We present a case of a 47-year-old woman with a mechanical mitral valve prosthesis and recurrent myocardial infarction. The most common etiology of spontaneous myocardial infarction is an acute coronary syndrome caused by rupture or erosion of an atherosclerotic plaque. However, the differential diagnosis in the patient described below also included infarction due to embolization or coronary spasm. It can be challenging to discriminate between the different causes of myocardial infarction based on interpretation of symptoms, physical examination, laboratory tests, and electrocardiography alone. This report illustrates the value of coronary angiography with invasive coronary spasm provocation testing using intracoronary acetylcholine to identify the etiology of her recurrent myocardial infarctions.