ABSTRACT
A 41-year-old man was admitted because of syncope. The electrocardiogram showed torsade de pointes (Tdp) with no long QT interval and the coupling interval of the initial beat of Tdp was 240 ms. Heterogeneity of ventricular refractoriness was observed together with shortness of the effective refractory period measured at the right ventricular inflow site where the paced QRS morphology was the same as that of the initial beat of Tdp. Verapamil could suppress frequent ventricular premature complexes with a short coupling interval, which lead to Tdp. Polymorphic ventricular tachycardia was induced by triple ventricular extrastimuli. A pure potassium channel blocker was successful in inhibiting polymorphic ventricular tachycardia inducibility by prolongation of refractoriness. These results suggested that triggered ventricular premature complexes may be represent the initiating mechanism, whereas the shortness of local refractory period and heterogeneity of ventricular refractoriness may play a role in the development and the maintenance of the Tdp.