1.4.5 Myocardial oxygen consumption
In reviewing the physiological processes involving the cardiovascular system, it is appropriate to consider the oxygen requirements of the heart muscle itself. Oxygen is delivered to the myocardium by coronary blood flow This flow principally occurs during diastole. Myocardial oxygen requirements are increased by raised heart rate, and high heart rates have the additional effect of decreasing the time available for coronary blood flow. Increased oxygen conis also required for conditions in which contractility and afterload are greater than normal. Abnormalities which reduce the capacity of oxygen supply to meet demand lead to an increased wall stiffness, which reduces diastolic filling and increases afterload, and may result in arrhythmia’s.