QT prolongation and ventricular fibrillation in acute myocardial infarction.

Fourteen acute myocardial infarction (AMI) patients with early ventricular fibrillation (VF) were compared to 27 control patients without VF with regard to the corrected QT interval (QTc) and the QRS duration. Patients with complete bundle branch block (BBB) had been excluded. The QTc tended to be longer in the VF group than in the controls, but the difference, 13 msec, disappeared after exclusion of a further 5 VF patients and one control with QRS duration greater than 0.10 sec of other configurations than complete BBB. In the long QT syndrome of various types, VF is characteristically preceded by diastolic waves (DW) with larger amplitudes than the preceding T waves. None of the 5 AMI patients with an evaluable recording of the onset of VF, showed DWs preceding the arrhythmia. The results of this study do not support the opinion that VG is associated with a prolonged QT interval in AMI in the same way as in the long QT syndrome. The longer QT interval in patients with VF seems to be mainly secondary to the longer QRS duration.