How viscous is the beating heart?: Insights from a computational study.

Area of Science:

• Biomedical Engineering
• Computational Biology
• Cardiovascular Mechanics

Background:

• Accurate human heart modeling necessitates understanding tissue rheology, encompassing both elastic and viscous properties.
• While cardiac tissue's elastic properties are well-researched, its viscous behavior remains debated, impacting model fidelity.

Purpose of the Study:

• To investigate the influence of viscous timescales on human cardiac tissue behavior using a viscoelastic model.
• To determine the significance of viscosity in cardiac mechanics within physiological heart rate ranges.

Main Methods:

• Utilized a viscoelastic adaptation of the Holzapfel Ogden model for cardiac tissue simulations.
• Analyzed stress-relaxation curves, pressure-volume loops, and strain profiles across varied viscosity parameters.
• Employed a four-chamber human heart model to assess physiological relevance.

Main Results:

• The time window chosen for model calibration significantly affects parameter identification.
• Viscous relaxation effects were found to be negligible on the overall cardiac behavior during physiological timescales.
• Model calibration time windows strongly influence parameter identification.

Conclusions:

• For simulations within the physiological range of a human heart beat, a hyperelastic approximation of cardiac tissue is adequate.
• Viscosity may play a more critical role in pathological conditions affecting cardiac contraction or relaxation.