Background Dilated cardiomyopathy (DCM) is commonly associated with functional mitral regurgitation and often raised left atrial pressure (LAP).
Methods We studied 35 DCM patients (17 with normal LAP and 18 with raised LAP (left ventricular end-diastolic volume (LVEDV) 168 ± 23 ml) and compared them with 15 normal individuals (LVEDV 130 ± 28 ml). Mitral annulus anteroposterior, commissure diameters, sphericity index (SI), annulus area (mitral valve area; MVA), and non-planar angle between leaflet projections were measured using real-time 3D transthoracic echocardiography.
Results In DCM, all mitral annulus measurements except SI were greater than normal (p<0.005). Despite changes in left ventricular cavity size, DCM with normal LAP behaved normally showing enlargement of anteroposterior (p<0.05) and SI (p<0.01) at end-systole versus end-diastole. In DCM with raised LAP, only SI was greater at end-systole versus end-diastole (p = 0.05). In them, mitral annulus anteroposterior (p<0.005), SI (p<0.01), and MVA (p<0.05) were larger than those in DCM with normal LAP (see table and fig).
Conclusion MVA and subvalvar apparatus are uniformly dilated in DCM. In the absence of raised LAP the mitral annulus behaves normally, becoming more spherical at end-systole, a shape change that is attenuated by high LAP. This and the further increase in anteroposterior diameter, SI and MVA may partly contribute to the development of functional mitral regurgitation, frequently seen in DCM with raised LAP.