The Role of Wall Shear Stress in the Assessment of Right Ventricle Hydraulic Workload

Abstract

Pulmonary hypertension (PH) is a devastating disease affecting approximately 15-50 people per million, with a higher incidence in women. PH mortality is mostly attributed to right ventricle (RV) failure, which results from RV hypotrophy due to an overburdened hydraulic workload. The objective of this study is to correlate wall shear stress (WSS) with hemodynamic metrics that are generally accepted as clinical indicators of RV workload and are well correlated with disease outcome. Retrospective right heart catheterization data for 20 PH patients were analyzed to derive pulmonary vascular resistance (PVR), arterial compliance (C), and an index of wave reflections (Γ). Patient-specific contrast-enhanced computed tomography chest images were used to reconstruct the individual pulmonary arterial trees up to the seventh generation. Computational fluid dynamics analyses simulating blood flow at peak systole were conducted for each vascular model to calculate WSS distributions on the endothelial surface of the pulmonary arteries. WSS was found to be decreased proportionally with elevated PVR and reduced C. Spatially averaged WSS (SAWSS) was positively correlated with PVR (R 2 ¼ 0.66), C (R 2 ¼ 0.73), and Γ (R 2 ¼ 0.5) and also showed promising preliminary correlations with RV geometric characteristics. Evaluating WSS at random cross sections in the proximal vasculature (main, right, and left pulmonary arteries), the type of data that can be acquired from phase-contrast magnetic resonance imaging, did not reveal the same correlations. In conclusion, we found that WSS has the potential to be a viable and clinically useful noninvasive metric of PH disease progression and RV health. Future work should be focused on evaluating whether SAWSS has prognostic value in the management of PH and whether it can be used as a rapid reactivity assessment tool, which would aid in selection of appropriate therapies.

Patient-specific computational modeling of blood flow in the pulmonary arterial circulation

“…Tang et al [4] showed that computationally measured WSS is decreased in adult PH, when compared against a healthy control population, which we recently correlated with impedance [22]. Truong et al [3] used phase-contrast MRI to confirm the same finding in pediatric patients.…”

“…Further computational work, comparing pulmonary hemodynamics in the PH patient population with a healthy dataset, revealed a decreased in WSS PH [4], which we recently correlated with an increase in impedance using a similar computational framework [22]. However, the considerations critical to computational modeling of the pulmonary vasculature or the mechanisms driving this WSS decrease remain unaddressed.…”

4D magnetic resonance flow imaging for estimating pulmonary vascular resistance in pulmonary hypertension

“…Based on computational modeling results, an increase in PVR has been shown to be proportional to a decrease in WSS, which is also a function of the velocity gradient (4). This is consistent with the fact that vorticity decreases concurrently with an increase in PVR in all generations of the vascular tree (31).…”

“…This increase in resistance inevitably impacts blood flow patterns in the proximal vessels (4) that are also partially governed by changes in vascular distensibility, morphology, and right ventricular (RV) ejection behavior.…”

Simulation of unsteady blood flows in a patient‐specific compliant pulmonary artery with a highly parallel monolithically coupled fluid‐structure interaction algorithm

“…() Our previous studies have also shown that CFD results in the pulmonary circulation are consistent with observational studies in pulmonary hypertension and highly correlated with functional clinical markers of pulmonary vascular disease. ()…”