Left atrium by echocardiography in clinical practice: from conventional methods to new echocardiographic techniques

Abstract

Although often referred to as "the forgotten chamber", compared with left ventricle (LV), especially in the past years, the left atrium (LA) plays a critical role in the clinical expression and prognosis of patients with heart and cerebrovascular disease, as demonstrated by several studies. Echocardiographers initially focused on early detection of atrial geometrical abnormalities through monodimensional atrial diameter quantification and then bidimensional (2D) areas and volume estimation. Now, together with conventional echocardiographic parameters, new echocardiographic techniques, such as strain Doppler, 2D speckle tracking and three-dimensional (3D) echocardiography, allow assessing early LA dysfunction and they all play a fundamental role to detect early functional remodelling before anatomical alterations occur. LA dysfunction and its important prognostic implications may be detected sooner by LA strain than by volumetric measurements.

Figure 1

LA dimensions: anteroposterior diameter in parasternal long-axis view (a); longitudinal and transverse diameters in 4-chamber view (b).

Figure 2

Three different atrial volumes during cardiac cycle.

Figure 3

Measurement of left atrial volume from biplane method of disks (modified Simpson's rule) using apical 4-chamber (a) and apical 2-chamber (b) views at ventricular end-systole (maximum volume).

Figure 4

Atrial contraction: wave (a) at mitral inflow (a), peak retrograde diastolic (Ar) velocity at pulmonary venous flow (b) by pulsed Doppler, and late diastolic (A′) velocity by pulsed wave tissue imaging (c).

Figure 5

Left atrial strain (a) and strain rate (b) curves by Doppler. Left atrial reservoir function is studied by peak systolic value (ball), left atrial conduit function by peak early diastolic value (square), and left atrial pump function by peak late diastolic value (triangle).

Figure 6

Left atrial deformation (strain) by speckle tracking. During reservoir function, atrial S increases, reaching a positive peak (systolic peak), at the end of atrial filling, before the mitral valve opening, during LV systole. After mitral valve opening, during conduit phase, atrial S decreases, until reaching a plateau, during diastasis, followed by a second positive peak, during early diastole, before LA contraction. Then there is a negative peak, at the end of atrial contraction.

Figure 7

Left atrial volumes by LVQ Auto 4D echocardiography. (a) Left atrial full-volume data sets are acquired. (b) After manually initializing one point to identify the mitral valve plane and another point for the centre of LA roof, the program automatically identifies the endocardial surface both in end-systole and in end-diastole. (c) Atrial maximum (max) and minimum (min) volumes are obtained and displayed in curve, in numeric values, and in 3D image (in red).

Figure 8

Left atrial volumes by TomTec 4D echocardiography. (a) After LA full-volume data acquisition, TomTec software displays LA in 3 different apical planes (4-chamber; 2-chamber, long-axis). (b) The endocardial border is surrounded on end-diastolic and end-systolic frames and, if needed, manually corrected. (c) Atrial maximum (max) and minimum (min) volumes are obtained using semiautomated border detection algorithm and displayed in numeric values and in 3D image (in green).