Cardiac compression causing fatal acute ST-segment elevation myocardial infarction

STEMI: rare initial presentation of a mediastinal mass supplied by the RCA

In the setting of severe septic shock, a 70-year-old woman had an ST segment myocardial infarction with ST elevations in the inferolateral leads. On cardiac catheterisation, no obstructive pathology was noted. Chest imaging revealed a large mediastinal mass measuring 8.5×6.5×7.5 cm in the visceral compartment of the mediastinum, with contrast enhancement from the right coronary artery (RCA). A biopsy was preformed and cytology was consistent with a well-differentiated neuroendocrine neoplasm. On review of the cardiac catherisation, it was noted that the mass was deriving blood supply from the RCA. Myocardial infarction with non-obstructive coronary arteries (MINOCA) is a rare but well-documented phenomenon. In this case, MINOCA was caused by coronary steal syndrome in the setting of profound hypotension. Immediate management is with haemodynamic support; there is no role for coronary intervention.

A rare cause of myocardial infarction with non-obstructive coronary arteries-case report of ST-segment elevation myocardial infarction caused by a mediastinal mass

INTRODUCTION

ST-segment elevation myocardial infarction (STEMI) is attributable to an occluded coronary artery in almost 90% of patients. Accordingly, restoration of coronary perfusion as early as possible, preferably with primary percutaneous coronary intervention, is the recommended treatment by the European Society of Cardiology, to maximise myocardial salvage. However, not all cases of STEMI are because of coronary artery occlusion. ST-segment elevation myocardial infarction that occurs in the absence of obstructive coronary artery disease on angiography has been termed myocardial infarction with non-obstructive coronary arteries (MINOCA).

CASE PRESENTATION

A 44-year-old man was admitted with retrosternal chest pain radiating to the left arm and jaw, and electrocardiography showed extensive anterior ST-segment elevation. Emergency coronary angiography showed all three coronary arteries were patent with Thrombolysis in Myocardial Infarction-3 flow and no evidence of dissection or thrombus. The ST-elevation and pain resolved spontaneously. Troponin-T level rose from <3 ng/L on arrival to 549 ng/L at 12 h. Subsequent cardiac magnetic resonance imaging (MRI) showed a structurally normal heart (without late gadolinium enhancement) but detected an incidental large, lobulated (90 × 31 × 71 mm) mediastinal mass containing multiple cysts in the anterior mediastinum with inflammation and oedema of the parietal pericardium. Tissue biopsy confirmed Hodgkin's lymphoma and the patient was initiated on chemotherapy.

DISCUSSION

Some 3% of ST-segment myocardial infarctions occur in the absence of obstructive coronary disease (MINOCA), is more frequent in younger patients. Cardiac MRI is a useful tool to both identify some of the potential causes of MINOCA and also to confirm the diagnosis of infarction. Some 26% of MINOCA patients have significant biochemical evidence of myocardial injury but have a normal cardiac MRI. This case illustrates a very rare cause of myocardial infarction in a young patient with unobstructed coronary arteries, and highlights the need in such cases for further detailed imaging of the myocardium and thorax to establish the diagnosis and initiate appropriate treatment.