Hypomagnesemia in heart failure with ventricular arrhythmias. Beneficial effects of magnesium supplementation

Objective. To assess the role of electrolyte imbalance in cardiac arrhythmi as associated with congestive heart failure. Design. Serum magnesium and potassium levels, urine magnesium excretion and the incidence of ventricular arrhythmias were assessed throughout the stud y. The patients who displayed complex arrhythmias after the first week of h ospital medication were randomized 2 : 1 to double-blind magnesium suppleme ntation or placebo. Setting, The study was carried out in one municipal hospital, providing pri mary care. Subjects. A total of 588 consecutive patients were screened for eligibility (clinical heart failure greater than or equal to 6 months; NYHA class II-I V; left ventricular ejection fraction less than or equal to 40%; sinus rhyt hm; serum creatinine less than or equal to 2 mg dL(-1)). A total of 78 pati ents entered and 68 patients completed the study. Interventions. Intravenous administration of magnesium (magnesium sulphate 8 g in 250 mt of 5% glucose or placebo (250 mL Of 5% glucose) over 12 h. Main outcome measures, (i) Incidence of ventricular arrhythmias in patients with hypomagnesemia: (ii) effects of magnesium supplementation on ventricu lar arrhythmias. Results. On admission, hypomagnesemia was found in 38% and excessive magnes ium loss in 72% of patients. Serum magnesium levels were lower and urine ma gnesium excretion was greater in patients with complex ventricular arrhythm ias, both on admission and after treatment for heart failure. Intravenous a dministration of magnesium caused a significant decrease in the number of v entricular ectopic beats IP < 0.0001), couplets (P < 0.003) and episodes of nonsustained ventricular tachycardia (P < 0.01). Conclusions, Hypomagnesemia, probably related to increased urine magnesium excretion, is an essential feature of heart failure associated with complex ventricular arrhythmias. These arrhythmias can be alleviated/abolished by magnesium supplementation.