Hypertension In Childhood

Introduction

Pediatric hypertension is an increasingly recognized public health issue in Canada, largely driven by the rising prevalence of childhood obesity. For the MCCQE1, understanding the distinction between primary and secondary hypertension, appropriate measurement techniques, and Canadian-specific management guidelines is crucial.

As a future physician, you must embody the CanMEDS Medical Expert role to accurately diagnose this “silent” condition and the Health Advocate role to promote lifestyle modifications early in life.

Definition and Classification

Unlike adults, pediatric blood pressure (BP) thresholds are not static numbers (until age 13). They are based on age, sex, and height.

Definitions (Hypertension Canada Guidelines)

• Normal BP: SBP and DBP < 90th percentile.
• Elevated BP: SBP and/or DBP $\ge$ 90th percentile but < 95th percentile.
• Hypertension: SBP and/or DBP $\ge$ 95th percentile.
• Adolescents ($\ge$ 13 years): Adult criteria apply ($\ge$ 120/80 mmHg is elevated; $\ge$ 130/80 mmHg is hypertension).

Staging of Hypertension

Measurement Technique

Improper measurement is the most common cause of false-positive diagnoses. The MCCQE1 often tests the technical aspects of BP measurement.

Etiology: The Age Factor

A fundamental concept for the MCCQE1 is the inverse relationship between age and the likelihood of secondary hypertension.

• Younger children are more likely to have Secondary Hypertension.
• Adolescents are more likely to have Primary (Essential) Hypertension.

Clinical Presentation

Most children are asymptomatic. Hypertension is usually detected during routine screening.

Symptomatic Hypertension

When symptoms occur, they suggest severe hypertension or a secondary cause:

• Headache
• Dizziness
• Epistaxis
• Visual changes
• School performance decline

Hypertensive Emergency

Presents with End-Organ Damage (EOD):

• CNS: Seizures, altered mental status (Hypertensive encephalopathy).
• Cardiac: Heart failure, pulmonary edema.
• Renal: Acute kidney injury, hematuria.

Investigations

The goal is to identify secondary causes and assess for target organ damage.

1. Initial Workup (All Patients with Persistent HTN)

• Urinalysis: Protein, blood (Renal parenchymal disease).
• Chemistry: Electrolytes, Urea, Creatinine (Renal function, Conn’s syndrome/Aldosteronism).
• Fasting Lipids & Glucose: Metabolic syndrome screening.
• Renal Ultrasound: Structural abnormalities.

2. Specific Investigations (Driven by Clinical Picture)

• Echocardiogram: To assess for Left Ventricular Hypertrophy (LVH) — the most common evidence of target organ damage.
• Doppler US / CTA / MRA: If renovascular disease is suspected (e.g., abdominal bruit).
• Plasma Aldosterone/Renin Ratio: If hypokalemia is present.
• Urine Catecholamines: If pheochromocytoma is suspected (palpitations, sweating).
• Polysomnography: If obstructive sleep apnea is suspected.

Management

Management aligns with Hypertension Canada Guidelines.

Non-Pharmacological (First Line)

Unless the patient has Stage 2 HTN or symptoms, start with lifestyle changes for 6 months.

• Diet: DASH diet (Dietary Approaches to Stop Hypertension), reduced sodium intake.
• Weight Management: Crucial for primary hypertension.
• Physical Activity: Moderate-to-vigorous physical activity 40 min/day, 3-4 days/week.

Pharmacological Therapy

Indications for initiating medication:

1. Symptomatic hypertension.
2. Secondary hypertension.
3. Target organ damage (e.g., LVH on Echo).
4. Diabetes Mellitus (Types 1 or 2).
5. Persistent hypertension despite 6-12 months of lifestyle modification.
6. Stage 2 Hypertension (often immediate start).

First-Line Agents:

• ACE Inhibitors (e.g., Enalapril) or ARBs: Preferred, especially if diabetes or proteinuria is present.
  • Contraindication: Pregnancy (teratogenic). Counsel adolescent females.
• Long-acting Calcium Channel Blockers (e.g., Amlodipine).
• Thiazide Diuretics.

Note: Beta-blockers are generally no longer first-line for uncomplicated primary hypertension in children, unless there is a specific indication (e.g., post-Coarctation repair).

Canadian Guidelines Summary

The Hypertension Canada guidelines for children emphasize:

1. Screening: Blood pressure should be measured at all appropriate visits in children $\ge$ 3 years old.
2. Target BP:
   • Uncomplicated HTN: < 95th percentile.
   • Chronic Kidney Disease (CKD): < 50th percentile (using ABPM) or < 90th percentile (office).
3. ABPM: Ambulatory Blood Pressure Monitoring is recommended to rule out White Coat Hypertension (common in children) and identify Masked Hypertension.

Key Points to Remember for MCCQE1

• Cuff Size: Too small = falsely high BP.
• Coarctation: Always check femoral pulses and BP in legs if upper extremity BP is high.
• Etiology Rule: The younger the child and the higher the BP, the more likely the cause is secondary.
• Renovascular Disease: Most common cause of secondary hypertension in children (Fibromuscular Dysplasia).
• First Step: Confirm elevated oscillometric reading with auscultation.
• Medication: ACE inhibitors are excellent first-line agents but require counseling regarding teratogenicity in adolescent females.

Sample Question

Case Presentation

A 12-year-old female presents to your clinic for a routine health maintenance examination. She has no specific complaints. Her past medical history is unremarkable. On physical examination, her height is at the 50th percentile and weight is at the 45th percentile. Her blood pressure is measured at 142/88 mmHg using an automated oscillometric device. A repeat measurement 5 minutes later is 138/86 mmHg. Physical examination reveals a systolic bruit heard over the mid-abdomen. Femoral pulses are strong and equal to brachial pulses. Urinalysis is normal.

Question

Which one of the following is the most appropriate next step in the management of this patient?

• A. Reassure and recheck blood pressure in 6 months
• B. Initiate lifestyle modifications and review in 3 months
• C. Start Amlodipine 5 mg daily
• D. Order renal Doppler ultrasonography
• E. Order a 24-hour urine collection for catecholamines

Explanation

The correct answer is:

• D. Order renal Doppler ultrasonography

Rationale

This clinical vignette presents a classic scenario of Secondary Hypertension due to suspected Renovascular Disease (specifically Fibromuscular Dysplasia).

1. Clinical Reasoning: The patient is relatively young (12 years old) and non-obese, which lowers the probability of primary essential hypertension. The blood pressure is significantly elevated (Stage 2 range for her likely percentiles).
2. Key Finding: The presence of an abdominal bruit is highly specific for renal artery stenosis.
3. Management: While lifestyle modifications (Option B) are part of general management, they are insufficient for suspected secondary hypertension with such high readings. Reassurance (Option A) is inappropriate given the severity. Starting medication (Option C) immediately without a diagnosis is incorrect; you need to identify the etiology first, especially when a correctable cause is suspected. Pheochromocytoma (Option E) is a differential, but an abdominal bruit points much more strongly toward a vascular etiology than a catecholamine-secreting tumor (which would typically present with palpitations, sweating, and episodic HTN).
4. Investigation: Renal Doppler ultrasonography (or CTA/MRA) is the diagnostic modality of choice to evaluate for renal artery stenosis.

References

1. Hypertension Canada. (2020-2022). Hypertension Canada Guidelines for Diagnosis, Risk Assessment, Prevention, and Treatment of Hypertension in Adults and Children. https://guidelines.hypertension.ca/ 
2. Flynn, J. T., et al. (2017). Clinical Practice Guideline for Screening and Management of High Blood Pressure in Children and Adolescents. Pediatrics.
3. Medical Council of Canada. (2023). MCCQE Part I Objectives: Hypertension.
4. Dionne, J. M., et al. (2020). Hypertension Canada’s 2020 Comprehensive Guidelines for the Prevention, Diagnosis, Risk Assessment, and Treatment of Hypertension in Adults and Children. Canadian Journal of Cardiology.