A 63-year-old man presented to the emergency department with 8 hours of waxing-and-waning substernal chest pressure. The patient had previously undergone coronary artery bypass graft surgery in 1992, with the left internal mammary anastomosed to the left anterior descending artery and a reverse saphenous vein graft anastomosed to a large circumflex marginal vein. The right coronary artery was nondominant and without disease. Following coronary artery bypass graft surgery, the patient returned to an active lifestyle without symptoms. Relevant medical history also included hypertension and hypercholesterolemia. Medications included aspirin, 325 mg/d, a 3-hydroxy-3methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor (statin), and an angiotensin-converting enzyme inhibitor combined with a low-dose diuretic.Physical examination results were notable for a blood pressure of 126/70 mm Hg and a heart rate of 70/min. Lung fields were clear. The S 1 and S 2 were normal, but there was an S 4 gallop. Distal pulses were intact. His admission electrocardiogram (FIGURE 1) demonstrated diffuse ischemic changes, including ST-segment elevation in lead aVR. Laboratory evaluation demonstrated the following values: peak troponin I, 5.65 ng/mL (reference range, 0-0.50 ng/mL); creatine kinase, 603 U/L (reference range, 24-170 U/L); and creatine kinase-MB fraction, 14% (reference range, 0%-3%).