ePLAR - The echocardiographic Pulmonary to Left Atrial Ratio - A novel non-invasive parameter to differentiate pre-capillary and post-capillary pulmonary hypertension.

BACKGROUND: Right heart catheterisation is the gold-standard for differentiating pre-capillary pulmonary hypertension (high mean pulmonary artery pressure, normal pulmonary wedge pressure) from post-capillary physiology (elevated pulmonary wedge pressure). The new non-invasive parameter, ePLAR (echocardiographic Pulmonary to Left Atrial Ratio) is calculated from the maximum tricuspid regurgitation continuous wave Doppler velocity (m/s) divided by the transmitral E-wave:septal mitral annular Doppler Tissue Imaging e'-wave ratio (TRVmax/E:e'). METHODS: Pulmonary hypertension patients (mean pulmonary artery pressure>25mmHg, n=133, 66 male, average 65.0±16.8years) were classified by right heart catheterisation as pre-capillary or post-capillary [subdivided into isolated post-capillary (diastolic pulmonary gradient <7mmHg) or combined pre- and post-capillary cases]. The ePLAR values of these groups were compared to each other and to a population sample of 16,356 population reference echocardiograms. RESULTS: ePLAR values for the normal reference population of 16,356 echocardiograms (age 56±16.6years) were 0.30±0.09m/s. Pre-capillary pulmonary hypertension patients (n=35, 26 male, PAPsys 63.9±16.6mmHg, PAPdiast 24.1±7.3mmHg, PAPmean 37.9±9.4mmHg, PCWP 10.6±2.7mmHg) had significantly higher ePLAR values than post-capillary cases (n=98, 40 male, PAPsys 59.9±17.6mmHg, PAPdiast 25.0±7.4mmHg, PAPmean 38.1±9.8mmHg, PCWP 23.5±6.4mmHg)-ePLAR 0.44±0.22m/s vs 0.20±0.11m/s (p<0.001). ePLAR values were significantly lower in isolated post-capillary pulmonary hypertension than in combined pre- and post-capillary cases (0.18±0.08m/s vs 0.28±0.18m/s, p<0.001). CONCLUSIONS: ePLAR is a simple echocardiographic parameter which can accurately differentiate the smaller subset of patients with pre-capillary pulmonary hypertension from the more common post-capillary aetiology. The use of this easily obtained echocardiographic parameter has the potential to enhance non-invasive triage of patients for specific pulmonary vasodilator therapy.