What are the primary causes of aortic dissection?

Causes of Aortic Dissection

Hypertension is the single most important modifiable risk factor for aortic dissection, present in 85% of patients with ruptured aneurysms and serving as the primary driver of aortic wall stress that leads to dissection. 1

Primary Risk Factors

Hypertension and Atherosclerotic Disease

• Hypertension is the dominant risk factor, found in 85% of patients with ruptured aneurysms and 52% of those with non-ruptured aneurysms 1
• Chronic hypertension causes medial degeneration, smooth muscle cell necrosis, and fibrotic changes in elastic structures, increasing vessel stiffness and vulnerability to shear stress 1
• Smoking and hypercholesterolemia are additional atherosclerotic risk factors that increase aortic aneurysm and dissection incidence 1
• Atherosclerotic changes compromise nutrient supply to the media through intimal thickening and adventitial fibrosis, resulting in medial thinning and increased rupture risk 1

Genetic and Connective Tissue Disorders

• Marfan syndrome and mutations in TGFBR1/TGFBR2 genes predispose to dissection at smaller aortic diameters (≤5.0 cm), with surgical intervention recommended at diameters as small as 4.0 cm 1
• Mutations in smooth muscle contractile proteins (beta-myosin heavy chain, alpha-actin) impair smooth muscle cell function and compromise aortic structural integrity 1
• Loeys-Dietz syndrome and Ehlers-Danlos syndrome increase dissection risk at younger ages 2
• More than half of patients presenting with dissection have aortic diameters <5.5 cm, and dissection can occur even with normal aortic diameter 1

Traumatic Causes

Blunt Trauma

• High-speed accidents account for 15-20% of aortic trauma deaths, with 95% of injuries occurring at the aortic isthmus (site of greatest stress) and only 5% at the ascending aorta 1
• Aortic rupture after blunt chest trauma is frequently associated with myocardial contusion, leading to cardiac failure, myocardial infarction, and tamponade 1
• Chronic traumatic aneurysms tend to become symptomatic or rupture within 5 years 1

Iatrogenic Causes

• Cardiac catheterization (diagnostic or interventional procedures) can cause aortic dissection 1
• Prior aortic valve replacement is associated with subsequent dissection risk, with variable intervals between valve replacement and dissection 1
• The mechanism involves jet lesions producing post-stenotic ascending aortic dilatation similar to aortic stenosis and regurgitation 1
• Resuscitation procedures can lead to aneurysm formation and aortic rupture 1

Inflammatory and Infectious Causes

Vasculitis and Autoimmune Disease

• Takayasu arteritis causes inflammatory infiltrate, smooth muscle and fibroblast necrosis, and fibrosis within the aortic wall 1
• Giant cell arteritis (temporal arteritis and disseminated forms) affects large and medium-sized vessels 1
• Behçet's disease and rheumatoid arthritis-associated aortitis can lead to aortic wall weakening 1
• Autoimmune diseases severely affect the vasa vasorum, decreasing blood supply to the media 1

Infectious Aortitis

• Syphilitic aortitis (luetic aortitis) is the principal cardiovascular manifestation of syphilis, found mainly in the ascending aorta but can involve distal segments 1
• Suppurative bacterial or fungal aortitis is rare but causes focal vessel wall destruction with subsequent aneurysm formation and/or rupture 1

Toxic and Drug-Related Causes

• Cocaine and amphetamine use are associated with aortic aneurysm formation and dissection in humans 1
• These represent newly detected etiologies with direct toxic effects on the aortic wall 1

Structural Abnormalities

• Bicuspid aortic valve increases dissection risk at younger ages 2
• Coarctation of the aorta predisposes to dissection both above and below the coarctation site, typically manifesting in the third decade of life or later in untreated cases 3
• Aortic valve disease (stenosis and regurgitation) creates abnormal hemodynamic stress patterns 1

Demographic and Clinical Risk Factors

• Advanced age (65-75 years) carries the highest incidence at 35 cases per 100,000 people per year 4
• Male gender confers greater population attributable risk 5, 2
• Dyslipidemia, though 60% of patients have cholesterol levels <240 mg/dL 1

Common Clinical Pitfall

The mechanism of spontaneous dissection remains incompletely understood—whether an intimal tear precedes dissecting hematoma or intramural hemorrhage from vasa vasorum ruptures into the lumen is still debated, with approximately 4-10% of dissections showing no identifiable intimal tear 1