Secondary hypertension

Epidemiology

• In ALLHAT trial, about 30% of patients had resistant hypertension
• In a hypertension clinic, 6% of patients referred to them had secondary hypertension

Differential Diagnosis

• Medication/lifestyle non-adherence
  • Salt intake
  • NSAIDs
  • Stimulants
  • Alcohol
  • Withdrawal from medications or recreational drugs
  • Pain
• Poor medication choice
  • White coat hypertension
  • Transient hypertension
• Drugs: glucocorticoids, stimulants (including caffeine, pseudephedrine, cocaine), OCP, NSAIDs
• Renal causes
  • Renal artery stenosis
  • Fibromuscular dysplasia (FMD)
  • Polyarteritis nodosa (PAN)
  • Systemic sclerosis
  • Intrauterine growth restriction (IUGR)
• Endocrine causes
  • Hyperaldosteronism
  • Pheochromocytoma
  • Thyroid disease
  • Hyperparathyroidism
• Other
  • Obstructive sleep apnea
  • Drugs/alcohol

Approach/Template

• Accurate BP evaluation; that is, do they have high blood pressure?
• Is it primary or secondary? What is the cause?
• Is there end-organ damage?
• Global cardiovascular risk assessment
• Based on the above, what is the optimal BP treatment target?
• Best drugs available for treatment
• Arranging ongoing follow-up

When to Investigate

• All patients should be screened for OSA and intrinsic renal disease with urinalysis
• Symptomatic presentation with urgency or emergency
• Younger than 20 years or older than 50 years
• Unprovoked hypokalemia or hypokalemia on low-dose diuretic

History

• Lifestyle factors
• Substance addiction
• Substance withdrawal
• Medication adherence
• Endocrine causes
• Vascular causes
• Obstructive sleep apnea

Exam

• BMI and waist circumference
• Proper BP including bilateral and orthostatic
• ABPM is best >> AOBP > ROBP > casual office BP
  • Ideally includes nocturnal sleeping BP
• Evidence of end-organ damage
• Evidence of endocrine/secondary causes
  • Cushingoid?
  • Coarctation
• RAS

Investigations

• Urinalysis in all people
• STOP-BANG or sleep study in all people
• Electrolytes, creatinine, CBC
• TSH, calcium/albumin, urinalysis, A1c, lipids
• Consider
  • CXR showing rib notching for coarctation (from enlarged intercostal arteries)
  • Renin-aldosterone (renin better than aldo, if only one is available)
• If renin suppressed, is essentially diagnostic for primary hyperaldosteronism
• Try to get them off RAS-inhibiting therapies (use alpha-blockers and CCBs instead)

Further Readings

• Hypertension Canada Guidelines 2018
• AHA/ACC Guidelines 2017