Shackling prisoners in hospital
Authors: L. Dillner
Journal: BMJ (1996)

<h3>Background</h3> MINOCA is a clinical diagnosis of an acute coronary syndrome type presentation with non-obstructive coronary arteries (stenosis ≤50%) on coronary angiography. It accounts for 5% to 15% of all AMI (acute myocardial infarction) presentations. Aetiology may include plaque disruption with transient occlusion, coronary artery dissection, coronary artery spasm, coronary microvascular obstruction, myocarditis or embolic phenomena. Given the range of aetiologies and potential variability in therapeutic implications, further investigation beyond lumenography may be indicated such as CMR(cardiac MRI) and or intra coronary imaging and provocation testing if clinical suspicion of coronary disease remains high despite initially non-obstructive angiographic appearances. <h3>Purpose</h3> The aim of this study is to establish the prevalence of different aetiological diagnoses using CMR in patients with (MINOCA) and raised troponin. <h3>Methods</h3> A single centre retrospective observational study of STEMI(ST elevation myocardial infarction) patients admitted for primary PCI between Jan 2016 till sept 2019 and had non-obstructive coronary arteries (stenosis ≤50%). Consecutive patients presenting as STEMI, with chest pain or syncope and ECG evidence of ST elevation were included. Patient level data was collected from electronic records and local STEMI data base. CMR results of patients admitted to the primary PCI centre were examined to ascertain the aetiology. Troponin levels recorded from PPCI centre. <h3>Results</h3> A total of 1687 STEMI patients presented for primary PCI from Jan 2016 to Sep 2019. Of these STEMI patients 7.7% (n=130) had angiographically proven non-obstructive coronary arteries [male (73.8%), female (26.2%)] [figure 1]. Of these 130 patients 55.3% were repatriated to their base hospital according to national STEMI policy and further investigations were undertaken locally if at all, but not recorded in this study. Of the 130 patients with non-obstructive coronaries 44.7% (n=58) were managed in the PPCI centre. Troponin levels were elevated in 2% of patients with non-obstructive coronaries. Of patients with ST elevation who subsequently had an high troponin 59% (n=18) underwent CMR during the index admission or within 30 days. Of these CMR scans 83% (n=15) were abnormal and 3 patients (23%) had a normal CMR [table 2], most common abnormality (33%) was myocardial infarction. <h3>Conclusion</h3> Non-obstructive coronaries were found in 2% of all STEMI presentations in this study. CMR can be instructive as to the aetiology of MINOCA, and yields a diagnosis in the majority of cases (83%). However, despite non-obstructive coronary angiography myocardial infarction remains the most common diagnosis in patients with ST elevation and raised troponin, greater consideration may need to be given to intracoronary imaging or investigation of cardio embolic sources of infarction to ensure appropriate secondary prevention. <h3>Study Limitations</h3> This study has some limitations, it is a retrospective analysis and data from a single Irish primary PCI centre. Furthermore, majority of patients with STEMI and non-obstructive coronary arteries after undergoing coronary angiography were transferred to base hospital and further data on the investigations to ascertain the aetiology of presentation was not available. Also, intracoronary provocation testing and intracoronary imaging was not performed in any of these patients to further clarify coronary cause of presentation.