Primary mitral regurgitation is due to valve disease which may be caused by:
- redundant cusp mitral leaflet prolapse (a 'floppy' mitral valve). This is the commonest cause of mitral regurgitation in Europe and North America.
- rheumatic mitral regurgitation - this is frequently associated with mitral stenosis and aortic valve disease. Chordal rupture does not occur in this condition. The cusps are shrunken and fibrotic.
- ischaemic heart disease - a mild degree of mitral regurgitation (late systolic murmur) often follows inferior infarction. This condition is relatively benign unless there is papillary muscle rupture.
- localised cardiomyopathy affecting a papillary muscle - this is a rare cause of primary mitral regurgitation.
- connective tissue disease (eg Marfan's syndrome, Ehlers Danlos, osteogenesis imperfecta) may result in degenerative valve changes
- in elderly women - calcification of the mitral ring (very rare)
Secondary mitral regurgitation occurs secondary to a dilated left ventricle e.g. in dilated cardiomyopathy, ischaemic heart disease, acute myocarditis) but is seldom severe. This may be difficult to distinguish from end-stage primary regurgitation.