Hypertension in adolescents – the race against time Published on 20th September, 2013

Brian Rayner, MBChB, FCP, MMed, Division of Nephrology and Hypertension, University of Cape Town

Introduction:
 
Hypertension or raised blood pressure (BP) was previously rare in children and adolescents, but the prevalence is dramatically changing mainly due to the critical influence of childhood obesity. Ten years ago at the Hypertension Clinic at Groote Schuur Hospital referral of children and adolescents with hypertension was uncommon and usually associated with defined secondary causes, but in the past 10 years we have seen a dramatic increase in referrals. It is increasingly difficult to cope with the increasing numbers, and it is therefore imperative to develop policies regarding the prevention, evaluation, treatment and referral of young hypertensives.
 
Prevalence:
 
In 1977 hypertension in children was considered to be extremely rare and would almost always prompt a search for an underlying secondary cause. [1] In South Africa statistics released by the Medical Research Council show that according to the South African Demographic and Health Survey 2003 and National Income Dynamics Study Health the prevalence of hypertension in the age group has risen 225% from 4% in 1998 to 11% in 2008. [2]
 
Pathogenesis:
 
The pathogenesis of this dramatic increase in prevalence is related to the childhood epidemic of obesity.  In cohort study of 1111subjects with mean age of 10.5 years followed for a mean 4.5 years the effect of adiposity was minimal until the BMI percentile reached 85, where there was a fourfold increase in effect. [3] In South Africa the prevalence of overweight/obesity in the age group 15-24 in 2008 was 13% in men and 38% in females. This was paralleled by extremely high levels of physical inactivity in this same age group – 36% in men and 52% in women. [3]Other factors involved in the pathogenesis of childhood primary hypertension are family history of hypertension, low birth weight and reduced nephron number (Barker-Brenner Hypothesis) and elevated uric acid. [1,4]
 

Importance:

The importance of elevated BP in childhood is several fold. Firstly childhood BP especially systolic tracks BP into adulthood, secondly it is associated with subclinical cardiovascular disease and thirdly and more importantly significant elevations in overall mortality, cardiovascular mortality and coronary heart disease in particular according to the Harvard Alumni Health Study. [1,5]

Definition:

BP is lower in children and it therefore imperative to consult age, gender and height norms for BP. Hypertension according to the 4th Report on hypertension children normotension is defined as BP persistently < 90th centile and hypertension as BP persistently > the 95th. [6] From the practical perspective adult norms should be used for children > 12 years of age. Assessment of BP should not be done with a single reading but frequent measurements, and many instances a full 24 ambulatory BP monitoring to avoid incorrect labeling.

Evaluation:

In the evaluating of a child with elevated BP it is imperative to consider the relative frequency of primary and secondary hypertension as this will direct evaluation. In infants >99% have a secondary cause. This falls to 70-85% in school-age children and to 5-15% in adolescents. Important pointers to primary hypertension will be older children and adolescents, obesity, and a family history of hypertension, type 2 diabetes and cardiovascular disease. All patients should undergo a careful clinical evaluation searching for secondary causes e.g. bruits, radio-femoral delay, urinalysis, etc. In the drug history particular attention needs to be paid to abuse of cocaine and Tik, and the use of oral contraceptive drugs. The most common secondary cause of hypertension in children are renal parenchymal and renovascular disease, and it is essential at the very least that all patients undergo a dipsticks urine, creatinine, and an ultrasound of the kidneys. Electrolytes, uric acid, fasting glucose and lipogram, ECG and echocardiogram are also essential. More specialized tests may be required, but usually performed at specialist level.

Treatment:

Treatment of hypertension in children has not been established in randomized controlled clinical trials, although several classes of drugs have been successfully evaluated for efficacy and safety in children. Decisions on treatment decisions are based on expert opinion. All children with hypertension or borderline BP (or pre-hypertension) should undergo lifestyle changes in particular to increase aerobic exercise and reduce weight and salt intake. 

Reasonable indications for pharmacological therapy are – symptomatic or severe hypertension, secondary hypertension, hypertension with overt target organ damage, type 1 and 2 diabetes and persistent hypertension refractory to lifestyle intervention. [1]The 4thReport recommends diuretics, beta blockers, calcium channel blockers (CCBs) and ACE inhibitors or angiotensin receptor blockers (ARBs) as suitable drugs for initiation of treatment. [6]However in the author’s opinion due to the long term metabolic effects of diuretics and beta blockers, ARBs or ACE inhibitors and/or CCBs are the preferred initial drugs and diuretics and beta blockers should be reserved for specific indications and in those with more resistant hypertension.

Ground breaking research suggests that lowering uric acid reduces BP in adolescents. [7]

Referral

Ideally all adolescents with hypertension should be evaluated at specialist level but given the increasing numbers it is no longer possible in the public sector. The primary care practitioner should consider referral if there is severe hypertension with target organ damage, and signs, symptoms or investigations suggesting a secondary cause. Overweight adolescents with a family history of hypertension, type 2 diabetes and cardiovascular disease should be evaluated and treated in the primary care setting.

Conclusion:

In conclusion the young hypertensive is becoming increasingly common due mainly to obesity in children. Every effort needs to be made to improve the lifestyle of our children to prevent this growing epidemic. All adolescents should have their BP measured especially if they are overweight, sedentary and have a family history of hypertension. If elevated, they should undergo further evaluation. Recommendations regarding evaluation and treatment of young hypertensives are made.

References:

  1. Flynn JT. Hypertension in children. In: Kaplan’s Clinical Hypertension 9th Edit, 2006: Lippincott Williams and Wilkins, Philadelphia.

  2. Bradshaw D, Steyn K, Levitt N, Nojilana B. Non-communicable diseases – the race against time. www.mrc.ac.za/policybriefs/raceagainst.pdf, accessed 19th Sept 2013

  3. Tu W, Eckert GJ, DiMeglio LA, Yu Z, Jung J, Pratt JH. Intensified Effect of Adiposity on Blood Pressure in Overweight and Obese ChildrenHypertension; 2011: 58: 818-824.

  4. Feig DI, Soletsky B, Johnson RJ. Effect of allopurinol on blood pressure of adolescents with newly diagnosed essential hypertension: a randomized clinical trial. JAMA 2008; 300: 924-32.

  5. Gray L, Lee IM, Sesso HD, Batty GD. Blood Pressure in Early Adulthood, Hypertension in Middle Age, and Future Cardiovascular Disease Mortality HAHS (Harvard Alumni Health Study. J Am Coll Cardiol 2011; 58: 2396-403.

  6. Falkner B, Daniels SR. Summary of the fourth report on the diagnosis, evaluation, and treatment of high blood pressure in children and adolescents. Hypertension 2004; 44: 387-8.

  7. Soletsky B, Feig DI. Uric Acid Reduction Rectifies Prehypertension in Obese Adolescents. Hypertension 2012; 60: 1148-1156

 

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