A 68-year-old man presents with the sudden onset of severe upper back pain that started one day ago. The pain is sharp, constant, and radiates between his scapulae. He has a history of hypertension controlled with lisinopril and a 30 pack-year smoking history. He recalls being told he had a heart murmur ten years ago but did not follow up. He denies any chest pain, syncope, or recent trauma but admits to mild dyspnea. Initial laboratory studies, including a complete blood count, basic metabolic panel, and cardiac troponins, are unremarkable.