Pulmonary Blood Volumes on CT Predict Residual Pulmonary Hypertension Post-Pulmonary Endarterectomy

Pulmonary blood volumes (PBV), currently not assessed by computed tomography pulmonary angiography (CTPA), could provide additional information to routine investigations performed for chronic thromboembolic pulmonary hypertension (CTEPH). We investigated CTPA-based PBV in evaluating hemodynamic outcome from pulmonary endarterectomy (PEA) surgery. A deep learning-based CTPA vascular segmentation model, differentiating arteries and veins, was applied for automated PBV measurements in CTEPH patients who underwent PEA at UK's national CTEPH service. Pulmonary arteries were compartmentalised into "central" (main pulmonary and proximal lobar) and "intrapulmonary". Mean pulmonary arterial pressure >30 mmHg post-PEA defined "clinically relevant" residual PH. Logistic regression models applying CTPA-based PBV to identify residual PH were trained and tested on the discovery and validation cohorts respectively. Paired pre- and postoperative CTPA, in the discovery (n=71) and validation (n=102) cohorts showed that central pulmonary artery volume and total artery to vein volume ratio (A-VR) decreased and pulmonary vein volume increased with hemodynamic improvement post-PEA. Preoperative central pulmonary artery volume and A-VR helped identify patients at risk for clinically relevant residual PH post-PEA (AUROC 0.88 and 0.82 in the discovery and validation cohorts). Postoperative central pulmonary artery volume, A-VR and pulmonary vein volume helped to non-invasively identify patients without clinically relevant residual PH (AUROC 0.91 and 0.88 in the discovery and validation cohorts). Automated quantification of CTPA-based PBV at diagnosis can help stratify risk for residual PH in patients managed with PEA. Utilizing CTPA-derived PBV post-PEA to identify patients without residual PH can potentially reduce the need for routine postoperative right heart catheterization.