"Torsade de pointes" initiated by electrical ventricular stimulation

Four cases are described in which electrical stimulation of the right ventricle produced the ventricular arrhythmia known as "torsade de pointes". This arrhythmia has previously been described as classically occurring in the context of the chronic bradycardias, particularly when there is also hypokalemia and a long QT interval, being most frequently initiated by a ventricular extrasystole occurring relatively late during ventricular repolarization. One patient had suffered a recent anterior myocardial infarction and developed the arrhythmia during rapid pacing for atrial flutter, when the electrode catheter had inadvertently entered the right ventricle. In the other three patients the arrhythmia was produced during the ventricular extrastimulus test performed during routine diagnostic electrophysiological investigation.