The significance of normal lung regions on quantitative CT in pulmonary hypertension

Abstract

<b>Background:</b> The criteria of discrimination between Group 1 and 3 pulmonary hypertension (PH) includes the severity of lung parenchymal change in chest computed tomography (CT), but the significance of normal lung regions (NLR) on quantitative CT in PH patients is little known. <b>Aims:</b> We aimed to clarify whether quantitative NLR is associated with the outcomes of PH patients. <b>Methods</b> We retrospectively investigated 1471 cases who underwent right heart catheterization and found 543 PH patients. Patients with Group 2, 4, 5 PH were excluded. We extracted their whole lung regions (WLR) on CT using 3D image analysis system (SYNAPSE VINCENT). Then, we removed low and high attenuation areas (-1024 to -950HU and -750 to -200HU) and defined the remaining area as NLR. We examined the association of %NLR (NLR to WLR) to prognosis and responses to the PH-targeted therapy. Responder was defined by improvement of delta% pulmonary vascular resistance or 6-minute walk distance &gt; 15%. <b>Results:</b> 160 patients (mean age; 53 years old and female; 70%) were included. The mean %NLR was 75.3±14.4%. Logistic regression analysis showed %NLR was associated with 3-year survival rate (p&lt;0.0001) and the optimal cut point in ROC analysis was 78.4% (AUC: 0.76). In Kaplan-Meier analysis, survival of patients with %NLR higher than 78.4 was better than that of patients with %NLR lower than 78.4 (5-year survival; 84.4% vs 46.1%, p&lt;0.0001). Multivariate analysis revealed that %NLR lower than 78.4 was the only significant prognostic factor (p=0.033). Also, %NLR higher than 78.4 was associated with responder (p=0.0001). <b>Conclusions:</b> %NLR is associated with the outcomes of PH patients. It could be helpful for deciding their treatment plans.