USMLE Question #606: Real Exam Question with Answer & Explanation

A 50-year-old male is brought to the emergency department due to an acute onset chest pain that radiates to his jaw. An ECG reveals ST segment elevation in leads II, III and a VF. He undergoes percutaneous coronary intervention with stenting without any complications. The patient is discharged from the hospital three days later with aspirin and clopidogrel. He returns to the emergency department eight weeks later due to recurrent chest pain which he describes as a sharp pain that worsens when he lies flat. The pain does not radiate or improve with nitroglycerin tablets. Vitals reveal a blood pressure of 135/87 mmHg, a heart rate of 84/ min, a temperature of 38.0°C (100.5°F) and a respiratory rate of 12/min. Oxygen saturation is 98% on room air. Physical examination reveals a harsh three component extra heart sound heard best at the left lower sternal border. An ECG is obtained which reveals diffuse ST elevations. The most likely cause of the current findings is