Afterload is a measure of pressure against which ventricles must pump to force blood out into arteries. All other things being equal, the greater the afterload, the smaller the stroke ante therefore cardiac output. Systemic hypertension is defined as a resting blood pressure greater than 140 mmHg/90 mmHg on three separate occasions of being treated with antihypertensive medications. Hypertension is more prevalent in the population. In the United States, more than 70% of men and women aged 75 and have hypertension.