Interstitial fluid-solid interaction within aneurysmal and non-pathological human ascending aortic tissue under...

Area of Science:

• Biomedical Engineering
• Cardiovascular Research
• Tissue Mechanics

Background:

• Aortic dissection is a critical complication of aneurysms.
• The role of interstitial fluid-solid interaction in aortic tissue mechanics is not fully understood.
• Structural changes in aneurysmal tissue may alter biomechanical properties.

Purpose of the Study:

• To quantify the shear force between interstitial fluid and medial lamellae in human ascending aorta.
• To investigate how this fluid-solid interaction differs between aneurysmal and non-pathologic tissue.
• To determine the contribution of this interaction to the propensity for aortic dissection.

Main Methods:

• Sinusoidal shear deformation (1 Hz, 50 cycles) applied to tissue samples.
• Frequency analysis of total shear stress versus time response.
• Measurement of interaction ratio (3 Hz/1 Hz amplitude ratio) under varying deformation amplitudes and directions.
• Evaporation tests to assess free water content.

Main Results:

• Significant 1 Hz, 3 Hz, and 5 Hz frequency components were identified in shear stress response.
• Aneurysmal tissue exhibited a statistically smaller interaction ratio (3 Hz/1 Hz) in the circumferential direction at 25% amplitude.
• Free water content was similar in both aneurysmal and non-pathologic tissues.
• The 3 Hz component, visible in stress-time curves, quantifies fluid-solid interaction.

Conclusions:

• Structural changes in aneurysmal tissue increase interstitial fluid-medial solid interaction shear force.
• This increased force contributes to the propensity for aneurysmal dissection.
• Aneurysmal dissection susceptibility is not dependent on interstitial fluid amount or wall thickness.
• Frequency analysis of shear stress provides a method to measure otherwise difficult-to-isolate fluid-solid interactions.