Speckle-tracking RV free wall strain
RV lateral free wall strain had the best accuracy among the four
echocardiographic parameters. It consistently outperformed other
parameters in identifying different levels of RV systolic dysfunction
and was most accurate with severe RV systolic dysfunction. We identified
cutoff levels of lateral RV free wall strain of <23.5% and
<20.5 % that accurately detects for moderately and severely
reduced RV systolic function, respectively. Although the RV free wall
strain technically measures more of the longitudinal deformation of the
RV myocardium, it has been validated as a global function parameter in a
variety of diseases with promising results and predicting prognosis .
Compared to LV, base-to-apex shortening plays a more important role in
RV systolic function due to its distinct muscle fiber architecture. This
also partially explained the superiority of longitudinal RV strain in
assessing RV systolic function. In addition, speckle-tracking RV strain
also has the unique advantage of being angle-independent, and able to
measure the intrinsic myocardium deformation. An issue of using RV
strain is the different reference values generated by the software
package from different vendors; one should be cautious when comparing RV
strain data from different studies. The ease of performance for
sonographers comparing all four modalities in descending order are
TAPSE, S’, FAC and RV strain. Theoretically, RV myocardial strain should
be superior to localized velocity measurements such as S’. Our study
demonstrates strain is superior to other echo parameters as compared
with Cardiac MRI as the standard.
In conclusion, conventional one-dimensional echocardiographic
parameters, such as S’ and TAPSE, were well-validated and have the
advantage of simplicity, reproducibility and are less dependent on image
quality. However, either TAPSE or S’ in our study were not as good as
reported in prior RV dysfunction studies. The 2-dimensional parameters,
RV FAC and RV free wall strain were superior in accuracy. The ease of
performance for sonographers comparing all four modalities in descending
order are TAPSE, S’, FAC and RV strain.
Considering the availability, reproducibility, accuracy and the
correlation to prognosis, our results suggested that RV free wall strain
is the preferred choice for RV functional assessment among the four
echocardiographic parameters.
As a final comment, the AUC of all four parameters improved with
worsening RV dysfunction, which reflects the challenge in detecting mild
to moderate RV dysfunction in clinical practice. Despite the relatively
good AUC data, all the four echocardiographic parameters only had modest
correlations with CMR RVEF. This implied a substantial limitation on 1-
or 2-dimensional assessment of RV systolic function. In clinical
practice, these parameters can serve as surrogates of RV dysfunction
concerning their availability and relatively low costs. However, when
accurate assessment of RV systolic function is warranted, 3-dimensional
tools like cardiac MRI should be the preferred choice when it’s
available.