Floppy mitral valves (grades 2-4) have an incidence of approximately 4-5% in routine necropsies, with higher grades directly causing death via endocarditis or severe regurgitation.
In the study of 1984 routine hospital necropsies the mitral valve was examined from the left atrium in the intact heart with a pressure head of water in the left ventricle. The valve was graded from grade 0 (normal) to grade 4: grade 1, expansion of a small part of one cusp only; grade 2, over one-third of the posterior cusp or one-half of the anterior cusp expanded, with intact chordae; grade 3, ruptured chordae; grade 4, chordal fusion to ventricular wall. The frequency ofgrade 2 to 4 floppy valves rose with age with an overall incidence of 3 9 per cent in men and 5-2 per cent in women. Grade 1 floppy valves have no clinical significance. Grade 2 floppy valves were found to be associated with auscultatory signs but often only contributed to cardiac failure or were coincidental findings. Grade 3 and 4 floppy valves were direct causes of death from bacterial endocarditis and/or severe mitral regurgitation.
Davies et al. (1978) studied this question.