Sundeep R Bhat, MD, is an Emergency Medicine Resident in the Stanford/Kaiser Emergency Medicine Residency Program in CA. E-mail: sbhat@stanford.edu. Gus M Garmel, MD, FACEP, FAAEM, is a Senior Emergency Medicine Physician at the Kaiser Santa Clara Medical Center, Co-Program Director of the Stanford/Kaiser Emergency Medicine Residency Program, and Clinical Professor (Affiliated) of Surgery (Emergency Medicine) at Stanford University School of Medicine in CA. He is also a Senior Editor for The Permanente Journal. E-mail: gus.garmel@kp.org. Figure 1. Thoracic Aortic Dissection Although plain film chest radiograph may be used to screen for a widened mediastinum (Image A) which suggests thoracic aortic dissection, computed tomography (CT) angiography or traditional angiography are gold-standard tests and should be obtained in any stable patient for whom dissection is suspected.1,2 Thoracic aortic dissection is generally classified using the Stanford scheme, although some texts and cardiothoracic surgeons still use the DeBakey classification (types I III). Image B demonstrates dissection flaps seen in both the ascending and descending aorta (Stanford Type A—any involvement of the ascending aorta irrespective of site of intimal tear or distal extension).2 Complications of Type A dissections include aortic valve insufficiency, dissection into coronary vessels causing acute myocardial infarction, and dissection into the pericardial sac (Image C) causing hemopericardium and possible tamponade physiology.1 Type A dissection requires immediate surgical intervention. Image D shows an intimal flap in the descending aorta only (Stanford Type B). Patients with uncomplicated Type B dissections are typically managed medically, with blood pressure control by pharmacologic intervention.1,2 A