Discussion:
In our study comprising 500 consecutive patients with a broad spectrum
of cardiovascular disorders, we evaluated the accuracy of commonly used
echocardiographic parameters, including peak systolic annular velocity
(s’), tricuspid annular plane systolic excursion (TAPSE), RV fractional
area change (RV FAC), as well as RV strain, compared to CMR RV ejection
fraction (RVEF) in assessing RV systolic function. To the best of our
knowledge, this is the largest study that contains a variety of patient
population and compares echocardiographic parameters with RVEF measured
by CMR . This is also the first study to demonstrate the superior
accuracy of RV free wall strain compared to other echocardiographic
parameters to distinguish RVEF < 45% and RVEF
<30%.
Similar to previous studies , we choose CMR measured RV ejection
fraction (RVEF) as our reference standard for RV systolic function
assessment. CMR enjoys the advantage of 3D volumetric information and
high spatial resolution to analyze the distinctive geometry of RV, which
is usually difficult to obtain by using 2D echocardiography
measurements. The accuracy and reproducibility of using CMR for
quantitative RV assessment have been demonstrated in multiple clinical
studies. As a functional parameter, RVEF reflects the contractility of
right heart myocardium, and can be affected by RV preload, afterload,
and other general variables including age, sex and body mass index. Age
and gender did not differ significantly between the groups in our study,
but the percentage of men was higher in Group B.
Among the four echocardiographic parameters, our results indicate that
RV strain and RV FAC are in general superior to TAPSE and S’ in
accuracy, when compared with CMR RVEF by both spearman’s correlation and
ROC curve analyses. Our results demonstrated a comparable or better
reproducibility of each parameter, compared to prior studies. This
finding suggests that two-dimensional parameters are superior two
one-dimensional parameters and implies the importance of using
two-dimensional or even three-dimensional tools for accurate RV function
assessment concerning its complex geometry.