Typically, essential hypertension is recognized in the third decade of life and progresses slowly over many years. Studies emphasize not only the strong familial incidence of essential hypertension but also that young children of hypertensive parents tend to have pressures at the upper limits of normal. In some children these pressures remain at the upper limits of normal and rise with age, and it might be these who in the third decade have pressures recognized as being above an arbitrary level and thus are diagnosed as having essential hypertension.
Whether the cause of essential hypertension is genetic, environmental, or a mixture of both is unknown, and we do not know if this is a single disease or a syndrome common to many different diseases. Adults with essential hypertension have various combinations of high, normal, and low renin and aldosterone concentrations, so that they are different physiologically.
Similar studies have not yet been reported in children. Recently, abnormal fluxes of sodium and potassium across the red cell membranes have been found in essential hypertension. Hypercalcemia (mild) and failure of the kidneys to produce dopamine in response to a salt load have also been suggested as causal mechanisms. The role of renal antihypertensive factors has been supported by the finding that patients with renal failure secondary to essential hypertension lose their hypertension after renal transplantation. Central nervous system factors and resetting of baroreceptors are also important, and an imbalance of endothelial dilator and constrictor factors has been invoked. Recently there has been interest in the association between hypertension and increased concentrations of angiotensinogen, and investigators have found linkage between the angiotensinogen gene locus and essential hypertension.
Essential hypertension is diagnosed from a family history and by excluding other causes of hypertension. In adults, lowering blood pressure by various means can reduce the cardiovascular complications of hypertension, even if it is fairly mild. However, no one has yet used medications to treat children with mild essential hypertension, because the long-term effects of the available drugs are unknown. Probably the wisest course would be use of preventive measures such as eliminating causes of stress, avoiding obesity and smoking, taking regular exercise, and eating a prudent diet. Salt intake should be reduced. Medications should, however, be used if blood pressure is high or if there are signs that it is causing damage.
Before hypertensive children are allowed to do strenuous exercise, formal exercise testing may be valuable. Maximal pressures over 230 mm Hg systolic or 130 mm Hg diastolic are taken by some authorities as reason to bar strenuous exercise because of concern about the cumulative effects of stressing the vascular system.
Renovascular disease causing hypertension is uncommon but should be considered seriously in investigating significant hypertension; it is proportionately more common in children than in adults.
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