Torsade de pointes and long QT syndrome following major blood transfusion.

We report a rare complication following transfusion of a large volume of blood in an adult patient. An electrophysiological disturbance of the cardiac cycle with prolongation of the QT interval developed, which was followed by recurrent episodes of torsade de pointes, a unique form of ventricular tachycardia. The most likely cause of this acquired long QT syndrome was hypomagnesaemia secondary to massive blood transfusion. Treatment with a magnesium infusion restored the QT interval to normal and temporary ventricular pacing prevented further ventricular arrhythmias.