Can a myxomatous (abnormal, mucous-like) mitral valve cause embolic stroke?

Myxomatous Mitral Valve and Embolic Stroke Risk

Myxomatous mitral valve disease can potentially cause embolic stroke, but the evidence for this association is mixed and the risk appears to be relatively low in the absence of other risk factors. 1

Pathophysiological Mechanism and Risk Assessment

Myxomatous mitral valve disease, commonly manifesting as mitral valve prolapse (MVP), has been studied extensively regarding its relationship to stroke risk:

• Early case series and control studies suggested an association between MVP and stroke 1, 2
• However, later studies including the Framingham Heart Study failed to consistently replicate these results 1
• More recent evidence from Avierinos et al. found that people with MVP had an excess lifetime risk of stroke or TIA (RR 2.2) 1

The potential mechanisms for embolic stroke in myxomatous mitral valve disease include:

1. Formation of thrombi on the abnormal valve surface
2. Dislodgement of valve tissue fragments
3. Platelet-fibrin aggregates forming on the valve surface

Management Approach Based on Clinical Presentation

For Patients WITHOUT Prior Embolic Events:

• For patients with myxomatous mitral valve/MVP who have not experienced systemic embolism, unexplained TIAs, or ischemic stroke:
  • No specific antithrombotic therapy is recommended 1
  • Manage these patients according to standard primary prevention guidelines for vascular events 1

For Patients WITH Prior Embolic Events:

• For patients with myxomatous mitral valve/MVP and a history of ischemic stroke or TIA:
  • Antiplatelet therapy is recommended rather than anticoagulation 1
  • The ACCF/AHA guidelines specifically recommend aspirin therapy for patients with MVP who experience TIAs (Class I; Level of Evidence C) 1
  • Warfarin is only recommended for these patients if they also have mitral regurgitation, AF, or left atrial thrombus (Class I; Level of Evidence C) 1

For Patients with Recurrent Events:

• For patients with recurrent thromboembolic events despite antiplatelet therapy:
  • Consider more intensive evaluation for cardiac sources of embolism 1
  • Warfarin may be considered in these cases, particularly if mitral regurgitation, AF, or left atrial thrombus is present 1

Risk Factors That Increase Stroke Risk in Myxomatous Mitral Valve

Certain factors increase the risk of stroke in patients with myxomatous mitral valve/MVP:

• Older age 1
• Mitral valve thickening 1
• Development of atrial fibrillation 1
• Severe mitral regurgitation 3
• Multiple scallop involvement (as in Barlow's disease) 3

Clinical Pearls and Pitfalls

• Diagnostic pitfall: MVP is often discovered only after a stroke event occurs. In one study, MVP was documented prior to brain illness in only 4 of 24 patients 2
• Management pitfall: Avoid unnecessary anticoagulation in patients with isolated MVP without other risk factors, as the bleeding risk may outweigh the benefit 1
• Monitoring recommendation: Patients with myxomatous mitral valve should be monitored for development of significant mitral regurgitation, which may increase stroke risk 3, 4
• Differential diagnosis: When evaluating stroke in patients with myxomatous mitral valve, consider other potential cardiac sources of embolism, as myxomatous mitral valve may be a coincidental finding rather than the cause 5

Special Considerations

It's important to distinguish myxomatous mitral valve disease from mitral annular calcification (MAC), which is a separate entity with its own stroke risk profile. The Framingham Heart Study found that MAC was associated with a 2.1 times greater risk of stroke, independent of traditional risk factors 1, 6.

For patients with both myxomatous mitral valve disease and autoimmune conditions (such as lymphocytic thyroiditis), closer monitoring may be warranted due to potentially higher risk of complications 4.