Importance of left ventricular contraction for left atrial reservoir function

The determinants of left atrial (LA) reservoir function have not been clarified.

To elucidate the effect of left ventricular (LV) contraction on LA reservoir volume (ΔV_LA), volume change due to mitral annular downward motion and aortic root anterior motion, which are related to LV contraction during systole, was calculated in 72 consecutive subjects [42 patients without any cardiac disease (control group), 13 patients with heart failure with reduced ejection fraction (HFrEF group) and 17 with preserved ejection fraction (HFpEF group)]. LA volume was calculated using the modified Simpson's method of bi-plane 2-D echocardiograms. ΔV_LA was the difference between the maximum and minimum LA volumes. LA volume change according to mitral annular motion (ΔV_MA) and aortic root motion (ΔV_AR) were calculated by assuming an oval frustum and dented wedge, respectively.

In the normal control group, ΔV_AR + ΔV_MA was 11.7 ml on average, correlating to ΔV_LA (r = 0.55, p < 0.01), and the contribution rate to LA reservoir volume ((ΔV_AR + ΔV_MA)/ΔV_LA) was 56% on average. In both, the HFrEF and HFpEF groups, ΔV_AR, ΔV_MA, and the contribution rate were significantly smaller than those in normal control group. Stroke volume correlated to ΔV_AR and ΔV_MA. The larger the maximum LA volume was, the smaller the contribution rate was. The smaller the rate was, the higher the systolic pulmonary artery pressure was.

Both mitral annular motion and aortic root anterior motion, which are related to ventricular contraction, are important for the LA reservoir volume recruitment.