Abstract Background Acute Pulmonary Embolism (PE) is a pervasive condition with a wide spectrum of clinical severity. Risk stratification hinges on assessment of right ventricular dysfunction and biomarker evidence of myocardial strain. However, existing grading systems for radiographic clot burden (e.g., Qanadli and Mastora scores) have shown limited prognostic. Decisions regarding advanced therapy are guided by markers of RV performance without direct measures of pulmonary vascular compromise. Computational fluid dynamics (CFD) has emerged as a powerful tool for quantifying hemodynamics in the pulmonary vasculature. Prior studies have demonstrated its utility in estimating changes in pressure with stenting in peripheral pulmonary artery stenosis. For this study, we applied CFD to patients with intermediate-risk PE to characterize pulmonary arterial flow dynamics and explore the use of simulated pressure metrics as predictors of response to interventions. Methods Patients with intermediate-risk acute PE who underwent mechanical thrombectomy at the University of Pittsburgh were included (n = 4). Age- and sex-matched healthy controls (n = 3) were obtained from the Vascular Model Repository, an NIH-supported database of vascular geometries. For each subject, 3D reconstructions of the pulmonary arteries were generated from contrast-enhanced CT angiography using SimVascular, an open-source platform for CFD. Cardiac output and invasive pulmonary artery pressures were used to define inlet and outlet boundary conditions. Simulations were performed under steady-state conditions to evaluate wall shear stress (WSS) and pressure metrics, such as fractional flow reserve (FFR) calculated for each vessel generation. These parameters were compared between PE patients and healthy controls, and correlated with the post-thrombectomy decrease in mPAP. Results While surface averaged WSS of the entire domain decreases with dilatation of the largest vessels, we found a 2-fold increase in WSS when surface averages taken along the vessel centerlines were normalized by the local cross-sectional area, indicating that more individual vessels experience high WSS. Maximal WSS also demonstrated an order of magnitude increase when compared to healthy controls. Unilateral FFR was reduced in PE patients. Interestingly, a strong negative correlation (-0.94) was found between the average branch generation at which minimum FFR was calculated and the pressure reduction with mechanical thrombectomy. This suggests that CFD could better stratify patients likely to improve. Conclusion This study demonstrates the utility of CFD in characterizing post-thrombectomy hemodynamics in PE. Notable alteration of WSS warrant raise a possible mechanistic explanation for the development of post-PE syndromes. CT calculated FFR represents a promising tool for assessment of treatment response to mechanical thrombectomy. This abstract is funded by: None
Gilani et al. (Fri,) studied this question.