PEDIATRIC HYPERTENSION: challenges in diagnosis and treatment
With increasing obesity over the past decade, recent studies show a rise in pediatric hypertension with incidence rate of 4%-24% in obese children. Researchers observed a linear relationship between adiposity and hypertension.
Hypertension is more prevalent among boys as compared to girls predominantly affecting Hispanic and non-Hispanic African americans.Children classified as obese (body mass index [BMI] 95% to 98%) had a twofold increase in hypertension compared with healthy weight children, and severely obese (BMI >99%) have a fourfold increase.
The American Heart Association (AHA) and the American Academy of Pediatrics (AAP) recently updated guidelines for diagnosing pediatric hypertension. It is very important to diagnose early or prehypertension as it may lead to hypertension in adulthood and is associated with various co-morbidities.
AAP has updated hypertension in 2017 from the previous Fourth report(2004). In the Fourth report prehypertension was defined as blood pressure greater than 120/90mmHg(90th centile) to 95th centile based on age,gender and height normograms. Hypertension was defined as SBP and/or DBP greater than the 95th percentile.
The 2017 updated AAP guidelines include:
-prehypertension has been reclassified as elevated blood pressure.
-for children above 13 years classification is same as per adult AHA 2017.
-The definitions of elevated blood pressure under the age of 13 years remains SBP and/or DBP in the 90th to 94th percentiles. Stage 1 hypertension is defined as blood pressure readings in the 95th to 99th percentiles, and stage 2 hypertension is defined as blood pressure readings greater than the 95th percentile plus 12 mm Hg.
Current AAP guidelines say that all children should be screened annually for hypertension from the age of 3 years. Children with risk factors such as obesity, renal disease, coarctation of the aorta, diabetes, or is on a medication that can increase blood pressure need to screened at every healthcare visit. Also children under the age of 3 years with prematurity, low birth weight, kidney dysmorphia, or a maternal history of smoking should also have the blood pressure monitored at their routine wellness visits.
Pediatric hypertension can be classified as either primary(essential) or secondary. Hypertension that develops secondary to identifiable cause is labelled as secondary hypertension. Primary hypertension that does not have an identifiable secondary cause is therefore a diagnosis of exclusion.
Some of identified risk factors for development of primary hypertension are as follows:
1.Family history of hypertension or cardiovascular disease
2. Male gender
3. Hispanic decent
4. African American decent
6. Insulin resistance
7. Sleep disorders
8. Low birth weight
9. Maternal history of smoking
10. Chronic kidney disease
11. Elevated uric acid levels
Secondary hypertension can be caused by several pathologies which need to be excluded prior to diagnosing primary hypertension. Various medical conditions such as cushings syndrome, coarctation of aorta, renal artery stenosis, congenital adrenal hyperplasia, hyperthyroidism, drug-induced, pheochromocytoma, obstructive sleep apnea and renal parenchymal disease.
Any child over the age of 3 years with obesity or other risk factors known to predispose them to the development of hypertension should have their blood pressure measured at every health care encounter.As stress and anxiety may alter BP recordings, multiple measurements of blood pressure should be made during an office visit if a child has an elevated blood pressure and the average used to determine blood pressure classification. Practitioners need to be aware of the pediatric normograms for comparison of blood pressures in the office and to assist in early diagnosis of pediatric hypertension.
Once a child is diagnosed to have hypertension classify staging as discussed earlier and further workup is recommended to look for etiology. In stage 2 hypertension , evaluation for end-organ damage is warranted that include renal ultrasonography and echocardiography (to look for LVH).
Basic workup in a child with diagnosed hypertension includes:
As discussed earlier pediatric hypertension is classified into 3 categories- elevated blood pressure, stage 1 HTN and stage 2 HTN.
A child with BP recording between 90th centile to 95th centile is considered to have elevated BP. The first recommended intervention is lifestyle modifications. These can include:
Decreasing dietary sodium
Nutrition management or consultation with a registered dietician
Encouragement of physical activity (guidelines can be discussed)
Promotion of healthy sleep patterns
The child should then be followed again in 6 months. If blood pressure remains elevated after 12 months, ambulatory blood pressure monitoring and further work-up should be considered to rule out secondary causes. If the BP fails to normalize following conservative management, pharmacological management can be considered.
Stage 1 HTN:
A child(<13yrs) is labelled as stage 1 HTN if blood pressure remains over the 95% percentile but less than the 99% percentile. For an adolescent (>13 year old), this is defined as a blood pressure between 130/80 and 139/89.
In an asymptomatic child initial line of management would be life style modification, conservative measures and close followup. Even after 3 followup visits if there is persistant HTN consider pharmacological management.
Stage 2 HTN:
Stage 2 hypertension is defined as a blood pressure greater than the 95% + 12 mmHg or greater than 140/90, whichever is lower.In a child with stage 2 HTN it is recommended to measure blood pressure in upper limb and lower limb at each visit.Once diagnosed t have stage 2 schedule a followup visit within a week, followed by ambulatory blood pressure measurement. Subequent workup wit laboratory and radiological evaluation to be done as discussed earlier.
Lifestyle modifications should fully be maximized prior to consideration of initiating pharmacologic therapy. However, if a child's blood pressure is staying in the stage 2 category, he or she has LVH on echocardiography, or he or she is symptomatic, then a pharmacologic agent should be initiated. Initial treatment is recommended with an angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB), long-acting calcium channel blocker, or thiazide diuretic. Beta blockers are not recommended as initial agents. ACEi and ARBs are conintraindicated in pregnancy.
For children started on pharmacologic management, follow-up every 4 to 6 weeks is recommended initially for dose titration and then every 3 to 6 months for monitoring.
Long term complications:
Persistant elevated blood pressure may have long term implications on small blood vessels leading to target organ damage such as eyes,kidneys,heart,brain and arteries. Various studies have shown correlation between elevated blood pressure in childhood and cardiovascular disease in adulthood. LVH is a known surrogate marker for morbidity and mortality associated with pediatric hypertension.
Microalbuminuria is a marker of potential development of hypertensive kidney injury in children, and a positive test should prompt pharmacologic treatment. In adults treatment with ACEi and ARBs has reduced proteinuria but similar results were not reproduced in pediatric studies.
Damage to the microvasculature affecting the retina is another known complication of pediatric hypertension. Hence in stage 2 HTN a formal retinal examination is recommended.
It has been demonstrated that if hypertension is controlled some of the target organ damage may be reversible.
The incidence of primary hypertension in pediatrics has closely mirrored the increasing rates of obesity in the pediatric population.Preventing obesity is the key factor in primary prevention of hypertension.
Physical activity is a key component to the prevention of pediatric obesity and hypertension and one of the first recommended lifestyle modifications for those diagnosed with elevated blood pressure or hypertension. Currently the CDC recommend a goal of 60 minutes of moderate-to-vigorous physical activity daily for children ages 6 to 17 years; and for children under 6 year old it is recommended to be active throughout the day. Adults should help find activities to keep children active and encourage the children to remain engaged in these activities. Also nutrition management and sleep hygiene are also key components to prevention and lifestyle modifications.