Mitral Valve Operations

Surgery is the definitive management for both mitral stenosis and mitral regurgitation. The more severe the stenosis or regurgitation, the greater the benefit of surgical intervention. However medical management is important in the treatment of co-existent ventricular failure or atrial fibrillation, the prevention of endocarditis with antibiotics and anticoagulation where indicated.

Those patients who are not currently considered to warrant surgical intervention because of the mild degree of stenosis or regurgitation should be reviewed at regular intervals with repeat echocardiography to re-evaluate both the degree of stenosis and cardiac function. At this review the overall management plan can be agreed with the patient, and any subsequent need for surgery assessed.

Surgical options for the treatment of mitral stenosis are:¹

• Balloon valvuloplasty: best results are obtained when the valve shows commissural fusion, is pliable, is not heavily calcified, and has little or no disease of the subvalvular apparatus.
  • Most cases are now performed by percutaneous balloon mitral valvotomy.²
  • Suitability is determined by valve morphology and the amount of mitral regurgitation present.¹
  • If the valve is unfavourable for this procedure, open commissurotomy or mitral valve replacement is required.
  • Before balloon valvuloplasty, a transoesophageal echocardiogram is performed to look for the presence of clot in the left atrium or left atrial appendage. If thrombus is present, balloon valvuloplasty is abandoned, and the patient is begun on warfarin therapy for several months. A repeat transoesophageal echocardiogram is then performed and valvuloplasty can be performed if the thrombus has disappeared.¹
  • 65% of patients are free of restenosis 10 years after the procedure.¹
• Open mitral valvotomy
  • With recent emphasis on mitral valve conservation, this procedure is ideal for those patients thought not to be candidates for balloon valvuloplasty because of poor valve morphology.
  • When the valve can be conserved, it avoids the risks of prosthetic valves and also avoids the need for anticoagulation in patients in sinus rhythm.¹
• Valve replacement
  • In cases in which rheumatic involvement of the valve precludes conservation, mitral valve replacement is performed.
  • The operative risk is 3% to 8% in the absence of pulmonary hypertension and other comorbidities.¹

Indications for surgery

• The more advanced the patient's symptoms, the greater the survival advantage of surgical correction compared with medical therapy.¹ Therefore surgery is indicated once more than mild symptoms are present, e.g. dyspnoea despite control of atrial fibrillation
• Pulmonary hypertension (but when pulmonary hypertension has developed, surgical complications and mortality are increased.¹
• Operation is required before atrial fibrillation becomes irreversible.
• Calculated valve area < 1.5 cm sq with signs of critical stenosis.
• Gradient of more than 10 mmHg across valve.

Results

• Closed mitral valvotomy: mortality 3%, risk of perioperative embolism 2%; restenosis 2% per year.
• Open mitral valvotomy: mortality 3%; less risk of embolism; long-term function is better.
• Mitral valve replacement: mortality 7%; risk of embolism and thrombosis 5%.

There are three types of surgical correction for mitral regurgitation:²

• Mitral valve repair
  • Advantages include the lowest operative mortality, preserved postoperative left ventricular function and excellent long-term results (reoperation is required in less than 10% of patients in experienced hands).²
  • Repair avoids the risks of a prosthetic valve, i.e. thromboembolism from mechanical valves and valve deterioration with bio-prosthetic valves.²
• Mitral valve replacement with chordal preservation
  • In most cases when repair is impossible, it is possible to retain at least the posterior leaflet connections. This produces better outcomes than ablation of the entire apparatus.
  • Although this operation is better than a standard valve replacement with destruction of the valve apparatus, both procedures lead to the potential complications of prosthetic valves.²
• Mitral valve replacement with removal of the mitral apparatus
  • Has the highest operative mortality and worst postoperative left ventricular function.²
  • It should therefore be reserved for those patients for whom preservation of existing mitral apparatus is impossible.
  • Destruction of the mitral valve apparatus leads to as much as the 25% reduction in ventricular function.²

Indications for surgery

• Symptoms, especially dyspnoea
• Severe mitral regurgitation confirmed by echocardiography and angiography.²
• Asymptomatic patients with left ventricular dysfunction: surgery is necessary in order to prevent further and irreversible left ventricular failure from developing.
• Severe mitral regurgitation with either atrial fibrillation or pulmonary hypertension needs prompt referral.
• Poor left ventricular function may preclude surgery.
• Although advancing age is not a barrier to surgery for mitral regurgitation, there is an increased risk of surgery in the elderly and this may affect the decision as to whether to operate in some cases.²
• Operative intervention for ischaemic mitral regurgitation has a worse prognosis than non-ischaemic mitral regurgitation.

• Management of mitral valve prolapse may require valve surgery, particularly in those patients who develop a flail mitral leaflet due to rupture of chordae tendineae or their marked elongation.³
• Most such valves can be repaired successfully, especially when the posterior leaflet of the mitral valve is predominantly affected.
• Mitral valve repair for mitral valve prolapse is associated with excellent long-term survival and remains superior to mitral valve replacement beyond 10 years and up to 20 years after surgery.
• Anterior leaflet mitral valve repair is associated with a higher risk for reoperation than posterior leaflet repair.
• Symptoms of heart failure, severity of mitral regurgitation, presence or absence of atrial fibrillation, LV systolic function, LV end-diastolic and end-systolic volumes, and pulmonary artery pressure (rest and exercise) all influence the decision to recommend mitral valve surgery.
• Recommendations for surgery in patients with mitral valve replacement and mitral regurgitation are the same as for other forms of non-ischaemic severe mitral regurgitation.