A 48-year-old man comes to the emergency department due to chest pain. The pain started suddenly in the retrosternal area 8 hours ago and is constant. The patient did not have shortness of breath, syncope, dizziness, or lightheadedness. His ECG showed ST-segment elevation, and he was admitted to undergo immediate catheterization and stent placement. Two weeks after the initial hospitalization, the patient had sudden onset of sharp pain in the chest, worsening with deep inspiration. Blood pressure is 130/90 mm of Hg, pulse 98/min; the temperature is 100 F (37.8 C), respiratory rate 20/min. On physical examination, heart sounds are normal and regular. Bilateral lung fields are clear. A scratchy sound is heard along the left sternal border. ECG reveals the following finding shown in the exhibit.