Should a patient with mitral valve prolapse (MVP) and elevated Antistreptolysin O (ASO) titer be treated for rheumatic heart disease?

Management of Elevated ASO in Patients with Mitral Valve Prolapse

Patients with mitral valve prolapse (MVP) and elevated antistreptolysin O (ASO) titers should not be treated for rheumatic heart disease unless there is clear evidence of rheumatic involvement of the mitral valve. An elevated ASO titer alone is insufficient to diagnose rheumatic heart disease in the presence of MVP.

Distinguishing MVP from Rheumatic Heart Disease

Diagnostic Considerations

• MVP is a common congenital form of valve disease characterized by:

  • Midsystolic click(s) on auscultation
  • Valve prolapse ≥2 mm above mitral annulus in long-axis parasternal view
  • Leaflet thickness ≥5 mm
  • Mitral regurgitation typically presenting as high-velocity eccentric jet in late systole 1

• Rheumatic heart disease has distinct echocardiographic features:

  • Commissural fusion
  • Leaflet thickening at the edges
  • Restricted leaflet mobility
  • Often associated with mitral stenosis (though not always)

Interpreting Elevated ASO Titers

• ASO titers indicate recent streptococcal infection but do not necessarily indicate rheumatic heart disease
• Research has shown that the persistence of elevated anti-streptococcal group A carbohydrate antibodies is specific to patients with rheumatic mitral valve disease and not to those with MVP 2
• The frequency of elevated ASO titers is not significantly different between MVP patients and normal individuals 2

Management Algorithm

1. Confirm MVP diagnosis with two-dimensional and Doppler echocardiography 3, 1

2. Evaluate for rheumatic features:

   • Look for echocardiographic evidence of rheumatic involvement
   • Check for history of rheumatic fever with Jones criteria
   • Assess for mitral stenosis (uncommon in pure MVP)

3. Decision pathway:

   • If clear evidence of rheumatic heart disease exists:

     • For patients with rheumatic mitral valve disease, long-term warfarin therapy is reasonable with a target INR of 2.5 (range 2.0-3.0) 3

   • If only MVP features are present (even with elevated ASO):

     • Reassurance about benign prognosis 3, 1
     • No specific treatment for elevated ASO titer
     • For MVP patients with history of stroke or TIAs, long-term antiplatelet therapy is reasonable 3
     • For MVP patients with atrial fibrillation, warfarin therapy is recommended for patients >65 years or those with hypertension, MR murmur, or heart failure 3

Important Clinical Considerations

• MVP and rheumatic heart disease can coexist. Some studies suggest that postinflammatory changes from rheumatic fever may contribute to MVP in certain patients 4

• The American College of Cardiology/American Heart Association guidelines do not recommend treating MVP patients for rheumatic heart disease based solely on elevated ASO titers 3

• While 80% of patients with a history of rheumatic fever and an apical systolic murmur may have MVP on echocardiography 4, this does not mean that all MVP is rheumatic in origin

Common Pitfalls to Avoid

1. Overdiagnosis of rheumatic heart disease based solely on elevated ASO titers without other supporting evidence

2. Unnecessary anticoagulation in MVP patients without appropriate indications, exposing them to bleeding risks

3. Missing true rheumatic involvement by assuming all valve abnormalities are due to MVP

4. Failure to provide appropriate prophylaxis - patients with MVP and regurgitation should receive endocarditis prophylaxis during dental procedures 5

By carefully distinguishing between MVP and rheumatic heart disease through comprehensive echocardiographic assessment, clinicians can avoid inappropriate treatment while ensuring proper management of each condition according to established guidelines.