Importance of the Left Atrium: More Than a Bystander?

Abstract

Left atrial size and function parameters are associated with adverse outcomes in multiple disease states, including heart failure with reduced and preserved ejection fraction. Recent data suggest that phasic left atrial function and left atrial stain measurements also hold prognostic information. Three-dimensional echocardiography provides more accurate and reproducible quantification of left atrial volumes than 2-dimensional echocardiography when compared with cardiac magnetic resonance reference standards. Greater accessibility to these advanced imaging techniques allows for the integration of these parameters into routine clinical practice.

Keywords: Diastolic dysfunction; Left atrial appendage; Left atrium; Strain; Three-dimensional echocardiography.

Fig. 1.

TEE examination of the LAA before Watchman occluder device implantation, including 2DE images of the LAA at 0°, 45°, 90°, and 135° (A–D), pulsed Doppler LAA velocities (E), and 3DE enface of the LAA ostium (F).

Fig. 2.

TTE examinations of LAA morphologies: chicken wing (A), cactus (B), windsock (C), and cauliflower (D).

Fig. 3.

Left atrial reservoir, conduit, and booster LA function in relation to the cardiac cycle (top) with the corresponding LA volume curves during these phases (bottom). The maximal volume (V_max) at end-systole just before the opening of the mitral valve, minimal volume (V_min) at end-diastole before mitral valve closure, and the volume before atrial contraction (V_preA) before mitral valve reopening at the time of the P wave on ECG. TASV is V_max − V_min and the AASV is the V_preA − V_min, which represents the LA booster phase.

Fig. 4.

Apical 4-chamber images of the LA depicting both the area-length and biplane method of disks equations for calculation of LA volumes.

Fig. 5.

Example of an apical 4-chamber view, optimized to depict maximal length of the LV (left). In this view, the LA is foreshortened, in contrast with an LA-focused view specifically optimized to visualize the atrium at its maximal length (right). Atrial foreshortening occurs because the long axes of the ventricle are not the same, as depicted in this 3D reconstruction of both left heart chambers (center).

Fig. 6.

Example of the LA cavity cast shown at 2 different phases of the cardiac cycle depicting the minimal and maximal LAV and the corresponding time curve depicting the LAV throughout the cardiac cycle from 0% to 100% of the R-R interval (left). Linear regression and Bland-Altman analyses of 2DE and 3DE measurements of maximal LAV. Correlation coefficients (r values) are shown; solid horizontal lines depict the bias of each technique (mean difference from the CMR reference, whereas dashed lines indicate the limits of agreement; 2 standard deviations around the mean difference) (right).

Fig. 7.

Dynamic HeartModel A.I. application display showing the dynamic contours on the automatically aligned AP4, AP3, and AP2 views along with the volume waveform and the 3D shell of the left atrial and ventricular cavity.

Fig. 8.

LA strain time curves and an electrocardiogram using an R-wave zero reference (A) and P-wave zero reference point (B). Using the R-wave reference point, the total LA strain is positive and the sum of the early and late diastolic strain. Using the P-wave reference point, the total LA strain is the sum of the negative and positive strain.

Fig. 9.

Peak longitudinal strain curves are depicted as the mean of each subgroup of diastolic dysfunction from grade 0 to grade 4. Diastolic dysfunction grade based on the 2009 ASE guidelines.