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The Effect of Diltiazem, a Calcium Channel—Blocking Drug, on Cardiac Rate and Rhythm in Hyperthyroid Patients
Elio Roti, MD;
Mara Montermini, MD;
Sergio Roti, MD;
Eliana Gardini, MD;
Giuseppe Robuschi, MD;
Roberta Minelli, MD;
Mario Salvi, MD;
Marina Bentivoglio, MD;
Umberto Guiducci, MD;
Lewis E. Braverman, MD
Arch Intern Med. 1988;148(9):1919-1921.
Abstract
Tachycardia and tachyarrhythmias are frequent in patients with thyrotoxicosis, especially in the elderly. Since myocardial calcium uptake is increased in thyrotoxic rats, the efficacy of the calcium channel—blocking drug diltiazem in decreasing heart rate and the incidence of arrhythmias was evaluated in 11 hyperthyroid patients. All patients were studied with a 24-hour Holter monitor prior to the beginning of sole diltiazem therapy (120 mg given every eight hours), on the tenth day of therapy, and five days after therapy was discontinued. Heart rate significantly decreased by 17% during diltiazem treatment (96.5 ± 3.7 systoles/min vs 79.9 ± 3.2 systoles/min [mean ± SE]) and returned to baseline values five days after the therapy was discontinued (100.7 ± 3.4 systoles/min). Similarly, the number of premature ventricular extrasystoles per hour was significantly decreased (18 ± 7 vs 2 ± 1). In three patients, asymptomatic bouts of supraventricular tachycardia, paroxysmal atrial fibrillation, or ventricular tachycardia disappeared during diltiazem therapy. These findings suggest that calcium-blocking drugs may be extremely useful as adjunctive therapy for thyrotoxicosis in the presence of angina, congestive failure, and tachyarrhythmias.
(Arch Intern Med 1988;148:1919-1921)
Author Affiliations
From the Cattedra di Endocrinologia e Patologia Costituzionale, Universita di Parma, Italy (Drs E. Roti, Montermini, Gardini, Robuschi, Minelli, Salvi, and Bentivoglio); the Servizio di Cardiologia, Ospedale S Maria Nuova, Reggio Emilia, Italy (Drs S. Roti and Guiducci); and the Division of Endocrinology and Metabolism, University of Massachusetts Medical School, Worcester (Dr Braverman).
Footnotes
Accepted for publication April 15, 1988.
Reprint requests to the Division of Endocrinology and Metabolism, University of Massachusetts Medical Center, 55 Lake Ave N, Worcester, MA 01655 (Dr Braverman).
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