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Transfer function comparisons of rat aortic wall image and intravascular pressure harmonic responses
H O Stinnett1, M L Hennes, V S Link
1UND School of Medicine, University of North Dakota, Grand Forks 58202-9037, USA.
Biomedical Sciences Instrumentation
|January 1, 1995
Summary
The study found that rat thoracic aortic wall and intraluminal pressure responses to dynamic pressure inputs are similar. This suggests the chosen transfer function accurately models aortic wall and fluid dynamics.
Area of Science:
- Biomedical Engineering
- Cardiovascular Physiology
- Fluid Dynamics
Background:
- Understanding the dynamic mechanical properties of the thoracic aorta is crucial for diagnosing and treating cardiovascular diseases.
- Previous models often simplified the complex interactions between aortic wall mechanics and intraluminal pressure dynamics.
Purpose of the Study:
- To investigate the relationship between rat thoracic aortic outer wall area (Do) and intraluminal pressure (Po) responses under dynamic pressure inputs.
- To validate a specific transfer function model (Do/Pi = Po/Pi) for describing these dynamic interactions.
Main Methods:
- Utilized in vitro Sprague-Dawley rat thoracic aortas subjected to swept frequency pressure inputs (2-200 Hz) superimposed on various static pressures (20-200 mm Hg).
- Employed high-speed video imaging for outer wall area (Do) and intravascular pressure sensors for intraluminal pressure (Po) measurements.
- Analyzed data using Fast Fourier Transform (FFT) and polynomial equation fitting to Bode plots, comparing transfer function coefficients (a1, a0, b2, b1).
Main Results:
- Statistical and graphical comparisons showed no significant differences in the transfer function coefficients (a1, a0, b2, b1) between the outer wall area (Do/Pi) and intraluminal pressure (Po/Pi) responses.
- Coefficients b2 and b1 varied with static pressure levels, indicating pressure-dependent inertial and viscous effects.
- Coefficient a1 remained relatively constant, suggesting independence from static pressure and highlighting fluid viscosity's role.
Conclusions:
- The study supports the working hypothesis that the outer wall area and intraluminal pressure exhibit similar dynamic responses.
- The validated transfer function provides a robust model for analyzing aortic wall and intraluminal fluid dynamics.
- The findings offer insights into the inertial (b2), viscous (b1), and elastic (a0) properties of the aortic system.