The patients were divided into two groups: the aspirin group taking LDA before ACh test (n = 221)
and the no aspirin group not taking aspirin (n = 2568). At baseline, the prevalence of old age,
diabetes mellitus, hypertension, and hyperlipidemia were higher in the aspirin group. During the
ACh test, the incidence of significant CAS, ischemic chest pain, as well as severe and multivessel
spasm was higher in the aspirin group. The response rate to lower ACh dose was higher in the
aspirin group. Multivariate analysis showed that the previous use of LDA was an independent
predictor of CAS (adjusted odds ratio, 1.6, 95% confidence interval, 1.0—2.3; p = 0.031). However,
it is likely that the association of LDA and CAS that we have observed is not causal but may be
hypothesis generating due to significant baseline differences. Further, male gender, old age,
lipid-lowering drugs, baseline spasm, and myocardial bridge were independent predictors of
CAS. LDA was more frequently associated with CAS and ischemic symptoms, as well as severe and
multivessel spasm, suggesting the patients who have received LDA would require more intensive
medical therapies and close follow up.