How is acquired von Willebrand syndrome (AVWS) managed in patients with aortic stenosis?

Management of Acquired von Willebrand Syndrome in Aortic Stenosis

Overview

Aortic valve replacement is the definitive treatment for acquired von Willebrand syndrome (AVWS) in patients with severe aortic stenosis, as it directly addresses the underlying pathophysiological mechanism and resolves the bleeding tendency. 1

Pathophysiology

Severe aortic stenosis creates high shear stress across the stenotic valve, leading to:

• Mechanical disruption of high-molecular-weight (HMW) von Willebrand factor multimers
• Development of type 2A acquired von Willebrand syndrome
• Impaired primary hemostasis and platelet function under high shear stress

This condition is present in 67-92% of patients with severe aortic stenosis and correlates significantly with the severity of valve stenosis 2.

Clinical Manifestations

AVWS in aortic stenosis typically presents as:

• GI bleeding (often from arteriovenous malformations)
• Epistaxis
• Ecchymoses
• Mucosal bleeding

Clinical bleeding occurs in approximately 20% of patients with severe aortic stenosis 3.

Diagnostic Evaluation

Laboratory Testing

• Complete blood count and iron studies
• VWF antigen level and activity
• VWF collagen binding activity (VWF:CB)
• VWF:CB/VWF:Ag ratio (pathological in most patients with AVWS) 4
• VWF multimer analysis (gold standard) to detect loss of HMW multimers

Cardiac Evaluation

• Echocardiography to confirm and quantify AS severity
• Measurement of peak and mean gradients across the aortic valve
• Calculation of aortic valve area

GI Evaluation

• Endoscopy to identify potential bleeding sources, particularly arteriovenous malformations

Management Algorithm

1. Acute Bleeding Management

• Endoscopic intervention for active GI bleeding
• Temporary hemostatic support:
  • Desmopressin (DDAVP) - may temporarily increase VWF levels
  • VWF-containing concentrates
  • Platelet transfusions for severe bleeding

2. Definitive Treatment

• Aortic valve replacement - this is the only curative treatment 5
  • Rapidly restores normal VWF structure and function
  • Normalizes VWF multimers within 24 hours after surgery 2
  • Provides permanent correction in the absence of patient-prosthesis mismatch

3. Post-Procedural Monitoring

• Monitor for resolution of bleeding symptoms
• Follow hemoglobin levels
• Repeat VWF studies at 1 week and 6 months post-procedure
• Ensure effective orifice area of prosthesis is adequate (>0.8 cm²/m² of body surface area) to prevent recurrence 2

Special Considerations

Patient Selection for Valve Replacement

• Symptomatic severe AS patients should undergo valve replacement regardless of bleeding status 3
• In asymptomatic patients with severe AS and significant bleeding due to AVWS, valve replacement should be considered 3

Potential Pitfalls

1. Patient-prosthesis mismatch - can lead to recurrence of AVWS if effective orifice area is <0.8 cm²/m² 2
2. Underlying inherited VWD - Some patients with severe bleeding in AS may have undiagnosed inherited von Willebrand disease that becomes clinically apparent due to the additional acquired defect 6
3. Incomplete evaluation - Failure to recognize AVWS as the cause of bleeding can lead to unnecessary GI procedures without addressing the underlying cause

Long-term Outcomes

Studies show that VWF multimers remain normalized more than 6 months after valve replacement, indicating permanent resolution of AVWS in most patients 4.

Conclusion

AVWS is common in patients with severe aortic stenosis and directly correlates with stenosis severity. Aortic valve replacement provides rapid and usually permanent correction of the hemostatic defect and should be considered the definitive treatment for bleeding related to AVWS in aortic stenosis.