Question: A 63-year-old man presents to the emergency department with the sudden onset of excruciating chest pain, which he describes as a tearing sensation. He was diagnosed with essential hypertension 20 years ago, but he is not compliant with his medications. On physical examination, the temperature is 37.1°C (98.8°F), heart rate is 95/min, and blood pressure is 195/90 mm Hg in the right arm and 160/80 mm Hg in the left arm. The pulses are absent in his right leg and diminished in his left leg. A chest X-ray shows a widened mediastinum. Which of the following is the next best step?

Answer: CT scan

Choices:
A. CT scan
B. Intravenous sodium nitroprusside
C. Surgery
D. D-dimer
E. Intravenous ultrasound