ePLAR: Echocardiographic Pulmonary to Left Atrial Ratio

ePLAR: Echocardiographic Pulmonary to Left Atrial Ratio

ePLAR is a simple echocardiographic estimation useful in differentiating pre-capillary from post capillary pulmonary hypertension [1].

ePLAR = TR Vmax/(Mitral E/e’)

ePLAR: Echocardiographic pulmonary to left atrial ratio

TR Vmax: Maximum velocity of tricuspid regurgitation jet by Doppler echocardiography in m/s

E: E wave in the mitral flow Doppler

e’: Septal mitral annular tissue Doppler velocity

ePLAR values are lower in post-capillary pulmonary hypertension. E/e’ reflects left ventricular filling pressure which is left atrial pressure. TR Vmax reflects the pulmonary artery systolic pressure. That is how TR Vmax divided by E/e’ is a pulmonary to left atrial ratio.

ePLAR can be used to triage patients for pulmonary vasodilator therapy non-invasively. It may be noted that right heart catheterization is the gold standard for differentiating pre-capillary from post capillary pulmonary hypertension. Pulmonary capillary wedge pressure is elevated in post-capillary pulmonary hypertension.

In a study of 16,356 echocardiograms, normal reference value of ePLAR was 0.30±0.09m/s [1].

Elevated ePLAR in acute submassive pulmonary embolism suggests increased transpulmonary gradients even in the absence of acute elevation of pulmonary arterial pressure [2]. Estimation of ePLAR increases the sensitivity of echocardiography in submassive pulmonary embolism. An ePLAR of ≥ 0.3 m/s had a sensitivity of 70%. This is in comparison with 29% sensitivity of TRVmax ≥ 2.9 m/s and 32% for reduced TAPSE (Tricuspid Annular Plane Systolic Excursion).

Comparison of changes in ePLAR with exercise between iron man athletes and age matched controls showed a two fold increase in ePLAR [3]. This corresponded to a four fold increase in pulmonary pressures compared to systemic pressure in ironman athletes. It is known that though both systemic and pulmonary vascular resistance decreases with exercise, the reduction is more in systemic vascular resistance. As mentioned earlier, ePLAR is a marker of transpulmonary gradient. Authors of the study mentioned that previous studies have suggested that this can lead to right ventricular dysfunction [4], right ventricular arrhythmias and even sudden cardiac death in endurance athletes.

References

1. Scalia GM, Scalia IG, Kierle R, Beaumont R, Cross DB, Feenstra J, Burstow DJ, Fitzgerald BT, Platts DG. ePLAR – The echocardiographic Pulmonary to Left Atrial Ratio – A novel non-invasive parameter to differentiate pre-capillary and post-capillary pulmonary hypertension. Int J Cardiol. 2016View Post Jun 1;212:379-86.
2. Scalia IG, Scalia WM, Hunter J, Riha AZ, Wong D, Celermajer Y, Platts DG, Fitzgerald BT, Scalia GM. Incremental Value of ePLAR-The Echocardiographic Pulmonary to Left Atrial Ratio in the Assessment of Sub-Massive Pulmonary Emboli. J Clin Med. 2020 Jan 17;9(1):247.
3. Tran M, Kwon A, Holt D, Kierle R, Fitzgerald B, Scalia I, Scalia W, Holt G, Scalia G. Echocardiographic Pulmonary to Left Atrial Ratio (ePLAR): A Comparison Study between Ironman Athletes, Age Matched Controls and A General Community Cohort. J Clin Med. 2019 Oct 22;8(10):1756.
4. La Gerche A, Claessen G, Dymarkowski S, Voigt JU, De Buck F, Vanhees L, Droogne W, Van Cleemput J, Claus P, Heidbuchel H. Exercise-induced right ventricular dysfunction is associated with ventricular arrhythmias in endurance athletes. Eur Heart J. 2015 Aug 7;36(30):1998-2010.