Echocardiographic Strain Assessment
Strain assessment was performed off-line using vector velocity imaging
(Siemens Acuson SC 2000, version 5). All images analyzed were obtained
at 50-80 frames per second at end expiration. The region of interest was
traced with a point-and-click approach on the endocardium of the RV free
wall at end-diastole in the RV-focused apical four-chamber view. A
broader region of interest was subsequently generated and manually
adjusted if necessary. The Program automatically divided the RV free
wall into three segments and performed the analysis of the deformation
frame by frame. This process allowed an automated confirmation of the
contour and generated deformation values. The peak strain values from
the three free wall segments were averaged, and the mean value was taken
as the RV free wall strain (RVFWS) (5,7,11, 12, 13).
For the right atrium (RA), the endocardial border was traced in the
apical 4-chamber view, excluding the appendage and the Eustachian valve
from the RA cavity. RA longitudinal strain curves were generated
throughout the cardiac cycle with R-R gating. Accuracy of the automated
border tracking was verified and manually adjusted if needed. Tracking
was repeated three times, and averages were used for analysis as
reported in guidelines (5,8, 11). The peak RA reservoir strain in
ventricular systole, conduit strain in early diastole and peak
contractile phase strain during atrial systole/ late diastole were
measured and expressed as percentage. RA total reservoir phase and RA
contractile phase were assessed by measuring the corresponding peak
strains. The conduit strain was calculated as the difference between RA
total reservoir strain and RA contractile strain (Figure 1 ).
To assess intra- and inter-observer reproducibility of RA reservoir,
conduit, and contractile strain, thirteen randomly sampled analyses were
repeated twice by the same observer and by a second observer without
knowledge of previous findings, respectively.