Left Atrial Mechanics
Left atrial (LA) enlargement has long been recognized as a marker of increased cardiovascular risk 24. However, impaired LA phasic function evident by reduced strain occurs prior to LA enlargement and may be an early marker of risk25. Thin atrial walls challenge deformation analysis, however a growing body of evidence utilizing LA strain is accumulating and recent guidelines for standardization of LA deformation have been published26.
The LA functions as a reservoir for pulmonary venous return during ventricular systole, as a conduit during early ventricular filling, and as a contractile booster pump that contributes to late ventricular filling. Atrioventricular deformation are closely interrelated and governed by the concepts of atrioventricular coupling. Reservoir function is dependent on both on atrial volume and compliance, as well as LV systolic longitudinal annular excursion. Conduit function is dependent on the atrioventricular pressure gradient created during LV diastolic recoil. Atrial contractile function is dependent on both intrinsic pump function and late diastolic ventricular afterload.