Mechanisms of myocardium-coronary vessel interaction

Area of Science:

• Cardiovascular Physiology
• Biomechanical Engineering
• Computational Fluid Dynamics

Background:

• The precise mechanisms linking myocardial contraction to coronary blood flow are not fully understood.
• Existing models of myocardium-vessel interaction (MVI) fail to explain all observed coronary flow patterns.
• Intramyocardial pressure (IMP) generation and its effect on coronary vessels require further elucidation.

Purpose of the Study:

• To investigate which myocardium-vessel interaction (MVI) mechanisms, individually or in combination, accurately predict coronary blood flow.
• To test the hypothesis that a specific combination of MVI mechanisms is necessary to replicate observed coronary flow features.
• To provide a more complete physical basis for understanding intramyocardial pressure (IMP) and coronary flow regulation.

Main Methods:

• Analyzed three fundamental MVI mechanisms: time-varying elasticity, myocardial shortening-induced intracellular pressure, and ventricular cavity-induced extracellular pressure.
• Employed physical principles (conservation of mass, force equilibrium) within a data-driven vascular network model.
• Coupled mechanical properties of myocardium and vessel walls using stress analysis to simulate responses to blood pressure and external loading.

Main Results:

• No single MVI mechanism could independently replicate the measured dynamic vascular pressure, diameter, and flow velocity data.
• A combined model incorporating cavity-induced extracellular pressure and shortening-induced intramyocyte pressure showed strong agreement with most experimental data.
• The proposed combined MVI model successfully predicts transmural vascular dynamics and coronary flow features.

Conclusions:

• The interaction between ventricular cavity pressure and myocardial shortening is crucial for explaining coronary blood flow dynamics.
• This combined MVI mechanism provides a more accurate physical basis for intramyocardial pressure (IMP) than previously proposed models.
• Findings enhance understanding of normal coronary phasic flow and have implications for diagnosing and treating coronary artery and microcirculatory diseases.