Diseases of the Aorta¶

Chapter 291 | Part 6: Disorders of the Cardiovascular System

KEY CLINICAL POINTS¶

Aortic aneurysms are defined as pathologic dilation of the aortic wall, classified as true (all three layers) or false (pseudoaneurysm).
Thoracic aortic aneurysms ≥ 4.5 cm and abdominal aneurysms ≥ 5.5 cm require surgical intervention, with thresholds adjusted for genetic syndromes.
Aortic dissection is classified by Stanford (Type A: ascending aorta; Type B: distal aorta) and DeBakey (I: ascending to descending; II: ascending; III: descending) systems.
Acute aortic syndromes include dissection, intramural hematoma, penetrating ulcer, and rupture, with management guided by imaging and hemodynamic stability.
Infective aortitis (e.g., syphilis, tuberculosis) and vasculitides (e.g., Takayasu, giant cell arteritis) cause aortic inflammation and aneurysm formation.

1. DEFINITION & OVERVIEW¶

The aorta is the primary conduit for systemic blood flow. Aneurysms are pathologic dilations of the aortic wall, while aortic dissection involves intimal tears and false lumen formation. Acute aortic syndromes encompass dissection, intramural hematoma, penetrating ulcer, and rupture.

Table 291-1: Etiology and Associated Factors of Aortic Diseases¶

Disease Type	Etiology	Associated Factors
Aortic Aneurysm	Degenerative/sporadic, heritable, infective, traumatic	Aging, smoking, hypertension, atherosclerosis, genetic syndromes
Aortic Dissection	Intimal tear with media disruption	Hypertension, atherosclerosis, trauma, connective tissue disorders
Aortitis	Inflammatory/immune-mediated	Infectious (syphilis, TB), vasculitides (Takayasu, giant cell arteritis), autoimmune disorders

1.1 Aortic Aneurysm Classification¶

Aneurysms are categorized by morphology (fusiform vs. saccular) and location (thoracic vs. abdominal). Thoracic aneurysms ≥ 4.5 cm and abdominal aneurysms ≥ 5.5 cm require surgical evaluation, with lower thresholds for high-risk patients (e.g., Marfan syndrome).

1.2 Acute Aortic Syndromes¶

Includes aortic dissection, intramural hematoma, penetrating atherosclerotic ulcer, and rupture. These conditions are characterized by sudden onset of severe chest pain, hemodynamic instability, and risk of life-threatening complications.

2. EPIDEMIOLOGY¶

Abdominal aortic aneurysms (AAAs) are more common in males (>65 years) and smokers. Thoracic aneurysms are associated with genetic syndromes (Marfan, Loeys-Dietz). Aortic dissection peaks in 6th-7th decades, with male predominance (2:1 ratio).

2.1 Risk Factors¶

Smoking, hypertension, atherosclerosis, genetic disorders (Marfan, Ehlers-Danlos), connective tissue abnormalities, and inflammatory conditions (vasculitides).

2.2 Demographics¶

AAAs: 1–2% prevalence in men >50 years. Aortic dissection: 2:1 male-to-female ratio, peak incidence 60–70 years. Syphilitic aneurysms: 90% involve ascending aorta.

3. ETIOLOGY & PATHOPHYSIOLOGY¶

Aneurysms result from degradation of elastin/collagen, inflammation, oxidative stress, and biomechanical stress. Genetic mutations (e.g., TGFBR1, COL3A1) contribute to heritable syndromes. Infectious agents (syphilis, TB) and vasculitides (Takayasu) cause inflammatory aortitis.

3.1 Degenerative Aneurysms¶

Primary cause of thoracic aneurysms. Atherosclerosis, hypertension, and smoking accelerate medial degeneration, leading to elastin/collagen loss and wall weakening.

3.2 Heritable Disorders¶

Marfan syndrome (fibrillin-1 deficiency), Loeys-Dietz syndrome (TGFBR1/2 mutations), Ehlers-Danlos syndrome (COL3A1 mutations) cause medial degeneration and rapid aneurysm growth.

3.3 Infectious Causes¶

Syphilis (periaortitis), tuberculosis (granulomatous destruction), and mycotic aneurysms (bacterial/fungal infection at atherosclerotic plaques).

4. CLINICAL FEATURES¶

Symptoms vary by condition: asymptomatic aneurysms, chest/abdominal pain, dysphagia, hoarseness, or acute rupture. Aortic dissection presents with tearing chest pain radiating to back, while acute occlusion causes severe ischemia of lower extremities.

4.1 Aortic Dissection¶

Sudden severe chest pain (tearing), hypotension, pulse deficits, and neurological deficits (e.g., hemiplegia from carotid occlusion).

4.2 Acute Occlusion¶

Severe rest pain, pallor, and absent distal pulses in lower extremities. Often due to embolism from cardiac sources or in situ thrombosis.

4.3 Aortitis¶

Systemic symptoms (fever, weight loss), abdominal pain, and complications like ureteral obstruction (retroperitoneal fibrosis).

5. DIFFERENTIAL DIAGNOSIS¶

Differentiate aortic dissection from myocardial infarction, pulmonary embolism, and acute coronary syndromes. For aneurysms, consider congenital anomalies (e.g., coarctation), mycotic aneurysms, and vasculitides.

5.1 Acute Chest Pain¶

Compare with myocardial infarction (ECG changes, troponin) and pulmonary embolism (D-dimer, CT pulmonary angiogram).

5.2 Abdominal Mass¶

Differentiate from renal cell carcinoma, lymphadenopathy, or other abdominal masses using imaging and lab tests.

6. INVESTIGATIONS & DIAGNOSIS¶

Imaging (CT, MRI, TTE/TEE) and lab tests (D-dimer, troponin) are critical. Aortic dissection is diagnosed with CT/MRI, while aneurysms are assessed by ultrasound, CT, or MRI.

6.1 Diagnostic Imaging¶

CT angiography (gold standard for dissection), MRI for non-contrast evaluation, and TTE/TEE for proximal aortic assessment.

6.2 Laboratory Tests¶

Elevated inflammatory markers (ESR, CRP) in vasculitis; positive serology (RPR, FTA-ABS) for syphilis; blood cultures for mycotic aneurysms.

7. MANAGEMENT & TREATMENT¶

Medical therapy ( β -blockers, ACE inhibitors) for asymptomatic aneurysms; surgical repair (open or endovascular) for symptomatic cases. Acute dissection requires urgent intervention with surgical or endovascular repair.

7.1 Medical Therapy¶

β -blockers (propranolol, metoprolol) to reduce heart rate and blood pressure; ACE inhibitors for hypertension control.

7.2 Surgical Repair¶

Open repair for thoracic aneurysms ≥ 5.0 cm or symptomatic cases; endovascular stent grafting for abdominal aneurysms and certain thoracic cases.

7.3 Acute Dissection¶

Immediate surgical repair for Type A dissections; endovascular repair for Type B if complications (e.g., propagation, rupture) are present.

8. PROGNOSIS & COMPLICATIONS¶

Rupture risk increases with aneurysm size (5-year risk: 1–2% for <5 cm vs. 20–40% for >5 cm). Complications include aortic regurgitation, cardiac tamponade, and life-threatening hemorrhage.

8.1 Rupture Risk¶

Thoracic aneurysms: 2–7% annual risk for >6 cm; abdominal aneurysms: 2–3% for <4.0 cm, 7% for >6 cm.

8.2 Long-Term Outcomes¶

10-year survival ~60% after repair; higher risk in Marfan syndrome and Loeys-Dietz syndrome due to rapid aneurysm growth.

9. SPECIAL CONSIDERATIONS¶

Pregnancy increases dissection risk in the third trimester; trauma patients may present with traumatic aneurysms. Genetic testing is recommended for familial syndromes (e.g., Marfan, Loeys-Dietz).

9.1 Pregnancy¶

Increased risk of aortic dissection in third trimester; avoid NSAIDs and monitor for hypertension.

9.2 Genetic Syndromes¶

Genetic testing for Marfan (FBN1), Loeys-Dietz (TGFBR1/2), and Ehlers-Danlos (COL3A1) syndromes to guide surveillance and treatment.

10. KEY POINTS & CLINICAL PEARLS¶

Aortic aneurysms ≥ 4.5 cm (thoracic) or ≥ 5.5 cm (abdominal) require surgical evaluation. 2. Aortic dissection is a medical emergency with high mortality if untreated. 3. Endovascular repair is preferred for abdominal aneurysms and certain thoracic cases. 4. Genetic testing is critical for hereditary syndromes (e.g., Marfan). 5. Monitor for complications like aortic regurgitation and rupture in chronic cases.