B68-05 Small Vessel Volume Predicts Severity of Pulmonary Hypertension in Combined Pulmonary Fibrosis and Emphysema

Abstract Intro Vascular pruning, characterized by a reduction in the number of small pulmonary blood vessels and a subsequent increase in the larger vessels, is a hallmark of pulmonary hypertension (PH). The severity of PH in chronic lung disease has been shown to be closely related to the degree of small vessel volume loss. Pulmonary blood vessel volume can be measured using quantitative CT (qCT) to determine total pulmonary blood vessel volume and the fractional volume contained in vessels 5mm2 (BV5%) and vessels 10 mm2 (BV10%). Distal pruning of the arterial bed in COPD-PH has been shown to reduce BV5% and subsequently increase BV10%, however this has yet to be demonstrated in CPFE. We aimed to differentiate the contribution of vascular pruning from that of parenchymal changes on the development and severity of pulmonary hypertension in CPFE. Methods Patients with a diagnosis of CPFE and pulmonary hypertension were included in this retrospective analysis. CT scans completed nearest the date of each patient’s right heart catheterization (RHC) were analyzed using a qCT program (Coreline) which conducted lung texture and lung vessel volume analysis. RHC data was collected as well, with a PVR 5 WU defined as severe PH in CPFE. ROC and logistic regression were performed to evaluate associations between quantitative CT measurements and severe PH. Results We identified 92 patients with CPFE-PH. 29 had severe PH. Between those with severe PH and non-severe PH, the degree of fibrosis (24.3% ± 13.7% vs 22.6% ± 14.4%) and emphysema (11.9% ± 12.5% vs 14.1% ± 15.4%) was similar, while BV5/TBV (.31 ± .15 vs .46 ± .11, p .05) and BV5/BV10 (.39 ± .19 vs .58 ± .11, p .05) were significantly lower in the severe PH group. BV5/TBV and BV5/BV10 ratios effectively predicted severe PH (AUC .79, AUC .81 respectively) and a cut off of BV5/BV10 0.5 (via Youden’s statistic) can predict severe PH (OR 27.6, 95% CI 8.3-91.8; p .01) even when accounting for fibrosis (OR 1.0, 95% CI 0.98-1.1, p = 0.43) and emphysema (OR 0.99, 95% CI 0.95-1.03, p = 0.47) respectively. Conclusion This retrospective analysis demonstrates that the degree of vascular pruning in CPFE as measured by BV5/BV10 predicts the severity of pulmonary hypertension independently of the amount of parenchymal destruction (fibrosis and emphysema), and that there was no significant difference in the degree of parenchymal changes between non-severe and severe PH. This abstract is funded by: None