© 2000 by European Society of Cardiology
ELECTROPHYSIOLOGY
Dose-related cardiac electrophysiological effects of intravenous magnesium. A double-blind placebo-controlled dose-response study in patients with paroxysmal supraventricular tachycardia
1Department of Cardiology, Skejby Sygehus, University Hospital Aarhus, Denmark; 2Centre for Clinical Pharmacology, Aarhus University Aarhus, Denmark
Abstract
AIMS: The role of magnesium as an antiarrhythmic drug is yet not conclusive. Therefore, we performed a double-blind, randomized, placebo-controlled dose-response study of cardiac electrophysiological effects of intravenous magnesium.
METHODS AND RESULTS: Thirty-six patients undergoing an electrophysiological evaluation for paroxysmal supraventricular tachycardia were randomized to one of the following dosages of intravenous magnesium (0, 5, 10 or 20 mmol). Conventional electrophysiological variables for sinus node function, atrial, atrioventricular node and ventricular conduction and refractoriness were measured before and after magnesium administration. Prolongation of the atrial–His interval was found at 5 mmol of magnesium compared with placebo and no further prolongation was observed at higher doses (–3±8, 11±9, 7±15, 11±16, for the dosages of 0, 5, 10 and 20 mmol of magnesium, respectively, P< 0·05). Measures of sinus node function, intra-atrial conduction and conduction through the Purkinje system were unaffected by magnesium. Male gender was associated with prolongation in atrial effective refractory period, in contrast to shortening in females: 2±43, 35±44, 36±33, 13±12 ms for males and 3±6, –12±11, –13±12, 0±23 ms for females, respectively (P< 0·001).
CONCLUSION: Atrioventricular node conduction was prolonged by 5 mmol intravenous magnesium and no further prolongation was observed at higher dosages. At dosages of 5 and 10 mmol magnesium the atrial effective refractoriness was prolonged in males and shortened in females.
Key Words: Magnesium, arrhythmia, electrocardiography, atrioventricular node conduction, cardiac refractoriness
Correspondence: Evald Høj Christiansen, MD, PhD, Department of Cardiology, Skejby University Hospital, DK-8200 Aarhus N, Denmark.
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