). Open-heart operations for correction of mitral incompetence and for treatment of the grossly diseased stenosed valve are becoming commonplace, and the results of valve replacement are now promising. This advance is in part due to the surgeon's improved anatomical knowledge, but some details of the structural relations of the valve are not widely known, and there is still a need for standardization of terminology. An effort is made in this paper to systematize the description of this complex valve and to orientate it in relation to the surrounding structures that must be avoided at operation. We also present data of the dimensions of the valve, which may be of interest to anatomists and surgeons. Familiarity with the normal measurements of the component parts of the valve will, at operation, help the surgeon to assess the exact mechanical reason for valve insufficiency.
MATERIALS AND METHODSThe following descriptions are based upon observations made during intra-cardiac operations and dissections of fresh human hearts which were later preserved in diglycerol stearate by the method described by Kramer (1938). These specimens, if correctly prepared, retain their true features and relationships and can be conveniently studied or used for teaching purposes.The dimensions of the valve were taken from 10 normal hearts. The mitral leaflets with the annulus, chordae, and papillary muscles were removed, and the valve was flattened out in a single plane by dividing its ring at the lateral commissure and by half splitting the medial papillary muscle mass. The opened-out valves were then pinned to cork boards during fixation in formalin and were finally waxed with diglycerol stearate.Measurements were made with point dividers and an ordinary metric ruler. To determine the surface areas, the leaflets were traced on graph paper and the enclosed squares were counted.
ANATOMYVarious names have been given to the leaflet of the mitral valve that is related to the aorta. It has been called the aortic, the septal, the ventral, the antero-medial or the anterior leaflet. Multiple names have also been given to the commissures and papillary muscles. The terminology we suggest, whilst neither original nor absolutely precise, is simple and descriptive. Figure 1 shows the four valves orientated to the saggital plane of the body. The mitral leaflet nearest the aortic valve is the anterior leaflet, and the one opposite is the posterior leaflet. The commissure pointing towards the mid-line is the medial, and the one opposite is the lateral. The papillary muscles, being related to the commissures, are also referred to as medial and lateral.The fibrous skeleton of the heart provides the key to understanding the anatomical relationships of the mitral valve. Its keystone is the aortic root, which is the extension of the aorta below the aortic valves, and is the thickest most rigid part of the skeleton. Fibrous extensions from the aortic root form the scaffold for the pulmonary, tricuspid, and mitral rings. Figure 2 is a diagram of the fibrous ...
