Magnesium deficiency frequently develops in patients with
congestive heart failure and may increase susceptibility to lethal arrhythmias and
sudden death via multiple pathophysiologic mechanisms. The effects of peroral
magnesium supplementation were investigated in a randomized, double-blind, crossover trial involving 21 patients with stable
congestive heart failure secondary to
coronary artery disease. All were receiving long-term
loop diuretics, and had normal renal function, and low or normal serum
magnesium concentrations. Subjects alternately received enteric-coated
magnesium chloride (15.8 mmol
magnesium per day) and placebo for 6 weeks.
Magnesium therapy increased serum
magnesium from 0.87 +/- 0.07 to 0.92 +/- 0.05 mmol/liter (p < 0.05), serum
potassium from 4.0 +/- 0.3 to 4.3 +/- 0.4 mmol/liter (p < 0.01) and urinary
magnesium excretion from 2.82 +/- 0.96 to 4.74 +/- 2.38 mmol/24 hours (p = 0.001). There was no significant change in heart rate or Doppler cardiac index, but mean arterial pressure decreased from 91 +/- 10 to 87 +/- 10 mm Hg (p < 0.05) and systemic vascular resistance from 1,698 +/- 367 to 1,613 +/- 331 dynes s cm-5 (p = 0.047). The frequency of isolated
ventricular premature complexes was reduced by 23% (95% confidence interval [CI] 6 to 37%; p < 0.02), couplets by 52% (95% CI 30 to 65%; p < 0.001) and
nonsustained ventricular tachycardia episodes by 24% (95% CI 15 to 49%; p < 0.01). Plasma
epinephrine decreased from 447 +/- 535 to 184 +/- 106 pg/ml (p = 0.02), but there was no corresponding change in plasma
norepinephrine or heart rate variability.(ABSTRACT TRUNCATED AT 250 WORDS)