Left atrial function in volume versus pressure overloaded left atrium.

Left atrial (LA) pressure and volume overload both result in cavity enlargement and complications. LA volume has been shown to predict such complications, but it does not reflect myocardial function, which can be accurately assessed using myocardial deformation measurements. We hypothesized that volume overloaded LA have maintained myocardial function compared to pressure overloaded ones. We tested this hypothesis in 44 patient (mean age 62 ± 12 years) with LA volume overload (LAVOL) due to severe mitral regurgitation (MR) with no indirect signs of elevated left ventricular (LV) filling pressures based on Doppler measured isovolumic relaxation time >60 ms. We compared them with 24 (mean age 64 ± 12 years) patient with LA pressure overload (LAPOL) who proved to have PCWP >15 mmHg on right heart catheterization. Twenty-seven healthy controls (mean age 57 ± 10 years) constituted a control group. Patients with LAVOL had larger LA volumes, higher LV ejection fraction, global LV strain (LVGLS) and transmitral and pulmonary veins flow velocities (p < 0.05) and better LA atrial strain rate (LASR) function compared to LAPOL (p < 0.001). In LAVOL, the LASR during atrial contraction (LASRa) was lower than in controls (p < 0.05) indicating LA mechanical disturbances. LVGLS correlated with peak atrial longitudinal systolic strain in the whole group (r = -0.65, p < 0.001) and less so with LASRa (r = -0.43, p < 0.001) CONCLUSION: Irrespective of a smaller LA volume, LAVOL had less negative effect on LA myocardial function than LAPOL. Thus, monitoring atrial myocardial contraction might be useful in following patients with significant MR.