Mitral regurgitation with rupture of normal chordae tendineae.

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Abstract
A description is given of 6 patients in whom there was severe mitral incompetence associated with supple voluminous leaflets, annular dilatation, and rupture of hlstologically normal chordae tendineae. All were subjected to operation, and 4 survived. The chordae were replaced in 4. It is believed that in these cases, and possibly in 2 others with endocardlal cushion defects, rupture was not due to local chordal disease. The hypothesis is advanced that the chordae ruptured because they were not adapted to resist the pressures thrown upon them by progressive mitral regurgitation caused by dilatation of the annulus of the valve. A cause of mitral regurgitation preceding the chordal rupture must, therefore, be present to account for the annular dilatation. The original, minor incompetence may be due to any congenital or acquired lesion, and such were found in 5 of the cases presented. All the patients were known to have had heart murmurs many years before the onset of serious cardiac symptoms. Only after the annulus has dilated sufficiently to impair wide surface apposition of the leaflets, do the chordae come under pathological strain. Chordal rupture results in sudden aggravation of the incompetence, and serial rupture may then occur. Artificial chordae resist little strain during ventricular systole. It is suggested that the function of chordae tendineae is to restrain the leaflet edges early in ventricular systole, so converting them to cup-shaped structures, the surfaces of which can oppose. As a result of the wide support which the leaflets then provide for each other, the chordae of a competent valve are relieved of the burden of resisting the full left ventricular pressure.