Echocardiographic Pulmonary Left Atrial Ratio (ePLAR): Is it a Clinically Useful, Noninvasive Measure to Help Identify Patients with Left Heart Causes of Pulmonary Hypertension?

Background: ePLAR (tricuspid regurgitation Vmax/mitral E:E’) has been proposed to be a non-invasive technique in assessing transpulmonary gradient (TPG). It has been validated to differentiate between pre- and post-capillary causes of pulmonary hypertension (PHT) among patients undergoing right heart catheterisation. We evaluated ePLAR in a large clinical cohort of patients from the echocardiography database at Sir Charles Gairdner Hospital.Methods: Patients were classified using diagnostic codes based on the updated clinical classification of PHT. Left-heart disease (Group 2) patients with multiple diagnostic codes (n=1029) were excluded. Non-normally distributed variables (including ePLAR) were log transformed where appropriate.Results: 4529 patients (57% men, 69±14yrs) were classified accordingly: group 1 (pulmonary arterial hypertension, 10%), group 2 (left-heart disease, 78%), group 3 (lung disease, 8%), group 4 (chronic thromboembolic disease, 3%), and group 5 (unclear multifactorial mechanisms, 1%). 2114 (47%) patients had an estimated PASP>40mmHg. Mean ePLAR was found to be lower in patients with left heart disease compared with other diagnostic groups (0.169 vs 0.236, p<0.001) overall, with similar findings in those with PASP>40mmHg (0.161 vs 0.246, p<0.001). ePLAR was superior to other echocardiographic measures of left-heart disease by ROC analysis (AUC=0.736, p<0.05), with a cutoff of ePLAR<0.21 to be of high discriminatory value in identifying left-heart causes of PHT.Conclusions: ePLAR was shown to distinguish patients with left heart disease from other causes of elevated PASP. In combination with clinical assessment, this study supports the use of ePLAR to identify elevated TPGs when evaluating patients with PHT.