1. Overview
Mitral valve replacement (MVR) is performed when clinically significant mitral valve dysfunction requires intervention but durable, hemodynamically satisfactory repair is not feasible. Successful replacement depends on more than excising a diseased valve and implanting a prosthesis. The operation must respect the complex three-dimensional relationships of the mitral annulus, aortic root, circumflex coronary artery, atrioventricular conduction tissues, and left ventricular (LV) subvalvular apparatus. Prosthesis type, implantation level, and preservation of ventricular–annular continuity influence both early function and long-term outcomes.
The three-part series addresses indications and morphology, operative anatomy and technique, and selection of mechanical versus bioprosthetic valves with their associated antithrombotic strategies. Although many principles apply across age groups, prosthesis selection and annular growth create distinct challenges in pediatric and congenital cardiac surgery.
2. Indications and Preoperative Evaluation
2.1 When replacement is favored over repair
Mitral repair is generally preferred when it can restore durable competence without clinically important stenosis. In degenerative mitral regurgitation (MR), especially isolated posterior leaflet prolapse, experienced centers frequently achieve durable repair. Therefore, leaflet prolapse alone is not an indication for replacement. MVR becomes more appropriate when the anatomy is not reliably repairable, repeated repair has failed, or satisfactory repair would leave substantial residual MR or an unacceptable transmitral gradient. Contemporary guidelines emphasize mechanism-specific assessment and durable repair when feasible [1,2].
Relevant substrates include diffuse rheumatic leaflet thickening and commissural fusion, heavily calcified or fibrotic leaflets, complex multisegment prolapse with inadequate tissue quality, destructive infective endocarditis, and selected congenital malformations with severely abnormal leaflet or subvalvular anatomy. Rheumatic mitral stenosis may require replacement when the valve is unsuitable for commissurotomy. Severe mitral annular calcification can make both repair and replacement technically challenging; it requires individualized assessment rather than automatically favoring replacement.
Intervention is determined by symptoms, lesion severity, ventricular size and function, pulmonary pressures, atrial fibrillation, and the natural history of the underlying lesion. Severe primary MR, secondary MR, and mitral stenosis have different guideline pathways. Replacement should not be viewed as a substitute for establishing the correct physiological indication.
2.2 Imaging and operative planning
Transthoracic and transesophageal echocardiography define leaflet motion and morphology, annular dimensions, chordal abnormalities, papillary muscle position, stenosis or regurgitation mechanism, ventricular function, and associated lesions. Three-dimensional imaging can clarify commissural anatomy, clefts, calcification, and leaflet–annular relationships. Cardiac CT is particularly useful when extensive annular calcification, aortic–mitral continuity abnormalities, or unusual congenital anatomy makes operative exposure difficult.
The preoperative assessment should specifically establish whether annular enlargement, complex calcium management, or preservation of abnormal subvalvular structures will be necessary. In children, the anticipated effective orifice area and the likelihood of outgrowing the prosthesis are central considerations.
3. Surgical Anatomy
3.1 Leaflets, commissures, and annulus
The mitral valve comprises an anterior leaflet and a posterior leaflet divided conventionally into P1, P2, and P3 scallops, corresponding to anterior leaflet regions A1, A2, and A3. The anterolateral and posteromedial commissures join the two leaflets. The anterior annulus is continuous with the aortic root through the aorto-mitral curtain; the posterior annulus is related to the atrioventricular groove.
The two fibrous trigones anchor the fibrous continuity at either end of the aorto-mitral curtain. The anterior annulus is relatively fibrous, whereas the posterior annulus includes a more variable, dynamic muscular–fibrous interface. These differences influence where sutures can be placed safely and securely.
3.2 Structures at risk
Circumflex coronary artery. The left circumflex artery courses in the left atrioventricular groove, near the posterior and lateral mitral annulus. Its distance from the annulus varies with coronary dominance and individual anatomy. Deep or poorly oriented annular sutures can cause direct injury, distortion, or occlusion. Anatomical studies and surgical reports document this mechanism [3,4]. The coronary venous structures are also close to the groove.
Aortic root and aorto-mitral curtain. Sutures placed too high through the anterior fibrous continuity can distort an adjacent aortic cusp or damage the aortic–mitral junction. Aggressive annular debridement can compromise the fibrous skeleton, especially in active infection or severe calcification.
Conduction tissue. The atrioventricular node and penetrating His bundle lie near the central fibrous body and right fibrous trigone, rather than uniformly alongside the mitral annulus. Deep sutures or debridement near this region may produce heart block. In atrioventricular septal defects and other congenital abnormalities, the conduction axis can be displaced; the expected adult anatomic course cannot be assumed.
Subvalvular apparatus. Primary, secondary, and basal chordae connect the leaflets to the papillary muscles. The anterolateral and posteromedial papillary muscles are embedded in LV myocardium. Their connection with the annulus contributes to normal ventricular shape and mechanics, and must be considered when planning leaflet excision.
4. Operative Strategy and Technical Sequence
4.1 Exposure and initial assessment
Most surgical MVR procedures are performed on cardiopulmonary bypass with cardioplegic arrest, although access routes vary with patient anatomy and prior surgery. Left atrial exposure may be obtained through a standard interatrial-groove incision or a transseptal approach. Adequate exposure should permit inspection of both commissures, the entire annulus, and the subvalvular apparatus without excessive traction.
Before resection, reassess whether repair is possible and identify leaflet segments or chordae suitable for preservation. Inspect the annulus for calcification, tissue deficiency, abscess, or prior suture material. The intended valve size and seating plane should be considered before removing tissue irreversibly.
4.2 Leaflet resection versus preservation
Conventional replacement historically involved extensive excision of both leaflets and chordae. Modern techniques often preserve the posterior leaflet and its chordal attachments; preservation of selected anterior leaflet chordae or broader subvalvular continuity may also be feasible. Experimental and clinical studies support the importance of annulo-papillary continuity for LV geometry and postoperative function, although the optimal amount and method of preservation depend on valve pathology [5,6].
Posterior leaflet retention may be achieved by keeping the leaflet near its annular attachment and incorporating it into the prosthetic suture line. Anterior leaflet tissue may be resected centrally while retaining supported chordal segments, sometimes repositioned to avoid interference. Complete preservation is inappropriate if retained tissue obstructs the LV outflow tract, impedes prosthetic leaflet or disc motion, or leaves infected or severely calcified tissue behind.
In destructive endocarditis, removal of infected structures and adequate debridement take priority. In severe rheumatic disease, shortening, fusion, or calcification of chordae may prevent safe retention. The operative goal is preservation of useful ventricular continuity without compromising prosthetic function.
4.3 Annular sutures, sizing, and seating
Following lesion-specific resection and debridement, size the annulus using the dedicated manufacturer sizers. Prosthesis labeling does not necessarily correspond to identical internal diameters across models. Avoid forceful oversizing: an oversized prosthesis can deform the annulus, interfere with neighboring structures, or impair seating. Undersizing may produce patient–prosthesis mismatch and elevated postoperative transmitral gradients, particularly in small annuli.
Interrupted pledgeted mattress sutures are commonly used, although pledget placement and suture technique vary. Suture purchase should incorporate sound annular tissue without unnecessarily penetrating into the atrioventricular groove or adjacent structures. Retained leaflet segments must lie away from the prosthetic occluders and flow orifice.
Intra-annular versus supra-annular implantation. An intra-annular prosthesis is seated within the native annular plane. Supra-annular placement positions the sewing cuff more atrially and is sometimes used when anatomy or limited annular dimensions make a conventional seat difficult. In pediatric surgery, supra-annular positioning may permit an acceptable initial valve diameter, but can alter left atrial inflow geometry and complicate later re-replacement. Neither position is universally superior; the deciding factors are annular support, clearance, effective orifice, and surrounding anatomy.
For a bileaflet mechanical prosthesis, rotational orientation should be checked relative to the LV walls, retained chordae, septum, and outflow tract. An “anti-anatomical” orientation is used by some surgeons to optimize clearance, but it is not a universal rule for every prosthesis or anatomy. Verify unrestricted motion of both occluders before and after tying sutures.
4.4 Completion assessment
After valve seating, inspect the circumference for gaps, trapped tissue, loose sutures, and distortion. Confirm that preserved chordae and leaflet remnants cannot obstruct the prosthesis. De-air the left ventricle and left atrium carefully.
Post-bypass transesophageal echocardiography should establish prosthetic leaflet or disc mobility, a physiologically interpretable transmitral gradient, absence of significant paravalvular regurgitation, LV and right ventricular function, and no new LV outflow obstruction. Hemodynamic interpretation must account for heart rate, cardiac output, prosthesis model and size. New regional LV dysfunction, unexplained ventricular arrhythmia, or ischemic ECG changes should raise concern for circumflex injury, particularly after deep posterior annular sutures. A substantial paravalvular leak, restricted occluder movement, or clinically important obstruction warrants immediate reassessment and often revision.
5. Prosthesis Selection
5.1 Mechanical valves
Modern mechanical mitral prostheses provide long service life and are particularly attractive when the patient's expected survival extends well beyond the likely durability of a tissue valve. Mechanical durability does not mean freedom from complications: thrombosis, thromboembolism, hemorrhage, pannus formation, paravalvular leakage, and infective endocarditis remain potential causes of morbidity.
The principal disadvantage is lifelong vitamin K antagonist therapy, generally warfarin. The ability to maintain a stable international normalized ratio (INR), access to monitoring, bleeding risk, occupation, and pregnancy plans should be incorporated into shared decision-making. Direct oral anticoagulants are not substitutes for warfarin in patients with mechanical valves [1,2].
5.2 Bioprosthetic valves
Bioprosthetic mitral valves usually eliminate the requirement for lifelong valve-related anticoagulation after the early postoperative period, unless another indication exists, such as atrial fibrillation. However, structural valve deterioration is progressive and variable. Calcification, leaflet tearing, fibrosis, and stenosis or regurgitation may necessitate reintervention. Degeneration generally occurs earlier in younger patients; the shorthand estimate of 10–15 years is not a fixed expected lifespan for an individual valve [7,8].
A bioprosthesis may be favored when anticoagulation is contraindicated, reliable warfarin management is impractical, pregnancy considerations are particularly important, or the patient accepts a greater likelihood of later valve intervention. Transcatheter mitral valve-in-valve implantation may be an option for selected failing bioprostheses, but anatomical eligibility, residual gradients, and LV outflow obstruction risk must be assessed.
5.3 Pediatric and congenital considerations
In a growing child, the prosthesis must accommodate present cardiac output without causing obstruction, yet the patient may eventually develop functional stenosis as body size increases. Mechanical valves are often selected for durability, but anticoagulation management in infancy and childhood is demanding. The small annulus, prosthetic sewing cuff, relationship to the LV outflow tract, and potential for supra-annular placement must be evaluated individually. Future re-replacement and the possibility of annular enlargement should inform the initial strategy.
6. Anticoagulation and Long-Term Management
For a contemporary mechanical valve in the mitral position, the usual warfarin target is INR 3.0, with a therapeutic range of 2.5–3.5. The 2025 ESC/EACTS guideline allows higher targets in patients with specified additional prothrombotic factors; therefore, individual targets must be selected from the applicable prosthesis-specific guidance and patient risk profile [2]. Warfarin is commonly initiated postoperatively once bleeding is controlled, with parenteral anticoagulation bridging as appropriate for the mechanical mitral position. Perioperative interruption later in life requires careful thrombosis-versus-bleeding assessment.
For surgical bioprosthetic MVR, the 2020 ACC/AHA guideline considers warfarin to a target INR of 2.5 reasonable for 3–6 months after surgery in patients at low bleeding risk; longer-term therapy depends on rhythm, thromboembolic risk, and other indications [1]. Antiplatelet practice and early antithrombotic approaches should be reconciled with current guidelines and individual bleeding risk, rather than extrapolated from aortic valve practice.
Surveillance includes an early postoperative echocardiographic baseline, periodic clinical and echocardiographic evaluation, and prompt reassessment for symptoms, new murmurs, embolic events, hemolysis, or suspected prosthesis dysfunction. Patient education should address anticoagulation adherence, INR fluctuations, interactions with medications and diet, pregnancy planning, and infective endocarditis prophylaxis when indicated.
7. Complications and Reintervention
Early complications include bleeding, low cardiac output, paravalvular regurgitation, prosthesis obstruction, circumflex compromise, LV outflow obstruction, arrhythmias, and conduction disturbances. An elevated transmitral gradient requires correlation with flow, heart rate, valve model, pressure recovery, and imaging evidence of obstruction before diagnosing patient–prosthesis mismatch.
Late complications differ by valve type. Mechanical valves are vulnerable to thrombosis, anticoagulant-related hemorrhage, pannus formation, and embolic complications. Bioprostheses are vulnerable to structural deterioration, while both can develop endocarditis, nonstructural dysfunction, or paravalvular leak. Repeat surgery or transcatheter intervention is guided by mechanism, severity, anatomy, and operative risk.
8. Key Surgical Principles
- Repair first when durable: MVR is appropriate when satisfactory long-term repair cannot reasonably be achieved.
- Respect periannular anatomy: Protect the circumflex artery, aorto-mitral curtain, fibrous trigones, and conduction structures.
- Preserve useful subvalvular continuity: Retain chordal–papillary connections when safe, without restricting prosthetic motion or LV outflow.
- Optimize sizing and seating: Avoid annular distortion, paravalvular gaps, and clinically important patient–prosthesis mismatch.
- Individualize prosthesis selection: Mechanical durability must be balanced against warfarin-associated burden; tissue-valve freedom from lifelong valve-related anticoagulation must be balanced against degeneration.
- Verify the completed operation: Assess prosthetic mobility, gradients, paravalvular leakage, ventricular performance, and ischemia before leaving the operating room.
References
- Otto CM, Nishimura RA, Bonow RO, et al. 2020 ACC/AHA guideline for the management of patients with valvular heart disease. J Am Coll Cardiol. 2021. DOI: 10.1016/j.jacc.2020.11.018.
- 2025 ESC/EACTS Guidelines for the management of valvular heart disease. Eur J Cardiothorac Surg. 2025. DOI: 10.1093/ejcts/ezaf276.
- Cornu E, Lacroix P, Christides C, Laskar M. Coronary artery damage during mitral valve replacement. J Cardiovasc Surg (Torino). 1995. PMID: 7629211.
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- Pomerantzeff PM, Brandão CM, Amato MC, et al. Randomized study comparing mitral valve replacement with and without preservation of mitral ring–chordae tendineae–papillary continuity. Arq Bras Cardiol. 1993. PMID: 8311748.
- Bourguignon T, Espitalier F, Pantaléon C, et al. Bioprosthetic mitral valve replacement in patients aged 65 years or younger: long-term outcomes with the Carpentier–Edwards PERIMOUNT pericardial valve. Eur J Cardiothorac Surg. 2018. DOI: 10.1093/ejcts/ezy029. PMID: 29444229.
- Malvindi PG, Mastro F, Kowalewski M, et al. Durability of mitral valve bioprostheses: a meta-analysis of long-term follow-up studies. Ann Thorac Surg. 2020. DOI: 10.1016/j.athoracsur.2019.07.024. PMID: 31472130.