A 42-year-old man with a history of Marfan syndrome presents to the emergency room with severe, sudden, tearing chest pain radiating to the abdomen and back. The pain has progressively shifted downward over the past several hours. He admits to recent cocaine use and has a history of hypertension, previously treated with hydrochlorothiazide, which he discontinued due to thunderclap headaches. He smokes one pack of cigarettes daily. Vital signs: Temperature: 99.8 °F Heart rate: 108 beats/min (right arm); 94 beats/min (left arm) Blood pressure: 198/105 mm Hg (right arm); 170/94 mm Hg (left arm) Respiratory rate: 19 breaths/min Oxygen saturation: 94% on room air On physical examination, the patient has asymmetric pulses and signs of intravenous drug use (track marks, scarring). An electrocardiogram reveals wide QRS complexes, and a chest X-ray shows a widened mediastinum (as shown below). Laboratory findings include normal troponin and D-dimer levels.Which of the following is the most likely diagnosis in this patient?
