Noncoronary collateral myocardial blood flow

Area of Science:

• Cardiovascular Physiology
• Cardiac Metabolism
• Coronary Circulation

Background:

• Chronic coronary occlusion can lead to reduced blood flow to the heart muscle.
• Left ventricular hypertrophy (LVH) increases the heart's workload and oxygen demand.
• Understanding collateral circulation is crucial for managing ischemic heart disease.

Purpose of the Study:

• To investigate the presence and characteristics of noncoronary collateral flow in normal hearts.
• To determine how factors like cardiac arrest, perfusion pressure, and blood viscosity affect this flow.
• To assess the potential for myocardial oxygenation in arrested hearts.

Main Methods:

• Utilized a canine model with induced chronic coronary occlusion and/or left ventricular hypertrophy.
• Measured luminal-left ventricular flow under various conditions: cardiac arrest (aortic cross-clamping), reduced perfusion pressure (50 mm Hg), and hemodilution.
• Quantified collateral flow in milliliters per 100 grams per minute (ml/100 gm/min).

Main Results:

• Demonstrated variable amounts of noncoronary collateral flow (0.2 to 16 ml/100 gm/min) in normal hearts.
• Observed peak flow during aortic cross-clamping (cardiac arrest).
• Noted a significant decrease in flow at lowered perfusion pressure and a slight increase with reduced blood viscosity.

Conclusions:

• Noncoronary collateral pathways provide a significant blood supply to the heart, even in the absence of coronary occlusion.
• Cardiac arrest via aortic cross-clamping does not necessarily result in myocardial anoxia due to collateral flow.
• These findings have implications for understanding myocardial protection during cardiac surgery and in ischemic conditions.