Percutaneous Transvenous Mitral Commissurotomy (PTMC) Procedure: Step-by-Step Guide
PTMC is the recommended first-line therapy for symptomatic patients with severe mitral stenosis (valve area ≤1.5 cm²) who have favorable valve morphology without left atrial thrombus or moderate-to-severe mitral regurgitation. 1
Patient Selection Criteria
Before proceeding with PTMC, proper patient selection is crucial:
Ideal Candidates:
- Symptomatic patients with severe MS (valve area ≤1.5 cm²)
- Favorable valve morphology (Wilkins score ≤8)
- Absence of left atrial thrombus
- No moderate-to-severe mitral regurgitation
- Mobile, relatively thin valve leaflets free of calcium
- Minimal subvalvular disease
Contraindications:
- Left atrial thrombus (absolute contraindication)
- Moderate to severe mitral regurgitation (grade 3-4)
- Severe or bicommissural calcification
- Absence of commissural fusion
- Severe concomitant valvular disease
Pre-Procedural Evaluation
- Comprehensive echocardiography to assess:
- Mitral valve area and gradient
- Valve morphology and mobility
- Commissural fusion pattern
- Subvalvular apparatus
- Pulmonary artery pressure
- Transesophageal echocardiography to rule out left atrial thrombus
- Assessment of mitral regurgitation severity
PTMC Procedure Steps
1. Patient Preparation
- Administer local anesthesia at access site
- Establish venous access via right femoral vein
- Administer prophylactic antibiotics
- Continuous hemodynamic monitoring
2. Right Heart Catheterization
- Insert a pigtail catheter into the right femoral artery for pressure monitoring
- Perform baseline hemodynamic measurements
- Record baseline mitral valve gradient
3. Transseptal Puncture
- Advance a Brockenbrough needle through a transseptal sheath to the fossa ovalis
- Perform transseptal puncture under fluoroscopic guidance
- Confirm left atrial position by pressure measurement and contrast injection
- Administer heparin after successful left atrial entry
4. Left Atrial Access and Measurements
- Advance the transseptal sheath into the left atrium
- Measure left atrial pressure
- Perform left atrial angiography if needed
5. Balloon Selection and Preparation
- Select appropriate balloon size based on patient's height
- For Inoue balloon technique (most commonly used):
- Prepare the balloon catheter according to manufacturer's instructions
- Test balloon inflation outside the body
- Deflate completely before insertion
6. Crossing the Mitral Valve
- Advance a guidewire from the left atrium into the left ventricle
- In difficult cases with critical stenosis, use an AR-1 diagnostic catheter to facilitate left ventricular entry 2
- For very difficult cases, exchange for a stiffer guidewire with small pre-formed loops at the tip
7. Balloon Positioning and Inflation
- Track the balloon catheter over the guidewire into the left ventricle
- Position the balloon across the mitral valve
- Partially inflate the distal portion of the balloon in the left ventricle
- Pull back until resistance is felt at the mitral valve
- Complete balloon inflation to dilate the valve commissures
- For Inoue technique, perform stepwise inflations at increasing balloon diameters
8. Assessment and Repeat Inflations
- Measure transmitral gradient after each inflation
- Assess for mitral regurgitation by left ventriculography or echocardiography
- Continue with incremental balloon inflations until:
- Adequate reduction in transmitral gradient is achieved
- Mitral valve area increases to >1.5 cm²
- Significant mitral regurgitation develops
- Both commissures are split
9. Final Hemodynamic Assessment
- Measure post-procedure mitral valve gradient
- Calculate final mitral valve area
- Assess for complications:
- Mitral regurgitation (most common complication, occurs in ~8.4% of cases) 3
- Left-to-right atrial shunt
- Cardiac tamponade
- Systemic embolism
10. Removal and Closure
- Remove all catheters and sheaths
- Achieve hemostasis at access sites
- Apply pressure dressing
Post-Procedure Management
- Monitor for complications for at least 24 hours
- Perform echocardiography within 24 hours to assess:
- Final mitral valve area
- Presence and severity of mitral regurgitation
- Left-to-right shunting across the atrial septum
- Resume anticoagulation if indicated
Potential Complications and Management
- Severe mitral regurgitation (3.3%): May require urgent mitral valve replacement if caused by leaflet rupture 3
- Cardiac tamponade: Immediate pericardiocentesis
- Systemic embolism: Urgent neurological evaluation and appropriate management
- Atrial septal defect: Usually small and clinically insignificant; monitor for shunt
Procedural Success Indicators
- Increase in mitral valve area to >1.5 cm²
- Reduction in mean transmitral gradient
- Decrease in left atrial pressure
- Improvement in pulmonary artery pressure
- No significant increase in mitral regurgitation
Special Considerations
- In patients with left atrial appendage thrombus, PTMC may be considered after 2-3 months of adequate anticoagulation if repeat TEE shows thrombus resolution 4
- The procedure should only be performed by experienced operators with immediate surgical backup available 1
- Technical success rates exceed 90% in optimal candidates with complication rates below 3% 4
PTMC provides excellent immediate and long-term outcomes in properly selected patients, with sustained improvement in 80-90% of patients over 3-7 years 4, 5.