[Blood vessels in normal and abnormal mitral valve leaflets]

The incidence and the distribution of blood vessels were examined in normal and abnormal mitral valve leaflets.

Normal valves were obtained from 12 autopsy cases without cardiovascular disease (8 men, 4 women, 33 to 93 years of age). Twenty-one abnormal valves were obtained at the time of mitral valve replacement (12 men, 9 women, 16 to 78 years of age). Clinical and pathological diagnoses were rheumatic valvular disease (RVD: n=8), floppy mitral valve (FMV: n=9), and healed infective endocarditis (HIE: n=4, 1 with RVD, 3 with FMV). The number of vessels was counted at the surgical excision line of the valvular rings by immunohistochemical study using Factor VIII related antigen and CD34. Histologic studies were also made at the 5 mm distal line from the ring in normal valves, and at the vertical line to the ring in abnormal valves.

In normal valves, the number of vessels at the ring area, except in myocardial tissues that extended from the left atrium to the auricularis, ranged from 3 to 184. Vessels were also found at the 5 mm distal area from the ring in 6 valves out of 12. Vessels were mainly distributed near the commissure areas of the auricularis and/or the spongiosa and were extended with myocardial tissues. There was no difference in the number of vessels related to age or sex. In RVD, the number of vessels at the ring area ranged from 22 to 517 in 8 anterior leaflets (AML) and 2 to 151 in 5 posterior leaflets (PML). Many vessels also appeared in the distal spongiosa of the leaflets, and arterioles were frequently found in these areas. In FMV, a few (3 and 6) vessels were found in 2 leaflets (AML: 2/8, PML: 0/4). In HIE, the number of vessels was 216 in the case with RVD, and 3 to 110 in cases with FMV.

At the ring area, normal mitral valve leaflets were supplied with nutrition from blood vessels that mainly extended from the left atrium with myocardial tissues. In RVD, the vessels branched from previously existing capillaries, extending to the distal area, and increased in number. Mechanical stress during opening and closing of the leaflets contributes to the arterialization of these vessels. In FMV, the number of capillaries, which is smaller than in normal valves, might be related to the progression of this disorder. In HIE with valvular disease, the number of vessels is related to the preexisting disease.