What is the diagnostic approach to a patient with primary and secondary hypertension?

Diagnostic Approach to Primary and Secondary Hypertension

The diagnostic approach to hypertension requires a systematic evaluation to distinguish between primary (essential) hypertension (90-95% of cases) and secondary hypertension (5-10% of cases), with early detection and appropriate management being crucial to prevent hypertension-mediated organ damage and reduce cardiovascular risk. 1, 2

Initial Blood Pressure Assessment

• Confirm hypertension diagnosis with multiple measurements:
  • Office BP ≥140/90 mmHg on at least 2 occasions
  • Consider out-of-office measurements (home or ambulatory monitoring) to rule out white coat or masked hypertension 1

BP Classification	Systolic (mmHg)	Diastolic (mmHg)	Action
Normal	<120	<80	Remeasure within 3 years
Elevated	120-129	<80	Confirm with out-of-office measurements
Hypertension	≥130	≥80	Confirm within days or weeks

Comprehensive History Taking

1. Blood Pressure History:

   • Duration and previous levels of hypertension
   • Previous antihypertensive medications and their effects/side effects
   • Medication adherence patterns 1

2. Risk Factor Assessment:

   • Family history of hypertension, premature cardiovascular disease, diabetes
   • Personal history of cardiovascular disease, diabetes, dyslipidemia, CKD
   • Lifestyle factors: diet (salt, fat intake), alcohol consumption, smoking, physical activity
   • Psychosocial factors and history of depression 1

3. Symptoms Suggesting Secondary Hypertension:

   • Muscle weakness/tetany, cramps (hypokalemia/primary aldosteronism)
   • Flash pulmonary edema (renal artery stenosis)
   • Sweating, palpitations, headaches (pheochromocytoma)
   • Snoring, daytime sleepiness (obstructive sleep apnea)
   • Symptoms of thyroid disease 1

4. Medication Review:

   • Substances that can raise BP: oral contraceptives, NSAIDs, steroids, decongestants, cocaine, amphetamines, erythropoietin, cyclosporin 1

Physical Examination

1. Basic Measurements:

   • Blood pressure in both arms (sitting and standing)
   • Heart rate (30 seconds or longer if arrhythmias present)
   • Height, weight, BMI, waist circumference 1

2. Cardiovascular Assessment:

   • Pulse rate/rhythm/character
   • Jugular venous pressure
   • Apex beat location and characteristics
   • Heart sounds, murmurs, gallops
   • Peripheral pulses (absence, reduction, asymmetry)
   • Carotid, abdominal, femoral bruits 1

3. Signs Suggesting Secondary Hypertension:

   • Cushing's features (moon face, buffalo hump, striae)
   • Enlarged kidneys (polycystic kidney disease)
   • Neck circumference >40 cm (sleep apnea)
   • Enlarged thyroid
   • Neurofibromatosis stigmata (pheochromocytoma)
   • Radio-femoral delay (coarctation of aorta) 1

Laboratory Investigations

Basic Investigations (All Patients)

• Blood tests:

  • Sodium, potassium
  • Serum creatinine and eGFR
  • Fasting glucose
  • Lipid profile 1

• Urine tests:

  • Dipstick urinalysis
  • Albumin-to-creatinine ratio 1, 2

• 12-lead ECG:

  • Detection of atrial fibrillation
  • Left ventricular hypertrophy
  • Ischemic heart disease 1

Additional Investigations (Based on Clinical Suspicion)

Imaging Studies

• Echocardiography: LVH, systolic/diastolic dysfunction, atrial dilation
• Renal ultrasound: Kidney size, structure, obstruction
• Carotid ultrasound: Plaques, stenosis
• CT/MR angiography: Renal artery stenosis, adrenal lesions
• Fundoscopy: Retinal changes, hemorrhages, papilledema 1

Specialized Tests for Secondary Hypertension

Suspected Cause	Recommended Screening Test
Primary aldosteronism	Aldosterone-to-renin ratio
Renovascular hypertension	Renal Doppler ultrasound, CT/MR angiography
Pheochromocytoma	Plasma/24h urinary metanephrines
Obstructive sleep apnea	Overnight polysomnography
Cushing's syndrome	24h urinary free cortisol, dexamethasone suppression
Thyroid disease	TSH
Hyperparathyroidism	PTH, calcium, phosphate
Coarctation of aorta	Echocardiogram, CT angiogram [2]

When to Suspect Secondary Hypertension

• Severe or resistant hypertension (BP >140/90 mmHg despite 3 medications)
• Sudden onset or worsening of hypertension
• Age of onset <30 years (especially before puberty)
• Malignant or accelerated hypertension
• Presence of specific clinical clues from history/examination
• Hypokalemia without diuretic use
• Significant target organ damage disproportionate to duration of hypertension 3

Cardiovascular Risk Assessment

• Evaluate additional risk factors:
  • Age >65 years
  • Male sex
  • Heart rate >80 beats/min
  • Increased body weight
  • Diabetes
  • High LDL-C/triglycerides
  • Family history of CVD
  • Early-onset menopause
  • Smoking habits
  • Psychosocial factors 1

Common Pitfalls in Hypertension Diagnosis

1. Failure to confirm hypertension with multiple measurements and out-of-office readings
2. Overlooking secondary causes in high-risk patients (young, severe, or resistant hypertension)
3. Attributing resistant hypertension to secondary causes when medication non-adherence is the issue 4, 5
4. Inadequate screening for target organ damage
5. Missing white coat or masked hypertension by relying solely on office measurements 1

Diagnostic Algorithm

1. Confirm hypertension diagnosis with multiple measurements
2. Perform basic evaluation (history, physical exam, basic labs, ECG)
3. Assess cardiovascular risk and target organ damage
4. Screen for secondary causes if clinical suspicion exists:
   • Young age (<30 years)
   • Severe or resistant hypertension
   • Sudden onset or worsening
   • Specific clinical clues
5. Perform targeted investigations based on suspected secondary cause
6. Refer to specialists for complex cases of secondary hypertension 1, 2, 6

By following this systematic approach, clinicians can effectively distinguish between primary and secondary hypertension, leading to appropriate management strategies and improved patient outcomes.