Conversion of longstanding atrial flutter to sinus rhythm and transient complete A-V block following oral administration of verapamil. Report of a case.

In a patient with ischaemic heart disease chronic atrial flutter reverted to sinus rhythm during treatment with oral Verapamil, given at dosage of 240 mg once a day in order to prevent spontaneous angina. Such an unexpected event was accompanied by a remarkable sinus node depression and by a transient complete a-v block, that gradually subsides leaving a slight permanent a-v conduction delay. Either a higher bioavailability of the drug or an extremely increased sensitivity of the receptors can explain such a marked electrophysiological effect at a moderate drug dosage.