Hypomagnesemia in heart failure with ventricular arrhythmias. Beneficial
effects of magnesium supplementation.
Ceremuzynski L; Gebalska J; Wolk R; Makowska E
J Intern Med 2000 Jan;247(1):78-86
OBJECTIVE: To assess the role of electrolyte imbalance in cardiac arrhythmias
associated with congestive heart failure. DESIGN: Serum magnesium and
potassium levels, urine magnesium excretion and the incidence of ventricular
arrhythmias were assessed throughout the study. The patients who displayed
complex arrhythmias after the first week of hospital medication were randomized
2:1 to double-blind magnesium supplementation or placebo. SETTING: The
study was carried out in one municipal hospital, providing primary care.
SUBJECTS: A total of 588 consecutive patients were screened for eligibility
(clinical heart failure >/=6 months; NYHA class II-IV; left ventricular
ejection fraction </=40%; sinus rhythm; serum creatinine </=2 mg
dL-1). A total of 78 patients entered and 68 patients completed the study.
INTERVENTIONS: Intravenous administration of magnesium (magnesium sulphate
8 g in 250 mL 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 ventricular arrhythmias. RESULTS: On admission, hypomagnesemia was
found in 38% and excessive magnesium loss in 72% of patients. Serum magnesium
levels were lower and urine magnesium excretion was greater in patients
with complex ventricular arrhythmias, both on admission and after treatment
for heart failure. Intravenous administration of magnesium caused a significant
decrease in the number of ventricular ectopic beats (P < 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.