Aortic Dissection

Key points

• Aortic dissection is the entry of blood into intima-media space of thoracic aorta, with an intimal tear resulting in creation of a false lumen, which then extends in either direction
• Sixty-five percent of dissections occur in ascending aorta
• Presents as sudden severe chest pain and varying degrees of hemodynamic instability depending on the extent of the dissection. Other classic features include pulse deficits, asymmetric blood pressures, and an evolving aortic regurgitation murmur
• Aortic dissection is a medical emergency. Arrange immediate transfer to the hospital if aortic dissection is suspected
• Imaging studies, most commonly transesophageal echocardiography, computed tomography (CT) scan with contrast or magnetic resonance imaging (MRI), should clinch the diagnosis
• Emergency and medical (conservative treatment) with β-blockers, calcium-channel blockers, and nitroprusside to decrease cardiac contractility and lower blood pressure
• Selected patients require emergency open surgical intervention; less urgent and invasive surgical procedures include endovascular grafting

Background

Description

• Entry of blood into intima-media space of thoracic aorta, with an intimal tear resulting in creation of a false lumen
• False lumen may extend in an anterograde or retrograde direction
• Location of dissection: ascending aorta 65%, descending aorta 20%, aortic arch 10%, and abdominal aorta 5%
• Usual presentation is with sudden, severe, central, tearing chest pain
• Cardinal signs are pulse deficits, asymmetric blood pressures, and an evolving aortic regurgitation murmur
• Range of symptoms and signs depends on location of dissection, degree of extension, presence of vascular branch (and end-organ) involvement, and presence of rupture
• May present as acute myocardial infarction, acute aortic regurgitation, cardiac tamponade, cardiovascular collapse, limb ischemia, syncope, stroke, or spinal cord syndrome
• Medical emergency that requires urgent assessment in the hospital
• Measures to reduce blood pressure important before surgery or when patient unsuitable for surgery
• Often requires emergent surgical repair
• DeBakey Classification:
  • Type I: Beginning in ascending with involvement of arch aorta
  • Type II: Confined to ascending aorta only
  • Type III: Beginning in descending aorta
• Stanford Classification:
  • Type A: Involvement of ascending aorta
  • Type B: No involvement of ascending aorta

Epidemiology

Incidence and prevalence

Incidence:

• 0.05 to 0.10 out of 1,000 per year
• 2,000 new cases per year in U.S.
• 1 in 350 autopsies
• 6% to 9% have Marfan syndrome

Prevalence:

• Since mortality is so high in untreated patients, no prevalence data are available

Demographics

Age:

• Peak incidence 60 to 70 years
• 30 to 40 years in Marfan syndrome

Gender:

• Males are affected twice as commonly as females

Genetics:

• Marfan syndrome and Ehlers-Danlos syndrome predispose to aortic dissection. Defect is in the fibrillin-1 gene

Causes and risk factors

Causes

Common causes:

• Hypertension (80%)
• Bicuspid aortic valve, congenital (7%-14%)
• Connective tissue diseases: Marfan syndrome (6%-9%), Ehlers-Danlos syndrome

Rare causes:

• Rare congenital abnormalities: unicuspid aortic valve, coarctation of the aorta
• Pregnancy, especially in the third trimester (in patients with a connective tissue disease)
• Giant cell arteritis (cranial arteritis) and other inflammatory vasculitides
• Cocaine use, especially in males
• Chest trauma, such as in motor vehicle collision unrelated to use of shoulder harness or successful airbag deployment
• Rarer causes of hypertension, such as systemic lupus erythematosus and other connective tissue diseases, polycystic kidneys, and hypertension associated with Cushing syndrome
• Weight lifting
• Iatrogenic during percutaneous coronary angiography or intervention (0.02% of coronary procedures; 27% of iatrogenic cases); post aortic cross-clamp or arteriotomy for graft placement (69% of cases)

Serious causes:

• Marfan syndrome and Ehlers-Danlos syndrome associated with cystic medial necrosis of the aorta which predisposes to dissection

Risk factors

• Aortic surgery (dissection may occur at the site of aortic incisions or cross-clamping)
• Following use of intra-aortic balloon pump
• Following implantation of aortic stent graft

Screening

Not applicable.

Primary prevention

Summary approach

• Control of hypertension is the cornerstone in prevention of aortic dissection
• Attention to other modifiable cardiac risk factors (eg, cholesterol, smoking, obesity) is also recommended

Population at risk

• Hypertension
• Congenital bicuspid aortic valve
• Connective tissue diseases such as Marfan syndrome and Ehlers-Danlos syndrome
• Patients who sustain acute chest trauma, such as during a motor vehicle collision

Preventive measures

Alcohol and drugs:

• Excessive alcohol intake can contribute to hypertension
• Numerous prescription and over-the-counter drugs are associated with hypertension, including oral contraceptives and corticosteroids
• Several drugs of abuse are associated with hypertension, particularly cocaine and amphetamine
• Tobacco use may worsen hypertension

Diet:

• A low-salt diet should be advised to patients who are hypertensive

Physical activity:

• Exercise should be encouraged in hypertensive patients

Other:

• Other measures to reduce cardiovascular risk include weight loss for obesity, smoking cessation, and treatment of underlying hyperlipidemia