Pathomorphological aspects, aetiology and natural history of acquired mitral valve stenosis.

Commissural fusion, leaflet thickening and alteration of the subvalvular apparatus are dominant mechanisms causing clinically important mitral stenosis (MS) of rheumatic origin. Calcification and a consequent decrease in leaflet mobility are subsequent features in rheumatic MS and may be the primary mechanisms in MS of degenerative origin. In 1051 consecutive patients with pure or predominant MS requiring surgical intervention, aetiology was rheumatic in 76.9%, infective in 3.3%, degenerative (severe annular and leaflet calcification) in 2.7% and congenital (Lutembacher syndrome) in 1.2%; it was the result of systemic lupus erythematosus (n = 4), carcinoid heart disease (n = 2), endomyocardial fibrosis (n = 2) and rheumatoid arthritis (n = 2) in less than 1%, while in 14.5% of these patients aetiology remained unclassified. The natural history of rheumatic MS is characterized by an asymptomatic latent period, following the initial rheumatic fever (RF). In a prospective study of MS (n = 159) the mean interval between RF and the appearance of symptoms was 16.3 +/- 5.2 years. Twenty-five years after the initial RF 8% of the patients were still asymptomatic, 9% were class II (NYHA), 33% class III and 50% had been operated or were class IV. Progress from mild to severe disability took 9.2 +/- 4.3 years on average. When valve surgery was indicated but refused by the patients, survival with medical treatment was 0.44 +/- 0.06 after 5 years, 0.32 +/- 0.08 after 10 years and 0.19 +/- 0.09 after 15 years.(ABSTRACT TRUNCATED AT 250 WORDS)