The Woodruff School

SUMMARY

Prosthetic heart valves have been used for over 50 years to replace diseased native valves but still lead to severe complications such as hemolysis, platelet aggregation, and thromboembolic events. These complications lead to the requirement of life long anti-coagulation therapy that also carries serious side effects. These significant problems have been linked to blood damage caused by non-physiological stresses on blood elements caused by the complex flow fields that arise due to prosthetic heart valve design. In order to reduce the severity of these complications, the blood damage that occurs in flows through prosthetic heart valves must be well understood. Improving prosthetic heart valve design and ultimately reducing the severe complications associated with it requires accurate knowledge of the flow dynamics and the quantification of blood damage. The aim of this research is to numerically study blood damage that occurs in bileaflet mechanical heart valves (BMHVs) during the full cardiac cycle. Computational research has not yet been performed on full BMHV geometries for the full cardiac cycle with the presence of realistic platelets in order to quantify blood damage due to a lack of a sophisticated suspension flow method. The blood damage analysis of this research will be performed using computational simulations of suspended particle flow. Computational simulations can give unprecedented detail on flow dynamics through artificial heart valves that would not be possible through current experimental techniques. The use of an accurate multiphase flow solver can also be used to quantify blood damage and platelet activation by modeling suspended platelets. The numerical simulations will use a fluid-solid coupling method that combines lattice-Boltzmann fluid modeling with the novel external boundary force method. The lattice-Boltzmann method (LBM) has been shown to be an effective method for modeling fluid flow. Extensive literature has been published detailing the comparable accuracy of the lattice-Boltzmann method to traditional methods of modeling fluid dynamics. In addition to being accurate, the LBM employs locally centered calculations to model fluid flow, making it optimal for parallel computing. This is especially useful in modeling artificial heart valve flows, which are computationally very expensive. The fluid-solid coupling will employ the novel external boundary force (EBF) method, which has been validated as 2nd order accurate.

SUBJECT:	Ph.D. Proposal Presentation

BY:	Brian Yun

TIME:	Thursday, November 18, 2010, 1:00 p.m.

PLACE:	Whitaker Ford Building, 2110

TITLE:	Simulations of Pulsatile Flow through Bileaflet Mechanical Heart Valves Using a Suspension Flow Model: To Assess Blood Damage

COMMITTEE:	Dr. Cyrus K. Aidun, Co-Chair (ME) Dr. Ajit P. Yoganathan, Co-Chair (BME) Dr. G. Paul Neitzel (ME) Dr. Don P. Giddens (COE) Dr. W. Robert Taylor (BME)

SUMMARY Prosthetic heart valves have been used for over 50 years to replace diseased native valves but still lead to severe complications such as hemolysis, platelet aggregation, and thromboembolic events. These complications lead to the requirement of life long anti-coagulation therapy that also carries serious side effects. These significant problems have been linked to blood damage caused by non-physiological stresses on blood elements caused by the complex flow fields that arise due to prosthetic heart valve design. In order to reduce the severity of these complications, the blood damage that occurs in flows through prosthetic heart valves must be well understood. Improving prosthetic heart valve design and ultimately reducing the severe complications associated with it requires accurate knowledge of the flow dynamics and the quantification of blood damage. The aim of this research is to numerically study blood damage that occurs in bileaflet mechanical heart valves (BMHVs) during the full cardiac cycle. Computational research has not yet been performed on full BMHV geometries for the full cardiac cycle with the presence of realistic platelets in order to quantify blood damage due to a lack of a sophisticated suspension flow method. The blood damage analysis of this research will be performed using computational simulations of suspended particle flow. Computational simulations can give unprecedented detail on flow dynamics through artificial heart valves that would not be possible through current experimental techniques. The use of an accurate multiphase flow solver can also be used to quantify blood damage and platelet activation by modeling suspended platelets. The numerical simulations will use a fluid-solid coupling method that combines lattice-Boltzmann fluid modeling with the novel external boundary force method. The lattice-Boltzmann method (LBM) has been shown to be an effective method for modeling fluid flow. Extensive literature has been published detailing the comparable accuracy of the lattice-Boltzmann method to traditional methods of modeling fluid dynamics. In addition to being accurate, the LBM employs locally centered calculations to model fluid flow, making it optimal for parallel computing. This is especially useful in modeling artificial heart valve flows, which are computationally very expensive. The fluid-solid coupling will employ the novel external boundary force (EBF) method, which has been validated as 2nd order accurate.