1. analyzing the effect of stent geometry
for polymeric aortic HEART valves
Atieh Y. Koupaei, Brandon L. Moore , David L. Bark Jr. , David A. Prawel, Lakshmi P. Dasi
Department of Mechanical Engineering, Colorado State University
School of Biomedical Engineering, Colorado State University
Introduction
Aortic valve disease is one of the major causes of death.
Several drawbacks are associated with existing bioprosthetic and
mechanical HVs such as durability and thrombosis, respectively.
Polymeric aortic prosthetic HVs can overcome durability issues, may
be designed to reduce antithrombotic therapy, and may reduce
current production costs.
Results
Particle Image Velocimetry
Parameters to recover regurgitation fraction:
Long Profile
No Arch
1) H/D Effect
2) h/D Effect
Acceleration
Peak
Deceleration
Distole
Acceleration
Peak
Deceleration
Distole
The aim of this work is to initiate the design of low-cost tri-leaflet polymeric AHVs, by determining geometries that result in hemodynamic performance comparable to bioprosthetic HVs.
Short Profile
Short Arch
Short Profile
Short Arch
Medium Profile
Long Arch
Short Profile
Medium Profile
𝝎 𝒛 ( 𝒔 −𝟏 )
velocity field along the center plane of one leaflet shows that adding arches to the leaflets results in a more stable and developed fluid flow in the upstream.
Methods & Materials
Design and Manufacturing
Short Arch
Medium Profile
High Profile
TopPart
Bottom Part
Arch Length = h
Long Profile
No Arch
3) Flexible Stent Effect
ABS
Height = H
A HV design with low profile is desired to reduce obstruction of other structures in the heart. Adding arches or flexibility will help achieve better commissural contact while having lower profile. 𝝅𝑫
Short Profile Rigid Stent
LLDPE
uPrint SE
Short Arch
Medium Profile
Height to Diameter Aspect Ratio
Low profile
Medium profile
High profile
H/D
0.6
0.7
0.88
Short Profile Flexible Stent
𝑹𝑺𝑺 ( 𝒅𝒚𝒏𝒆𝒔 𝒄𝒎 𝟐 )
Reynolds shear stresses are higher in the shorter profile valve, but they show similarity to the reported values for RSS. The maximum values were primarily concentrated around the centerline.
Valves without arch
Regurgitation percentage analysis
Parameters used to design leaflets
No arch
Short arch
Long arch
h/D
0.081
0.116
Summary
Higher stent profiles resulted in better coaptation.
Arches reduce the gap between leaflets and increase coaptation.
A flexible stent adds a degree of freedom to the stent posts and results in much better coaptation.
Further hemodynamic analysis needs to be performed to characterize valve performance.
Flexible stent
High profile no arch
Short profile no arch Short Profile short arch
Short profile long arch Medium profile no arch
Medium profile short arch Flexible stent short profile
Valves with arch
Aortic Flow Rate (Lit/min)
Experiments
Flow Loop Setup for Imaging & PIV
Acknowledgements
Research reported in this abstract was supported by the National Institutes of Health under award number R01HL
Time (s)
Increment in HV height shows decrement in regurgitation. the short profile is preferred and can result in approximately similar regurgitation with added arches
References
1. Yacoub MH & Takkenberg JJM, Nat Clin Pract Card, 2:60-61, 2005.
2. Black MM & Drury PJ The Pathology of Devices, , 1994.
3. Yap CH et al., Biomech Model Mechan, 11:171–82, 2012.
4. Moore BL & Dasi LP ASME 2013 Summer Bioengineering Conference,
V01AT04A009-V01AT04A009, 2013.
5. Leo, Hwa Liang, et al. Fluid dynamic assessment of three polymeric heart
valves using particle image velocimetry, Annals of biomedical engineering
34.6, , 2006
Aortic Pressure
Ventricular Pressure
LabVIEW Controlled
Regurgitation Percentage = 𝑅𝑒𝑣𝑒𝑟𝑠𝑒 𝐹𝑙𝑜𝑤 𝑇𝑜𝑡𝑎𝑙 𝐹𝑙𝑜𝑤
Heart Rate 60BPM Ave. Cardiac Output 5 L/min
Normal BP 120/80 mmHg
SB3C 2015 Summer
Biomechanics, Bioengineering, and Biotransport Conference
Snowbird, Utah, June 17-20, 2015