The leaflets from 40 mitral valves obtained from autopsy and surgical material were studied histologically. Eight valves, from subjects without heart disease who ranged from premature infants to 38 year old adults, were used as controls. Twenty-two valves were from patients with left ventricular hypertrophy, and 10 valves were from patients with rheumatic stigmata of old rheumatic disease causing long-standing mitral insufficiency or stenosis, or both. Well defined bundles of striated muscle were found in all cases, except in 2 infants, 1 premature and 1 that was 7 weeks old. In left-sided cardiac lesions, there seemed to be a correlation between the development of these bundles and the degree of muscular hypertrophy. Muscular vessels accompanied the bundles. The most striking hypertrophy of these muscular bundles was found in cases with changes caused by previous rheumatic valvulitis, even though there were interruptions caused by fibrosis, sometimes with focal calcification. Again, muscular vessels accompanied these bundles. These observations are interpreted as evidence of the active function of muscular fibers in the mitral valve. Like the rest of the myocardium, these fibers respond to strain by undergoing hypertrophy.
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine