Research that appeared in the American Heart Journal (June 1993;125:1645-1649) looked at the effect IV magnesium sulfate had on patients with congestive heart failure.  Magnesium was given intravenously to patients with congestive heart failure, arrhythmia and with serum magnesium levels lower than 2.0 mg/dl. The patients all had at least 10 premature ventricular depolarizations per hour as determined by a six hour ambulatory electrocardiograph reading.  There was a significant decrease in premature ventricular depolarizations from treatment with magnesium.  A study that appeared in the Journal of the American College of Cardiology (1990;16 (4):827-831) found 19% of a sampling of 199 patients with congestive heart failure had low serum magnesium. Considering that serum magnesium is a poor way to determine deficiency, it would be interesting to see what RBC magnesium levels were in this group of patients.

Patients with congestive heart failure seem to benefit from magnesium supplementation. A double-blind, placebo-controlled study appeared in the International Journal of Cardiology (2009; 134(1): 145-7) that involved 79 patients with severe congestive heart failure.  The subjects were randomly selected to receive either magnesium orotate or a placebo for one year. The survival rate was higher in the magnesium group (75.7% compared to 51.6% in the placebo group). Also, symptoms improved in 38.5% of the patients receiving magnesium. In 56.3% of the placebo group symptoms became more severe.

Drugs that are used by heart patients may deplete magnesium. Research appearing in Magnesium Bulletin (1994;16(3):98-100) demonstrated that treatment with ACE inhibitors deplete magnesium.