Association between Aspirin Therapy and Clinical Outcomes in Patients with Non-Obstructive Coronary Artery Disease: A Cohort Study

Presence of non-obstructive coronary artery disease (CAD) is associated with increased prescription of cardiovascular preventive medications including aspirin. However, the association between aspirin therapy with all-cause mortality and coronary revascularization in this population has not been investigated. Among the cohort of individuals who underwent coronary computed tomography angiography (CCTA) from 2007 to 2011, 8372 consecutive patients with non-obstructive CAD (1-49% stenosis) were identified. Patients with statin or aspirin prescription before CCTA, and those with history of revascularization before CCTA were excluded. We analyzed the differences of all-cause mortality and a composite of mortality and late coronary revascularization (> 90 days after CCTA) between aspirin users (n = 3751; 44.8%) and non-users. During a median of 828 (interquartile range 385-1,342) days of follow-up, 221 (2.6%) mortality cases and 295 (3.5%) cases of composite endpoint were observed. Annualized mortality rates were 0.97% in aspirin users versus 1.28% in non-users, and annualized rates of composite endpoint were 1.56% versus 1.48%, respectively. Aspirin therapy was associated with significantly lower risk of all-cause mortality (adjusted HR 0.649; 95% CI 0.492-0.857; p = 0.0023), but not with the composite endpoint (adjusted HR 0.841; 95% CI 0.662-1.069; p = 0.1577). Association between aspirin and lower all-cause mortality was limited to patients with age ≥ 65 years, diabetes, hypertension, decreased renal function, and higher levels of coronary artery calcium score, low-density lipoprotein cholesterol and high-sensitivity C-reactive protein. Among the patients with non-obstructive CAD documented by CCTA, aspirin is associated with lower all-cause mortality only in those with higher risk.