Torsade de pointes: the long-short initiating sequence and other clinical features: observations in 32 patients.

The clinical setting, precipitating factors, electrocardiographic features and response to treatment of 32 patients with torsade de pointes were reviewed. Thirty-one patients had underlying cardiac disease and 30 patients had a previous underlying cardiac arrhythmia. Antiarrhythmic medications, often in association with electrolyte abnormalities (such as hypokalemia and hypomagnesemia) were the most common precipitating factors. In 22 of 26 patients, the serum drug levels of the antiarrhythmic agents were found to be within the therapeutic range. However, before the administration of agents known to prolong the QT interval, 20 of the 32 patients had, either alone or in combination, baseline prolongation of the QT interval, hypokalemia or hypomagnesemia. All patients had QTc interval prolongation (mean 0.59 second) immediately before the development of torsade de pointes. Marked lability of T wave morphology was frequently noted. Cardiac pacing was the only consistently effective mode of therapy. A characteristic long-short ventricular cycle length as the initiating sequence was found in 41 of 44 episodes of torsade de pointes. Reported data support the high frequency of this electrocardiographic feature of torsade de pointes in which its onset could be analyzed. It is suggested that this electrocardiographic characteristic will aid in both establishing the diagnosis of torsade de pointes and distinguishing it from other polymorphic forms of ventricular tachycardia.