'Idiopathic' acute myocardial infarction in a young patient with noncompaction cardiomyopathy.

Isolated left ventricular noncompaction (LVNC) is a rare hereditary cardiomyopathy characterized by prominent intraventricular trabeculations separated by deep intertrabecular recessus. While cardiac ischemia due to microvascular dysfunction is common in these patients, ST-segment elevation myocardial infarction (STEMI) is rare and usually seen as a consequence of coincidental coronary artery disease. We report the case of a 20 year-old male patient admitted to our emergency department with a complaint of squeezing chest pain who was subsequently diagnosed with STEMI according to electrocardiographic findings, although an emergent coronary angiogram demonstrated normal coronary arteries. Echocardiography revealed isolated LVNC, and the diagnosis was confirmed via magnetic resonance imaging. Repeat coronary catheterization with acetylcholine infusion and coronary flow reserve measurement failed to demonstrate vasospasm or microvascular dysfunction. As no apparent cause was found, this case was designated 'idiopathic' myocardial infarction. Coronary thromboembolism due to stagnation of blood in the left ventricular cavity remained as the most probable mechanism underlying myocardial infarction.