In the early years of valve surgery, annular dilatation was considered the primary cause of mitral valve regurgitation. With the exception of McGoon’s techniques of posterior leaflet plication, the usual repair techniques involved pledgetted sutures placed at the commissures or fabric bands supporting the annulus, in such a manner that the mitral valve orifice was constricted arbitrarily to two finger breaths and the posterior leaflet advanced toward the anterior leaflet ( Fig. 8-1 ). Recurrent mitral valve regurgitation or stenosis was frequent as a result of dysfunction of the leaflets, the persistent process of annular dilatation, and the fibrous transformation of the plicated commissure. These palliative techniques of narrowing annuloplasties were progressively abandoned while during the same period mechanical prostheses became available. The concept of remodeling annuloplasty using prosthetic rings introduced in 1968 revived the interest in valve repair and opened the way to reconstructive valve surgery . Three important characteristics differentiate the “annular remodelling concept” from “annular narrowing”: (1) the prosthetic ring restores the normal systolic size and shape of the annulus without impairing leaflet motion; (2) ring selection is based on precise measurements of the leaflet tissue; (3) the ring stabilizes the annulus and eliminates the risk of recurrent deformation.
THE TWO GOLDEN RELATIONSHIPS
The mitral valve can be compared to an entrance gate or a French door: the leaflets are the doors; the mitral annulus is the frame. Any distortion or alteration of one or both of these components leads to dysfunction. To restore normal function, the geometry of each component must be reconstructed. If the frame is deformed, its reconstruction is guided by the size and the shape of the doors. If the doors are deformed, they should be repaired to fit the shape and the size of the frame. If both the frame and the doors are deformed they must be reconstructed so that their respective size and shape match perfectly. The same principles apply to the mitral valve. Prosthetic rings with optimal shape and size are used to restore the normal annular configuration, a condition for optimal leaflet coaptation.
Restoring the shape of the annulus implies restoring the normal systolic relationships between the transverse diameter and the anteroposterior diameter ( Fig. 8-2 ). During systole, the shape of a normal annulus is ovoid with the transverse diameter, T , being greater than the anteroposterior diameter, A (T > A) , with a 4:3 ratio (a) . In mitral valve regurgitation, this relationship is reversed, with A being greater than T (b) . This deformation involves predominantly the posterior annulus and, to a lesser extent, the anterior annulus. It may be symmetrical (b) or asymmetrical (c) . Whatever the deformation, the implanted ring restores a normal shape to the annulus (d) .
The remodeling ring restores the normal systolic shape and size of the annulus, a condition needed for optimal leaflet coaptation. It also prevents further deformation.
Restoring the size of the annulus implies restoration of an optimal relationship between the mitral orifice area and the surface area of the leaflets, a sine qua non condition for the leaflets to fully coapt during systole with a regular surface of coaptation. In mitral valve regurgitation, this relationship is modified because of either an orifice that is too large or a surface area of leaflet tissue that is too small, or both. Whatever the discrepancy, the ring corrects the anomalies in a durable fashion.
REMODELING PROSTHETIC RINGS
Three types of “disease specific rings” ( Fig. 8-3 ) ( Table 8-1 ) have been developed to satisfy the anatomical requirements of the three most common diseases. *
* Carpentier-Edwards Classic Ring, Carpentier-Edwards Physio Ring and Carpentier-McCarthy-Adams Etiologix IMR ring (Edwards LifeSciences).
| Ring Size | Orifice Area (mm 2 ) | Transverse Diam. | Vert. Diam. | |
|---|---|---|---|---|
| External | Internal | External | ||
| Classic Ring | ||||
| 26 | 2.88 | 31.2 | 24.3 | 14.7 |
| 28 | 3.39 | 33.2 | 26.3 | 16.0 |
| 30 | 3.95 | 35.2 | 28.3 | 17.3 |
| 32 | 4.55 | 37.2 | 30.3 | 18.6 |
| 34 | 5.19 | 39.2 | 32.3 | 20.9 |
| 36 | 5.86 | 41.2 | 34.3 | 21.1 |
| 38 | 6.59 | 43.4 | 36.4 | 22.4 |
| 40 | 7.36 | 45.4 | 37.5 | 23.7 |
| Physio Ring | ||||
| 24 | 2.74 | 28.7 | 22.9 | 15.2 |
| 26 | 3.25 | 30.7 | 24.9 | 16.4 |
| 28 | 3.80 | 32.9 | 26.9 | 18.0 |
| 30 | 4.40 | 34.9 | 28.9 | 19.2 |
| 32 | 5.04 | 37.1 | 30.9 | 20.7 |
| 34 | 5.72 | 39.1 | 32.9 | 22.0 |
| 36 | 6.45 | 41.2 | 34.8 | 23.3 |
| 38 | 7.22 | 43.2 | 36.8 | 24.8 |
| 40 | 8.04 | 45.3 | 38.7 | 26.11 |
| Ischemic Ring (IMR) | ||||
| 24 | 2.28 | 28.2 | 21.8 | 12.7 |
| 26 | 2.70 | 30.1 | 23.7 | 14.9 |
| 28 | 3.17 | 32.1 | 25.7 | 15.0 |
| 30 | 3.67 | 34.0 | 27.6 | 16.2 |
| 32 | 4.21 | 35.9 | 29.5 | 17.3 |
| 34 | 4.77 | 37.8 | 31.4 | 18.5 |
The Classic ring was primarily designed for rheumatic valvular disease . Its titanium core provides the optimal rigidity that is necessary to achieve the remodeling of a highly fibrotic annulus. The ring is open, however, to provide some flexibility and to allow adaptation of its geometry to individual anatomical variations of the annulus in both the anteroposterior configuration (saddle shape) and the posteroseptal dimension.
The Physio ring , designed preferably for degenerative valvular diseases , has a larger anteroposterior diameter and a larger orifice area. It is a semirigid structure composed of alternate layers of Elgiloy and Mylar plastic material. Its unique anteroposterior selective flexibility provides a shock-absorbing structure while maintaining appropriate support in the transverse dimension to preserve the remodeling effect. The saddle shape of the ring conforms to the contour of the annulus, particularly at the anterior leaflet where the bulging of the aorto-mitral curtain during systole is preserved.
The Ischemic ring (IMR ring) was specifically designed for patients with ischemic, type IIIb dysfunction . It has a rigid titanium structure to ensure non-deformability. Its reduced anteroposterior diameter and asymmetrical shape compensate the tethering of the P2 and P3 segments observed in this setting.
Remodeling annuloplasty rings secure the annulus in a systolic position. This ensures an optimal surface of coaptation.
RING SELECTION
Measurement of the Anterior Leaflet
Regardless of the type of ring, ring selection is based on the measurement of the anterior leaflet, first its base and then its height ( Table 8-1 ).
The measurement of the base of the anterior leaflet requires placement of two landmark sutures at the commissures ( Fig. 8-4 ). The commissures (a) should not be confused with the trigones, which are larger and deeper structures not visible from an atrial view.
Whenever the commissures are difficult to identify because of tissue thickening or jet lesions ( b ), one of the following maneuvers may be helpful:
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Identify the characteristic fanlike commissural chordae that arise from the corresponding papillary muscle (c) .
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Visually extend the commissural edge of the anterior leaflet towards the annulus (d) .
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Exert traction on the main chordae of the anterior leaflet to create a furrow, which visualizes a commissural line (e) .
Once the commissural sutures have been placed, traction is applied on them to slightly distend the base of the anterior leaflet. Then the distance between these two sutures (the intercommissural distance) is measured using specifically designed sizers ( Fig. 8-5 ). Each sizer presents two notches, which should be positioned to match the commissural sutures. One sizer may then look too small (a) or too large (b) or fit perfectly (c) . In the first case, one should select a larger sizer; in the second case, a smaller sizer should be selected.
Many imperfect results following valve repair are due to improper sizing of the anterior leaflet and inadequate ring selection.
The measurement of the height of the anterior leaflet is then carried out. The leaflet is unfurled by vertical downward traction on the marginal chordae using either two nerve hooks ( Fig. 8-6 ) or a right angle clamp ( Fig. 8-7 ). The sizer selected from the measurement of the intercommissural distance is positioned to cover the entire surface area of the stretched anterior leaflet.
Three situations can be observed ( Fig. 8-7 ):
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In more than 90% of the cases, a good correlation is found between the intercommissural distance and the height of the anterior leaflet, as demonstrated by the free edge of the anterior leaflet not extending more than 2 mm beyond the inferior edge of the sizer. In this case, the ring number is selected according to the sizer, and the type of ring according to the pathological process: a Classic ring when dealing with a rheumatic valvular disease, a Physio ring in degenerative valve disease, an IMR ring in ischemic valve disease. In the case of discrepancy between two sizes, one should choose the larger size, except in patients with type IIIb dysfunction.
- •
If the free edge of the anterior leaflet extends 2 to 4 mm beyond the inferior edge of the selected sizer, a one size larger Physio ring is used to prevent the risk of systolic anterior motion (SAM) of the anterior leaflet ( Chapter 15 ).
- •
In rare instances, the free edge of the anterior leaflet extends 5 mm or more beyond the inferior edge of the selected sizer. In this case, a one size larger Classic ring should be selected, the vertical diameter of which is increased by bending its extremities to match the height of the anterior leaflet.
Measurement of the Posterior Leaflet
Measurement of the posterior leaflet is not required to size the ring but is necessary to avoid SAM of the anterior leaflet. The height of each posterior leaflet segment is measured after unfurling the leaflet tissue by traction on the marginal chordae ( Fig. 8-8 ). In the great majority of cases, the leaflet height is between 10 and 15 mm. If the height of any segment is up to or greater than 20 mm, the height of this segment should be reduced to avoid SAM.
