Comparative assessment of chordal preservation versus chordal resection during mitral valve replacement

Left ventricular function often deteriorates after mitral valve replacement for mitral regurgitation. It has been postulated that disruption of the mitral valve apparatus at operation is a major mechanism of postoperative dysfunction. The hypothesis tested in this investigation was that chordal preservation results in more favorable left ventricular function. Sixty-nine patients with isolated mitral regurgitation who underwent mitral valve replacement were studied before and 6 months after operation by treadmill exercise testing, catheterization, echocardiography, and radionuclide angiography. Nine patients underwent mitral valve replacement with preservation of the entire mitral apparatus and five with preservation of the posterior leaflet and attached chordae. The remaining 55 had mitral valve replacement with complete excision of the native valve. Preoperatively, there were no differences among groups in age, gender, exercise capacity, cardiac index, rest or exercise ejection fraction, fractional shortening, or pulmonary artery pressures. There were four perioperative deaths (7%) and eight late deaths among the 55 patients with chordal resection but no early or late deaths of patients whose chordae were preserved (p = 0.05). In patients in whom the chordae were excised, exercise capacity, left ventricular systolic dimensions, and cardiac index did not improve after mitral valve replacement, and left ventricular function deteriorated, as evidenced by a reduction of both the resting and exercise ejection fractions (from 46% ± 13% to 31% ± 13%, p = 0.0001, and from 49% ± 12% to 37% ± 14%, p = 0.0007, respectively) and fractional shortening (from 34% ± 10% to 26% ± 14%, p = 0.0001). In contrast, exercise capacity improved after mitral valve replacement in patients in whom the entire apparatus was spared (by 4 ± 3 minutes, p = 0.05), left ventricular systolic dimensions decreased (from 44 ± 8 to 36 ± 9 mm, p = 0.03), and left ventricular function was maintained or improved, as evidenced by preservation of the resting ejection fraction (preoperative, 50% ± 14%; postoperative, 54% ± 11%; p = no significant difference), exercise ejection fraction (46% ± 16% versus 52% ± 9%, p = no significant difference), fractional shortening (from 31% ± 9% to 28% ± 9%, p = no significant difference), and an increase in the cardiac index (from 2.0 ± 0.3 to 2.7 ± 0.5 L/min/m², p = 0.05). No statistically significant differences between posterior chordal resection only and preservation of the entire apparatus were found. These data demonstrate that postoperative survival, exercise capacity, and left ventricular function are better in patients who undergo mitral valve replacement with chordal preservation than in patients in whom the chordae are excised.