Mitral regurgitation after cardiac transplantation.

The contribution of the left atrium to mitral valve competence was assessed using the model of altered atrial size and geometry created by atrial anastomosis during cardiac transplantation. Sixteen patients underwent Doppler and 2-dimensional echocardiography after orthotopic transplantation. Mitral regurgitation was present in 14 of 16 patients. Left atrial geometry was uniformly abnormal, in a "snowman" configuration. Compared with 16 normal control subjects, the transplanted left atria were dilated (23 +/- 6 vs 13 +/- 3 cm2 during ventricular systole, p less than 0.001). Mitral valve anular diameter indexes, anular systolic reduction and ventricular function were normal in both groups. Ventricular volumes were small in the transplanted heart relative to donor body size (15 +/- 5 vs 20 +/- 8 cm3/m2 in systole, p less than 0.05). The ratio between ventricular length and anular diameter was smaller in the transplant patients (0.87 +/- 0.1 vs 1.0 +/- 0.2, p less than 0.05). In the presence of abnormal left atria, mitral regurgitation may occur without other structural abnormalities of the mitral apparatus. This study suggests that the left atrium plays an important role in mitral valve competence for primary cardiac disease associated with left atrial enlargement, even in the absence of intrinsic mitral valve disease or left ventricular dysfunction.