Electrocardiographic abnormalities in patients with cluster headache on verapamil therapy

Abstract

High dose verapamil is an increasingly common preventive treatment in cluster headache (CH). Side effects include atrioventricular block and bradycardia, although their incidence in this population is not clear. This audit study assessed the incidence of arrhythmias on high dose verapamil in patients with cluster headache. Of three hundred sixty-nine patients with cluster headache, 217 outpatients (175 men) received verapamil, starting at 240 mg daily and increasing by 80 mg every 2 weeks with a check electrocardiogram (EKG), until the CH was suppressed, side effects intervened, or to a maximum daily dose of 960 mg. One patient had 1,200 mg/day. Eighty-nine patients (41%) had no EKGs. One hundred eight had EKGs in the hospital notes, and a further 20 had EKGs done elsewhere. Twenty-one of 108 patients (19%) had arrhythmias. Thirteen (12%) had first-degree heart block (PR > 0.2 s), at 240 to 960 mg/day, with one requiring a permanent pacemaker. Four patients had junctional rhythm, and one had second-degree heart block. Four patients had right bundle branch block. There was bradycardia (HR < 60 bpm) in 39 patients (36%), but verapamil was stopped in only 4 patients. In eight patients the PR interval was lengthened, but not to >0.2 s. The incidence of arrhythmias on verapamil in this patient group is 19%, and bradycardia 36%. We therefore strongly recommend EKG monitoring in all patients with cluster headache on verapamil, to observe for the potential development of atrioventricular block and symptomatic bradycardia.