Browsing by Author "Huo, Yunlong"

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    Compensatory enlargement of Ossabaw miniature swine coronary arteries in diffuse atherosclerosis
    (Elsevier, 2015-03) Choy, Jenny S.; Luo, Tong; Huo, Yunlong; Wischgoll, Thomas; Schultz, Kyle; Teague, Shawn D.; Sturek, Michael; Kassab, Ghassan S.; Department of Biomedical Engineering, School of Engineering and Technology
    Studies in human and non-human primates have confirmed the compensatory enlargement or positive remodeling (Glagov phenomenon) of coronary vessels in the presence of focal stenosis. To our knowledge, this is the first study to document arterial enlargement in a metabolic syndrome animal model with diffuse coronary artery disease (DCAD) in the absence of severe focal stenosis. Two different groups of Ossabaw miniature pigs were fed a high fat atherogenic diet for 4 months (Group I) and 12 months (Group II), respectively. Group I (6 pigs) underwent contrast enhanced computed tomographic angiography (CCTA) and intravascular ultrasound (IVUS) at baseline and after 4 months of high fat diet, whereas Group II (7 pigs) underwent only IVUS at 12 months of high fat diet. IVUS measurements of the left anterior descending (LAD), left circumflex (LCX) and right coronary (RCA) arteries in Group I showed an average increase in their lumen cross-sectional areas (CSA) of 25.8%, 11.4%, and 43.4%, respectively, as compared to baseline. The lumen CSA values of LAD in Group II were found to be between the baseline and 4 month values in Group I. IVUS and CCTA measurements showed a similar trend and positive correlation. Fractional flow reserve (FFR) was 0.91 ± 0.07 at baseline and 0.93 ± 0.05 at 4 months with only 2.2%, 1.6% and 1% stenosis in the LAD, LCX and RCA, respectively. The relation between percent stenosis and lumen CSA shows a classical Glagov phenomenon in this animal model of DCAD.
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    Which diameter and angle rule provides optimal flow patterns in a coronary bifurcation?
    (Elsevier, 2012-04-30) Huo, Yunlong; Finet, Gérard; Lefevre, Thierry; Louvard, Yves; Moussa, Issam; Kassab, Ghassan S.; Department of Surgery, IU School of Medicine
    The branching angle and diameter ratio in epicardial coronary artery bifurcations are two important determinants of atherogenesis. Murray's cubed diameter law and bifurcation angle have been assumed to yield optimal flows through a bifurcation. In contrast, we have recently shown a 7/3 diameter law (HK diameter model), based on minimum energy hypothesis in an entire tree structure. Here, we derive a bifurcation angle rule corresponding to the HK diameter model and critically evaluate the streamline flow through HK and Murray-type bifurcations. The bifurcations from coronary casts were found to obey the HK diameter model and angle rule much more than Murray's model. A finite element model was used to investigate flow patterns for coronary artery bifurcations of various types. The inlet velocity and pressure boundary conditions were measured by ComboWire. Y-bifurcation of Murray type decreased wall shear stress-WSS (10%-40%) and created an increased oscillatory shear index-OSI in atherosclerosis-prone regions as compared with HK-type bifurcations. The HK-type bifurcations were found to have more optimal flow patterns (i.e., higher WSS and lower OSI) than Murray-type bifurcations which have been traditionally believed to be optimized. This study has implications for changes in bifurcation angles and diameters in percutaneous coronary intervention.