In patients with variant angina, previous data have been inconclusive as to whether basal coronary artery tone is elevated at the spastic sites and nonspastic sites. The purpose of this study was to assess the basal coronary artery tone and to evaluate the responsiveness to acetylcholine and ergonovine in patients with variant angina.

Basal coronary artery tone was assessed by obtaining the percent increase in coronary artery diameter induced by nitroglycerin in 66 patients with variant angina and 26 control subjects. We also compared the basal coronary tone and the constrictive responses to acetylcholine and ergonovine between the 31 patients with variant angina whom spasm was provoked by the low doses of acetylcholine(Ach; intracoronary, 20µg) or ergonovine(Erg; intravenous, 50µg)(Group 1) and the 35 patients provoked by higher doses of acetylcholine(intracoronary, 100µg ) or ergonovine(intravenous cumulative dose of 350µg)(Group 2).

Patients with variant angina whom spasm was provoked by low doses of acetylcoline and ergonovine, have a more tendency of combine fixed disease(mix disease), multivessel spasm and high disease activity.

Basal coronary artery tone at the spastic sites was significantly elevated in the Group 1 in whom spasm was provoked by low doses of acetycholine and ergonovine than that in Group 2(44±17 vs 13±11%, respectively, p<0.05). Basal coronary artery tone of spasm-related artery, but not nonspasm related artery, at the non spastic site was greater in the Group 1 than that in Group 2 (26±14 vs 16±10%, respectively, p<0.05). In the patients with variant angina in whom spasm was provoked by higher dose of acetylcholine or ergonovine, basal coronary artery was comparable at the spastic and nonspastic sites and was not different from that in the control subjects. The magnitude of vasoconstrictive responses to acetylcoline and ergonovine, at the nonspastic sites, were also greater in Group 1 than those in Group 2 and the control groups(Ach; 40±20 vs 26±11. 27±12% : Erg ; 37±18 vs 12±8, 13±10%, respectively, p<0.05).

These findings suggest that elevated basal coronary artery tone of the spastic sites and nonspastic sites of spasm-related artery in patients with variant angina may be related to occurrence of coronary spasm.