Coronary microcirculation in the beating heart

Area of Science:

• Cardiovascular Physiology
• Biomedical Engineering

Background:

• Coronary hemodynamics are characterized by a distinct phase opposition between arterial and venous flow.
• Intramyocardial capacitance and variable resistance vessels play a critical role in cardiac function.

Purpose of the Study:

• To elucidate the functional components of intramyocardial capacitance vessels during diastole.
• To investigate the impact of cardiac contraction on coronary vascular resistance.

Main Methods:

• Analysis of coronary artery and vein velocity waveforms.
• In vivo observation of arteriolar dimensions during the cardiac cycle.

Main Results:

• Coronary arteries show predominantly diastolic flow, while veins exhibit systolic flow.
• Intramyocardial capacitance vessels possess unstressed volume and ordinary capacitance components during diastole.
• Arterioles in the mid-wall and subendocardium narrow during systole, increasing vascular resistance.

Conclusions:

• The phase-opposed flow patterns are fundamental to coronary hemodynamics.
• Unstressed volume and ordinary capacitance are key functional aspects of diastolic intramyocardial capacitance.
• Cardiac contraction significantly modulates coronary vascular resistance through vessel narrowing.