. In a patient with type B. W.P.W. syndrome, complicated with atrial flutter Verapamil induced a preferential stimulation through the anomalous pathway. Right BBB which was obvious during the attack of atrial flutter, was hidden by the type B W.P.W. syndrome, the right branch being shunted by the anomalous pathway. The infrequency of atrial flutter in type B W.P.W. syndrome is emphasized.