Positive influence of aspirin on coronary endothelial function: Importance of the dose.

Aim: To investigate the effects of different doses of aspirin on coronary endothelial function.

Methods: The study included 139 Japanese subjects (mean age, 60 years; 53 women) with angiographically normal coronary arteries. Patients were distributed into Group I (n = 63), who was administered aspirin and Group II (n = 76), the control, who were not administered aspirin. Group I was further divided into Group Ia (n = 50, low-dose aspirin, 100 mg) and Group Ib (n = 13, high-dose aspirin, 500 mg). After a routine coronary angiography, acetylcholine (ACh; 3 and 30 μg/min successively) and nitroglycerin (NTG) were infused into the left coronary ostium over 2 min. The change in the diameter of the coronary artery in response to each drug was expressed as the percentage change from baseline values.

Results: The patient characteristics did not differ between the two groups. The change in coronary diameter in response to ACh was greater in Group I than in Group II (P = 0.0043), although the NTG-induced coronary vasodilation was similar between groups. ACh-induced dilation was greater in Group Ia than in Group Ib (P = 0.0231). Multivariate regression analysis showed that a low-dose of aspirin (P = 0.0004) was one of the factors associated with ACh-induced dilation at 30 μg/min.

Conclusion: In subjects with angiographically normal coronary arteries, aspirin only had a positive influence on coronary endothelial function at the low dose of 100 mg. This improvement of coronary endothelial function may be involved in the preventive effect of aspirin against future coronary events.