Besides annular dilatation, the mitral valve annulus can be severely affected by other specific pathological processes, such as extensive calcification or abscesses. In rare circumstances, the annulus may present either a post-traumatic or an idiopathic pseudoaneurysm. These lesions are frequently associated with other valvular or subvalvular lesions, which should be addressed during the same operative procedure. The annulus itself requires specific techniques of reconstruction, the surgical management of which proceeds in two steps: annular decalcification or debridement followed by annular reconstruction.
ANNULAR DECALCIFICATION
The calcification process is often associated with a degenerative valvular disease with preserved pliable leaflets ( Fig. 9-1 ). In most patients it is limited to the annulus but may extend to the leaflet tissue, the ventricular myocardium, and/or the papillary muscles, raising the question of whether the calcium formation should be completely excised before a reconstructive valve procedure is performed, or partially excised, or even left in place followed by a palliative valve procedure. Herein we describe the complete excision of the calcium formation and annular reconstruction, which is our preferred technique in most instances.
The calcium formation is generally encapsulated into a fibrous sheath that can be easily dissected, thus allowing the calcium formation to be removed “en bloc” .
Annular decalcification is carried out by en bloc removal of the calcium bar.
In the typical setting of extensive calcification of the posterior annulus associated with a P2 prolapse, the base of the posterior leaflet is first detached from the calcium bloc and the prolapsing segment is resected (b) . This provides adequate exposure of the calcified annulus ( Fig. 9-2 ).
Decalcification is initiated by incising the endocardium at the atrial and ventricular limits of the calcium formation using a sharp blade knife (a) . The tip of the blade should be oriented in a way that the surrounding tissue is separated from the calcium bar (inset) . Preserving the thin fibrous sheath encapsulating the calcium bar allows an en bloc resection without calcium fragmentation, thus avoiding the use of rongeurs (b) . The dissection is performed by developing a circumferential plane from one extremity of the calcium bar towards the other end, ensuring the entire calcium bloc is removed. The removal of calcium facilitates the exposure of the atrioventricular connective tissue and fat, which contain the circumflex artery and the coronary sinus. The left atrial and ventricular edges are usually covered with a fibrous tissue strong enough to hold the sutures used for the reconstruction of the annulus (inset) .
DEBRIDEMENT OF ANNULAR ABSCESSES
Several types of annular abscesses can be observed in bacterial endocarditis. The lesions affecting the anterior annulus are usually extensions of vegetations and abscesses involving the aortic valve. The lesions affecting the posterior annulus are usually extensions of vegetations involving the posterior leaflet. The resulting abscess may extend to the adjacent myocardium. The operation is carried out step-by-step with the following special precautions to prevent widespread contamination of the surrounding tissues.
- •
A separate operating table and instruments are used for the debridement.
- •
The surgeon should wear two pairs of gloves.
- •
The edges of the surgical field and the left atrium should be protected by Betadine-impregnated towels.
- •
As soon as the lesions are exposed, multiple specimens should be harvested and sent to bacteriology and pathology for analysis.
- •
Debridement consists of excising with scissors all infected and necrotic tissues until healthy tissues are exposed ( Fig. 9-3, a, b ). Curettes should be used with caution as they may spread the infection by destroying the organized underlying tissue. During this process, instruments are dipped in Betadine at repeated short intervals.
FIGURE 9-3
- •
Once all infected tissues have been removed, the towels protecting the edges of the surgical field and the instruments are removed and replaced by new drapes and new instruments while the surgical team changes gloves.
- •
Application of local antiseptic solution at repeated intervals is carried out during the entire reconstruction phase.
Annular debridement with scissors rather than curettes should remove all infected tissues.
ANNULAR RECONSTRUCTION
Depending upon the extension of the annular decalcification or debridement, two techniques are used to restore atrioventricular continuity.
Conventional Technique
The standard technique ( Fig. 9-4 ) is indicated whenever the ventricular extension is limited. Whatever the cause of annular separation or dehiscence following decalcification, debridement, or pseudoaneurysm, a fibrous tissue usually covers both the atrial and the ventricular edges (a) . The atrioventricular continuity is restored by taking advantage of this fibrous tissue using direct 2-0 braided vertical sutures without pledgets. Pledgets are not recommended because they can produce localized myocardial ischemia by compression. The advantage of such reconstruction is to use living tissues without foreign material interposition or compression. The vertical 2-0 braided sutures, called “figure-of-eight-mattress sutures,” are placed into the atrial and ventricular edges. Each suture is first passed through the atrial edge and then through the ventricular edge (b) , thus avoiding injury to the circumflex vessels. The suture is passed once more in the same manner through the atrial edge and the ventricular edge (c) , thus achieving a figure-of-eight stitching (d) . Then this suture is passed upwards through the atrial edge so that all sutures are brought out on the atrial side (e) . All ventricular bites are oriented vertically along the longitudinal axis of the ventricle to preserve myocardial vascularization. For the same reason, these sutures should involve approximately one third of the thickness of the myocardial wall and be at least 1 cm wide (b) , taking advantage of any fibrous tissue or papillary muscle remnants identified at the surface of the endocardium. By exerting progressive but firm traction on the two ends of each set of figure-of-eight mattress sutures while displacing downward the atrial edge with forceps , the atrioventricular continuity is restored (e) . Figure-of-eight mattress sutures also reduce the size of the annulus and displace the surrounding fat and the circumflex vessels away from the reconstructed annulus. During this critically important maneuver of atrial sliding, one should avoid pulling up the ventricular edge towards the atrium. On the contrary, the atrium edge should be displaced towards the ventricle with forceps (inset) .
