LA strain measurements can be obtained by two dimensional (2D) speckle tracking echocardiography (STE). Longitudinal strain and strain rate curves are generated for each of six atrial segments, obtained from the apical four and two chamber views.

In the reservoir phase, as the LA fills and stretches, there is positive atrial strain that reaches its peak in systole at the end of LA filling, prior to opening of the mitral valve. Following this, passive LA emptying ensues with opening of the mitral valve resulting in decreased atrial strain with negative deflection of the strain curve up to a plateau period which is analogous to diastasis. LA reservoir strain (LARS), or peak atrial longitudinal strain or LA systolic strain, is measured at the end of the reservoir phase.

Statistical significant of LA reservoir strain to estimate high HFA-PEFF score (≥5) in multiple linear regression analysis.

Relative importance of left atrial reservoir strain among variables, including component of HFA-PEFF score, using supervised machine learning algorithm (random forest analysis) to estimate high HFA-PEFF score (≥5). LA reserver strain was measured using Automated Functional Imaging (AFI) of the left atrium 3.0 version (GE Healthcare)