Stroke volume - afterload definition & hypertension

• Pressure (or other resisting force) that ventricles must overcome to push open semilunar valves and eject blood. ▪ Normally, the left ventricle blood pressure must overcome arterial pressure in the aorta. ▪ Abnormally high blood pressure, or hypertension, increases aortic pressure which must be overcome by higher left ventricular pressure. ▪ Eventually, ventricular pressure builds to overcome the elevated arterial blood pressure and blood is ejected from the heart. IN Increased afterload makes ejection more difficult and decreases stroke volume (and cardiac output). ▪ When afterload decreases the cardiac output, other mechanisms help bring it back to normal. • Preload is increased via feedback mechanisms. • Contractility is increased.

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