MMCTS
(September 18, 2009). doi:10.1510/mmcts.2008.003640
Copyright © 2009 European Association for Cardio-thoracic Surgery
Procedure
Mitral annuloplasty
Francesco Maisano,
Raja Skantharaja,
Paolo Denti,
Andrea Giacomini and
Ottavio Alfieri*
Department of Cardiac Surgery, San Raffaele Hospital Milan, Via Olgettina 60, 20132 Milan, Italy
* Corresponding author: Tel.: +39-02-2643 7109; fax: +39-02-2643 7125. ottavio.alfieri{at}hsr.it
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Summary
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Annuloplasty is an essential component of surgical mitral valve repair to stabilize the repair and improve leaflet coaptation, decrease the stress on the leaflets and sutures, and increase the durability of the reconstructive procedure. Different annuloplasty methods and devices are available. The procedure can be carried out with minimal risks and satisfactory effects if choice of the appropriate device, sizing and implant technique follow a standardized approach which is described below.
Key Words: Mitral annuloplasty • Mitral valve repair
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Introduction
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Annuloplasty is the most commonly performed procedure at the time of open heart surgical mitral valve repair either as a standalone maneuver or in combination with leaflet or subvalvular repair. The rationale of surgical mitral annuloplasty is to optimize annular dimensions and/or shape in order to improve leaflet coaptation. A number of different techniques and devices have been developed.
Annular anatomy
The mitral annulus (Photos 1 and 2) is an anatomical as well as a functional unit, strictly linked to the other elements of the mitral and aortic valve. The annulus, from a functional perspective, is the hinge structure of the mitral leaflets. The annulus is spread over a 3D surface (Photo 2), commonly referred to as saddle-shaped, with high points (relative to the apex) in the central portion of the anterior and posterior annulus, and the deepest points at the commissures.
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Photo 1 Anatomy of normal mitral annulus with the surrounding structure and 3D echo images (frontal and sagittal view).
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Conventionally, the mitral annulus is divided into two components: the anterior fibrous portion and the posterior muscular portion. The two components are divided by the trigones. The anterior annulus length is about 1/3 of the overall circumference. The anterior portion is in continuity with the aortic valve (mitro-aortic continuity), and from a strict anatomical standpoint, there is no structure between the aortic and the mitral leaflets which can be defined as the annulus. This portion is known to be unexpandable or fixed, although data have been accumulated to support the evidence that this portion may elongate over time, as the left ventricle dilates (as it has been demonstrated in patients with dilated cardiomyopathy). In addition, this portion is fully dynamic; it participates actively in the mitro-aortic interaction, moving towards the posterior annulus to increase left ventricular outflow tract (LVOT) size in systole and to enhance leaflets coaptation, while it shifts towards the septum in diastole to increase diastolic mitral valve opening. Preservation of dynamic function of this portion could be relevant to reduce structural stresses on the anterior leaflet. The posterior portion of the annulus is in continuity with both the atrial and ventricular muscle. The posterior annulus is known to be primarily affected by dilatation of the ventricle, and most annuloplasty procedures are directed at reducing this portion of the annulus.
Although several studies have been dedicated to clarify mitral annulus anatomy and structure, less is known about normal function and dimensions. The normal functioning annulus tends to be smaller in late diastole/early systole (some studies showed that annulus becomes smaller and more oval in late diastole thanks to atrial contraction) and larger and more round in mid diastole. However, more needs to be done to fully understand annular function. Even more confusing is the definition of annular dilatation. Annular measurements are taken in systole, recording the septolateral (SL) and the intercommissural dimensions. Commonly this is obtained by 2D-echocardiography, using absolute measures. But from a functional standpoint, annular dilatation can be defined as the condition where the annular surface area is greater than the sum of the combined surface areas of the leaflets: this condition can be named as annular-to-leaflet mismatch, and annuloplasty can now be defined as a procedure to correct annular-to-leaflet mismatch by decreasing annular dimensions. More data will be available in the future in this field as 3D reconstructions will become more commonly performed in patients undergoing valve repair.
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Surgical procedure step-by-step
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The aim of mitral valve annuloplasty is to correct annular-to-leaflet mismatch by restoring normal ratio between the annular size and leaflet surface area in order to increase the surface of coaptation. In addition, the annular shape can be adjusted to restore normal geometry or to counteract leaflet or subvalvular abnormalities. The role of annuloplasty is often underestimated, and failure to perform a well-conducted annuloplasty step can be a reason for early as well as long-term failures. The critical steps of the procedure are: suture placement, sizing and choice of the type of ring.
Annulus suture placement
Annuloplasty is usually performed after leaflet lesion correction. Before suture placement, identification of the landmarks is mandatory including the commissures, the central portion of the anterior and posterior leaflets and the trigones. Identification of the trigones is done by pulling the edge of the anterior leaflet with forceps (Videos 1 and 2).
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Video 1 Identification of right trigone.
The trigone is identified by pulling the free edge of the anterior leaflet. The trigone can be felt with a gentle pressure of the nerve hook. The commissure is medial (to the right) of the trigone, a few millimeters away.
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Video 2 Identification of left trigone.
The same maneuver is done for the anterior (or left) trigone, which is usually more difficult to identify.
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Commissures are identified by the typical fan-shaped chordae (Videos 3 and 4).
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Video 3 Exposure of posterior commissure.
The commissure is identified by the typical fan-shaped chorda, which originates from the papillary muscle and stems with ramifications directed to both the anterior and the posterior leaflet. Identification of the commissure is mandatory to orient the ring correctly.
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Video 4 Exposure of anterior commissure.
The anterior commissure is also identified by exposing the commissural chorda with a nerve hook.
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Central portion of the leaflets is defined by geometrical assessment, with additional observation of the subvalvular apparatus. The anatomical centre of the leaflets (A2-P2) is defined as the area supported by chordae originating from both papillary muscles. Several 2-0 multifilament sutures are passed around the valve leaflets. Usually, a complete ring implant requires at least 10–12 sutures, while a partial ring requires 8–10 sutures. More sutures are needed when undersized annuloplasty is performed or etiologic rings are used. Sutures should be placed deep in the fibrous tissue of the annulus, taking care not to penetrate the leaflet tissue and not to catch secondary chordae. To reduce this risk and to better grasp the annular fibrous tissue, the base of the leaflets is pulled up with forceps while the annular suture is thrown. The surrounding structures are kept in mind to avoid any lesion (AV node, circumflex artery, coronary sinus, aortic valve). Some surgeons use interlocking sutures to get a more robust attachment of the ring to the annulus. The sequence of suture placement we recommend is as follows: care is taken to place one suture in each commissure and to mark them in order to later on position them precisely on the annular prosthesis to avoid distortion. The 1st suture is placed in the posteromedial commissure (all sutures are passed backhand) (Video 5), another three sutures are passed along the anterior leaflet (Video 6), taking care to keep the sutures symmetrically spaced (Videos 7 and 8).
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Video 5 Placement of the 1st suture.
Once the main landmarks of the native annulus are identified, suture placement is initiated. We recommend to put the first suture in the anterior annulus, beginning with the posterior commissural stitch. The suture is positioned medial to the trigone, across the commissure. The base of the leaflets is pulled up with forceps while the annular suture is thrown. Care is taken to avoid the underlying conduction tissue (the suture should not go too deep in the ventricle).
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Video 6 2nd suture across the trigone.
The second suture is placed from the right trigone towards the middle of the anterior leaflet. The point of the needle is directed towards the apex to avoid inadvertent lesions or entangling of the aortic cusps. The suture should enter and exit the annulus 1–2 mm away from the hinge point of the leaflets (see the end of the movie showing the maneuver to identify the hinge point by moving the leaflet up and down).
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Video 7 3rd suture in the middle of the anterior annulus.
The anterior annulus sutures are placed with the tip of the needle oriented towards the apex to avoid inadvertent aortic leaflet puncture. The middle suture is placed taking care that the position corresponds to the middle portion of the anterior annulus to avoid distortion or excessive tension on the sutures or on the valve structures after the ring will be implanted.
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Video 8 4th suture, towards the anterior (left) trigone.
This is considered the most difficult stitch. It is important to use the left hand to expose the annulus and to have the needle well directed away from the aortic valve. The suture should be placed across the annulus, 2 mm away from the hinge point.
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The anterior annulus sutures are placed keeping the tip of the needle oriented towards the apex to avoid inadvertent aortic leaflet puncture. A 5th suture is placed across the anterolateral commissure (Video 9).
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Video 9 Anterior commissure suture.
This is also a difficult stitch. The tissue can be fragile at this point and careful handling should be advisable. In addition, the suture can damage several surrounding structures including the aortic valve and the circumflex artery. The suture should be placed across the commissure. Careful placement of commissural sutures is mandatory, particularly when rigid rings are selected.
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The remaining sutures are placed in anticlockwise fashion until reaching back the posteromedial commissural suture (Video 10).
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Video 10 Posterior annulus sutures.
These remaining sutures are placed in anticlockwise fashion, the first and the last suture must land in the trigonal areas, to join the previously placed sutures.
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In case only posterior annuloplasty is performed, the first and the last suture must land in the trigonal areas. Sutures are kept organized, eventually using a suture guide system (particularly in minimally invasive procedures). Use of alternate color sutures is helpful to avoid confusions.
In case sliding plasty or other techniques requiring detachment of the base of the leaflets are performed, the annuloplasty sutures are conveniently passed before resuspension of the detached leaflets, and using a different technique: the suture is passed from the atrial to the ventricular side across the fibrous portion of the exposed annulus, then, a superficial bite of the underlying ventricular myocardium is passed; finally, the suture is again brought from the ventricular to the atrial side. This technique provides two benefits: it reduces the tendency of the suture to fold the annular edge, and it reduces the risk of perivalvular leaks.
Another different technique for annuloplasty suture placement can be used in case of calcium debridement of the annulus, where the free edges of the decalcified area are re-attached with a figure of eight suture, and a last pass of the same suture again towards the atrium.
Sizing
Sizing, according to manufacturers specifications, is usually made according to three measures: intertrigonal distance, intercommissural distance and surface of the anterior leaflet. To size the intertrigonal and intercommissural distance, the properly placed sutures can be used to spread the anterior annulus and to match these landmarks to the sizers (Video 11).
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Video 11 Sizing.
Sizing can be done either before (our preferred method) or after the sutures are placed in the annulus. The anterior leaflet is spread and the sizer is positioned above it to match its dimensions. Note the trigonal markers showing that the intertrigonal distance of the prosthesis is smaller than the annular intertrigonal distance. Hence a 29 mm ring in this case will be too small. The 31 sizer, instead, shows a good matching of the intertrigonal distance, as well as a good matching of the surface area of the ring to the sizer.
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To size the anterior leaflet surface, the leaflet is pulled up using a right-angled clamp and it is spread to match to the device-specific sizers. The sizer with the closest landmarks to the anatomy of the specific patient is chosen. In case of intermediate sizes, usually the larger size is chosen. Size is also chosen according to the posterior leaflet size: in case of low height of the leaflet, a smaller size (one size) annuloplasty device may be used, and the opposite in case of redundant leaflets (as it is the case in myxomatous valves) to avoid systolic anterior motion (SAM) of the mitral valve. It is important to re-make the sizing after the suture placing (Video 12).
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Video 12 Sizing re-assessment after suture placement.
Sizing can be re-assessed before final decision, after the sutures are placed in the annulus. In this case, the sutures may serve as a landmark to choose the ring size.
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Completion of the procedure
The annular prosthesis is prepared according to the manufacturer's specifications. Sutures are passed through the device first, taking care of spacing and distribution (Videos 13 and 14).
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Video 13 Passing the sutures through the ring prosthesis.
This step is usually considered less demanding. However, great care should be taken to avoid confusion, and to maintain the symmetry and the distribution of the sutures between the annulus and the ring.
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Video 14 Passing the sutures through the ring prosthesis (Continued).
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It is mandatory for most cases to exactly match the position of the commissural stitches. Once all sutures are placed, the annuloplasty device is parachuted in place (Video 15).
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Video 15 Parachuting the prosthesis.
Once the sutures are all placed in the ring prosthesis, it is parachuted down on the annulus to proceed with suture knot-tying.
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After knot tying (Video 16), the holder of the ring is removed (Video 17). In case of flexible rings, they are kept attached to their scaffold to avoid purse string effect. Sutures are tied down, and cut. Scaffold removed cutting the retaining sutures and valve competence is usually checked with water testing (Video 18).
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Video 16 Knot-tying and suture cutting.
When implanting flexible rings, it is fundamental to keep the ring holder in position to avoid shrinking of the prosthesis and undersizing while knot-tying. Sutures are then cut as short as possible.
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Video 17 Holder removal.
After knot-tying, the holder is removed. Note that a flexible ring looks round-shaped if no pressure is applied to the valve (see next video).
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Video 18 Water testing.
Water testing is the final step of valve repair. Care is taken not to exert excessive traction on the heart to avoid distortion of the annulus as well as the subvalvular apparatus. Note that as the ventricle is pressurized with saline injections, the annulus becomes more oval and saddle-shaped.
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Current devices and choice of the prosthesis
Annuloplasty devices (Photo 3) can be classified into categories relative to geometry, structure, indication and function: relative to geometry, rings can be classified as complete (also known as D shape) and partial (also known as C shape or bands) and 2D or 3D shaped rings. Relative to structure, the rings are classified as rigid, semirigid and flexible. Relative to indications, there is a new generation ring family dedicated to treat specific etiologies [particularly to treat functional mitral valve (MR) and myxomatous degeneration]. Relative to function, annuloplasty rings are classified as static and dynamic (adjustable).
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Photo 3 (1) Carpentier-Edwards classic annuloplasty rings. (2) Carpentier-Edwards physio annuloplasty ring. (3) Cosgrove-Edwards annuloplasty system. (4) Edwards GeoForm annuloplasty ring. (5) Medtronic-Duran flexible annuloplasty ring. (6) St Jude tailor annuloplasty ring and band. (7) Sorin-CarboMedics Flo annuloplasty ring. (8) Genesee Sculptor annuloplasty ring (adjustable). (9) Kalangos Bio-ring. (10) Carpentier-McCarthy-Adams IMR ETlogix. (11) Edwards Myxo ETlogix.
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There is no consensus regarding the selection criteria for the annuloplasty rings, although some publications recently addressed this issue [1]. Usually, complete rigid rings are preferred to treat functional MR, undersizing the prosthesis to overcome leaflet tethering, while flexible or semirigid rings, either complete or partial are more often used to treat degenerative MR.
The new generation etiology specific rings have been designed with specific shapes to compensate for the anatomical or functional abnormalities of the underlying disease. The Geoform ring is characterized by a reduced SL dimension to specifically address central regurgitation in patients with tethered leaflets in functional MR. The IMR ring is more specifically designed to compensate for the subvalvular abnormalities of ischemic MR with jet originating from the posterior commissure. The Myxo ring is designed to compensate for the excess tissue in Barlow's disease and to reduce the risk of SAM in these patients, hence reducing the need for complex resections.
The adjustable rings (MiCardia Corporation, Irvine, CA – MMCTSLink 184, and Mitral Solutions Inc, Fort Lauderdale, FL – MMCTSLink 186, Photo 4) are a new family of dynamic rings, where annuloplasty size can be fine-tuned after implant, under echocardiographic guidance, in order to optimize leaflet coaptation under more physiologic conditions, overcoming the limitations of saline injection testing.
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Results
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Mitral valve repair for patients with degenerative disease is associated with low operative mortality and excellent long-term survival rate [1, 2, 3, 4, 5, 6, 7, 8, 9]. The goals of reconstructive surgery are preservation or restoration of normal leaflet motion, creation of a large surface of coaptation, and stabilization of the entire annulus with a remodeling annuloplasty. There are few specific results of annuloplasty as a standalone procedure, besides the setting of undersized annuloplasty for functional MR. Annuloplasty has been used to improve results of valve repair. In the Cleveland Clinic series the ten-year freedom from re-operation was 92.9% [3]. When compared with all other procedures, the technique of ring annuloplasty and leaflet resection was associated with decreased risk of re-operation. The risk of re-operation was also increased in patients who had leaflet resection without annuloplasty. Flameng et al. reported that the absence of annuloplasty had a predictive value for recurrence of regurgitation [6]. Failure to add an annuloplasty increases the risk of late re-operation [3, 6, 9] although, in most cases, annuloplasty is not performed for conditions which may affect long-term outcomes (such as annular calcification). The addition of an annuloplasty device is increasing durability of valve repair by improving coaptation, reducing the stress on the leaflets and on the suture lines, and by stabilizing the annular dimensions over time.
Few series reported satisfactory durability in selected patients with no addition of annuloplasty in order to reduce complications related to annuloplasty including: AV node lesions, ring dehiscences, infection and SAM [10, 11, 12]. However, in the absence of clear algorithms to predict the results of ringless repair, in open heart mitral repair the implant of an annuloplasty ring is strongly advisable to optimize the chance of long-term durability.
Results of newer rings, including the etiology specific and the dynamic rings are not yet available, but there is potential advantage in the fact that these rings will help improving coaptation in selected patients.
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Conclusions
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Appropriate ring selection, adequate sizing, and meticulous technique of implantation are critical for an optimal annuloplasty. However, annuloplasty is only one part of the mitral valve repair. A successful reconstructive operation also depends on the appropriate correction of the valve lesion affecting the leaflets and the subvalvular apparatus.
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References
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- Fedak PW, McCarthy PM, Bonow RO. Evolving concepts and technologies in mitral valve repair. Circulation 2008;117:963–974.[Free Full Text]
- David TE, Omran A, Armstrong S, Sun Z, Ivanov J. Long-term results of mitral valve repair for myxomatous disease with and without chordal replacement with expanded polytetrafluoroethylene sutures. J Thorac Cardiovasc Surg 1998;115:1279–1285.[Abstract/Free Full Text]
- Gillinov AM, Cosgrove DM, Blackstone EH, Diaz R, Arnold JH, Lytle BW, Smedira NG, Sabik JF, McCarthy PM, Loop FD. Durability of mitral valve repair for degenerative disease. J Thorac Cardiovasc Surg 1998;116:734–743.[Abstract/Free Full Text]
- Mohty D, Orszulak TA, Schaff HV, Avierinos JF, Tajik JA, Enriquez-Sarano M. Very long-term survival and durability of mitral valve repair for mitral valve prolapse. Circulation 2001;104:I1–I7.[CrossRef][Medline]
- De Bonis M, Lorusso R, Lapenna E, Kassem S, De Cicco G, Torracca L, Maisano F, La Canna G, Alfieri O. Similar long-term results of mitral valve repair for anterior compared with posterior leaflet prolapse. J Thorac Cardiovasc Surg 2006;131:364–370.[Abstract/Free Full Text]
- Flameng W, Herijgers P, Bogaerts K. Recurrence of mitral valve regurgitation after mitral valve repair in degenerative valve disease. Circulation 2003;107:1609–1613.[Abstract/Free Full Text]
- David TE, Ivanov J, Armstrong S, Christie D, Rakowski H. A comparison of outcomes of mitral valve repair for degenerative disease with posterior, anterior, and bileaflet prolapse. J Thorac Cardiovasc Surg 2005;130:1242–1249.[Abstract/Free Full Text]
- Deloche A, Jebara VA, Relland JY, Chauvaud S, Fabiani JN, Perier P, Dreyfus G, Mihaileanu S, Carpentier A. Valve repair with Carpentier techniques. The second decade. J Thorac Cardiovasc Surg 1990;99:990–1002.[Abstract]
- Perier P, Stumpf J, Götz C, Lakew F, Schneider A, Clausnizer B, Hacker R. Valve repair for mitral regurgitation caused by isolated prolapse of the posterior leaflet. Ann Thorac Surg 1997;64:445–450.[Abstract/Free Full Text]
- Maisano F, Caldarola A, Blasio A, De Bonis M, La Canna G, Alfieri O. Mid-term results of edge-to-edge mitral valve repair without annuloplasty. J Thorac Cardiovasc Surg 2003;126:1987–1997.[Abstract/Free Full Text]
- Barlow CW, Ali ZA, Lim E, Barlow JB, Wells WC. Modified technique for mitral repair without ring annuloplasty. Ann Thorac Surg 2003;75:298–300.[Abstract/Free Full Text]
- Duebener LF, Wendler O, Nikoloudakis N, Georg T, Fries R, Schäfers HJ. Mitral-valve repair without annuloplasty rings: results after repair of anterior leaflet versus posterior-leaflet defects using polytetrafluoroethylene sutures for chordal replacement. Eur J Cardiothorac Surg 2000;17:206–212.[Abstract/Free Full Text]
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Summary
Introduction
