The clinical perspective on childhood hypertension has changed over the past few decades. Previously, hypertension in childhood was considered to be due to secondary causes. Essential hypertension or primary hypertension was regarded as a disorder of adulthood. Currently, essential hypertension is viewed as a polygenic disorder that originates in childhood and is modified by environmental factors. This view, however, remains theoretical for very young children. In adolescence, on the other hand, characteristic patterns of essential hypertension are recognizable, and the diagnosis of essential hypertension can be made with clinical certainty. Secondary causes of hypertension, however, continue to occur in adolescence and occur with greater frequency than in adulthood.
The challenge to the clinician who cares for an adolescent with high blood pressure is to determine: (1) the extent to which the patient should be evaluated for underlying causes, ie, primary versus secondary cause; and (2) the appropriate treatment for the high blood pressure, ie, the risk versus benefit of drug therapy. These dilemmas will be the focus of this article.
A diagnosis of hypertension can be made more objectively with the benefit of improved blood pressure criteria. The reference standards for blood pressure according to chronological age were recently revised by the Second Task Force on Blood Pressure Control in Children.1 These blood pressure distribution curves, developed from substantial data available on United States children, provide a clear reference for clinical decision making. In adolescence, the 95th percentile, the level that defines high blood pressure, is lower than in previous publications. An adolescent with blood pressure levels above the 95th percentile on repeated measurements has high blood pressure and needs appropriate intervention. An adolescent with blood pressure measurements that fluctuate between the 90th and 95th percentile may be at risk for developing hypertension and may benefit from intervention directed at modifying risk factors.
Measuremenr of blood pressure during childhood and adolescence has become a standard component of routine health care. A single elevated blood pressure measurement is not a diagnosis, but a sign warranting further assessment. The best initial assessment of an elevated blood pressure reading is a repeat measurement. On repeat measurement, careful attention should be given to proper cuff size and position of the patient (reference values refer to measurements obtained from the right arm with the patient seated). The interval between repeat measurements is generally determined by the severity of the blood pressure elevation or the presence of clinical symptoms. For example, a measurement of 160/110 mmHg should be repeated within days, whereas a measurement of 134/84 mmHg could be repeated in weeks to months.
The blood pressure percentile curves provide a comparative reference for determining how a child's blood pressure deviates from the normal range. Blood pressure measurements that repeatedly exceed the 95th percentile document the presence of high blood pressure. To proceed with evaluation and treatment, clinical decisions are based on absolute values of blood pressure. Table 1 provides numerical values indicating mild, significant, and severe hypertension during adolescence.
Adolescents with significant and severe hypertension require evaluation for secondary causes of hypertension. These patients will need a careful history, physical examination, and directed diagnostic studies. Severe hypertension in adolescence is usually secondary to renal or renal-vascular disease. Suggested diagnostic studies for significant and severe hypertension in adolescents are provided in Table 2.
More than 50% of high blood pressure in adolescence will be due to primary or essential hypertension. Essential hypertension in adolescence is usually mild. Although mild hypertension may be secondary to underlying disorders, characteristics other than blood pressure level are helpful in identifying these cases. With our current understanding of essential hypertension in the young, the diagnosis no longer depends on a negative diagnostic evaluation but can be approached by considering the known characteristics and risk factors of early essential hypertension in the young.
A major characteristic of essential hypertension is a strong family history of hypertension. Usually, a parent is a known hypertensive and the family history will be positive for hypertension in grandparents, aunts, or uncles. Absence of any family history of hypertension makes the diagnosis of essential hypertension in an adolescent less likely.
Another characteristic of essential hypertension is excess weight in girls and increased height in boys. Several studies on growth and blood pressure have reported that although hypertensive girls are heavier than appropriate for height, hypertensive boys are taller but not necessarily heavier than their agematched peers with lower blood pressure. Because adolescent boys with high blood pressure are large for their age, a typical patient appearing in a physician's office is a high school athlete found to have high blood pressure during a physical exam for participation in competitive athletics.
Classification of Hypertension* in Adolescence
Other characteristics of essential hypertension in juveniles include a higher resting heart rate and a labile blood pressure pattern.2 A labile blood pressure pattern is one in which there is marked variability, particularly in systolic pressure, from one reading to another.
The major risk factors tor all cardiovascular diseases are a strong family history and excess body weight. Other risk factors include isolated systolic pressure elevation, elevated plasma cholesterol, and elevated fasting plasma insulin level. Higher serum uric acid levels are also associated with hypertension.
The evaluation of the adolescent with high blood pressure begins with repeated blood pressure measurements to confirm the elevation and to determine the degree. Concurrently, a history and physical exam provide data on possible secondary causes (eg, hyperthyroidism, renal disease, neurofibromatosis). The history and physical exam also address the associated risk factors for cardiovascular disease.
Adolescents with either significant diastolic hypertension or mild hypertension with no associated risk factors should have further diagnostic studies to identify or exclude underlying disorders, in particular renal causes of the hypertension. Adolescents with mild hypertension and the associated risk factors of a positive family history, excess body weight, or the hyperkinetic circulatory characteristics of high resting heart rate and labile blood pressure are likely to have early essential hypertension. In these cases, extensive diagnostic studies are not necessary; more benefit is obtained from efforts to modify health risk behaviors.
The hypertensive adolescent, like any other hypertensive patient, requires treatment. However, the term "treatment" does not necessarily indicate a lifetime of drug therapy. Adolescents with mild essential hypertension generally can be managed with nonpharmacologic treatments. Education of the adolescent and the parents about hypertension is an important element in management. High blood pressure usually is asymptomatic and is easy for the adolescent to disbelieve or ignore. Avoid conveying to the young patient the idea of hypertension as a disease. More benefit may be gained by teaching the hypertensive adolescent that there is a risk for future disease as a consequence of the high blood pressure and that this risk can be controlled. This relieves the adolescent of the burden of carrying a chronic disease. Also, teaching blood pressure control methods provides a dimension of self control. Education is the key to giving the adolescent the means to achieve self-control and ultimately to comply with the treatment plan.
Excess body weight in a hypertensive adolescent presents an obvious focus of treatment. Reduction of adiposity, although difficult to achieve, generally results in a reduction of blood pressure. J Weight reduction requires a combination of reduced calorie intake, change in eating patterns, and usually increased physical activity. Weight reduction is difficult for any patient and particularly for adolescents. In general, equal effort should be placed on the other nonpharmacologic parameters, such as physical activity and diet pattern, which will also contribute to weight control.
Diagnostic Studies for Evaluation of Hypertension In Adolescence
Diet change, in particular reduction in dietary sodium intake, has been a standard part of hypertensive therapy. The usuai sodium intake of adolescents is well beyond daily requirements. Reducing the daily sodium intake to 2500 mg is a reasonable goal which can be achieved by avoiding processed foods and the use of the salt shaker. Most prepared foods, including fast foods, now have nutrient information on the labels. The patient can keep a record of sodium intake and learn how to keep intake below 2500 mg daily.
A considerable body of evidence indicates that potassium induces natriuresis and vasodilatation.4 Potassium depletion results in an increase in blood pressure, and many hypertensives have a low potassium balance. Increasing potassium intake is beneficial in controlling blood pressure in many patients, in particular black patients.5 Therefore, replacing high sodium foods with potassium rich foods is another diet change helpful in blood pressure control in adolescents. Dietary calcium may also play a role in blood pressure regulation. However, the data on calcium remain controversial, and presently evidence is insufficient to recommend augmenting calcium intake.
Another component of diet, which has not been a focus of blood pressure control, is the role of refined sugar. Experimental evidence indicates that eating refined sugar results in an increase in blood pressure, independent of any increase in weight.6 A reduction in refined carbohydrate intake also results in a reduction in catecholamine excretion. A mechanism other than weight loss may relate the reduction of blood pressure with reduced refined carbohydrate (sugar) intake. Therefore, it is reasonable to encourage a reduction in sugar intake as part of diet therapy for blood pressure control.
Aerobic exercise is known to be beneficial in developing cardiovascular fitness. Reports also indicate that conditioning exercise reduces blood pressure in adolescents with high blood pressure.7 Evidence for a direct effect of exercise on blood pressure has been limited. Increased exercise has been thought to aid in weight control and in developing a sense of well being. However, the studies of Roccini et al have indicated that exercise may have a more specific role in blood pressure control. Overweight children were placed on one of three treatment regimens; diet, diet plus exercise, and no treatment control. Both diet and diet plus exercise groups lost equal amounts of weight. However, the blood pressure reduction was greater in the diet plus exercise group.8
Adolescents with high blood pressure should not be restricted from physical exercise unless the hypertension is severe or cardiac symptoms are present. Sufficient evidence shows that increasing physical activity is beneficial, and a daily schedule of 20 minutes of vigorous physical exercise should be part of the management plan. Because of the profound increase in blood pressure that occurs with intense isometric exercise, power weight lifting routines for body building should be discouraged. However, weight training routines that emphasize repetition with lighter weights can be continued. For example, if a weight cannot be lifted at least 20 repetitions per set, a lighter weight should be used.
Pharmacologic therapy for adolescents with hypertension is a difficult decision and requires weighing the risks of extended drug therapy versus the benefits of lowering the blood pressure. There are, however, cases in which antihypertensive drug therapy is indicated. Adolescents with persistent significant hypertension unresponsive to the nonpharmacologic maneuvers may benefit from a limited course of drug therapy. The purpose of lowering blood pressure is to prevent target organ injury from prolonged high blood pressure. If the decision whether to treat with drugs is equivocal, assessment of possible sites of pressure-induced injury may be helpful in arriving at a clinical decision. A retinal exam for vascular hypertensive changes, or an echocardiogram for cardiac structural change, such as increased left ventricular mass or intraventricular septal thickness, may provide the evidence to warrant institution of drug therapy. Compliance with drug therapy is better if medication is given in low doses for a limited time, such as 6 months, and then withdrawn. There are many available drugs that may be used for blood pressure control in adolescents as well as adults. Therapy should be begun with one category of drugs, eg, diuretic, ß-blocker, angiotensin converting enzyme inhibitor. If low doses of one category have an insufficient effect in lowering blood pressure, treatment should be changed to another category. Patients with renal disease or diabetes need more aggressive antihypertensive therapy. Even mild hypertension can accelerate deterioration of renal function in these patients.
Adolescents with high blood pressure should also be counseled to avoid drugs that contribute to blood pressure elevation, including oral contraceptives, nonsteroidal anti-inflammatory drugs, and ephedrinecontaining cold remedies.
The hypertensive adolescent requires a careful blood pressure evaluation. In most cases, extensive diagnostic studies will not be necessary, particularly if the patient exhibits characteristics of early essential hypertension. On the other hand, further evaluation should not be withheld in the absence of risk factors or the presence of significant hypertension. A management plan that includes patient education is appropriate for all adolescents with hypertension. In some, but not all, hypertensive adolescents, a limited course of medication may be beneficial.
1. Report of the Second Task Force on Blood Pressure Control in Children. Pediatrics 1987; 79:1-25.
2. Falkner B, Kushner H, Onesti G, et al: Cardiovascular characteristics or" adolescents who develop essential hypertension. Hypertension 1981; 3:251-258.
3. Rames LX, Clarke WR, Connor WE, et al: Normal blood pressure and the evaluation of sustained blood pressure elevation in childhood: The Muscatine study. Pediatrics 1978; 61:245-251.
4. Treasure J. Pkoth D: Role of dietary potassium in the treatment of hypertension. Hypertension 1985; 7:628-637.
5. Svetkey LP, Yarger WE, Feussner JR, et al: Double-blind placebo-controlled trial of potassium chloride in treatment of mild hypertension. Hypertension 1987; 9:444-450.
6. Young JB, Landsberg L: Effect of oral sucrose on blood pressure in the spontaneously hypertensive rat. Metabolism 1981; 30:421-424.
7. Hagberg JM , Goldring D, Ehsani AA, et al: Effect of exercise training on blood pressure hemodynamic features of hypertensive adolescents. Am ] Cardiol 1983; 52:763-768.
8. Rocchini AP, Katch M, Schork A, et al: Insulin and blood pressure during weight loss in obese adolescents. Hypertension 1987; 10:267-273.
Classification of Hypertension* in Adolescence
Diagnostic Studies for Evaluation of Hypertension In Adolescence