How is the mitral valve replaced?

How Mitral Valve Replacement is Performed

Mitral valve replacement is performed through a median sternotomy (or minimally invasive approach) using cardiopulmonary bypass, with the surgeon accessing the valve through an aortotomy or left atriotomy, excising the diseased valve, and suturing a mechanical or bioprosthetic valve into the mitral annulus—ideally preserving the subvalvular apparatus (chordae tendineae and papillary muscles) to maintain left ventricular function. 1, 2

Surgical Access and Technique

Standard Approach

• The conventional approach uses a median sternotomy with cardiopulmonary bypass and cardioplegic arrest. 1
• The mitral valve is accessed through either:
  • Left atriotomy (most common for isolated mitral procedures)
  • Trans-septal approach (alternative access route)
  • Aortotomy (when combined with aortic procedures, as described in hypertrophic cardiomyopathy cases) 1

Minimally Invasive Options

• Minimally invasive mitral valve replacement via right minithoracotomy/port access using direct vision, thoracoscopic, or robotic assistance produces similar outcomes to sternotomy when performed by highly experienced surgeons. 1

Critical Technical Principle: Chordal Preservation

When mitral valve replacement is necessary, the procedure should be performed with chordal-sparing techniques to preserve left ventricular function—this is a fundamental principle that distinguishes modern from historical approaches. 1, 3

• Preservation of the subvalvular apparatus (chordae tendineae and papillary muscles) maintains the geometric relationship between the mitral annulus and left ventricle, preventing postoperative ventricular dysfunction. 1
• This applies to both mechanical and bioprosthetic valve replacements 1

Valve Selection: Mechanical vs. Bioprosthetic

Mechanical Valves

• Require lifelong anticoagulation with warfarin but offer superior durability 1, 2
• Preferred in younger patients who can reliably manage anticoagulation 1
• In patients <65 years with functional mitral regurgitation requiring replacement, mechanical valves may be preferable given the need for durability 4

Bioprosthetic Valves

• Avoid long-term anticoagulation requirements but have limited durability (structural valve deterioration over 10-15 years) 1, 2
• In mitral stenosis patients, bioprosthetic valves are associated with significantly higher reoperation rates compared to mechanical valves 5
• Generally preferred in patients >65-70 years or those with contraindications to anticoagulation 1

When Replacement is Indicated vs. Repair

Replacement is Mandatory When:

• Repair has been attempted and failed—a poor repair is worse than replacement 1, 2
• Intrinsic valve pathology precludes durable repair: extensive calcification, rheumatic disease with severe leaflet restriction, or myxomatous degeneration affecting >50% of anterior leaflet 1
• In hypertrophic cardiomyopathy with muscular mid-cavity obstruction from anomalous papillary muscle when extended myectomy is not feasible 1

Critical Caveat:

Mitral valve replacement should NOT be performed for isolated severe primary mitral regurgitation limited to less than one-half of the posterior leaflet unless repair has been attempted and failed—this is a Class III (Harm) recommendation. 1

• For isolated posterior leaflet disease, repair achieves <1% operative mortality, 95% freedom from reoperation, and >80% freedom from recurrent moderate-to-severe MR at 15-20 years—outcomes that replacement cannot match 1, 2

Operative Mortality and Outcomes

Mortality Rates

• Isolated mitral valve replacement carries 2-6% operative mortality in experienced centers, approximately double that of repair (1-3%) 1
• Risk increases significantly in elderly patients with severe symptoms and pulmonary hypertension, those with prior cardiac surgery, or when combined with other cardiac procedures 1

Complications

• Complete heart block requiring permanent pacemaker occurs in 1-2% of cases 1
• Ventricular septal perforation (iatrogenic) has become uncommon (<1-2%) at experienced centers 1
• Thromboembolism and anticoagulation-related hemorrhage (mechanical valves) or structural valve deterioration (bioprosthetic valves) are long-term concerns 1, 2

Intraoperative Guidance

Transesophageal echocardiography or epicardial echocardiography is standard during mitral valve surgery to assess valve pathology, guide the surgical approach, and immediately evaluate the hemodynamic result. 1

Emerging Transcatheter Approaches

Transcatheter mitral valve replacement (TMVR) via transapical delivery is feasible in highly selected patients at prohibitive surgical risk, achieving 93% successful implantation and 87% freedom from cardiovascular mortality, stroke, and device malfunction at 30 days. 6

• This approach is reserved for patients with severe comorbidities precluding conventional surgery 1, 6
• Prosthetic leaflet thrombosis can occur and requires intensified anticoagulation 6

Key Pitfall to Avoid

The most critical error is performing mitral valve replacement when a durable repair is achievable—repair reduces operative mortality by approximately 50%, better preserves left ventricular function, and eliminates prosthetic valve complications. 1, 2, 3

• Patients requiring complex repairs should be referred to high-volume centers (>140 mitral operations/year) where repair rates reach 77% versus 48% at low-volume centers, with approximately 50% lower operative mortality 1, 2