Lung Ultrasound, Echocardiography, and Fluid Challenge for the Differential Diagnosis of Pulmonary Hypertension

Objectives: The differential diagnosis between pulmonary arterial hypertension (PAH) and postcapillary pulmonary hypertension (PH) in heart failure with preserved ejection fraction (HFpEF) is sometimes difficult despite guidelines-derived standardized step-by-step diagnostic algorithms. We therefore explored the added value of lung ultrasound to a previously validated echocardiographic score of right heart catheterization measurements. Methods: Patients referred for PH underwent a right heart catheterization, echocardiography, and lung ultrasound before and after rapid infusion of 7 mL/kg of saline. A 7-point echocardiographic score based on cardiac chamber dimensions and estimates of filling pressures was implemented for the prediction of precapillary PH. Pulmonary congestion was identified by lung ultrasound B lines. Results: The study enrolled 70 patients with PAH and 77 patients with HFpEF. The PAH patients had a higher echocardiographic score (3.5 ± 1.8 vs 1.6 ± 1.5; P < .001). The HFpEF patients had more B lines both before (8.1 ± 4.2 vs 5.1 ± 3.0; P < .001) and after fluid challenge (14.6 ± 5.4 vs 7.6 ± 3.5; P < .001) and a more important increase (Δ) of B lines after fluid challenge (6.5 ± 2.9 vs 2.5 ± 1.6; P < .001). The sensitivity and specificity of the echocardiographic score (cutoff ≥2) alone for PAH were 0.91 and 0.49, respectively (area under the curve of 0.78). The best diagnostic improvement was observed with addition of ΔB lines + E/e' post–fluid challenge to the echocardiographic score, with a significant increase of the area under the curve (0.98) and (with a cutoff given by the presence of echo score ≥2, ΔB lines <4 and E/e’ post < 11) a sensitivity of 0.90 (95% CI, 0.83; 0.97) and specificity of 0.84 (95% CI, 0.76; 0.93). Conclusions: Lung ultrasound combined with echocardiography at baseline and after fluid challenge has an incremental value for the differential diagnosis between PAH and PH-HFpEF.