Correlation of basal coronary artery tone with constrictive response to ergonovine in patients with variant angina

Objectives. This study was conducted to examine whether basal coronary artery tone is elevated at the spastic site in patients with variant angina and to determine the significance of basal artery tone in predicting provocation of coronary artery spasm. Background. Previous data have been conflicting on whether basal coronary artery tone is elevated in patients with variant angina. Methods. We assessed basal coronary artery tone by obtaining the percent increase in coronary artery diameter induced by nitroglycerin in 20 patients with variant angina and 24 control subjects. We also examined the correlation between basal coronary artery tone and the constrictive response to ergonovine. Results. In the patients with variant angina in whom spasm was provoked by the lower doses (1 or 5 μg) of ergonovine, basal coronary artery tone was greater (p < 0.05) at the spastic site (54 ± 15% or 36 ± 16%, respectively) than at the nonspastic site (40 ± 25% or 25 ± 15%, respectively). Basal coronary tone at the nonspastic site in these patients was greater (p < 0.01) than that in control subjects (15 ± 6%). In the patients with variant angina in whom spasm was provoked only by the higher doses (15 or 50 μg) of ergonovine, basal coronary artery tone was comparable at the spastic and nonspastic sites and was not different from that in control subjects. The diagnostic sensitivity and specificity of elevated basal coronary artery tone (≥40%) in predicting provocation of spasm were 26% and 98%, respectively. Conclusions. These results indicate that elevated basal coronary artery tone may be useful in predicting provocation of coronary spasm, but the normal level of basal coronary artery tone does not exclude such provocation.