Stanford A Aortic Dissection

58 F with left side weakness • Xray of the Week

Figure 1. Name the important findings on this CT Scan.

Figure 2. Stanford Type A aortic dissection. Blue arrows (A, C, E) pointing at intimal flaps in the ascending aorta, descending aorta, and common iliac arteries. The intimal flap separates the true lumen (smaller caliber) from the false lumen (larger caliber). Green arrows pointing at normal left common carotid artery (D, E). Red arrows pointing at the intimal flap in the right common carotid artery, indicating that dissection has extended into the arch vessels (B, D, E). Yellow arrows showing contrast in the right internal and external carotid arteries via retrograde flow (D).

Figure 3: Diagram of Stanford classification for aortic dissection. Stanford Type A involves the ascending aorta with or without descending aortic involvement. Stanford Type B involves the descending aorta distal to the left subclavian artery. Intimal flap is the piece of teared intima that separates the true aortic lumen from false aortic lumen. Diagram by Han Ngo.

Discussion:

Aortic dissection occurs when there is a tear in the intima of the aortic wall, resulting in blood leaking from the true lumen into the media. The blood that travels to the media creates a false lumen, which is separated from the true lumen by a layer of defective intima called the intimal flap (1). Aortic dissection is most commonly seen in elderly patients with systemic hypertension. Connective tissue disorders (e.g. Marfan’s syndrome, Ehlers-Danlos syndrome), bicuspid aortic valve, aortic coarctation, smoking, hyperlipidemia, cocaine use, deceleration trauma, and iatrogenic injury are other risk factors that have been associated with aortic dissection (2,3). Patients with aortic dissection classically present with sudden onset of severe chest pain, often described as “sharp” or “tearing” in sensation. Depending on the location of aortic dissection, patients may also present with a blood pressure difference between the two arms (4,5). Neurological symptoms such as syncope and stroke may also present if dissection extends into the carotid arteries (2-4,7). If left untreated, aortic dissection can be fatal within the first 24-48 hours due to aortic rupture or insufficient blood flow to the heart (6).

Aortic dissection can be categorized by the Stanford classification system (Figure 3). In Stanford Type A, aortic dissection occurs at the level of the ascending aorta, with or without descending aortic involvement. In Stanford Type B, aortic dissection affects the descending aorta distal to the left subclavian artery (3-6). Since Stanford type A has a higher risk of aortic rupture, it is treated more aggressively than Stanford Type B. Usually, Stanford Type A is treated surgically or with stent-graft placement while Stanford Type B is managed medically, primarily with blood pressure control (6).

Medical imaging is imperative for the diagnosis and treatment of Stanford Type A aortic dissection. Common imaging modalities currently used to confirm aortic dissection include CT, transesophageal echocardiography, and MRI with CT being the most common due to its wide availability, high accuracy, and ability to produce images rapidly (3). The key diagnostic finding on chest CT and MRI for Stanford Type A aortic dissection is the presence of an intimal flap in the ascending aorta, with or without the involvement of the descending aorta and common iliac arteries (Figures 2A, 2C, 2E). The intimal flap separates the aortic lumen into true and false lumens that can be distinguished based on size and contrast density: the false lumen is larger and has lower contrast density than the true lumen (3,8). In some Stanford Type A cases, dissection may also extend into the common carotid arteries (Figures 2D, 2E) and cause stroke and other serious neurological symptoms (9,10).

In summary, the key to successful management of Stanford Type A aortic dissection requires early clinical suspicion followed by correct choice of imaging tests to confirm the diagnosis and immediate surgical intervention. The dissected portion of aorta is replaced with a Dacron graft to prevent more blood flowing into the false lumen (6-8). For cases where the aortic dissection extends into the carotid artery, the ideal management is still unclear (10).

References:

1. Juang D, Braverman AC, Eagle K. Aortic dissection. Circulation. 2008;118(14). doi:10.1161/CIRCULATIONAHA.108.7999082

2. Alfson DB, Ham SW. Type B Aortic Dissections: Current Guidelines for Treatment. Cardiol Clin. 2017;35(3):387-410. doi:10.1016/j.ccl.2017.03.0073

3. Kamalakannan D, Rosman HS, Eagle KA. Acute aortic dissection. Crit Care Clin. 2007;23(4):779-vi. doi:10.1016/j.ccc.2007.07.0024

4. Hagan PG, Nienaber CA, Isselbacher EM, et al. The International Registry of Acute Aortic Dissection (IRAD): new insights into an old disease. JAMA. 2000;283(7):897-903. doi:10.1001/jama.283.7.8975

5. Salameh MJ, Ratchford EV. Aortic dissection. Vasc Med. 2016;21(3):276-280. doi:10.1177/1358863X166328986

6. Hiratzka LF, Bakris GL, Beckman JA et al. 2010 ACCF/AHA/AATS/ACR/ASA/SCA/SCAI/SIR/STS/SVM guidelines for the diagnosis and management of patients with thoracic aortic disease: executive summary. J Am Coll Cardiol 2010;55(14):1509–1544. doi:10.1016/j.jacc.2010.02.0108

7. Lee EW, Jourabchi N, Sauk SC, et al. An Extensive Stanford Type A Aortic Dissection Involving Bilateral Carotid and Iliac Arteries. Case Rep Radiol. 2013;2013.doi:10.1155/2013/607012

8. Nienaber CA, Clough RE. Management of acute aortic dissection. Lancet. 2015;385(9970):800-811. doi:10.1016/S0140-6736(14)61005-9

9. Bobelmann C, Poli S. Sonographic features of carotid artery dissection due to extension of aortic dissection: a case report. Ultrasound J. 2019;11(1):32. doi:10.1186/s13089-019-0147-2

10. Laser A, Drucker CB, Harris DG, et al. Management and outcomes of carotid artery extension of aortic dissections. J Vasc Surg. 2017;66(2):445-453. doi:10.1016/j.jvs.2016.12.137

Han Ngo is a medical student at Oakland University William Beaumont School of Medicine (OUWB) in Rochester, Michigan. She graduated from UCLA, receiving her B.S. degree in Biochemistry. Prior to starting medical school, Han spent 4+ years (including her undergraduate years) working as a medical scribe for a psychiatrist at Ronald Reagan UCLA Medical Center. Interested in radiology, Han is now serving as the President of both diagnostic radiology and interventional radiology interest groups at OUWB. She is also a committee member on the Medical Student Council of the Society of Interventional Radiology (SIR). After deciding on her specialty, Han plans to continue learning and striving to make a difference in patients’ lives.

Follow Han Ngo on Twitter @Han_Ngoo

All posts by Han Ngo

Kevin M. Rice, MD is the president of Global Radiology CME and is a radiologist with Cape Radiology Group. He has held several leadership positions including Board Member and Chief of Staff at Valley Presbyterian Hospital in Los Angeles, California. Dr. Rice has made several media appearances as part of his ongoing commitment to public education. Dr. Rice's passion for state of the art radiology and teaching includes acting as a guest lecturer at UCLA. In 2015, Dr. Rice and Natalie Rice founded Global Radiology CME to provide innovative radiology education at exciting international destinations, with the world's foremost authorities in their field. In 2016, Dr. Rice was nominated and became a semifinalist for a "Minnie" Award for the Most Effective Radiology Educator. He was once again a semifinalist for a "Minnie" for 2021's Most Effective Radiology Educator by AuntMinnie.com. He has continued to teach by mentoring medical students interested in radiology. Everyone who he has mentored has been accepted into top programs across the country including Harvard, UC San Diego, Northwestern, Vanderbilt, and Thomas Jefferson.

Follow Dr. Rice on Twitter @KevinRiceMD

All posts by Kevin M. Rice, MD