title: Patient-specific computational modeling of blood flow in the pulmonary arterial circulation.
abstract: Computational fluid dynamics (CFD) modeling of the pulmonary vasculature has the potential to reveal continuum metrics associated with the hemodynamic stress acting on the vascular endothelium. It is widely accepted that the endothelium responds to flow-induced stress by releasing vasoactive substances that can dilate and constrict blood vessels locally. The objectives of this study are to examine the extent of patient specificity required to obtain a significant association of CFD output metrics and clinical measures in models of the pulmonary arterial circulation, and to evaluate the potential correlation of wall shear stress (WSS) with established metrics indicative of right ventricular (RV) afterload in pulmonary hypertension (PH). Right Heart Catheterization (RHC) hemodynamic data and contrast-enhanced computed tomography (CT) imaging were retrospectively acquired for 10 PH patients and processed to simulate blood flow in the pulmonary arteries. While conducting CFD modeling of the reconstructed patient-specific vasculatures, we experimented with three different outflow boundary conditions to investigate the potential for using computationally derived spatially averaged wall shear stress (SAWSS) as a metric of RV afterload. SAWSS was correlated with both pulmonary vascular resistance (PVR) (R(2)=0.77, P<0.05) and arterial compliance (C) (R(2)=0.63, P<0.05), but the extent of the correlation was affected by the degree of patient specificity incorporated in the fluid flow boundary conditions. We found that decreasing the distal PVR alters the flow distribution and changes the local velocity profile in the distal vessels, thereby increasing the local WSS. Nevertheless, implementing generic outflow boundary conditions still resulted in statistically significant SAWSS correlations with respect to both metrics of RV afterload, suggesting that the CFD model could be executed without the need for complex outflow boundary conditions that require invasively obtained patient-specific data. A preliminary study investigating the relationship between outlet diameter and flow distribution in the pulmonary tree offers a potential computationally inexpensive alternative to pressure based outflow boundary conditions.
authors.affiliation: Department of Bioengineering, UC Denver - Anschutz Medical Campus, Children's Hospital Colorado, 13123 E. 16th Ave B100, Aurora, CO 80045, United States. Electronic address: vitaly.khefyets@ucdenver.edu.
authors.forename: Vitaly O
authors.initials: VO
authors.lastname: Kheyfets
authors.affiliation: The University of Texas at San Antonio, Department of Biomedical Engineering, San Antonio, TX 78249, United States; The University of Texas at San Antonio, Department of Biological Sciences, San Antonio, TX 78249, United States. Electronic address: lourdesriosblanco@hotmail.com.
authors.forename: Lourdes
authors.initials: L
authors.lastname: Rios
authors.affiliation: Western Pennsylvania Allegheny Health System, Allegheny General Hospital, McGinnis Cardiovascular Institute, Department of Radiology, Pittsburgh, PA 15212, United States; Western Pennsylvania Allegheny Health System, Allegheny General Hospital, McGinnis Cardiovascular Institute, Department of Cardiology, Pittsburgh, PA 15212, United States. Electronic address: TSMITH8@wpahs.org.
authors.forename: Triston
authors.initials: T
authors.lastname: Smith
authors.affiliation: Western Pennsylvania Allegheny Health System, Allegheny General Hospital, McGinnis Cardiovascular Institute, Department of Radiology, Pittsburgh, PA 15212, United States; Western Pennsylvania Allegheny Health System, Allegheny General Hospital, McGinnis Cardiovascular Institute, Department of Cardiology, Pittsburgh, PA 15212, United States. Electronic address: tschroe1@wpahs.org.
authors.forename: Theodore
authors.initials: T
authors.lastname: Schroeder
authors.affiliation: Western Pennsylvania Allegheny Health System, Allegheny General Hospital, McGinnis Cardiovascular Institute, Department of Radiology, Pittsburgh, PA 15212, United States; Western Pennsylvania Allegheny Health System, Allegheny General Hospital, McGinnis Cardiovascular Institute, Department of Cardiology, Pittsburgh, PA 15212, United States. Electronic address: JMUELLER@wpahs.org.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Mueller
authors.affiliation: Western Pennsylvania Allegheny Health System, Allegheny General Hospital, McGinnis Cardiovascular Institute, Department of Radiology, Pittsburgh, PA 15212, United States; Western Pennsylvania Allegheny Health System, Allegheny General Hospital, McGinnis Cardiovascular Institute, Department of Cardiology, Pittsburgh, PA 15212, United States. Electronic address: SMURALI@wpahs.org.
authors.forename: Srinivas
authors.initials: S
authors.lastname: Murali
authors.affiliation: Western Pennsylvania Allegheny Health System, Allegheny General Hospital, McGinnis Cardiovascular Institute, Department of Radiology, Pittsburgh, PA 15212, United States; Western Pennsylvania Allegheny Health System, Allegheny General Hospital, McGinnis Cardiovascular Institute, Department of Cardiology, Pittsburgh, PA 15212, United States. Electronic address: DLASORDA@wpahs.org.
authors.forename: David
authors.initials: D
authors.lastname: Lasorda
authors.affiliation: Western Pennsylvania Allegheny Health System, Allegheny General Hospital, McGinnis Cardiovascular Institute, Department of Radiology, Pittsburgh, PA 15212, United States; Western Pennsylvania Allegheny Health System, Allegheny General Hospital, McGinnis Cardiovascular Institute, Department of Cardiology, Pittsburgh, PA 15212, United States. Electronic address: AZIKOS@wpahs.org.
authors.forename: Anthony
authors.initials: A
authors.lastname: Zikos
authors.affiliation: Western Pennsylvania Allegheny Health System, Allegheny General Hospital, McGinnis Cardiovascular Institute, Department of Radiology, Pittsburgh, PA 15212, United States; Western Pennsylvania Allegheny Health System, Allegheny General Hospital, McGinnis Cardiovascular Institute, Department of Cardiology, Pittsburgh, PA 15212, United States. Electronic address: JSPOTTI@wpahs.org.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Spotti
authors.affiliation: University of Pittsburgh, Department of Medicine, Pittsburgh, PA 15261, United States. Electronic address: reillyj@pitt.edu.
authors.forename: John J
authors.initials: JJ
authors.lastname: Reilly
authors.affiliation: The University of Texas at San Antonio, Department of Biomedical Engineering, San Antonio, TX 78249, United States. Electronic address: ender.finol@utsa.edu.
authors.forename: Ender A
authors.initials: EA
authors.lastname: Finol
mesh_terms: D015331:Cohort Studies; D003198:Computer Simulation; D018450:Disease Progression; D006801:Humans; D010361:Patients; D011651:Pulmonary Artery / Q000502:physiology*; D012039:Regional Blood Flow
keywords: Boundary conditions; Computational fluid dynamics; Hemodynamics; Pulmonary hypertension; Pulmonary vascular resistance; Vessel diameter