Morphological Investigations of the Anterior Leaflet and its Chordae Tendineae in Canine Mitral Valves

Although mitral valve repair (MVR)—for mitral regurgitation (MR) secondary to chronic valvular heart disease (CVHD)— is becoming more common in veterinary medicine, there is little information about the morphology of the mitral valve apparatus that is used to guide veterinary surgeons. Therefore, we investigated the locations of MR using echocardiography in 12 client-owned dogs with MR. Nine (75%) of these dogs had MR arising from the tip of the anterior leaflet (AL). In addition, we investigated the morphology of the AL and its chordae tendineae by examining the heart specimens of 10 healthy beagles. The tip of the AL—determined by echocardiography as the cause of MR—was secured by the chordae tendineae (CT), which were thinner than those attached to the base of the AL on each papillary muscle (anterior and posterior papillary muscle; p = 0.0186 and p = 0.0198, respectively). In the normal AL, the free edge of the posterior half was broader than that of the anterior half (p = 0.0001). In conclusion, the CT attached to the tip of the AL might be a contributor of MR in dogs because of its thin nature. It should be reconstructed during MVR, since the tip of the valve cusp in the left ventricle is secured for mitral valve coaptation. The posterior half of the anterior leaflet might require the use of more artificial chords because of its wide free edge.