Introduction: The classical pathophysiological process underlying acute coronary syndromes has been considered to be plaque rup­ture followed by platelet activation and aggregation and subsequent thrombus formation leading to myocardial ischemia and infarction. A substantial number of patients with acute coronary syndromes appear to have normal or near normal (<50% stenosis) coronary arteries on angiography. Recently, this clinical entity has been coined MINOCA (Myocardial Infarction with Non-Obstructive Coronary Arteries). The purpose of this paper is to describe the proportion of MINOCA among ACS patients in Iceland.

Material and methods: We performed a retrospective analysis of all admissions for acute coronary syndromes at Landspitali University Hospital, the single coronary catheterization facility in Iceland, during a five year period between 2012 and 2016. All patients admitted for STEMI or NSTEMI that turned out to have normal or near normal coronary arteries were consecutively included in the study. For each patient the diagnosis was re-evaluated according to further assessments using a diagnostic algorithm specially constructed for this study.

Results: During the five year study period 1708 patients were studied with coronary angiography during first hospitalization for STEMI or NSTEMI. Among these, 225 (13.2%) had normal or non-obstructive coronary arteries with less than 50% luminal narrowing. The final diagnosis of these patients were plaque erosion / rupture in 72 indi­viduals (32%), myocarditis in 33 (14.7%), takotsubo cardiomyopathy in 28 (12.4%), type II myocardial infarction in 30 (13.3%), vasospastic angina in 31 (13.8%) and other or undetermined cause in 31 (13.8%) patients.

Conclusion: The proportion of MINOCA in Iceland is 13.2% of patients admitted for acute coronary syndromes. Plaque erosion / rupture was considered a likely cause in one third of patients with other causes beeing evenly distributed with approximately half that frequency.  Identification of the underlying cause of MINOCA would become more accurate with a consistent use of cardiac magnetic resonance imaging in these patients as it provided a definitive diagnosis in all of those ­studied.

Table I. Baseline characteristics.

Table II. Underlying cause of MINOCA 2012-2016.

Table III. Results of electrocardiogram, coronary angiography, echocardiography and troponin measurements.

Figure 1. Diagram for the diagnostic algorithm used in this study.

Figure 2. Proportion of MINOCA patients among those admitted for acute coronary syndromes 2012-2016.  MINOCA: Myocardial Infarction with Non-Obstructive Coronary Arteries.