Functional anatomy of severe mitral regurgitation in active rheumatic carditis

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Abstract

The mechanism of severe mitral regurgitation (MR) due to active rheumatic carditis is ill defined. This study involved 73 patients, aged 7 to 27 years (mean 13), with severe MR and active rheumatic carditis who were subjected to surgery. Sixty-one were studied retrospectively (group 1) and 12 prospectively (group 2). Active rheumatic carditis was diagnosed according to the modified Jones' criteria, morphologic appearances of the heart at operation and histology of the valve. All patients had preoperative 2-dimensional echocardiographic and intraoperative assessment of the mitral valve apparatus. The presence of mitral valve prolapse—defined as failure of leaflet edge coaptation resulting in systolic displacement of the free edge of the involved leaflet toward the left atrium—was determined in all patients. Mitral anular diameter and maximal systolic chordal length were measured at 2-dimensional echocardiography in group 2 patients and compared to values obtained from matched control subjects. Anular and chordal dimensions in 6 of the group 2 patients were correlated with precise measurements obtained at surgery. Mitral valve prolapse involving the anterior leaflet was detected on echocardiography and confirmed at surgery in 69 patients (94%). Mitral anular dilatation was observed at operation in 70 patients (96%). Maximal anular diameter was significantly greater (p < 0.0001) than in matched control subjects (37 ± 4 vs 23 ± 2 mm). The mean anular dimension measured at surgery (36 ± 3 mm) was similar to that obtained by echocardiography and individual values using the 2 methods correlated well (r = 0.93). Chordal elongation was observed in 66 patients at operation (90%). Maximal systolic chordal length was significantly greater (p < 0.01) than that in matched control subjects (23 ± 4 vs 17 ± 1 mm), individual values for chordal length at operation correlated well (r = 0.99) with 2-dimensional echocardiographic measurements. Severe MR in active rheumatic carditis is due to a combination of mitral anular dilatation, chordal elongation and prolapse of the anterior leaflet.

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    This study was supported in part by research grant L72 from the Chairman's Fund, Anglo American Corporation of South Africa (Ltd.) and by the Boris Wilson Cardiac Fund, University of the Witwatersrand.

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