eMedicine Specialties > Radiology > Vascular/Interventional

Aorta, Dissection

Author: Jackeline Gomez-Jorge, MD, Assistant Professor of Clinical Radiology, Department of Radiology, Vascular and Interventional Section, University of Miami/Jackson Memorial Medical Center
Contributor Information and Disclosures

Updated: Sep 5, 2008

Introduction

Background

Classic aortic dissection is a longitudinal split or partition in the media of the aorta. An intimal tear connects the media with the aortic lumen, and an exit tear creates a true and a false lumen. The smaller true lumen is lined by intima, and the false lumen is lined by media. Typically, flow in the false lumen is slower than in the true lumen, and the false lumen often becomes aneurysmal when subjected to systemic pressure. An acute aortic dissection is considered chronic at 2 weeks. The dissection usually stops at an aortic branch vessel or at the level of an atherosclerotic plaque.1,2

Most classic aortic dissections begin at 3 distinct anatomic locations: the aortic root; 2 cm above the aortic root; and just distal to the left subclavian artery. Ascending aortic involvement may result in death from wall rupture, hemopericardium and tamponade, occlusion of the coronary ostia with myocardial infarction, or severe aortic insufficiency.

Aortic intramural hematoma (AIH) is a more recently described entity in which no intimal flap is present. It results in a spontaneous medial hematoma that may be secondary to an infarction of the vasa vasorum of the adventitia. Aortic intramural hematoma accounts for approximately 25% of aortic dissections. Involvement of the ascending aorta, especially if the overall aortic diameter is greater than 5 cm, should be treated surgically to prevent rupture or progression to a classic dissection with intimal tear. Conservative management is indicated for AIH of the descending aorta.3,4,5,6,7,8

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Aorta, Trauma
Thoracic Aortic Aneurysm
Abdominal Aortic Aneurysm

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Pathophysiology

The pathogenesis of aortic dissection is not well understood, but the following are associated risk factors9,10 :

Mortality/Morbidity

The mortality rate increases when diagnosis is delayed; this is especially the case for ascending aortic dissections. The mortality rate is 1% per hour for the first 48 hours. However, patients who survive long enough to be hospitalized and who are without significant comorbidities usually survive. Occlusion of aortic branch vessels from aortic dissection may result in stroke, renal failure, mesenteric ischemia, lower-extremity ischemia, and paraplegia (caused by obstruction of the spinal artery). Interestingly, aortic intramural hematoma is rarely associated with significant narrowing of aortic branch vessels.

The incidence is approximately 2000 cases per year, but lack of reporting and the small number of autopsies performed lead to gross underestimations of the true incidence. Ischemic heart disease is roughly 1000 times more common than aortic dissection in patients who present to the ED with chest pain. However, once the diagnosis is suspected, it must be confirmed or refuted with an imaging study.

Race

Aortic dissection is more common in African-Americans, followed by whites. Untreated hypertension may account for the greater prevalence in African-Americans. Aortic dissection is least common in Asians.

Sex

Aortic dissections are more common in men than in women (ratio, 3:1) and in patients aged 35-85 years; the peak incidence occurs in those aged 50-65 years.

Aortic intramural hematoma (AIH) usually occurs in slightly older patients.

Presentation

  • Ripping or tearing pain in the intrascapular area
  • Abrupt onset of pain
  • Acute, severe chest pain (Anterior chest pain may mimic acute myocardial infarction.)
  • Pain extending to the neck or jaw
  • Altered mental status
  • Symptoms of cerebrovascular accident
  • Syncope
  • Limb paresthesias
  • Horner syndrome
  • Dyspnea
  • Dysphagia
  • Flank pain if the renal arteries are involved
  • Hypertension
  • Hypotension if associated with cardiac tamponade, hypovolemia, excessive vagal tone

Dissections of the aorta can be classified into types (see Image 1).

  • DeBakey classification
    • Type I: The entire aorta is involved.
    • Type II: Only the ascending aorta is involved.
    • Type III: Only the descending aorta is involved. Type IIIA involves the descending aorta as far as the diaphragm. Type IIIB involves the descending aorta below the diaphragm.
  • Stanford classification
    • Type A: The ascending aorta is involved.
    • Type B: The descending aorta is involved.

It is noteworthy that isolated dissections that begin in the aortic arch but do not involve the ascending aorta do not fit neatly into these classifications.

AIH is classified in a similar fashion.

Preferred Examination

Preferred examinations for aortic dissection include contrast-enhanced spiral CT transesophageal echocardiography (TEE) in the emergency setting and MRI for hemodynamically stable patients. TEE has an advantage over CT and MRI in its ability to evaluate the status of the aortic valve and the ostia of the coronary arteries. CT and MR angiography have largely replaced conventional diagnostic angiography in the assessment of aortic dissection.11,12,13,14

Several factors determine the best modality for the initial evaluation and postoperative follow-up. These factors include the following: stability of the patient's condition, the patient's renal function, suspected postoperative complication, and the availability of each imaging modality.

Maffei et al performed a randomized, controlled trial in which 44 patients (252 evaluations) were examined with TEE and CT.15 The authors concluded that both TEE and CT are atraumatic, safe, and accurate techniques for serial follow-up studies of patients treated for aortic dissection.

Limitations of Techniques

Three noninvasive studies are associated with high specificity and sensitivity for aortic dissection. CT and MRI are associated with a sensitivity and a specificity of 94-100% and 95-100%, respectively. Transesophageal echocardiography (TEE) is less sensitive and specific than spiral CT or MR, and TEE is operator-dependent. In addition, because of tracheal interposition, there is a 2 cm "blind spot" for TEE just proximal to the innominate arteries. Also, TEE is contraindicated in approximately 1% of patients (eg, TEE is contraindicated in patients with esophageal varices).

Differential Diagnoses

Aortic Regurgitation
Aortic Stenosis
Myocardial Infarct, Acute

Other Problems to Be Considered

Back pain, mechanical
Gastroenteritis
Hernias
Hypertensive emergencies
Myocarditis
Myopathies
Pancreatitis
Pericarditis and cardiac tamponade
Peripheral vascular injuries
Pleural effusion
Pulmonary embolism
Shock, hemorrhagic
Shock, hypovolemic
Thoracic outlet syndrome

More on Aorta, Dissection

Overview: Aorta, Dissection
Imaging: Aorta, Dissection
Follow-up: Aorta, Dissection
Multimedia: Aorta, Dissection
References
Further Reading
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References

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Further Reading

Aortic aneurysm and dissection.
Finnish Medical Society Duodecim.  2004 Feb 26.  Various pagings. [NGC Update Pending] NGC:004359
 
Acute chest pain - suspected aortic dissection.
American College of Radiology.  1995 (revised 2005).  5 pages.  NGC:004621
 
Screening for abdominal aortic aneurysms: recommendation statement.
United States Preventive Services Task Force.  1996 (revised 2005).  16 pages.  NGC:003960

The Society of Thoracic Surgeons practice guideline series: transmyocardial laser revascularization. Society of Thoracic Surgeons.  2003.  16 pages.  NGC:004052

Guidelines on the management of valvular heart disease.
European Society of Cardiology.  2007 Jan.  39 pages.  NGC:005534

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Keywords

aortic dissection, dissection of aorta, aortic intimal tear, pseudoaneurysm, aortic intramural hematoma, traumatic aortic dissection, AIH, aortic aneurysm

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Contributor Information and Disclosures

Author

Jackeline Gomez-Jorge, MD, Assistant Professor of Clinical Radiology, Department of Radiology, Vascular and Interventional Section, University of Miami/Jackson Memorial Medical Center
Jackeline Gomez-Jorge, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Radiology, American Heart Association, and American Medical Association
Disclosure: Nothing to disclose.

Medical Editor

Glenn Krinsky, MD, Chief of Abdominal Imaging Section, Associate Professor, Department of Radiology, New York University School of Medicine
Glenn Krinsky, MD is a member of the following medical societies: Alpha Omega Alpha and Radiological Society of North America
Disclosure: Nothing to disclose.

Pharmacy Editor

Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand
Disclosure: Nothing to disclose.

Managing Editor

John D Newell, Jr, MD, FACR, FCCP, FASER, Co-Director of Thoracic Imaging, UCDHSC; Director of Lung Imaging Center, Professor of Radiology and Professor of Medicine, Department of Radiology, University of Colorado Health Sciences Center, National Jewish Medical and Research Center; Univ. Colorado Hospital
John D Newell, Jr, MD, FACR, FCCP, FASER is a member of the following medical societies: American College of Chest Physicians, American College of Radiology, American Roentgen Ray Society, American Thoracic Society, Association of University Radiologists, Radiological Society of North America, and Society of Thoracic Radiology
Disclosure: Siemens Medical Grant/research funds Consulting; Forevision Technologies Ownership interest Consulting; Vida Corporation Ownership interest Board membership; TeraRecon Grant/research funds Consulting; eMedicine Honoraria Consulting

CME Editor

Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute
Robert M Krasny, MD is a member of the following medical societies: American Roentgen Ray Society and Radiological Society of North America
Disclosure: Nothing to disclose.

Chief Editor

Kyung J Cho, MD, FACR, William Martel Professor of Radiology, Interventional Radiology Fellowship Director, University of Michigan Health System
Kyung J Cho, MD, FACR is a member of the following medical societies: American College of Radiology, American Heart Association, American Medical Association, American Roentgen Ray Society, Association of University Radiologists, and Radiological Society of North America
Disclosure: Nothing to disclose.

 
 
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