Mitral Annuloplasty #2: Mitral Annulus and Suture Placement

The mitral annulus is not a simple circular ring but a dynamic, three-dimensional junction integrating the left atrium, left ventricle, mitral leaflets, and fibrous skeleton of the heart. Successful mitral annuloplasty therefore requires more than annular downsizing. The surgeon must understand regional annular anatomy, identify the leaflet hinge accurately, recognize surrounding structures at risk, and place each suture at an appropriate depth and trajectory while maintaining controlled exposure.

Three-dimensional echocardiographic studies in children confirm that the normal mitral annulus maintains a saddle-shaped configuration throughout childhood, while most annular and valvar dimensions increase with somatic growth [1]. More detailed dynamic analysis demonstrates that this saddle-shaped geometry persists across childhood but changes significantly during the cardiac cycle [2]. These observations emphasize an important reconstructive principle: the pediatric mitral annulus is a growing and mobile structure rather than a static ring.

1. The Mitral Annulus as a Dynamic Three-Dimensional Structure

The mitral annulus represents the transition between atrial tissue, ventricular myocardium, leaflet insertion, and the fibrous skeleton. Although it often appears approximately oval when viewed through the left atrium, its physiologic geometry is nonplanar.

The characteristic saddle shape has relatively elevated anterior and posterior regions and lower commissural regions. Three-dimensional imaging of structurally normal pediatric hearts demonstrates preservation of this configuration across age and body size [1]. Analysis across multiple phases of the cardiac cycle further shows that the annulus changes dynamically rather than maintaining a fixed geometry [2].

Most mitral dimensions increase with body size during childhood [1]. This has particular relevance to congenital mitral surgery: an annuloplasty that is appropriate for the current valve must also account for the child’s future somatic growth.

The annulus also contributes actively to valve competence. In children with mitral regurgitation, three-dimensional echocardiography has demonstrated annular dilatation together with reduced dynamic annular function compared with normal controls [3]. Annular remodeling can therefore improve leaflet coaptation when annular enlargement is an important component of the regurgitant mechanism.

However, congenital mitral regurgitation is rarely an annular disorder alone. Leaflet deficiency, clefts, commissural abnormalities, abnormal chordae, and papillary-muscle malposition may coexist. Annuloplasty should consequently be integrated into a mechanism-based repair rather than used to compensate for an unresolved leaflet or subvalvar abnormality.

2. Functional Regions of the Mitral Annulus

From the operative perspective, the mitral annulus can be divided broadly into anterior and posterior components.

Anterior Annulus

The anterior mitral annulus is closely associated with the fibrous skeleton of the heart and the aorto-mitral curtain. It extends between the fibrous trigones and is relatively less distensible than the posterior annulus.

The anterior leaflet is therefore related structurally to the left ventricular outflow tract and aortic root. During annuloplasty, the surgeon should recognize that the apparent leaflet insertion in this region does not correspond to a thick muscular ring. Annular sutures should capture secure fibrous tissue without unnecessarily deep penetration.

Posterior Annulus

The posterior annulus extends along the insertion of the posterior leaflet and is generally more compliant and susceptible to dilatation. This makes it an important target for annular remodeling.

Because the posterior annulus lies within the atrioventricular groove, the depth and direction of needle passage are particularly important. The operative objective is to obtain sufficient tissue purchase while avoiding unnecessary extension beyond the annular plane.

This regional distinction also explains why many reconstructive approaches emphasize posterior or commissural remodeling rather than uniform circumferential constriction.

3. The Leaflet Hinge and the Correct Suture Plane

A critical technical step is identifying the true leaflet hinge.

Annuloplasty sutures should generally capture firm annular tissue immediately external to the leaflet insertion. The surgeon must avoid two opposite errors.

If the stitch is placed too close to or through the leaflet:

• leaflet tissue may be incorporated,
• leaflet mobility can be restricted,
• effective leaflet height may be reduced,
• and thin tissue may tear under tension.

If the bite is excessively deep or placed too far from the hinge:

• unnecessary atrial or ventricular tissue may be captured,
• the geometry of the atrioventricular junction may be distorted,
• and surrounding structures may be endangered.

Thus, the ideal bite is neither a superficial leaflet stitch nor an indiscriminate deep transmural stitch. It should securely engage the annular tissue while preserving the mobility of the leaflet hinge.

4. Relationship to the Aorto-Mitral Curtain

The anterior mitral leaflet is in fibrous continuity with the aortic root through the aorto-mitral curtain, with the right and left fibrous trigones defining the lateral boundaries of this region.

This relationship is important during anterior annular suturing because the tissue is fundamentally different from the more muscular posterior annulus. The surgeon should identify the mitral hinge precisely and avoid unnecessarily deep or superiorly directed needle passage.

The literature supplied for this section defines pediatric annular morphology and clinical annuloplasty outcomes but does not establish an evidence-based “optimal” depth or trajectory for sutures in the aorto-mitral curtain. These aspects therefore remain primarily anatomy- and technique-driven rather than supported by comparative pediatric trials.

5. Posterior Annulus and Adjacent Structures

The posterior annulus lies close to the atrioventricular groove, including the expected courses of the circumflex coronary artery and coronary sinus. This proximity is an important operative consideration when selecting the depth and angle of posterior annular bites.

The practical principle is straightforward:

Capture enough annular tissue to provide durable fixation, but do not place the needle deeper than necessary.

The supplied pediatric literature does not quantify the relationship between annular suture depth and coronary or coronary-sinus injury and does not define a standardized safe depth. Consequently, direct anatomic orientation remains essential.

Unexpected regional ventricular dysfunction, ventricular arrhythmia, or difficulty separating from cardiopulmonary bypass after mitral repair should prompt a systematic assessment of possible causes, including the possibility of coronary compromise when anatomically relevant.

6. Beginning at the 6-o’Clock Position

In the illustrated operative sequence, the first annular stitch is placed at approximately the 6-o’clock position, corresponding to the central posterior annulus in the surgeon’s operative view.

This is a useful starting location because:

• the posterior annulus is usually well visualized,
• the surgeon can establish the desired bite depth and spacing early,
• and the initial suture can subsequently be used for traction.

The stitch may be placed using either a forehand or backhand motion according to needle orientation and surgeon ergonomics.

Once placed, the suture is gently retracted toward the surgeon. This transforms the first annuloplasty stitch into an exposure stitch, elevating the posterior annulus and improving visualization of the subsequent suture line.

In pediatric mitral surgery, where the operative field is small and annular tissue is thin, this controlled traction can materially improve needle placement.

7. First Direction of Suturing

From the 6-o’clock position, the illustrated technique initially advances toward approximately 4–5 o’clock.

The exact needle motion should be adapted to the local geometry rather than dictated by a rigid rule. The essential goals are:

1. direct visualization of the target tissue,
2. consistent annular purchase,
3. controlled needle entry and exit,
4. and avoidance of unnecessarily deep bites.

After reaching the lateral annular region, suturing continues counterclockwise toward the superior or approximately 12-o’clock region, using predominantly backhand stitches in the illustrated sequence.

The benefit of this approach is primarily ergonomic. The surgeon advances toward tissue that remains visible and accessible rather than forcing an awkward needle trajectory across an inadequately exposed annulus.

8. Returning to the 6-o’Clock Position

After completing one side, the surgeon returns to the original posterior reference point.

Sutures are then advanced in the opposite direction, clockwise from 6 o’clock toward approximately 8–9 o’clock, using forehand stitches in the illustrated technique.

As the needle holder approaches the superior annulus, the hand orientation changes and backhand stitches can be used to continue toward the 12-o’clock position.

This bilateral progression from the posterior midpoint provides several technical advantages:

• a consistent reference point,
• progressive exposure of each hemicircumference,
• controlled changes in hand position,
• and easier assessment of suture spacing and symmetry.

The sequence should nevertheless be regarded as an ergonomic strategy rather than an immutable rule. The safest needle motion is the one that provides optimal visualization and control for the particular patient and exposure.

9. Suture Depth, Spacing, and Direction

The quality of annuloplasty depends on three closely related variables: depth, spacing, and direction.

Depth

Each bite must provide sufficient tissue purchase for durability while avoiding excessive penetration.

There is no universal numeric depth applicable to all pediatric patients because annular thickness varies with:

• age,
• body size,
• congenital anatomy,
• ventricular hypertrophy,
• previous surgery,
• and location around the annulus.

The margin for error is particularly small in neonates and infants.

Spacing

Sutures should be distributed sufficiently evenly to avoid focal deformation or tissue crowding.

Excessively wide intervals may produce uneven remodeling. Conversely, excessively close sutures can bunch the annulus or increase the risk of tissue injury.

Direction

Needle trajectory should follow the local annular anatomy rather than simply being perpendicular to the surgeon’s field of view.

Controlled changes between forehand and backhand motions facilitate tangential and appropriately directed bites as the surgeon moves around the annulus.

The available pediatric studies do not directly compare specific stitch depths, spacing intervals, or forehand versus backhand sequences. These technical principles therefore remain based primarily on surgical anatomy and operative ergonomics.

10. Annuloplasty as Part of Congenital Mitral Valve Reconstruction

Mitral repair is generally preferred to valve replacement in children whenever a satisfactory reconstruction is achievable [4].

Congenital mitral regurgitation may require combinations of:

• cleft or deficiency closure,
• leaflet reconstruction,
• commissural procedures,
• chordal intervention,
• edge-to-edge techniques in selected anatomy,
• and annuloplasty [4].

The repair should therefore begin with identification of the dominant mechanism of regurgitation.

Annular reduction alone cannot reliably compensate for severe leaflet restriction, inadequate leaflet tissue, abnormal chordal architecture, or papillary-muscle malposition. Excessive annuloplasty used to overcome an unrepaired structural lesion may improve immediate competence at the cost of an inadequate valve orifice.

The surgical objective is not simply to eliminate regurgitation but to establish an appropriate balance between coaptation and effective mitral orifice area.

11. Pediatric Annuloplasty and Long-Term Durability

Long-term pediatric experience supports annuloplasty as an important component of congenital mitral repair.

In a series of 49 consecutive patients undergoing repair for congenital mitral insufficiency, commissural plication annuloplasty was frequently incorporated into a multimodal reconstructive strategy. There were no reported deaths, and actuarial freedom from reoperation was 85.6% at 13 years [5].

These results demonstrate that durable repair can be achieved in children, but they do not establish that a single annuloplasty technique is optimal for all congenital morphologies.

A larger retrospective study of 112 children with isolated congenital mitral regurgitation provides additional information regarding annular strategy. Patients were treated with rings ≥26 mm, rings <26 mm, or bands. Annuloplasty using rings ≥26 mm was associated with the lowest reoperation risk. Importantly, the mechanism of failure differed between groups: 13 of 14 reoperations after smaller rings were predominantly related to mitral stenosis, whereas 6 of 7 reoperations after band annuloplasty were predominantly related to recurrent regurgitation [6].

These observations illustrate the fundamental pediatric trade-off between inadequate annular stabilization and excessive restriction.

12. Growth Potential and Annular Remodeling

Somatic growth is a central issue in pediatric annuloplasty.

Because normal mitral dimensions increase with body size [1], a repair that fixes the annulus at an excessively small dimension may become restrictive as the child grows.

This concern has motivated the development of annuloplasty strategies designed to provide temporary stabilization while preserving subsequent annular development. Biodegradable annuloplasty rings have been proposed for this purpose. Published bench-to-clinical experience suggests that these devices can remodel and stabilize the annulus while maintaining three-dimensional motion and permitting growth after degradation [7].

The reported device degradation occurs without obvious adverse consequences in the reviewed experience, and pediatric growth potential appears to be preserved [7]. However, the available review does not provide comparative randomized pediatric evidence demonstrating superiority over conventional rings, bands, or suture annuloplasty.

Accordingly, growth preservation remains an important conceptual advantage, but the choice of annuloplasty technique must be individualized.

13. Avoiding Functional Mitral Stenosis

Over-reduction of the pediatric mitral annulus is a major concern.

Potential consequences include:

• elevated transmitral gradients,
• restricted leaflet opening,
• impaired left ventricular filling,
• pulmonary venous hypertension,
• and later reoperation as the child grows.

The long-term experience with artificial rings reinforces this principle. Smaller rings were associated predominantly with reoperation for stenosis, whereas less restrictive band techniques carried a greater risk of recurrent regurgitation [6].

Thus, the goal is not maximal annular reduction. The goal is the minimum effective remodeling necessary to restore durable leaflet coaptation while preserving an adequate valve orifice.

This balance is especially important when the native valve is intrinsically small or when leaflet and subvalvar abnormalities already restrict opening.

14. Intraoperative Assessment After Annuloplasty

After completion of annuloplasty, the repair should be assessed systematically.

Saline testing provides an initial evaluation of:

• leaflet coaptation,
• residual central or commissural leakage,
• gross restriction,
• and symmetry of closure.

However, saline testing is performed under nonphysiologic loading conditions.

After separation from cardiopulmonary bypass, echocardiographic assessment should evaluate:

• residual mitral regurgitation,
• transmitral gradient,
• leaflet mobility,
• coaptation,
• ventricular function,
• and any new regional abnormalities.

In pediatric patients, both residual regurgitation and excessive obstruction must be considered repair failures. A valve that appears completely competent but produces an excessive gradient may not represent an acceptable reconstruction.

15. Practical Surgical Principles

The operative strategy can be summarized as follows:

1. Identify the true leaflet hinge and annular plane before placing sutures.
2. Recognize the saddle-shaped, dynamic nature of the pediatric annulus.
3. Begin where exposure is optimal; the posterior midpoint provides a useful reference.
4. Use the initial posterior stitch for controlled annular traction.
5. Capture annular tissue without incorporating excessive leaflet tissue.
6. Avoid unnecessarily deep bites, particularly around the atrioventricular groove and anterior fibrous structures.
7. Adapt forehand and backhand movements to the local needle trajectory.
8. Maintain consistent suture depth and spacing rather than following circumference mechanically.
9. Integrate annuloplasty with correction of leaflet, chordal, commissural, and papillary-muscle abnormalities.
10. Avoid excessive annular reduction in a growing child.
11. Assess both residual regurgitation and functional stenosis after repair.

Key Concept

Mitral annuloplasty in congenital heart surgery is fundamentally an exercise in geometric restoration within a growing, dynamic annulus.

Three-dimensional pediatric data confirm that the annulus maintains a saddle shape while changing throughout the cardiac cycle and enlarging with somatic growth [1–3]. Clinical series demonstrate that annuloplasty can contribute to durable congenital mitral repair [5,6], but the long-term result depends on balancing adequate annular stabilization against excessive restriction.

The technical sequence—beginning posteriorly, using traction to improve exposure, and alternating forehand and backhand needle movements—provides a reproducible operative framework. Nevertheless, the sequence itself is secondary to the central surgical principle: every annular stitch should be placed according to the local anatomy, with sufficient tissue purchase to stabilize the repair but without unnecessary depth or distortion.

In children, successful annuloplasty must therefore satisfy three objectives simultaneously: restore leaflet coaptation, preserve an adequate mitral orifice, and respect the future growth and dynamic function of the valve.

References

[1] Jolley M, Ghelani SJ, Adar A, Harrild D. Three-dimensional mitral valve morphology and age-related trends in children and young adults with structurally normal hearts using transthoracic echocardiography. J Am Soc Echocardiogr. 2017. doi:10.1016/j.echo.2017.01.018.

[2] Amin S, Dewey H, Lasso A, Sabin P, Han Y, Vicory J, et al. Euclidean and shape-based analysis of the dynamic mitral annulus in children using a novel open-source framework. J Am Soc Echocardiogr. 2023. doi:10.1016/j.echo.2023.11.011.

[3] Bharucha T, Sivaprakasam M, Roman K, Vettukattil J. A multiplanar three dimensional echocardiographic study of mitral valvar annular function in children with normal and regurgitant valves. Cardiol Young. 2008. doi:10.1017/S1047951108002242.

[4] Quinonez LG, del Nido PJ. Valve reconstruction for congenital mitral valve disease. Multimed Man Cardiothorac Surg. 2015. doi:10.1093/mmcts/mmv007.

[5] Ohno H, Imai Y, Terada M, Hiramatsu T. The long-term results of commissure plication annuloplasty for congenital mitral insufficiency. Ann Thorac Surg. 1999. doi:10.1016/S0003-4975(99)00515-9.

[6] Van D, Pham NHM, Nguyen VMT, Nguyen PV, Phan P, Van CNM, Vuong NL. Isolated congenital mitral regurgitation repair in children: long-term outcomes of artificial ring. Ann Thorac Surg. 2021. doi:10.1016/j.athoracsur.2021.01.024.

[7] Myers P, Kalangos A. Valve repair using biodegradable ring annuloplasty: from bench to long-term clinical results. Heart Lung Vessels. 2013.