Percutaneous Balloon Mitral Valvotomy
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Direct answer
Percutaneous balloon mitral valvotomy is a catheter-based procedure that opens fused commissures in rheumatic mitral stenosis, using a balloon passed across the interatrial septum. It is preferred over surgery in symptomatic patients with favourable valve anatomy, defined by a Wilkins echo score of 8 or less. Left atrial or appendage thrombus, significant mitral regurgitation and unfavourable calcification exclude the procedure.
What you must remember
- Indication: symptomatic rheumatic mitral stenosis with a valve area of 1.5 cm² or less.
- Wilkins score: leaflet mobility, leaflet thickening, subvalvular thickening and calcification are each scored from 1 to 4, and a total of 8 or less is favourable.
- Left atrial thrombus: an absolute contraindication, and appendage clot is best excluded by transoesophageal echo.
- Mitral regurgitation: moderate or severe regurgitation is a contraindication, because valvotomy can worsen it.
- Access route: transseptal puncture from the femoral vein, usually guided by fluoroscopy and echo, with a single-balloon device commonly used.
- Complications: tamponade, systemic embolism, mitral regurgitation and restenosis are the main hazards, and an iatrogenic atrial septal defect remains after transseptal access.
- Alternative: surgical commissurotomy or valve replacement is used when valve anatomy is unsuitable.
A stepwise selection before the balloon
Outcome depends more on selection than on technique, so the work-up follows a fixed sequence before the procedure. Each step either confirms suitability or directs the patient to surgery.
- Confirm severity: Transthoracic echo shows a valve area of 1.5 cm² or less, measured by planimetry or pressure half-time, in a patient with breathlessness or exercise limitation.
- Score the valve: The Wilkins score adds four feature scores; 8 or less predicts a good result, while higher scores predict poor outcomes and favour surgery.
- Exclude thrombus: Transoesophageal echo looks for left atrial and appendage thrombus, because clot is an absolute contraindication to balloon dilatation.
- Grade regurgitation: Significant mitral regurgitation is excluded, since the valve is widened and regurgitation may worsen.
- Review the leaflets: Heavy calcification and subvalvular fusion are assessed, because they reduce the chance of an adequate opening.
- Perform and reassess: Transseptal balloon dilatation is carried out, and the valve area, mean gradient and any atrial septal shunt are reassessed by echo afterwards.
Where the procedure is wrongly chosen
Errors usually come from accepting a transthoracic finding without checking for the exclusion criteria.
- Trap: proceeding when a left atrial clot was seen only on transthoracic echo Correct: left atrial and appendage clot is best excluded by transoesophageal echo, and its presence rules out the procedure.
- Trap: offering balloon valvotomy despite significant mitral regurgitation Correct: the balloon widens the valve, so existing significant regurgitation can be aggravated, which makes surgery the safer choice.
- Trap: expecting a good result from a Wilkins score of 10 Correct: a score above 8 predicts a poor result and restenosis, so surgical commissurotomy or replacement is preferred.
Frequently asked questions
Which Wilkins echo score predicts a good outcome after balloon valvotomy?
A Wilkins echo score of 8 or less predicts a good outcome after percutaneous balloon mitral valvotomy. Higher scores indicate heavy leaflet and subvalvular change, which makes an adequate result less likely and favours surgical commissurotomy or valve replacement.
Which contraindications must be excluded before percutaneous balloon mitral valvotomy?
Left atrial or appendage thrombus, significant mitral regurgitation and unfavourable valve morphology must all be excluded before balloon valvotomy. Transoesophageal echo is the usual test for left atrial clot, because transthoracic imaging can miss appendage thrombus.
What complications can follow percutaneous balloon mitral valvotomy?
Complications of percutaneous balloon mitral valvotomy include cardiac tamponade, systemic embolism, new or worsened mitral regurgitation and restenosis. An iatrogenic atrial septal defect is also left after transseptal access, and it is usually monitored on echo.
What is the alternative when mitral valve anatomy is unsuitable?
Surgical commissurotomy or mitral valve replacement is the alternative when valve anatomy is unsuitable for balloon valvotomy. The Wilkins score guides this choice, because a higher score predicts a poorer result from the balloon.