Balloon Mitral Valvotomy for Mitral Stenosis
Balloon mitral valvotomy (BMV) is the first-line treatment for symptomatic patients with moderate to severe mitral stenosis who have favorable valve morphology, and is equally indicated for asymptomatic patients with pulmonary hypertension. 1, 2
Class I Indications (Definitive Recommendations)
BMV is definitively indicated in the following scenarios:
Symptomatic patients (NYHA class II-IV) with moderate to severe mitral stenosis (mitral valve area ≤1.5 cm²) who have favorable valve morphology, without left atrial thrombus or moderate-to-severe mitral regurgitation 1, 2
Asymptomatic patients with moderate to severe mitral stenosis and favorable valve morphology who have pulmonary hypertension (pulmonary artery systolic pressure >50 mm Hg at rest or >60 mm Hg with exercise), in the absence of left atrial thrombus or moderate-to-severe mitral regurgitation 1, 2
Defining Favorable Valve Morphology
The Wilkins echocardiographic score determines suitability for BMV, assessing four parameters: leaflet mobility, subvalvular thickening, leaflet thickening, and calcification (each graded 1-4). 1
Favorable anatomy includes:
- Commissural fusion with relatively pliable leaflets
- Balanced chordal attachments
- Minimal calcification
- Typically a Wilkins score ≤8 2
Patients with pliable, noncalcified valves and minimal subvalvular fusion achieve the best immediate and long-term results. 1
Class IIa Indication (Reasonable Option)
BMV is reasonable for patients with moderate to severe mitral stenosis who have a nonpliable calcified valve and are in NYHA functional class III-IV, when they are either not surgical candidates or at high surgical risk. 1
Class IIb Indications (May Be Considered)
BMV may be considered in these specific scenarios:
Asymptomatic patients with moderate to severe mitral stenosis and favorable valve morphology who develop new-onset atrial fibrillation, without left atrial thrombus or moderate-to-severe mitral regurgitation 1
Symptomatic patients with mitral valve area >1.5 cm² if there is evidence of hemodynamically significant stenosis based on pulmonary artery systolic pressure >60 mm Hg, pulmonary artery wedge pressure ≥25 mm Hg, or mean mitral valve gradient >15 mm Hg during exercise 1
Absolute Contraindications
BMV must not be performed in:
- Patients with moderate to severe mitral regurgitation at baseline 1, 2
- Presence of left atrial thrombus (must be excluded by transesophageal echocardiography) 1, 2
- Patients with mild mitral stenosis (mitral valve area >1.5 cm²) 1
Pre-Procedure Evaluation Algorithm
The ACC/AHA recommends this stepwise approach: 2
- Confirm rheumatic etiology through clinical history and echocardiographic findings
- Assess severity using transthoracic echocardiography (mitral valve area, mean gradient, pulmonary artery pressure) 1
- Evaluate symptoms and functional class
- Perform transesophageal echocardiography to exclude left atrial thrombus and assess mitral regurgitation severity 1, 2
- Calculate Wilkins score to determine valve morphology favorability 1, 2
- Exclude moderate-to-severe mitral regurgitation 2
- Proceed with BMV if all criteria are met
Special Populations and Outcomes
Severe Pulmonary Hypertension
Patients with severe pulmonary hypertension (pulmonary artery systolic pressure >60 mm Hg) can safely undergo BMV, though there is controversy regarding whether those with very severe pulmonary hypertension (>60-80 mm Hg) should undergo BMV versus mitral valve replacement. 1 Research demonstrates that pulmonary artery systolic pressure decreases significantly from 79±14 to 36.7±7.53 mm Hg at 12 months post-BMV in patients with severe pulmonary hypertension. 3 However, long-term event-free survival is slightly inferior compared to patients without severe pulmonary hypertension (77±6% at 10 years versus 89±1%). 3
Key predictors for normalization of pulmonary vascular resistance include: younger age, sinus rhythm (versus atrial fibrillation), lower baseline pulmonary artery pressure, and lower echocardiographic score. 4 Approximately 43% of patients may have persistently abnormal pulmonary vascular resistance despite successful BMV. 4
Asymptomatic or Minimally Symptomatic Patients
Research supports BMV in asymptomatic or minimally symptomatic patients (NYHA class I-II) with severe mitral stenosis and favorable valve morphology, showing superior long-term outcomes compared to symptomatic patients. 5 Freedom from restenosis at 10 years is 77±9% in minimally symptomatic patients versus 62±3% in severely symptomatic patients. 5
Moderate Mitral Regurgitation
While moderate-to-severe mitral regurgitation is listed as a contraindication in guidelines 1, one prospective study suggests BMV may be performed in patients with moderate mitral regurgitation with acceptable safety, though the risk of developing severe mitral regurgitation is higher (relative risk 4.87). 6 However, given the Class III guideline recommendation, BMV should not be performed in patients with moderate-to-severe mitral regurgitation in standard practice. 1, 2
Common Pitfalls and Caveats
Always perform transesophageal echocardiography before BMV to exclude left atrial thrombus, even if transthoracic echocardiography appears adequate 1, 2
Do not rely solely on mitral valve area for severity assessment; integrate mean gradient, pulmonary artery wedge pressure, and pulmonary artery pressure 1
Doppler half-time method may be inaccurate in patients with abnormal left atrial or left ventricular compliance, associated aortic regurgitation, or those who have had previous mitral valvotomy 1
Mitral regurgitation develops or worsens in approximately 43% of patients post-BMV, though most cases are mild 7
Older patients and those with atrial fibrillation are less likely to achieve normalization of pulmonary vascular resistance 4