Sotalol testing unmasks altered repolarization in patients with suspected acquired long-QT-syndrome--a case-control pilot study using i.v. sotalol.

Abstract

The aim of this pilot study was to evaluate provocative sotalol testing to unmask abnormal repolarization due to altered myocardial electrical properties as the key feature in acquired Long-QT-Syndrome. Reliable diagnosis and risk stratification for the individual patient are complicated by the multitude of mechanisms involved in acquired QT-prolongation. The combined influence of all components determines susceptibility to arrhythmias related to QT-prolongation. Twenty consecutive patients who had experienced torsades de pointes in association with QT-prolonging drugs were tested with i.v. D,L-sotalol (2mg/kg) with 24-h intensive care monitoring to evaluate the repolarization process by determining QT- and QTc-prolongations. Results were compared to age and sex matched controls. At baseline, no differences between control and study population with regard to QT and QTc were detected. After sotalol infusion, QTc increased from 422+/-17 to 450+/-22ms in controls and from 434+/-20 to 541+/-37ms in the study population. Torsades de pointes occurred in three out of 20 patients (15%) in the study population but in none of the control patients following i.v. sotalol testing. Controlled exposure to sotalol successfully identifies patients with normal QTc intervals but altered myocardial repolarization. This may be useful for clarifying diagnosis and pathogenesis of acquired Long-QT-Syndrome.