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.