Background: About 5-10 percent of all patients presenting with acute myocardial infarction (MI) and no other obvious non-coronary reason for MI such as arrhythmia have no coronary obstruction at coronary angiography. Recently, these patients were classified as Myocardial Infarction with Non-Obstructive Coronary Arteries (MINOCA). Recent analyses indicate that this is not a benign condition given an annual mortality of about 5 percent in the patients. However, data on incidence, predictors and prognosis of MINOCA are still limited.

Methods: This secondary analysis of the prospective FAST-MI study included 1532 patients presenting with symptoms suggestive for MI from 10/2015 until 21/2016 at a tertiary care heart center. All patients underwent a comprehensive cardiac assessment including ECG, echocardiography and a measurement of high-sensitivity troponin. Patients with non-obstructive coronary arteries and without obvious other reason for MI were scheduled for further work-up including MRT or intraluminal imaging if reasonable and tolerable for the patient. Diagnosis of MINOCA was made according to the position paper of the European Society of Cardiology (ESC) on MINOCA.

Results: From 1532 patients presenting with suspected MI, 542 fulfilled the criteria of the Universal Definition of Myocardial Infarction. 371 of these patients had available imaging data of coronary arteries. Out of these 371 patients, 276 showed significant coronary obstruction and were treated by coronary intervention (type I MI). In 95 patients no significant coronary obstruction was found. Among them 2 had acute myocarditis, and 1 had a cardioembolic coronary event and in the remaining 68 patients a type II MI was diagnosed based on an obvious non-cardiac reason for myocardial ischaemia such as severe arrhythmia or sepsis. Finally, 23 patients were identified who met the ESC criteria for MINOCA (6.2% of all MI). Patients diagnosed with MINOCA were further classified as recommended in the ESC consensus paper (Table). The most common etiology of MINOCA were thrombotic events without any detectable cardioembolic condition.

Conclusion: The present data demonstrate that about 6-7% of patients presenting with acute MI fulfill the criteria of MINOCA. Further work-up can reveal the mechanism causing this condition in the majority of patients with non-cardioembolic thrombotic events as the most common reason. Given the limited data on MINOCA, further research is needed to better understand the diagnostic and prognostic implications as well as the optimal treatment for this condition.