Hypertension - diagnosis, targets, stepped pharmacotherapy, secondary causes

1. Definition and clinical relevance

Hypertension is a sustained elevation of blood pressure (BP) above accepted thresholds, confirmed on repeated measurement. It is one of the most prevalent modifiable cardiovascular risk factors in Australia, affecting roughly one in three adults, and is a leading driver of stroke, ischaemic heart disease, heart failure, and chronic kidney disease. For an intern, the key time-critical decisions are: recognising hypertensive emergencies requiring same-day specialist review, distinguishing primary from secondary causes, and initiating or escalating pharmacotherapy at the right stage. Because hypertension is largely asymptomatic, it is almost always detected opportunistically, making every clinical encounter a screening opportunity.

2. Key values, thresholds, scoring systems

BP Classification (clinic measurement)

Ambulatory / Home BP Monitoring (ABPM / HBPM) Thresholds

Diagnosis rules

• Do not diagnose on a single reading. Confirm elevated readings on at least two further visits within three months.
• For severe hypertension (clinic systolic >= 180 mmHg or diastolic >= 110 mmHg), treatment can begin immediately without waiting for ABPM/HBPM confirmation.
• Isolated systolic hypertension: systolic >= 160 mmHg with normal diastolic. Treat the same as combined elevation.

Screening frequency

Treatment targets (widely accepted clinical norms)

3. Approach: presentation and differential

History

Most patients are asymptomatic. Symptoms, when present, suggest either severe elevation or target organ damage:

• Headache (typically occipital, morning), visual disturbance, or epistaxis at very high BPs
• Chest pain or dyspnoea: consider hypertensive heart failure or acute coronary syndrome
• Neurological symptoms: hypertensive encephalopathy or stroke
• Haematuria or frothy urine: renal involvement

Red flags requiring same-day specialist review: - BP > 180/110 mmHg with papilloedema or retinal haemorrhage (accelerated/malignant hypertension) - Suspected phaeochromocytoma: episodic headache, palpitations, diaphoresis, pallor, and labile or postural BP swings - New neurological deficit, chest pain, or acute pulmonary oedema in the context of severe hypertension

Medication and substance history: oral contraceptive pill, NSAIDs, decongestants, corticosteroids, calcineurin inhibitors, stimulants (cocaine, amphetamines), liquorice, and herbal preparations can all raise BP.

Examination findings pointing to secondary causes

Differential diagnosis of elevated BP

1. Primary (essential) hypertension: accounts for 90-95% of adult cases
2. Renal parenchymal disease: most common secondary cause overall
3. Renovascular disease: atherosclerotic renal artery stenosis (older patients, smokers, generalised atheroma) or fibromuscular dysplasia (younger women)
4. Primary hyperaldosteronism (Conn syndrome): suspect with hypokalaemia or resistant hypertension
5. Phaeochromocytoma
6. Cushing syndrome
7. Obstructive sleep apnoea: very common and underdiagnosed
8. Coarctation of the aorta: consider in young patients with upper-limb/lower-limb BP discrepancy
9. Drug or substance-induced

4. Investigations

Bedside

• Accurate BP measurement: patient seated quietly for several minutes, validated oscillometric device, correct cuff size, average of two readings
• Bilateral arm BP on first visit (difference > 15 mmHg suggests vascular disease)
• ABPM or HBPM to confirm diagnosis, exclude white-coat hypertension, and detect masked hypertension
• Fundoscopy: silver wiring, arteriovenous nipping, flame haemorrhages, cotton-wool spots, papilloedema

Bloods

Urine

• Dipstick for blood and protein
• Spot albumin:creatinine ratio (ACR) for microalbuminuria
• Urine microscopy if haematuria or proteinuria detected

Imaging and other

• ECG: left ventricular hypertrophy (LVH), ischaemia, arrhythmia
• Echocardiogram: if LVH suspected on ECG or clinically
• Renal Doppler ultrasound: high sensitivity and specificity for renal artery stenosis; first-line vascular imaging
• Renal ultrasound: size, scarring, polycystic disease
• CT angiography or MR angiography: if Doppler inconclusive and renovascular disease strongly suspected

5. Management

Non-pharmacological measures (all stages)

Lifestyle modification reduces BP and should be offered to every patient regardless of whether medication is started:

• Dietary sodium restriction (target < 2 g/day elemental sodium)
• DASH-style diet: high in fruit, vegetables, and low-fat dairy
• Weight reduction if overweight (each 1 kg loss reduces systolic BP by approximately 1 mmHg)
• Regular aerobic exercise: at least 150 minutes per week of moderate-intensity activity
• Alcohol reduction: no more than 2 standard drinks per day
• Smoking cessation (does not lower BP directly but reduces overall cardiovascular risk substantially)
• Treat obstructive sleep apnoea

Stepped pharmacotherapy

Step 1: Start with a single agent. First-line choices are:

• ACE inhibitor (ACEi), e.g. perindopril 5-10 mg daily, or angiotensin receptor blocker (ARB), e.g. irbesartan 150-300 mg daily. Preferred in diabetes, CKD with proteinuria, or heart failure with reduced ejection fraction. Avoid in pregnancy and bilateral renal artery stenosis.
• Long-acting dihydropyridine calcium channel blocker (CCB), e.g. amlodipine 5-10 mg daily. Preferred in older patients and isolated systolic hypertension.
• Thiazide or thiazide-like diuretic, e.g. indapamide 1.5 mg (SR) or 2.5 mg daily. Useful in volume-dependent hypertension and older patients.

Step 2: Combine two agents from different classes. The most evidence-supported combination is ACEi or ARB plus CCB, or ACEi/ARB plus thiazide-like diuretic.

Step 3: Triple therapy: ACEi or ARB plus CCB plus thiazide-like diuretic.

Step 4 (resistant hypertension): Add a fourth agent. Low-dose spironolactone 25-50 mg daily is the preferred add-on when eGFR and potassium allow. Alternatives include a beta-blocker, alpha-blocker (doxazosin), or centrally acting agent (moxonidine). Resistant hypertension is defined as BP remaining above target despite three agents at optimal doses including a diuretic, after excluding secondary causes and poor adherence.

Special populations

• Diabetes: ACEi or ARB first-line for renoprotection. Target < 130/80 mmHg.
• CKD with proteinuria: ACEi or ARB mandatory unless contraindicated. Monitor potassium and creatinine at 1-2 weeks after initiation or dose increase.
• Pregnancy: Labetalol, nifedipine (slow-release), or methyldopa are safe. ACEi, ARBs, and direct renin inhibitors are contraindicated.
• Elderly (>= 80 years): Start low, go slow. Avoid excessive lowering; target systolic 140-150 mmHg to prevent falls and orthostatic hypotension.
• Ischaemic heart disease: Beta-blocker plus ACEi or ARB preferred.

Hypertensive emergency

Accelerated (malignant) hypertension with end-organ damage (encephalopathy, acute kidney injury, pulmonary oedema, aortic dissection) requires immediate senior review and likely ICU/HDU admission. Aim to reduce mean arterial pressure by no more than 20-25% in the first hour to avoid ischaemic injury from rapid BP drop. IV labetalol or sodium nitroprusside are used in monitored settings. Do not use sublingual nifedipine (rapid uncontrolled drop).

Disposition

• Stage 1 with low cardiovascular risk: manage in primary care, review in 3-6 months
• Stage 2: initiate treatment, review in 4-6 weeks
• Severe or resistant: refer to specialist (general medicine, nephrology, or cardiology)
• Suspected secondary cause: refer for targeted investigation

6. Australian-specific considerations

Aboriginal and Torres Strait Islander peoples: Hypertension prevalence is substantially higher in Aboriginal and Torres Strait Islander communities, with earlier onset and higher rates of hypertensive renal disease. The annual 715 health assessment provides a structured opportunity to measure BP, calculate cardiovascular risk, and address modifiable risk factors in a culturally safe way. Engage with community health workers and Aboriginal health practitioners as part of the care team. Renal disease (including IgA nephropathy and diabetic nephropathy) is a major driver of secondary and accelerated hypertension in this population, so urine ACR and eGFR should be checked at every assessment.

Rural and remote settings: ABPM devices may not be readily available. Home BP monitoring with a validated device is a practical alternative for confirming diagnosis. Telehealth can support specialist review for resistant or secondary hypertension. Retrieval should be arranged early for hypertensive emergencies when local ICU capacity is limited.

PBS considerations: ACEi, ARBs, CCBs, and thiazide-like diuretics are all available on the PBS for hypertension. Spironolactone is PBS-listed for heart failure; its use in resistant hypertension may require authority or off-label prescribing discussion with the patient. Combination fixed-dose tablets improve adherence and are PBS-listed for several combinations.

Medication history in migrants and refugees: Traditional herbal remedies (including some Chinese, Ayurvedic, and Middle Eastern preparations) can contain compounds that raise BP or interact with antihypertensives. Ask specifically and non-judgementally.

Mandatory reporting: Severe uncontrolled hypertension may affect fitness to drive. Familiarise yourself with state-based driving authority notification requirements for patients with BP >= 180/110 mmHg who are non-compliant with treatment.

Clinical pearls

• A single elevated clinic reading is never sufficient to diagnose hypertension. Confirm with ABPM or HBPM, except when BP is >= 180/110 mmHg with end-organ damage, where treatment starts immediately.
• Each 2 mmHg rise in systolic BP carries approximately a 7% increase in ischaemic heart disease mortality and a 10% increase in stroke mortality, so even modest BP reductions translate to meaningful population-level benefit.
• Hypokalaemia plus hypertension should always prompt an aldosterone:renin ratio to exclude primary hyperaldosteronism before attributing the low potassium to a diuretic.
• Renal artery Doppler ultrasound is the first-line investigation for suspected renovascular hypertension and has high sensitivity and specificity.
• In resistant hypertension (BP above target on three optimised agents including a diuretic), add low-dose spironolactone as the fourth agent provided renal function and potassium are acceptable.
• Never use sublingual nifedipine for hypertensive emergencies: the uncontrolled BP drop risks stroke, MI, and death.