Patrick Perkins, MD
Wayne Leonhardt, BA, RT, RDMS, RVT
Summit Medical Center
Diagnostic Imaging
Oakland, CA

Patient is a 53 year old man who arrived in the Emergency room complaining of epigastric pain. He stated the pain at times radiated to his back and he felt pressure in his chest. He had no other symptoms. The patient's medical history included Hypertension and Nephrolithiasis. He smoked a pack of cigarettes a day and was obese. He was evaluated for a myocardial infarction. An EKG showed a normal sinus rhythm. Chest X-ray and all lab values were within normal limits. He had no rebound tenderness or nausea. He was given oxygen and started on Nitroglycerin and aspirin. The patient was admitted to the ICU for angina and observation. Subsequent Abdominal Ultrasound and Chest CT scans were ordered.

Clinical Diagnosis

CT Results: Apparent intimal flap in a portion of the proximal descending thoracic aorta on at least two sequences compatible with Stanford Type B dissection , which affects the descending aorta only (20-30 percent)1. No dissection was demonstrated in the Abdominal Aorta or distal thoracic Aorta, although blood pool concentration of contrast was not optimal at these levels which could obscure a flap. Patient was referred for immediate surgery.

DISCUSSION:
CT and MRI are the primary imaging modalities of choice used for detecting arterial dissection of the thorax and abdomen. Arterial dissections may be discovered during a routine abdominal sonogram. They most often originate in the chest and extend into the abdominal aorta. They can extend into the iliac arteries or into other aortic branches.

Arterial dissections result from a combination of factors: medial degeneration decreasing cohesiveness within the aortic wall, persistent aortic motion secondary to beating heart results in stress within the aortic wall, and hydrodynamic forces accelerated by hypertension. The term dissecting aneurysm can be misleading, because the artery affected is not always dilated. The preferred term is arterial dissection.

The classic sonographic appearance of an aortic dissection is a echogenic membrane that divides the arterial lumen into two compartments. The membrane consists of the intima and in some cases portions of the media. When blood enters the media of the vessel through a tear in the intima, a new lumen referred to as the false lumen is formed. The membrane moves freely with arterial pulsations. If the membrane is thick or if one lumen is thrombosed movement is limited or not at all. Use color duplex imaging to determine patency, stenosis, and or occlusion.2

References:
1 Radiology Review Manual (third edition) Wolfgang Dahnert, M.D.Department of Radiology Good Samaritan Regional Medical Center, Phoenix, Arizona. Williams & Wilkins, A Waverly Company, Philadelphia, 1996.

2 Introduction to Vascular Ultrasonography, (Fourth Edition) Zwiebel J. W., W.B. Saunders Company, Philadelphia,2000.