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J Thorac Cardiovasc Surg 1996;112:1117-1119
© 1996 Mosby, Inc.
BRIEF COMMUNICATIONS |
Leipzig, Germany, and Boston Mass.
From the Herzzentrum, University of Leipzig, Leipzig, Germany, and the Departments of Pathology and Cardiology, Children's Hospital, Harvard Medical School, Boston, Mass.
Received for publication Dec. 5, 1995 Accepted for publication Feb. 26, 1996.
Management of the mitral valve is the most critical component of the repair of common atrioventricular canal (CAVC).
1,2 Patients with normal karyotype have a significantly higher reoperation rate for postoperative mitral valve regurgitation (as great as 50%) than do patients with Down syndrome (as great as 10%). 2 This difference may be caused primarily by tissue scarcity, deficiency of the superior or inferior bridging leaflets, or both. On the basis of these observations, we recently developed a modified surgical technique for reconstruction of the tissue-deficient bridging leaflets of the mitral valve, with the objective of decreasing the prevalence of postoperative regurgitation in this difficult subset of cases.
In the repair of CAVC, we prefer to close the atrioventricular septal defect with a single glutaraldehyde-preserved pericardial patch. To avoid iatrogenic regurgitation of the mitral valve, the tricuspid valve, or both, it is imperative not to use too wide a patch. After assessment of valve anatomy, with particular attention to the coaptation of the bridging leaflets, a marking suture is placed to identify the point of creation of the base of the cleft in the mitral valve. Subsequently, the superior and inferior bridging leaflets are divided slightly to the right ventricular side. If sufficient valve tissue is available, the cleft separating the bridging leaflets is closed with multiple interrupted 6-0 polypropylene sutures (Prolene; Ethicon, Inc., Somerville, N.J.), up to the point at which the first set of chordal attachments is approached. The neoseptal leaflets of the tricuspid and mitral valves are anchored to the atrioventricular septal patch with multiple 5-0 braided sutures supported with small felt pledgets.
Scarcity or deficiency of leaflet tissue of the bridging leaflets may render closure of the cleft impossible. In this setting, patch augmentation of the tissue-deficient bridging leaflets may be a valuable technique. As a first step in the repair, if possible without causing undue tension, the free edges of the bridging leaflets are approximated with one or two interrupted 6-0 Prolene sutures (Fig. 1). An untreated autologous pericardial patch is tailored to the size and configuration of the defect. If the tissue defect extends up to the atrioventricular septal patch, the pericardial patch is first anchored to that patch with braided 5-0 sutures supported with felt pledgets. Subsequently, the pericardial patch is sutured to the edges of the bridging leaflets with 6-0 Prolene sutures, preferably with an interrupted suture technique. If the free edges of the bridging leaflets cannot be approximated without causing undue tension, the pericardial patch augmentation is extended up to the free edge of the neoseptal leaflet (Fig. 2). After repair of the mitral valve, the tricuspid valve, or both, 3 valve function is tested by forceful injection of normal saline solution into the respective ventricles. The atrial component of the atrioventricular septal defect is closed with the remaining glutaraldehyde-preserved pericardial patch. Echocardiography is routinely used to assess atrioventricular valve function and to exclude residual interatrial or interventricular communications and left ventricular outflow tract obstruction.
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Although the cleft between the bridging leaflets in CAVC may physiologically function as a commissure and be competent, we have major objections to the use of the term commissure in this setting. We believe that the term commissure (derived from the Latin cum and mittere, meaning "to send together"), as originally proposed by Carpentier 1 and later propagated by Anderson and coworkers, 4 should be reserved for a breach in the leaflet skirt of the atrioventricular valve that is supported by fan-shaped chordae tendineae inserting into a single papillary muscle group. By contrast, the chordae that are attached to the free edge of the superior and inferior bridging leaflets at the end of the cleft insert into two opposite papillary muscles: the chordae that control the superior bridging leaflet insert into the anterolateral papillary muscle group, whereas those controlling the inferior bridging leaflet insert into the posteromedial papillary muscle group. The tensor apparatus around the cleft does not pull the superior and inferior bridging leaflets together, but rather pulls them apart. Moreover, the cleft between the bridging leaflets is not supported by chordae.
In our experience and that of others, 2,5 in patients with CAVC and normal karyotype (as opposed to patients with Down syndrome), related to the often tenuous presence of two atrioventricular valve orifices, the bridging leaflets of the atrioventricular valve may scarcely be developed, are usually displaced inferiorly, and are (partially) attached to the "scooped out" ventricular crest, resulting in a marginal area of coaptation between the bridging leaflets and potential crowding of the left ventricular outflow tract. In this setting, even mild dilatation of the common atrioventricular valve orifice or mitral valve orifice as a result of volume loading of the left ventricle (as is the case after repair of CAVC) may render the mitral valve regurgitant, especially if it has been repaired in a trileaflet fashion. Although the trileaflet atrioventricular valve concept in CAVC, as propagated by Carpentier 1 and Anderson and coworkers, 4 is attractive from a surgical viewpoint because it allows preservation of the mitral valve in a natural configuration, we and others who have used this technique 2 have found that it can lead to unpredictable early and long-term results. Although there has been concern that bileaflet repair of the mitral valve may lead to leaflet scarring at the cleft closure site, potentially resulting in regurgitation or stenosis in the long-term, a recent clinical series in which the cleft was routinely approximated demonstrated that this type of repair holds up with time. 6 At a mean 59 months after repair, 137 of 146 survivors (94%) had only trivial or mild regurgitation of the mitral valve, and none had substantial stenosis. 6 This information eliminates one of our major concerns regarding the bileaflet approach.
The technique of patch augmentation of the tissue-deficient mitral valve described here is a useful adjunct for reconstruction of atrioventricular valves in CAVC, 3 with encouraging medium-term results. It is important to use untreated pericardial patch, as opposed to glutaraldehyde-preserved pericardial patch, because untreated patch is more mobile and pliable. In our experience, it has superior properties as a leaflet replacement material. The technique described here may be especially valuable in the occasional case of a patient with marginal or absent coaptation of the bridging leaflets in whom closure of the cleft results in excessive tension on the cleft repair, with inherent risk of dehiscence. Another, possibly even greater benefit of this technique is that maximal height of the reconstructed neoseptal leaflet can be obtained because the bridging leaflets are approximated truly side by side, resulting in the largest possible distance between the atrioventricular septal patch and the free edge of the neoseptal leaflet and adding more surface for coaptation with the mural leaflet. In the standard technique of closure of the cleft, this height is likely to be reduced to minimize tension on the cleft repair by anchoring the central segment of the cleft to the atrioventricular septal patch, rather than closing it side by side. Finally, an additional annuloplasty (especially of the inferoposterior commissure) may be necessary to achieve complete competence of the mitral valve.
Footnotes
(J THORAC CARDIOVASC SURG 1996;112:1117-9) 
References
This article has been cited by other articles:
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  J. A.M. van Son, P. Kinzel, and F. W. Mohr Pericardial patch augmentation of anterior tricuspid leaflet in Ebstein's anomaly Ann. Thorac. Surg., November 1, 1998; 66(5): 1831 - 1832. [Abstract] [Full Text] [PDF]
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J. A. M. van Son, T. Walther, and F. W. Mohr Patch Augmentation of Regurgitant Common Atrioventricular Valve in Univentricular Physiology Ann. Thorac. Surg., August 1, 1997; 64(2): 508 - 510. [Abstract] [Full Text]
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J. A. M. van Son, C. K. Phoon, N. H. Silverman, and G. S. Haas Predicting Feasibility of Biventricular Repair of Right-Dominant Unbalanced Atrioventricular Canal Ann. Thorac. Surg., June 1, 1997; 63(6): 1657 - 1663. [Abstract] [Full Text]
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