Effect of magnesium on anginal attack induced by hyperventilation in patients with variant angina.

To examine whether or not magnesium suppresses coronary spasm, the effect of magnesium infusion on anginal attacks induced by hyperventilation was studied in 20 patients with variant angina. In all patients, anginal attacks associated with ischemic ST segment changes on the electrocardiogram were repeatedly induced by hyperventilation. The study was performed in the early morning successively for 3 days. On days 1 and 3 (control studies), 50 minutes before the hyperventilation test, a 5% glucose solution was infused as a placebo. On day 2 (magnesium study), 50 minutes before the hyperventilation test, magnesium sulfate (0.27 mM/kg body wt) was infused during a 20-minute period. During the control studies, anginal attack was induced by hyperventilation in all 20 patients, whereas during the magnesium study, anginal attack was induced by hyperventilation in only six (30%) of the 20 patients (p less than 0.001 vs. control studies). The changes in arterial blood pH and PCO2 caused by hyperventilation were not significant between the control study and the magnesium study. Mean serum magnesium concentration increased from 2.2 +/- 0.2 to 6.0 +/- 0.5 mg/dl immediately after infusing magnesium and was 4.5 +/- 0.6 mg/dl before the hyperventilation test during the magnesium study. We conclude that magnesium suppresses anginal attacks induced by hyperventilation in patients with variant angina.