Impact of cardiac magnetic resonance on diagnosis, treatment and patient outcomes in acute myocardial infarction with non-obstructed coronary arteries: a value-based healthcare approach in a developing country (RF_TH_182)

Background: Myocardial infarction with non-obstructed coronary arteries (MINOCA) is a working diagnosis, and as international guidelines recommend, the underlying cause should always be sought. CMR provides a definitive diagnosis to guide appropriate clinical management: a surrogate of patient outcomes. Considering the increased expenditure of this noninvasive diagnostic tool, especially in resource-limited settings, this study focuses on how CMR refines diagnosis and impacts the treatment and prognosis of patients presenting with acute coronary syndrome

Methods: A retrospective cohort study of patients with a working diagnosis of MINOCA who were referred for CMR from January 2019 to July 2023. Baseline demographic characteristics and CMR parameters were described. We assessed the number of patients in whom nonischemic causes were identified after CMR and treatment was changed due to CMR diagnosis. The relationship between final diagnosis and major cardiac events at one year was evaluated.

Results: Of 1048 patients presenting with acute myocardial infarction, 14%(n=146) had a diagnosis of MINOCA. 38%(n=56) of MINOCA patients underwent CMR. Of the 56 patients, 61% were female, 41% had hypertension, 39% had hyperlipidemia, and 27% had diabetes. The average age was 59±14 years, left ventricular ejection fraction was 58±13%, and troponin was 902.16 ng/ml. CMR usage increased from 16% in 2019 to over 40% in 2022-2023 among MINOCA. The CMR diagnosis was infarction with unobstructed coronary arteries (INOCA) in 29%(n=16) of patients, myocarditis in 34%(n=19),takotsubo in 3%(n=2), and normal in 34% of patients (n=19; 5 classified as myocardial injury and 14 as type 2 myocardial infarction). CMR findings led to treatment modifications in 66% (n=37) of patients, primarily on dual antiplatelet therapy. No deaths occurred at the one-year follow-up. One patient had an ischemic stroke and had a diagnosis of INOCA. Troponin levels were higher in INOCA(p< 0.01).

Conclusion: CMR significantly influences the management of patients with MINOCA by allowing the reclassification of the underlying etiology in more than 70% of patients and leading to treatment adjustments in over 60%, underscoring the importance of systematic use of CMR in all patients with MINOCA despite the increase in cost. The low rate of cardiovascular events suggests a favorable short-term prognosis classic of MINOCA. However, longer-term follow-up is necessary to fully understand the predictive value of CMR in each MINOCA rule-in or rule-out setting.