Sinoatrial block induced by oral diltiazem

A 58-year-old man with variant angina who had no history suggestive of sinus node dysfunction experienced palpitation with pulse deficit after 8 days of diltiazem treatment, 240 mg per day. Electrocardiogram (ECG) revealed frequent occurrence of sinoatrial block. After discontinuation of diltiazem, an ambulatory ECG demonstrated gradual reduction of the occurrence of sinoatrial block, and no recurrence 8 hours after the last dose of the drug. One should note that diltiazem induces not only sinus node suppression and atrioventricular conduction disturbance, but also sinoatrial block.