What are the advantages and disadvantages of completely removing all leaflets during mitral valve replacement surgery?

Mitral Valve Replacement: Leaflet Preservation vs. Complete Removal

Direct Recommendation

Mitral valve replacement with preservation of the mitral apparatus (particularly the posterior leaflet and its chordae tendineae) is strongly preferred over complete leaflet removal, as preservation maintains left ventricular geometry and function, resulting in superior postoperative LV performance and survival. 1

Advantages of Leaflet Preservation

Hemodynamic Benefits

• Preservation of the mitral apparatus maintains left ventricular function by keeping the integral structural relationship between the mitral valve and LV intact, which is essential for normal LV shape, volume, and contractile function 1
• Patients with preserved apparatus demonstrate better postoperative ejection fraction and reduced LV end-diastolic pressures compared to those with complete leaflet excision 1
• In patients with ischemic mitral regurgitation and ejection fraction <35%, posterior leaflet preservation reduced operative mortality from 73% (8/11 deaths with excision) to 0% (0/7 deaths with preservation), p=0.035 2

Survival Advantage

• Multiple studies demonstrate enhanced postoperative survival with apparatus preservation compared to complete removal 1
• The survival benefit extends beyond 10 years and up to 20 years after surgery 1

Technical Feasibility

• Both anterior and posterior leaflets can be preserved using specialized techniques: the anterior leaflet can be divided into 3-4 tissue islands with attached chordae, transposed under the posterior leaflet, and secured with sutures 3
• Complete retention of all valvular and subvalvular tissue is achievable by reefing native leaflets into valve sutures 4

Disadvantages and Risks of Leaflet Preservation

Left Ventricular Outflow Tract Obstruction (LVOTO)

• LVOTO is the primary concern with leaflet preservation, particularly with anterior leaflet retention 1, 5
• Even with posterior leaflet-only preservation, LVOTO can occur with high-profile bioprostheses, creating gradients up to 64 mmHg between the septum and prosthetic strut 5
• Risk is heightened in patients with small LV cavities, hypertrophied septums, or when using bulky prosthetic valves 1

Prosthetic Valve Interference

• Retained leaflet tissue may theoretically interfere with prosthetic leaflet mobility, though this complication is rare with proper surgical technique 4
• Careful reefing and positioning of preserved tissue is essential to avoid mechanical obstruction 4, 3

Technical Complexity

• Leaflet preservation is more technically demanding than simple excision, requiring longer cardiopulmonary bypass times 1
• Success depends heavily on surgical expertise and experience 1

Disadvantages of Complete Leaflet Removal

Immediate LV Dysfunction

• Destruction of the mitral apparatus causes immediate left ventricular dysfunction by disrupting the structural support system integral to LV contraction 1
• Loss of the apparatus eliminates the mechanical advantage provided by chordal-papillary muscle continuity 1

Worse Postoperative Outcomes

• Complete excision results in inferior postoperative LV function compared to preservation techniques 1
• Higher operative mortality, particularly in patients with pre-existing LV dysfunction (EF <35%) 2

Long-term Functional Decline

• Patients experience progressive deterioration in LV geometry and contractile performance over time 1

Clinical Algorithm for Decision-Making

When to Preserve Leaflets (Preferred Approach)

• All patients undergoing MVR should have leaflet preservation attempted unless contraindicated 1
• Mandatory in patients with EF <35% to prevent catastrophic postoperative LV failure 2
• Particularly beneficial in ischemic mitral regurgitation with compromised LV function 2

When Complete Removal May Be Necessary

• Severe rheumatic disease with extensively calcified, thickened, or fused leaflets and chordae that cannot be safely preserved 1
• Massively distorted valve apparatus where preservation would create unacceptable LVOTO risk 1
• Active endocarditis with extensive tissue destruction precluding safe preservation 1

Specific Contraindications to Anterior Leaflet Preservation

• Small LV cavity dimensions 5
• Significant septal hypertrophy (>15-18mm) 1, 5
• Requirement for high-profile bioprosthetic valve in patients with narrow LVOT 5

Critical Pitfalls to Avoid

• Never perform complete apparatus excision in patients with EF <35% without compelling anatomic reasons, as mortality approaches 73% versus 0% with preservation 2
• Avoid bulky or high-profile prostheses when preserving leaflets in patients with borderline LVOT dimensions 5
• Do not attempt complex preservation techniques without adequate surgical experience; a failed preservation requiring conversion to replacement mid-procedure increases risk 1
• In rheumatic mitral stenosis specifically, posterior leaflet preservation may not provide the same hemodynamic benefits seen in regurgitant lesions, though it remains reasonable to attempt 6

The overwhelming evidence supports leaflet preservation as the standard approach, with complete removal reserved only for situations where the native apparatus is so severely diseased that preservation is anatomically impossible or would create prohibitive LVOTO risk. 1, 2