Compressibility of perfused passive myocardium

Area of Science:

• Cardiovascular Physiology
• Biomechanical Engineering

Background:

• Cardiac models often assume myocardium incompressibility.
• Myocardial perfusion with distensible vessels suggests potential compressibility.

Purpose of the Study:

• To quantify vascular volume changes in perfused myocardium under mechanical load.
• To challenge the assumption of cardiac tissue incompressibility.

Main Methods:

• Digital subtraction angiography used to measure vascular volume.
• Cyclic biaxial loading applied to passive, perfused canine interventricular septa.
• Vascular volume changes measured across varying perfusion pressures (0-120 mmHg).

Main Results:

• Perfused myocardium demonstrated significant vascular volume extrusion during loading.
• Volume changes increased with perfusion pressure, notably at 120 mmHg.
• Extruded fluid volume was comparable to that during active contraction.

Conclusions:

• The assumption of myocardial incompressibility is unrealistic for theoretical analyses.
• Cardiac models must incorporate tissue compressibility for greater accuracy.
• Mixture theory or similar approaches are recommended for future cardiac modeling.