Discussion
This study shows that the EDSPA is a reliable and reproducible, but
non-invasive estimate of right ventricular systolic pressure.
Importantly, it can be quickly and easily measured using widely
available echocardiographic processing software like Syngo Dynamics and
can be measured post-acquisition in standard echocardiographic views. An
EDSPA of < 39° suggests a main pulmonary artery mean systolic
pressure of > 20 mmHg. As such, it can be used as an
indication for more invasive measures in the cardiac catheterization
laboratory prior to treatment with anti-pulmonary hypertensives or in
titrating anti-pulmonary hypertensive therapies. As such, it is an
excellent tool for use in outpatient and inpatient screening for
pulmonary hypertension.
EDSPA has some significant potential advantages over other published
measurements such as the Eccentricity Index (EI). The measured angle is
independent of left ventricular dimensions or normal left ventricular
free wall motion, so it can be used for patients with abnormal left
ventricular size and function. This is especially important in patients
with left sided obstructive cardiac disease that can lead to pulmonary
hypertension, patients with volume loaded left ventricles, patients with
regional wall motion abnormalities, and patients with cardiac
dysynchrony. These are critical populations to track non-invasively. As
well, it is easy to reproduce and had low intra and interobserver
variability. Like the eccentricity index, it can be quickly measured
with common echocardiographic processing software already being used in
clinical care.
The limitations of our study include the interval between the
echocardiogram and cardiac catheterization which could lead to variation
in pulmonary pressures at different times and under different conditions
(i.e. level of sedation). However, given that echocardiograms are
usually performed in an outpatient non-sedated setting, these results
may be more generalizable and relevant to outpatient decision-making.
Also, although EDSPA does not precisely calculate right ventricular
systolic pressure, it does effectively triage patients into those who
qualify for at least mild pulmonary hypertension, and those who have
significantly elevated pressures who may need earlier direct assessment
or medication adjustment. Further studies with simultaneous
echocardiographic and catheterization measurements are indicated. As
well, there may have been variation in the level of sedation versus
anaesthesia under which the cardiac catheterizations were performed in
the pulmonary hypertension and atrial septal defect groups but this was
not studied. Finally, we excluded patients with concurrent congenital
heart disease and pulmonary hypertension in our study population. These
patients should be evaluated in the future to increase generalizability.
In conclusion, EDSPA is a useful and easily performed and interpreted
echocardiographic method for obtaining a semi-quantifiable measurement
of right ventricular pressure that is useful for identifying and
managing patients at risk for pulmonary hypertension.