Pathophysiology & Etiology

Until recently, high blood pressure was synonymous with hypertension; now, however, data suggest that there is considerably more to hypertension than increased blood pressure. Several metabolic and functional abnormalities have even been observed in the children of hypertensive patients prior to blood pressure elevation that are similar to, but of a lesser magnitude than, those found in their parents. Hypertension is also associated with insulin resistance and glucose intolerance. Insulin levels are consistently higher in hypertensive patients than in normotensive controls. This condition of hyperinsulinemia is worsened by thiazide diuretics, especially in the presence of b-blocker therapy. Hyperinsulinemia produces a proliferation of vascular smooth muscle and fibrous tissue and adversely affects the serum lipid profile.
Renin and angiotensin levels are also important factors in determining both the response to therapy and the prognosis. Hypertensive patients with high renin levels have a greater incidence of myocardial infarction than do similar patients with lower levels. Normotensive young adults with a family history of hypertension have been found to have thicker left ventricular (LV) walls and alterations of LV diastolic filling in comparison with control subjects. Although not frankly abnormal, these latter two findings are similar to but less severe than those observed in hypertensive patients. Renal reserve also appears diminished in the children of hypertensive parents.
Hypertension, therefore, is a multisystem disorder with involvement of the cardiovascular, neuroendocrine, and renal systems with a strong genetic component.
A. NATURAL HISTORY

Blood pressure gradually increases throughout childhood and adolescence. The best predictor of the level of future blood pressure is the relative level of blood pressure of a child in relation to his or her peers. During childhood and adolescence, body weight is a major determinant of blood pressure, with heavier children having higher blood pressures. High blood pressure is uncommon under the age of 20; if present, it is usually associated with renal insufficiency, renal artery stenosis, or coarctation of the aorta. The initial presentation of high blood pressure usually occurs in the third to the sixth decade, and blood pressure may fluctuate significantly during the early course of the disease. The prevalence of high blood pressure increases with age and is greater in men than women. In the elderly population, this reverses, and more women than men have high blood pressure.
Everyone should be screened for the presence of high blood pressure; testing should be done routinely in the physician's office or at one of the larger community screening activities. These activities are typically targeted at those at greater risk of high blood pressure: older individuals, individuals with previously high-normal blood pressures, blacks, sedentary individuals, and those with a family history of hypertension.
Burt VL, Whelton P, Rocella EJ, et al: Prevalence of hypertension in the U. S. adult population. Results of the Third National Health and Nutrition Examination Survey, 1988–91. Hypertension 1995;25:305.
B. ETHNIC AND SOCIOECONOMIC FACTORS

Blacks have both an earlier onset and a greater prevalence of high blood pressure than do whites, Asians, and Native Americans at all ages. Over the age of 50 years, hypertension is prevalent in more than 40% of black males, compared with approximately 27% in white males. Severe high blood pressure (diastolic BP at least 115 mm Hg) is five times more common in black men than in white men and seven times more common in black women than in white women. Blacks therefore tend to have more serious complications, especially strokes, from high blood pressure. Other factors also affect the prevalence of high blood pressure. Among all ethnic groups, less-educated individuals have a greater prevalence of high blood pressure than do more highly educated individuals, especially in lower socioeconomic groups.
The level of blood pressure elevation is directly related to total cardiovascular risk, and the presence of other cardiovascular disease risk factors, especially diabetes or dyslipidemia, is synergistic with high blood pressure.