Materials and methods (Half page)
• Describe the sample used in the test. (Sheep’s Heart)
• Discuss the heart dissection and sample extraction and preparation.
• A Zwick mechanical test machine is used to determine a force-displacement
relationship for aortic tissue. The sample dimensions and initial grip-to-grip
separation are recorded. Any pre-force (to remove slack from the sample)
should be subtracted when constructing a stress-strain curve so that the stressstrain curve passes through the origin.
Results and Analysis
• Present the stress strain diagrams for the aorta using the data specific to your
lab group.
• Provide a table of circumferential stress, circumferential strain, tangent
stiffness, and compliance for four different values of blood pressure
(equivalent to 80-120mmHg).
• Present a derivation of the windkessel model where the flow from the ventricle
to the aorta is described using a QUADRATIC EQUATION. Assume a stroke
volume of 70 ml and assume that the duration of systole if 0.2 s.
• Provide a Matlab code to implement the windkessel solution.
• Insert your value of compliance for the tested ovine aorta into the windkessel
model and plot the time-dependent change in blood pressure during one
cardiac cycle. Repeat this task using the published value of compliance for a
healthy human aorta.
• Note: If you are unable to complete the derivation of a windkessel model with
a Quadratic flow input, then use the solution for a linear flow input provided in
lecture notes.
• In your results section you should provide text outlining the important points
of every diagram and table that you include.
• All diagrams and tables should include captions.
Discussion
• Compare the values of elastic modulus and compliance to published data for
aortic tissue.
• Comment on the ability of the Windkessel model to model the pressure profile
of the aorta.
• Recommendations for more accurate tests and models?
References
Use a standard referencing format in the report (e.g. Harvard style)
Aortic Dissection
• Identify left ventricle
• Identify mitral valve/chordate tendinae/aortic valve
• Identify aorta/left coronary artery/right coronary artery
• Identify sinus of Valsalva
• Extract a cylindrical specimen of aorta
• Cut specimen in axial direction and observe spring-back due to residual stress in aorta
• Measure circumference of aorta
• Perform mechanical test on aorta constructing stress-strain curves for axial and
circumferential directions
Specimen number:
Circumference=