Reduced stress perfusion in myocardial infarction with nonobstructive coronary arteries

Background Myocardial infarction with nonobstructive coronary arteries (MINOCA) is a working diagnosis with several possible underlying causes. Early cardiovascular magnetic resonance imaging (CMR) is recommended, however cannot provide a diagnosis in 25% of cases. One pathophysiological mechanism may be coronary microvascular dysfunction (CMD) not possible to detect using standard CMR. Quantitative stress CMR perfusion mapping can be used to identify CMD, however it is currently unknown if CMD is present during long-term follow-up of MINOCA patients. Therefore, the aim of this study was to evaluate presence of CMD during long-term follow-up in MINOCA patients with an initial normal CMR scan. Methods MINOCA patients from the second multicenter Stockholm Myocardial Infarction with Normal Coronaries study (SMINC-2), with a normal CMR scan a median 3 days after hospitalization were investigated with comprehensive stress CMR median 5 years after the acute event, together with age- and sex-matched volunteers without symptomatic ischemic heart disease. Cardiovascular risk factors, medication and symptoms of myocardial ischemia measured by the Seattle Angina Questionnaire 7, were registered. Results In total, 15 patients with MINOCA and an initial normal CMR scan (59±7 years old, 60% female), and 15 age- and sex-matched volunteers, underwent CMR. Patients with MINOCA and an initial normal CMR scan had lower global stress perfusion compared to volunteers (2.83±1.8 vs 3.53±0.7 ml/min/g, p =0.02). There were no differences in other CMR parameters including global rest perfusion and myocardial perfusion reserve, hemodynamic parameters, or cardiovascular risk factors, except for a higher statin use in the MINOCA patient group compared to volunteers. Conclusions Global stress perfusion is lower in MINOCA patients during follow-up, compared to age- and sex-matched volunteers, suggesting CMD as a possible pathophysiological mechanism in MINOCA. Clinical Trial Registration Clinicaltrials.gov identifier NCT02318498 . Registered 2014-12-17.