Left atrial function in patients with mitral valve regurgitation

The purpose of this study was to assess left atrial (LA) function and myocardial mechanics in patients with degenerative mitral regurgitation (MR). Eighty patients with degenerative MR and twenty control subjects were included prospectively. LA volume (LAV) and right atrial (RA) volume (RAV) were measured with three-dimensional transthoracic echocardiography at three phases of the cardiac cycle as maximal volume (LAVmax and RAVmax), minimal volume (LAVmin and RAVmin), and volume before atrial contraction (LAVpre-A and RAVpre-A). From these volumes, active stroke volume (SV), distensibility, and emptying fraction were calculated. LA strain and strain rate were measured with vector velocity imaging on four- and two-chamber views. Left ventricular (LV) filling pressures were increased in patients with severe MR (E/E': 16 ± 4 vs. 10 ± 3 in control subjects). LAVmax, LAVmin, and LAVpre-A all increased with increasing MR volume. As LAVpre-A increased, both LA total SV (r = 0.68, P < 0.001) and passive filling volume (r = 0.76, P < 0.001) increased. LA active SV increased with LAVpre-A up to a certain point, upon which it decreased despite further increased LAVpre-A (r = 0.53, P < 0.001). LA late negative strain decreased with increasing MR volume. A positive correlation existed between LA late negative strain and LA active emptying fraction (r = 0.55, P < 0.001). In contrast, RA function was comparable between groups. In conclusion, LA contractility (active SV) increased in response to an increase in LA preload (LAVpre-A) up to a point beyond which LA contractility (active SV) decreased. Whether this is due to working of the LA at the descending limb of the Frank-Starling curve or mainly due to changes in afterload still remains unclear.