Electrophysiological methods in assessing cardiac effects of the tricyclic antidepressant imipramine.

The tricyclic antidepressant agent imipramine was tested intravenously in 8 healthy individuals with respect to its effect on sinus recovery time, intervals in His bundle electrograms and the duration of the repolarization in the right atrium and ventricle judged from the refractoriness and monophasic action potential duration. Sinus recovery time was unchanged after the drug. The interval between the His bundle deflection and the start of the QRS complex in the standard lead showed no consistent changes but increased to pathological values in two individuals. The duration of the repolarization decreased in the atrium--an effect which could be arrhythmia-provoking or arrhythmia-protecting. The duration increased at the ventricular level. This effect could explain the antiarrhythmic effect on ventricular ectopics observed in other investigations.