Limited efficacy of magnesium for the treatment of variant angina.

Some patients with variant angina show both ST segment elevation at rest and exercise-induced ST segment elevation. Magnesium deficiency has also been observed in patients with variant angina. This study investigated the correlation between the degree of magnesium deficiency and the efficacy of intravenous administration of magnesium in patients with variant angina. Fifteen patients with angiographically confirmed variant angina were assessed for magnesium deficiency and whether intravenous administration of magnesium (19.2 mEq/l) suppressed exercise-induced ST segment elevation. All 15 patients were studied with a magnesium retention test (0.2 mEq/kg over 4 hr) to analyze magnesium deficiency. In our study, magnesium retention rate in patients with variant angina was not higher than that of controls (57 +/- 24% vs 45 +/- 10%, NS). All 15 patients had anginal attacks during accelerated exercise combined with hyperventilation after placebo infusion, whereas only 8 patients had anginal attacks after magnesium administration. ST segment elevation occurred in 14 patients after placebo infusion, but in only 4 patients after magnesium administration. There were no correlations between disease activity, degree of magnesium deficiency or failure of suppression of ST elevation by the intravenous administration of magnesium. Intravenous administration of magnesium can suppress exercise-induced coronary spasms in some patients with variant angina, but the degree of magnesium deficiency did not correlate with the suppressions of exercise-induced ST elevation after magnesium administration. Intravenous administration of magnesium had limited efficacy in patients with variant angina and exercise-induced ST segment elevation.