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.