Morphologic features of the rheumatic mitral regurgitant valve by three-dimensional echocardiography.

BACKGROUND

Rheumatic fever remains a significant worldwide cause of mitral regurgitation (MR). We describe morphologic features of the rheumatic MR valve by quantitative 3-dimensional (3D) echocardiography.

METHODS

Eight healthy subjects and 16 patients with less than moderate (n = 7) or more than or equal to moderate (n = 9) rheumatic MR underwent 3D echocardiography by use of freehand transthoracic scanning. Left ventricular (LV) borders, mitral chordae, papillary muscles and annuli were traced at end-diastole (ED) and end-systole (ES) with LV surfaces and mitral annulus reconstructed in 3D. Regional LV function was quantified by myocardial thickening. Regional LV shape was assessed by alignment of diseased ED endocardial surfaces to a reference normal surface.

RESULTS

In the diseased group, LVs were more spheric and had regional shape abnormality in the area of anterior papillary muscle attachment. LV volumes, ejection fraction, and regional function in the areas of papillary attachment were not different. Mitral annular length and area were increased and correlated with LVED volume but were no different in height, sphericity, or beat-to-beat deformity. Chordal and papillary muscle lengths were not reduced. The interchordal angle (between the anterior and posterior chordae) was more acute in MR.

CONCLUSION

Alterations in LV geometry and mitral apparatus morphologic features contribute to rheumatic regurgitant disease. Consequent changes include malalignment of the papillary muscles and a narrowed interchordal angle that is opposite to the widening seen in MR from dilated cardiomyopathy. We hypothesize that leaflet involvement with retraction causes increased tension on the chordae, a reduction in the interchordal angle, and a consequent coaptation defect.