Complications resulting from the delayed clinical presentation of a left main coronary artery obstruction can be catastrophic. This case report presents a 73-year-old woman with severe aortic stenosis who underwent transcatheter aortic valve replacement with a core valve who, approximately 20 minutes after heparin reversal with protamine, became hypotensive and was unresponsive to vasopressor and inotropic therapy. Transesophageal echocardiography demonstrated global hypokinesis, which was highly consistent with the occlusion of the left main coronary artery. Angiography confirmed this diagnosis and demonstrated that valve positioning had not changed compared to post-placement examination. Here we report the partial covering of the ostium of the left main coronary artery by a core valve skirt that converted into a total occlusion following the initiation of heparin reversal with protamine and the value of multimodal imaging in the management of this case.