Most of coronary artery ectasia (CAE) patients have comorbid coronary atherosclerosis. It was lack of prognostic data for CAE patients with coronary heart disease (CHD) and for whom with acute myocardial infarction (AMI).To determine the overall prognosis for CAE patients.This study was a retrospective cohort study. Fifty-one patients with CAE and comorbid AMI (CAE + AMI) and 108 patients with CAE and comorbid CHD (CAE + CHD) were enrolled and matched to non-CAE subjects at a ratio of 1:3 using a propensity score method, respectively. Controls for CAE + AMI group were 153 AMI patients, controls for CAE group were 324 CHD patients and 329 participants with relatively normal coronary arteries (CON). We followed them up to observe major cardiovascular events (MACE).The Kaplan-Meier curves showed that the prognosis in CAE + AMI group was worse than in AMI group (5-year non-MACE rate: 62.70% vs. 79.70%, P = 0.010), the prognosis in CAE group was worse than in CHD and CON groups (5-year non-MACE rate: 74.10% vs. 85.80% and 96.70%, respectively, P = 0.000). The main MACEs in CAE + AMI and CAE groups were AMI reoccurrence (19.61% vs. 4.57%, P = 0.002) and re-hospitalization due to repeated angina pectoris (14.81% vs. 8.33% and 2.74%, P = 0.000), respectively. Additionally, the COX regression analysis revealed that the protective factors for preventing MACE in CAE + AMI group included antiplatelet agents (hazard ratio = 0.234, P = 0.016) and angiotensin-converting enzyme inhibitor/angiotensin receptor inhibitor (ACEI/ARB, hazard ratio = 0.317, P = 0.037). Whereas the main factor promoting MACE in CAE group was the degree of coronary stenosis (Gensini score, hazard ratio = 1.011, P = 0.022).The prognosis of patients with CAE + AMI was worse than that of those with AMI. The overall prognosis of patients with CAE was worse than that of those with CHD. CAE + AMI and CAE groups had different characteristics; the former was prone to AMI reoccurrence, and the latter was prone to repeated angina pectoris. To prevent MACE, medications, including antiplatelets and ACEI/ARBs, are indicated for patients with CAE + AMI, whereas prevention of the progression of atherosclerotic lesions is indicated for patients with CAE.Copyright © 2022 Liu, Gao, Liang and Zhao.