Clinical Concerns with Myxomatous Mitral Valve Disease
The primary clinical concerns with myxomatous degeneration of the mitral valve are progressive mitral regurgitation leading to left ventricular dysfunction, infective endocarditis, arrhythmias (particularly atrial fibrillation), sudden cardiac death, and thromboembolic events including stroke 1.
Major Complications
Progressive Mitral Regurgitation and Cardiac Dysfunction
The fundamental problem is that myxomatous degeneration causes loss of collagen from the valve leaflets with accumulation of glycosaminoglycans, leading to structural failure 1. This creates a spectrum of disease from focal prolapse (fibroelastic deficiency) to diffuse myxomatous degeneration (Barlow's syndrome) 2. The critical concern is that patients can experience acute clinical deterioration superimposed on chronic valve dysfunction, and once severe left ventricular impairment occurs, it may be irreversible 3.
The 2020 ACC guidelines emphasize that myxomatous disease represents varying degrees of pathoanatomic complexity 2. In diffuse myxomatous degeneration specifically, there is:
- Abnormal annular dynamics with poor contraction in early systole and abnormal enlargement in late systole
- Profoundly abnormal annular degeneration compared to focal disease
- Progressive increase in prolapse height and volume throughout systole 4
Life-Threatening Arrhythmias
Arrhythmias are a major concern, with 50% of elderly patients with myxomatous valves having significant documented arrhythmias requiring anti-arrhythmic therapy 5. This includes both atrial fibrillation and ventricular arrhythmias that can lead to sudden cardiac death 1.
Infectious and Thromboembolic Complications
Myxomatous valves are susceptible to:
- Infective endocarditis - the abnormal valve tissue provides a nidus for bacterial colonization 1
- Nonbacterial thrombotic endocarditis with systemic embolization - thrombi can form on the diseased valve and embolize to the brain, heart, and kidneys 6
- Stroke - through either embolic mechanisms or associated arrhythmias 1
Multi-Valve Involvement
A critical pitfall is missing associated valvular disease: 79% of patients with myxomatous mitral valves have concurrent myxomatous degeneration of the aortic valve 5. This can lead to combined mitral and aortic regurgitation requiring more complex surgical planning 7.
Timing of Intervention
The 2022 European Heart Journal guidelines highlight that the optimal timing of intervention remains controversial, particularly in asymptomatic patients without hemodynamic impairment 8. However, the evidence from surgical series demonstrates that postoperative mortality is directly related to preoperative functional disability and hemodynamic evidence of impaired left ventricular function 3.
Adverse prognostic factors requiring earlier consideration of intervention include:
- Age >50 years
- NYHA functional class IV symptoms
- Left ventricular end-diastolic pressure >12 mmHg
- Mean pulmonary arterial wedge pressure >16 mmHg 3
Surgical Complexity Considerations
The pathoanatomy determines repair feasibility 2. Focal posterior leaflet prolapse is straightforward to repair, but diffuse myxomatous degeneration with excess redundant tissue (Barlow's syndrome) requires more complex techniques including extensive posterior leaflet resection and remodeling, and carries risk of systolic anterior motion post-repair 2.