The Effect of Neuroleptics on Electrocardiograms

The changes observed in the ECG when chlorpromazine and imipramine derivatives are given seem to be related to the dosage used. The relative Q‐T duration, however, when chlorpromazine is administered in clinical dosage shows a highly significant prolongation. When the effect of thioridazine and chlopentixol on ECGs was studied in forty patients the changes observed were similar but slighter and partly attributable to the tachycardia. There was a difference in the increase of the heart rate in the groups of patients studied. Nevertheless, the incidence of T‐wave depression was the same both in patients treated with thioridazine in whom the increase in the heart rate, during therapy, was slight, and in those treated with chlopentixol, whose heart rate increased more heavily. An equal extension was noted in the relative Q‐T duration. In patients receiving neuroleptic drugs the magnitude of the ventricular gradient may be affected by the tachycardia. The shift to the left observed in the direction of this gradient does not, however, allow any definite conclusion. The result obtained suggests that the pathological component of the gradient is identical with the T vector, and the T‐wave changes probably resulted from some primary change in the repolarization due to the drugs tested.