國立陽明交通大學 機械工程學系
主題(Topic)：
Biofluid Mechanics of Human Fetal Hearts, and of Anti-thrombotic Blood Pumps
講者(Speaker)：
Dr. Yap Choon Hwai, Assistant Professor, Biomedical Engineering,National University of Singapore
時間(Date)：
12/27 (四)3:30pm – 5:00pm
地點(Venue)：
工程五館B1國際會議廳(EEB24)
Engineering Building 5 B1 International Conference Hall
Abstract:
In this talk, I will discuss two areas of work in biofluid mechanics.
In the first part, I will discuss our progress in investigating the fluid mechanics of human fetal hearts. The motivation for this work is the presentation of congenital Heart Malformations (CHM), which affects 0.6-1.9% of pregnancies, and include very severe malformations such as the Tetralogy of Fallot (TOF) and Hypoplastic Left Heart Syndrome (HLHS). Studies have shown that genetics can only account for a small number of cases of these malformations, leading to the hypothesis that non-genetic factors are responsible for their pathogenesis. Several studies have suggested that abnormal mechanical forces of blood flow to be one such factor. It is thus important to understand the mechanical force environments in the prenatal heart, and it consequential Mechanobiology, as this can lead to tools that can predict disease progression, and assist in fetal heart surgery planning. To investigate human fetal heart flow dynamics, we utilized 4D clinical ultrasound images to support computational fluid dynamics (CFD) simulations, which we have applied to both normal hearts and hearts with CHM. In both normal and diseased hearts, there were interesting ventricular diastolic vortex rings that interacted with one another and with the walls of the ventricle to elevate shear stresses. We discovered that the normal right ventricle also exhibited an interesting peristaltic-like motion, which reduced work done needed for ejection. Further, TOF right ventricles experienced higher intraventricular pressure gradients (IVPG), higher wall shear stresses, and featured more dynamic and chaotic vorticity compared to normal hearts, due to increased inflow via the tricuspid inlet and reduced stroke volumes. In contrast, the TOF left ventricles experienced much less significant changes from normal ventricles.
In the second part, I will discuss our translational efforts in making anti-thrombotic blood pumps. Blood pumps saves countless lives every day, and include those used in the ICU, in heart surgery, during hemodialysis and implanted blood pumps. However, blood pumps damage blood by exposing blood to high stresses, causing platelet activation and hemolysis, which leads to blood clots. For example, 7% of ICU patients put on the ECMO blood pump suffers from severe hemolysis, increasing mortality rate by 6 times. Another study shows that 18% of LVAD patients suffer from hemolysis, which reduces 1-year survivability from 89% to 39%. To date, this remains a major medical challenge. Our strategy to address this is the use of super-hydrophobic surfaces to coat blood pumps. Super-hydrophobic surfaces enables blood fluid to slip past their surface with greatly reduces drag forces, reducing blood stresses to reduce blood damage. We have fabricated super-hydrophobic materials that can withstand very harsh abrasion test conditions and still retain super-hydrophobicity, and which can reduce drag forces by a substantial amount. We also showed in preliminary experiments that such surfaces can reduce hemolysis.
In the first part, I will discuss our progress in investigating the fluid mechanics of human fetal hearts. The motivation for this work is the presentation of congenital Heart Malformations (CHM), which affects 0.6-1.9% of pregnancies, and include very severe malformations such as the Tetralogy of Fallot (TOF) and Hypoplastic Left Heart Syndrome (HLHS). Studies have shown that genetics can only account for a small number of cases of these malformations, leading to the hypothesis that non-genetic factors are responsible for their pathogenesis. Several studies have suggested that abnormal mechanical forces of blood flow to be one such factor. It is thus important to understand the mechanical force environments in the prenatal heart, and it consequential Mechanobiology, as this can lead to tools that can predict disease progression, and assist in fetal heart surgery planning. To investigate human fetal heart flow dynamics, we utilized 4D clinical ultrasound images to support computational fluid dynamics (CFD) simulations, which we have applied to both normal hearts and hearts with CHM. In both normal and diseased hearts, there were interesting ventricular diastolic vortex rings that interacted with one another and with the walls of the ventricle to elevate shear stresses. We discovered that the normal right ventricle also exhibited an interesting peristaltic-like motion, which reduced work done needed for ejection. Further, TOF right ventricles experienced higher intraventricular pressure gradients (IVPG), higher wall shear stresses, and featured more dynamic and chaotic vorticity compared to normal hearts, due to increased inflow via the tricuspid inlet and reduced stroke volumes. In contrast, the TOF left ventricles experienced much less significant changes from normal ventricles.
In the second part, I will discuss our translational efforts in making anti-thrombotic blood pumps. Blood pumps saves countless lives every day, and include those used in the ICU, in heart surgery, during hemodialysis and implanted blood pumps. However, blood pumps damage blood by exposing blood to high stresses, causing platelet activation and hemolysis, which leads to blood clots. For example, 7% of ICU patients put on the ECMO blood pump suffers from severe hemolysis, increasing mortality rate by 6 times. Another study shows that 18% of LVAD patients suffer from hemolysis, which reduces 1-year survivability from 89% to 39%. To date, this remains a major medical challenge. Our strategy to address this is the use of super-hydrophobic surfaces to coat blood pumps. Super-hydrophobic surfaces enables blood fluid to slip past their surface with greatly reduces drag forces, reducing blood stresses to reduce blood damage. We have fabricated super-hydrophobic materials that can withstand very harsh abrasion test conditions and still retain super-hydrophobicity, and which can reduce drag forces by a substantial amount. We also showed in preliminary experiments that such surfaces can reduce hemolysis.
About the speaker:
Dr. Yap Choon Hwai graduated with PhD from Georgia Institute of Technology, and worked as a postdoctoral scholar in University of Pittsburgh School of Medicine. He is currently an Assistant Professor in the Department of Biomedical Engineering in the National University of Singapore. Part of his research focus on the mechanics of prenatal cardiovascular system, and how abnormal blood flow mechanical force environment may be the cause of congenital heart malformations. His lab is the first to perform computational fluid dynamics (CFD) of human fetuses based on clinical ultrasound imaging, and pioneered a novel 4D imaging techniques with high-frequency ultrasound for image-based CFD of small animal embryonic hearts. Another part of his research is to fabricate low-thrombosis blood pumps using novel surface coating technologies.
