LA Morphological and Functional Parameters Assessment:
A stack of contiguous axial cine images covering LA and LAA was
acquired. Tissue-tracking approach was used to quantify LA strain and
phasic volumes from the cine images. Endocardial and epicardial LA
borders was defined at end-systole by a blinded operator. Using defined
borders in each view, the software tracked the LA myocardium in
subsequent frames. The operator validated the generated contours during
the cardiac cycle for quality control. Images with poor tracking were
excluded. In each frame, the LA volume was calculated. Maximum, minimum,
and pre-atrial contraction LA volumes (LAVmax, LAVmin, VPreA) were
extracted from volume curve. The point on the LA volume curve during
diastole just before the fast descent following a period of stability in
LA volume was defined as preatrial contraction volume. At that point,
the atrial strain rate was equal to zero. All measured volumes were
indexed to body surface area. The global longitudinal strain and strain
rate were calculated by averaging the strain values over whole LA.
The volumetric LA function parameters were calculated as follows:
Total LA EF (in %) = [(LAVmax - LAVmin)/LAVmax]x100
Active LAEF (in %) = [(VPreA - LAVmin)/ VPreA]x100
Passive LAEF (in %) = [LAVmax - VPreA)/LAVmax]x100