Structure, function, and dynamics of the mitral annulus: importance in mitral valve repair for myxamatous mitral valve disease

Abstract

The first successful open repair of a mitral valve for mitral insufficiency was performed by Dr. Dwight McGoon in 1958. He employed a triangular plication of the prolapsing portion of the posterior leaflet and no annuloplasty. Other surgeons subsequently introduced a variety of techniques. Of these, the repair techniques developed by Dr. Alain Carpentier, which incorporated both leaflet repair by a quadrangular resection and annuloplasty, soon proved to be the most effective and reproducible method at that time. Because of the limited knowledge of normal and pathological mitral valve function available in the late 1960s, this repair was based on anatomical and pathological studies obtained through autopsies as well as intraoperatively. While the Carpentier technique continues to be used widely, most centers have found it difficult to repair more than 50-60% of insufficient valves. Only a few centers have achieved higher early success rates. Most have done this by modifications of the classical techniques. Recent reports have documented high rates of recurrence of significant mitral regurgitation in the 5- to 10-year follow-up interval. Our own experience with the Carpentier technique began in 1983. By this time, a growing body of knowledge was accumulating that demonstrated the highly dynamic behavior and important interactions of the six elements of the mitral complex: the left atrium, leaflets, mitral annulus, chordae, papillary muscles, and left ventricle. Because the Carpentier technique uses leaflet resection and rigid or semi-rigid annuloplasty rings, it produces a substantial disruption of these important functions. The mitral annulus is flattened and fully immobilized, and the leaflets also are flattened at their annular attachment. The loss of surface area amd distortion of the subvalvular chordae and papillary muscles from the leaflet resection produces diminished or absent leaflet movement. The entire mitral valve is left in a highly stressed state. In order to overcome these problems, we developed a new technique called the American Correction (Figure 1). The mitral leaflets are never resected, regardless of size. Artificial polytetrafluoroethylene (PTFE) chordae are used to correct localized leaflets prolapse. A full, totally flexible annuloplasty ring is utilized. Most importantly, all adjustments of leaflet position and annular sizing are done during inflation of the heart, with pressurized normal saline delivered at 4 liters a minute into the cavity of the left ventricle. In a controllable fashion, the left ventricular intracavitary and aortic root pressure can be elevated to systolic levels. This produces a series of reproducible changes in the leaflets and annulus that can be correlated with the normally functioning mitral valve in the beating heart (Figures 2-5).