Myocardial Infarction With Nonobstructive Coronary Arteries (MINOCA) in Young Patients: A Retrospective Cohort Study of Pathophysiological Mechanisms and Risk Factors.

Background Myocardial infarction with non-obstructive coronary arteries (MINOCA) represents a heterogeneous group of ischemic injuries that occur despite the absence of flow-limiting stenosis on angiography. The condition accounts for approximately 5-15% of all acute myocardial infarctions and may affect younger adults who often lack conventional cardiovascular risk factors. Etiologic mechanisms are diverse and frequently non-atherosclerotic, including spontaneous coronary artery dissection (SCAD), vasospasm, microvascular dysfunction, and other dynamic processes. Because MINOCA encompasses multiple pathophysiological pathways, accurate exclusion of non-ischemic causes such as myocarditis, Takotsubo syndrome, pulmonary embolism, or systemic inflammatory states is essential, and advanced imaging techniques are often required to establish the ischemic nature of injury. Objective To compare the clinical characteristics and likely etiologic mechanisms of MINOCA in adults younger than 50 years versus those aged 50 years or older treated in a tertiary cardiology center, while also considering the potential influence of imaging availability, selection bias, and confounding variables on etiologic distribution. Methods A retrospective analysis was performed including 198 consecutive patients diagnosed with MINOCA between 2018 and 2023. The diagnosis followed the Fourth Universal Definition of Myocardial Infarction and required biochemical evidence of infarction with less than 50% stenosis in all major epicardial arteries and exclusion of alternative non-ischemic causes through clinical evaluation and imaging, particularly cardiac magnetic resonance when available. Clinical and demographic features, cardiovascular risk factors, and identified mechanisms were compared by age group. Continuous variables were analyzed using Student's t-test, and categorical variables using chi-square or Fisher's exact test. Logistic regression estimated the odds ratio (OR) for non-atherosclerotic mechanisms in younger versus older patients and included adjustment for relevant confounders based on clinical plausibility. The analytic approach accounted for missing imaging data through complete-case analysis, and sample sizes used in each statistical comparison are reported. Results Among 198 patients, 90 (45.5%) were younger than 50 years. Younger patients had a lower prevalence of hypertension and higher rates of obesity and stimulant or illicit drug use. An underlying mechanism was identified in 47.7% of the cohort. Non-atherosclerotic mechanisms predominated in younger adults, mainly SCAD and vasospasm, whereas plaque-related mechanisms were more common in older adults. The odds of an atherosclerotic mechanism were significantly lower among younger individuals (OR 0.36; 95% CI 0.15-0.88). Conclusions Young adults with MINOCA exhibit a distinct clinical profile characterized by fewer traditional risk factors and a higher prevalence of non-atherosclerotic causes. These findings highlight the importance of systematic etiologic investigation, including the role of cardiac magnetic resonance and intracoronary imaging, and suggest that age-informed diagnostic strategies may improve clinical management.