Relationship between diastolic shape (eccentricity) and passive elastic properties in canine left ventricle

Area of Science:

• Cardiovascular Physiology
• Biomechanical Engineering

Background:

• Understanding the passive elastic properties of the left ventricle (LV) is crucial for diagnosing diastolic dysfunction.
• Left ventricular (LV) eccentricity and volume changes influence its passive elastic behavior.

Purpose of the Study:

• To investigate the relationship between left ventricular (LV) eccentricity, volume, and passive elastic properties.
• To identify the volume at which elastic recoil forces emerge during diastole.

Main Methods:

• Eight instrumented open-chest dogs were used, with measurements of LV pressure, dimensions (anterior-posterior, base-apex), and mitral valve occlusion.
• Linear regression analysis was applied to relate midwall eccentricity to volume and peak mitral flow squared to the atrioventricular pressure gradient.

Main Results:

• A transitional volume (Vt) was identified, dividing cardiac cycles with and without elastic recoil forces during diastole.
• Vt was found to be analogous to the equilibrium volume (V0) derived from pressure-volume relationships.
• Dissipative constants were determined for cycles with and without elastic recoil, showing differences in energy dissipation during mitral flow.

Conclusions:

• The study defines a critical transitional volume (Vt) that signifies the onset of elastic recoil in the left ventricle.
• This finding provides insights into the mechanical behavior of the left ventricle during diastole and its passive elastic properties.
• The identified dissipative constants offer a quantitative measure of energy loss during mitral flow under different diastolic conditions.