Heart Rate..Part 2..oxygen Demand and Supply

The three major determinants of myocardial oxygen demand are heart rate, contractility, and wall tension.

Except at very high arterial pressures, changes in heart rate dominate the changes in energy demand, so that heart rate itself is an important indicator of myocardial oxygen demand.

The supply of oxygen to the heart is determined by coronary blood flow, hemoglobin concentration, and the saturation of the hemoglobin molecules.

Coronary blood flow is determined by the arterial pressure (especially in diastole for the left heart) and resistance to flow in

the coronary arteries.

When coronary vessels are normal, the reserve for coronary flow is very large and should be adequate even at heart rates 200 BPM.

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