Case Presentation: A 43 year-old man with history of alcohol abuse presented with progressive shortness of breath. He was found with severe pneumonia and subsequently developed cardiac arrest. Initial EKG suggested anteroseptal infarct, age undetermined; troponin was elevated with a peak of 0.188 ng/mL (normal <0.031 ng/mL). A left heart catheterization (LHC) revealed non-obstructive coronary artery disease and increased left ventricular (LV) end diastolic pressure. A transthoracic echocardiogram (TTE) showed severely reduced global LV systolic function, an ejection fraction (EF) of 10%, and LV dilatation with suggestion of a thrombus. The patient was aggressively diuresed, started on enoxaparin and continued on aspirin with high-dose statin. On hospital day 10, he developed crushing substernal chest pain and diaphoresis, and became hypotensive to 60/40 mm Hg. EKG showed new inferior lead ST segment elevation. An emergent LHC found 100% occlusion of the posterolateral branch of the right coronary artery; troponin peaked at 26.3 ng/mL. After successful balloon angioplasty, the patient was bridged to and discharged on warfarin as well as aggressive medical management. Repeat TTE 7 months later showed an improved EF of 40% and no LV thrombus.

Discussion: We describe an uncommon cause of ST elevation myocardial infarction (STEMI), suspected secondary to embolization of an LV thrombus. Studies show enoxaparin to be effective in resolving LV thrombi, with a mean treatment duration of 13 days. In our patient, enoxaparin was initiated just 2 days prior to his MI. The literature notes that most systemic emboli occur within the first weeks of thrombus discovery. Therefore, close observation is recommended during this period given the continued risk of embolization even with timely initiation of anticoagulation. This case also highlights an uncommon but life-threatening event. In one study of ‘first’ MIs, 2.9% were due to embolism, most commonly in the setting of atrial fibrillation. This distinction is important because, while the 30-day mortality rate for those with MI from embolism is similar to other MI patients, the 5-year all-cause and cardiac death rates are significantly higher. An embolic source of MI should be considered even in patients without atrial fibrillation, especially if the patient has known cardiomyopathy, lacks traditional cardiac risk factors or has had a prior LHC showing non-obstructive disease. Early identification of thrombus and rapid initiation of anticoagulation can be life-saving.

Conclusions: Embolic phenomena resulting in acute MI is relatively uncommon. Our case demonstrates the importance of considering this etiology of MI, especially in the setting of a known LV thrombus, and of remaining vigilant in the days after an LV thrombus is diagnosed.