A 4D Flow MRI Evaluation of the Impact of Shear-Dependent Fluid Viscosity on in vitro Fontan Circulation Flow.

A 4D Flow MRI Evaluation of the Impact of Shear-Dependent Fluid Viscosity on in vitro Fontan Circulation Flow. Am J Physiol Heart Circ Physiol. 2019 Oct 04;: Authors: Cheng AL, Wee CP, Pahlevan NM, Wood JC Abstract The Fontan procedure for univentricular heart defects creates a non-physiologic circulation where systemic venous blood drains directly into the pulmonary arteries, leading to multiorgan dysfunction secondary to chronic low-shear non-pulsatile pulmonary blood flow and central venous hypertension. Although blood viscosity increases exponentially in this low-shear environment, the role of shear-dependent ("non-Newtonian") blood viscosity in this pathophysiology is unclear. We studied 3D-printed Fontan models in an in vitro flow loop with a Philips 3T MRI scanner. A 4D flow phase-contrast sequence was used to acquire a time-varying 3D velocity field for each experimental condition. Based on blood viscosity of a Fontan patient cohort, 0.04% xanthan gum was used as a non-Newtonian blood analog; 45% glycerol was used as a Newtonian control fluid. MRI data was analyzed using GTFlow and Matlab software. The primary outcome, power loss, was significantly higher with the Newtonian fluid (14.8% [13.3%,16.4%] vs. 8.1% [6.4%,9.8%], p<0.0001). The Newtonian fluid also demonstrated marginally higher right pulmonary artery flow, marginally lower shear stress, and a trend toward higher caval flow mixing. Outcomes were modulated by Fonta...
Source: American Journal of Physiology. Heart and Circulatory Physiology - Category: Physiology Authors: Tags: Am J Physiol Heart Circ Physiol Source Type: research