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Michael F. O'Rourke, Link Between Macrocirculation and Microcirculation in Isolated Systolic Hypertension of Older Subjects, American Journal of Hypertension, Volume 22, Issue 5, May 2009, Page 469, https://doi.org/10.1038/ajh.2009.51
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Extract
The arteries have two functions—first as a conduit, and second as a cushion.1 Arteries distribute blood to the systemic organs and tissues (the conduit function) but they must also cushion pulsations from the left ventricle so that blood may flow evenly into the microcirculation (cushion function). Obstruction of an artery usually causes obvious ischemia or infarction of a tissue or organ, whereas stiffening causes more subtle changes predominantly upstream, where pulsatile pressure is increased in central arteries. Changes are not fully apparent in peripheral arteries such as the brachial.1,2 Increase in central pulsatile pressure adversely affects the heart, because the left ventricle must pump harder in systole, and has lower pressure to perfuse it during diastole through the coronary arteries. Consequences are left ventricular hypertrophy and predisposition to myocardial ischemia and heart failure.1
Effects of arterial stiffness on cushioning function have only recently been appreciated.3 In the arteries of young people, pulsations are effectively cushioned in the large elastic arteries so that energy lost in arterial pulsation is very low—perhaps 5–10% of energy lost driving blood through the narrow arterioles and capillaries.4 With aging, the elastic arteries stiffen and cannot cushion pulsations of flow. The flow pulsations extend down into vasodilated high flow organs—notable in the brain and kidneys. In consequence, pulsatile energy is absorbed in the microvessels of these organs, and this may be increased fourfold.3
