What is the incidence of aortic rupture in patients with a dilated aortic root and a bicuspid (two-cusped) aortic valve?

Incidence of Aortic Rupture in Dilated Aortic Root with Bicuspid Valve

The incidence of aortic dissection in patients with bicuspid aortic valve (BAV) and dilated aortic root is relatively low at approximately 3.1 cases per 10,000 patient-years, but represents an 8.4-fold increased risk compared to the general population 1.

Epidemiology and Risk Assessment

Incidence Data

• In a large retrospective cohort study of 642 BAV patients followed for a mean of 9 years, only 5 dissections occurred (3 ascending and 2 descending) 1
• Another study of 416 BAV patients followed for a mean of 16 years documented only 2 dissections 1
• Despite the low absolute incidence, the relative risk is significantly elevated compared to the general population (HR: 8.4; 95% CI: 2.1 to 33.5; p=0.003) 1

Risk Factors for Aortic Dissection

The risk of aortic dissection increases with:

• Aortic diameter ≥5.5 cm (primary threshold for intervention) 1
• Rapid growth rate of ≥0.5 cm per year 1, 2
• Family history of aortic dissection 1
• Specific BAV morphology (fusion of right and non-coronary cusps carries higher risk than right-left fusion) 1

Aortic Growth Patterns in BAV Patients

BAV patients demonstrate predictable patterns of aortic growth:

• Mean rate of diameter progression: 0.5 mm/year at sinuses of Valsalva (95% CI: 0.3-0.7) 1
• Mean rate of diameter progression: 0.5 mm/year at sinotubular junction (95% CI: 0.3-0.7) 1
• Mean rate of diameter progression: 0.9 mm/year at proximal ascending aorta (95% CI: 0.6-1.2) 1
• Some studies report growth rates up to 2 mm/year in certain patients 1

Surveillance Recommendations

For patients with BAV and aortic dilation:

• Aortic imaging at least annually for patients with significant dilation (>4.5 cm) 1
• More frequent imaging (every 4-12 weeks) during pregnancy 1
• Consider longer intervals between imaging for patients with milder dilation, stable measurements, and negative family history 1
• CT or MRI is indicated when echocardiography cannot fully assess aortic morphology 1

Intervention Thresholds

Current guidelines provide clear thresholds for surgical intervention:

Class I Recommendations (Strong)

• Operative intervention is indicated in asymptomatic BAV patients when aortic root or ascending aortic diameter reaches ≥5.5 cm 1

Class IIa Recommendations (Reasonable)

• Operative intervention is reasonable when aortic diameter is >5.0 cm with additional risk factors:
  • Family history of aortic dissection
  • Growth rate ≥0.5 cm per year 1, 2
• Consider aortic replacement when BAV patients undergo aortic valve replacement and the aortic diameter is >4.5 cm 2

Surgical Considerations

• Valve-sparing root replacement shows good results in specialized centers for BAV patients without severely deformed valves 1
• Supracoronary ascending aorta replacement may be an alternative to full root replacement in selected patients with moderate root dilation 3
• Hemodynamic function and valve stability after repair of BAV are comparable to those seen in tricuspid valves 4

Common Pitfalls in Management

1. Relying solely on absolute diameter without considering patient-specific factors (body size, family history, growth rate)
2. Failing to recognize that BAV patients may present with aortic dissection at younger ages than those with tricuspid valves 2
3. Inadequate imaging of the entire aorta (the ascending aorta beyond the sinuses is often the site of maximal dilation) 1
4. Inconsistent measurements between imaging modalities (CT measurements are generally more accurate than echocardiography) 2

Despite the relatively low absolute incidence of aortic dissection in BAV patients, the significantly elevated relative risk and potentially catastrophic consequences of dissection justify close monitoring and prophylactic intervention at established diameter thresholds.