Acute total occlusion of the left main stem (LMS) is a rare cause of myocardial infarction but carries a high risk of morbidity and mortality including presentation as sudden death. We describe the case of a 68-year-old woman who presented acutely with chest pain and ST segment elevation in lead aVR on her ECG suggestive of possible LMS occlusion. Emergency coronary angiography confirmed acute total LMS occlusion as well as an anomalous dominant right coronary artery. The patient underwent emergency percutaneous coronary intervention of the LMS with a good angiographic result and resolution of her symptoms. The patient was treated for acute left ventricular failure but made a gradual recovery and was discharged home 7 days after admission.