Pathophysiology of Hypertension
Hypertension (high blood pressure) is a disease of vascular regulation resulting from malfunction of arterial pressure control mechanisms (central nervous system, rennin-angiotensinaldosterone system, extracellular fluid volume.) the cause is unknown, and there is no cure. The basic explanation is that blood pressure is elevated when there is increased cardiac output plus increased peripheral vascular resistance.
The two major types of hypertension are primary (essential) hypertension, in which diastrolic pressure is 90 mm Hg or higher and systolic pressure is 140 mm Hg or higher in absence of other causes of hypertension (approximately 95 % of patients); and Secondary hypertension, which results primarily from renal disease, endocrine disorders, and coarctation of the aorta. Either of these conditions may give rise to accelerated hypertension – a medical emergency – in which blood pressure elevates very rapidly to threaten one or more of the target organs: the brain, kidney, or the heart.
Hypertension is one of the most prevalent chronic diseases for which treatment is available; however, most patients with hypertension are unaware, untreated, or inadequately treated. Risk factors for hypertension are age between 30 and 70; black; overweight; sleep apnea; family history; cigarette smoking; sedentary lifestyle; and diabetes mellitus. Because hypertension presents no over symptoms, it is termed the “silent killer.” The untreated disease may progress to retinopathy, renal failure, coronary artery disease, heart failure, and stroke.
Hypertension in children is defined as the average systolic or diastolic blood pressure greater than or equal to the 95th percentile for age and sex with measurement on at lease three occasions. The incidence of hypertension in children is low, but it is increasingly being recognized in adolescents; and it may occur in neonates, infants, and young children with secondary causes.