Intracoronary Acetylcholine-Induced Prolongation of the QT Interval and Torsade des Pointes in Long QT Interval Syndrome.

Abstract
A 75-year-old female had syncopal episodes from Torsade des Pointes (TdP). Her electrocardiogram showed a prolonged QT interval which was not associated with electrolyte imbalances or drug therapy. Similar electrocardio-graphic abnormalities were found in three family members. Electrophysiologic study showed a mildly prolonged effective refractory period of 260-290msec, but no tachyarrhythmia was induced. Coronary arteriography was normal but intracoronary acetylcholine unexpectedly induced a prolongation of the QT interval and TdP. Direct action of acetylcholine on the ventricular muscle was suggested.

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