Monday, February 22, 2010

Assessment and Management of Hypertension in Children and Adolescents

From Nature Reviews Cardiology

Brian W. McCrindle, MD, MPH

The epidemic of overweight and obesity in youth is increasing the prevalence of prehypertension and hypertension among children and adolescents.
The younger the child is at presentation and the more severe the blood pressure abnormality, the more likely a secondary cause of hypertension is to be present. Measurement of blood pressure in children requires adaptation to the age and size of the child.
Interpretation must be related to normative values specific for age, sex, and height.
Evaluation is primarily aimed at identifying secondary causes of hypertension, associated comorbidities, additional risk factors, and evidence of target-organ damage.
Ambulatory blood pressure monitoring is emerging as a useful tool for evaluation of some patients, particularly for those with suspected 'white coat' hypertension.

Management of prehypertension and hypertension is directed at the underlying cause, exacerbating factors, and the magnitude of the blood pressure abnormality.
Healthy behavioral changes are a primary management tool for treating hypertension and, more particularly, prehypertension and for addressing other cardiovascular risk factors, such as obesity.
Pharmacological management is reserved for patients with hypertension who do not respond to behavioral changes, have additional cardiovascular risk factors or diabetes, are symptomatic, or have developed target-organ damage.

Hypertension is a well-recognized cardiovascular risk factor in adults, contributing to morbidity and mortality from myocardial infarction, stroke, congestive heart failure, peripheral vascular disease, retinopathy, and end-stage renal disease.
No study has been of sufficient duration to determine whether hypertension identified in youth is related to cardiovascular disease in adulthood.
In addition, manifest atherosclerotic cardiovascular disease is extremely rare in childhood. nonetheless, evidence to support an association between elevated blood pressure and atherosclerosis in youth is available from pathology studies and studies of noninvasive markers of atherosclerosis.

Blood pressure assessment in youth, either by direct measurement (Bogalusa Heart Study)[1] or by inference (Pathobiological Determinants of Atherosclerosis in Youth Study),[2,3] is independently correlated with the percentage of intimal surface in the coronary arteries and aorta that are affected by early atherosclerotic lesions, including fatty streaks and fibrous plaques.
In addition, clustering of elevated blood pressure and other cardiovascular risk factors, as seen with the epidemic of the metabolic syndrome and obesity, is associated with an exponential increase in atherosclerotic vascular involvement. These correlations are also evident when noninvasive measures of vascular involvement are used in children and young adults.

ultrasonography has shown that increased blood pressure in children and adolescents is associated with endothelial dysfunction in systemic arteries, increased thickness of the arterial intima-media complex, impaired arterial compliance and distensibility, and increased levels of inflammatory markers.

Research using ultrafast CT has shown a positive correlation between blood pressure and coronary artery calcification in adolescents and young adults. These studies provide consistent and compelling evidence that the atherosclerotic process begins in youth, and is accelerated by increased blood pressure.

In addition to accelerated atherosclerosis, there is also evidence of target-organ damage—primarily left ventricular hypertrophy (LVH). LVH has been reported in about one third of children and adolescents with mild, untreated hypertension and in a greater proportion of those with persistent hypertension.[4,8,9] LVH can be concentric or eccentric, with concentric being associated with a higher risk of cardiovascular outcomes.[8]

The risk of LVH increases with the severity of hypertension in adolescents, but the odds of LVH are also increased in those with masked and milder hypertension (but not with 'white coat' hypertension), compared with normotensive adolescents.[10]

Lande et al. showed that, after matching for BMI, children with 'white coat' hypertension had greater left ventricular mass index than normotensive controls, but less than patients with persistent hypertension (26% with LVH).[11]

Studies have also shown that the presence of concomitant obesity further increases the prevalence of LVH in youths with hypertension.[9] In addition, LVH has been shown to be correlated with increased carotid intima-media thickness—an early marker for atherosclerosis—and increasing adiposity in children and adolescents with hypertension.[4] The working group of the National High Blood Pressure Education Program on Children and Adolescents recommended that the presence of LVH be used to influence therapeutic decisions in patients with hypertension.[12] In this Review, I provide a general overview of hypertension, highlighting evaluation and management aspects of this condition that are specific to infants, children, and adolescents.

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