A. Severe mitral annular calcification
B. Carcinoid valve disease
C. Rheumatic valve disease
D. Congenital mitral stenosis
By far the number one cause of MS is rheumatic valvular disease (RVD). This accounts for approximately 98% of all MS. RVD is more common in females than in males and up to 50% of the time, a person with newly diagnosed MS will not report a history of rheumatic fever as a child. The incidence of MS has drastically been reduced in the United States since the advent of antibiotics resulting in the aggressive treatment of Streptococcus pyogenes pharyngitis, the primary cause of rheumatic heart disease.
Many other causes of impaired LV filling exist and they can mimic MS in both hemodynamics and symptoms. LA myxomas are relatively common and occur as a part of the Carney complex. These slow growing tumors obstruct the mitral valve causing MS. Pulmonary vein stenosis after attempted radiofrequency ablation of atrial fibrillation can occur and this may mimic MS. Newer techniques have reduced this risk. The anterior leaflet of the mitral valve is the most common site for a infectious vegetation to form in patients with infective endocarditis. If the vegetation grows to a large enough size, as often occurs in fungal endocarditis, obstruction of LV filling may occur and symptoms of MS may develop. When the regurgitant jet from severe aortic regurgitation strikes the anterior leaflet of the mitral valve, mitral stenosis hemodynamics can occur (causing the Austin-Flint murmur). Some other rare causes of true MS include congenital MS, severe mitral annular calcification, and prosthetic valve dysfunction.