What is the incidence of rupture of a dilated aorta in patients with a bicuspid (Bicuspid Aortic Valve, BAV) valve?

Incidence of Aortic Rupture in Bicuspid Aortic Valve Patients with Dilated Aorta

The incidence of aortic rupture or dissection in patients with bicuspid aortic valve (BAV) and dilated aorta is approximately 0.1% per patient-year, with estimated 5-year risks of 0.4%, 1.1%, and 2.9% at aortic diameters of 45mm, 50mm, and 55mm respectively. 1

Epidemiology and Risk Factors

BAV is the most common congenital cardiac abnormality, affecting up to 2% of the general population 2, 3. Patients with BAV frequently develop aortic dilation (aortopathy), which can lead to potentially life-threatening complications:

• BAV patients tend to present with aortic dissection at younger ages than those with tricuspid valves 4
• The risk of dissection increases with:
  • Increasing aortic diameter (HR: 1.20; 95% CI: 1.05 to 1.36) 1
  • Advanced age (HR: 1.06; 95% CI: 1.01 to 1.12) 1
  • Family history of aortic dissection 4
  • Rapid aortic growth rate (≥0.5 cm per year) 4

Natural History of BAV Aortopathy

The natural progression of aortic dilation in BAV patients follows these patterns:

• In healthy BAV subjects: approximately 0.16 mm/year over 6 decades 5
• In older patients after aortic valve replacement: approximately 1.1 ± 0.15 mm/year 5
• Mean rate of diameter progression in BAV patients 4:
  • 0.5 mm per year at the sinuses of Valsalva (95% CI: 0.3 to 0.7)
  • 0.5 mm per year at the sinotubular junction (95% CI: 0.3 to 0.7)
  • 0.9 mm per year at the proximal ascending aorta (95% CI: 0.6 to 1.2)

Risk Stratification

The risk of aortic dissection or rupture can be stratified based on aortic diameter:

• Aortic diameter <45 mm: very low risk (<0.4% over 5 years) 1
• Aortic diameter 45-50 mm: low risk (0.4-1.1% over 5 years) 1
• Aortic diameter 50-55 mm: moderate risk (1.1-2.9% over 5 years) 1
• Aortic diameter >55 mm: high risk (>2.9% over 5 years) 1

Additional risk factors that warrant closer monitoring:

• Family history of aortic dissection 4
• Rapid growth rate (≥0.5 cm per year) 4
• Aortic coarctation 4
• Systemic hypertension 4

Management Recommendations

Based on the current guidelines, the following management approach is recommended:

1. Surgical Intervention:

   • Operative intervention is indicated when aortic diameter is >5.5 cm 4
   • Operative intervention is reasonable when aortic diameter is >5.0 cm with risk factors (family history of dissection or growth rate ≥0.5 cm/year) 4
   • Replacement of the ascending aorta is reasonable in BAV patients undergoing aortic valve replacement when the diameter is >4.5 cm 4

2. Surveillance:

   • Annual imaging for patients with significant aortic dilation (>4.5 cm) 4
   • More frequent imaging (at least every 6 months) for patients with rapid growth rates 4
   • Less frequent imaging for patients with mild dilation showing no change on sequential studies 4

3. Imaging Modalities:

   • TTE is indicated for initial evaluation and routine follow-up 4
   • CMR or MSCT is recommended for evaluation of the aorta, particularly in patients with enlarged aorta detected by echocardiography 4

Clinical Pitfalls and Caveats

1. Phenotypic Variation:

   • BAV with fusion of right and non-coronary cusps has a higher prevalence of aortic dilation (68%) compared to fusion of right and left coronary cusps (40%) 4
   • Different BAV phenotypes may require different management approaches 3

2. Body Size Considerations:

   • In short-statured patients (e.g., Turner syndrome with BAV), absolute aortic measurements may not accurately predict dissection risk 4
   • Consider aortic diameter index (≥2.5 cm/m²) or aortic root cross-sectional area-to-height ratio (≥10 cm²/m) in these patients 4

3. Surgical Expertise:

   • Outcomes are better when surgery is performed by experienced surgeons in centers with established expertise in aortic procedures 4
   • The risk of progressive aortic dilatation and dissection after aortic valve replacement in BAV patients remains controversial 4

4. Medical Therapy:

   • No proven drug therapies have been shown to reduce the rate of aortic dilation progression in BAV patients 4
   • Control of hypertension is warranted, but beta-blockers and ARBs have not shown definitive benefits in clinical studies 4

The management of BAV aortopathy requires careful consideration of multiple factors including aortic dimensions, valve function, growth rate, family history, and surgical expertise to optimize outcomes and minimize the risk of life-threatening complications.