The role of CMR in the evaluation of microvascular coronary dysfunction and in the diagnosis of other causes of MINOCA in patients with NSTEMI

Myocardial infarction without coronary artery obstruction (MINOCA) is 3 times more common in patients with NSTEMI compared to STEMI. The potential etiology of MINOCA can be divided in coronary and non-coronary causes. At the same time, an important role in its etiopathogenesis is played by microvascular coronary dysfunction (DCM). The aim of the study is to assess the feasibility of cardiac magnetic resonance (CMR) as a non-invasive method of evaluating DCM in patients with NSTEMI and in addition, to verify the substrate of MINOCA according to CMR. A diagnostic examination was carried out in 16 patients, of which coronary etiology was confirmed only in 1/3, the rest of the patients had a non-coronary etiology of the disease (myocarditis, hypertrophic cardiomyopathy and dilated cardiomyopathy). Microvascular coronary dysfunction (CDM) was determined in 30% of patients with non-coronary impairment (group I) and in 50% of those with coronary heart disease (group II) (χ² = 0.64, p> 0.05). Significant differences between groups were observed in the localization of fibrosis, so in group II, according to CMR, all patients had subendocardial fibrosis - 100%, while in group I, intramural fibrosis prevailed in 50% (n = 5), subepicardial fibrosis - 20% (n = 2) and in 20% (n = 2) both types of contrast enhancement were noted, χ² = 12.44 p < 0.05. In conclusion, CMR is an important diagnostic tool both in assessing the causes of MINOCA and in evaluating DCM in this category of patients. However, further studies are needed to improve the diagnostic accuracy of this method in the study of coronary microcirculation.