Hypertension

Hypertension

·        See Measuring Blood Pressure(Topic), for measurement

·        Is a risk factor not a disease

·        Definition:

o   No dividing line between normal and high blood pressure. There are arbitrary levels set based on the risk of complications (the main ones being stroke, MI, heart failure and renal failure)

o   In determining whether the blood pressure is „bad‟, take into account the systolic and diastolic pressure, age, sex, other diseases (eg DM, hyperlipidaemia), smoking. Older age is the greatest risk factor: treat high blood pressure in an older person regardless of other risk factors

o   WHO definitions:

o   Also classified according to retinopathy, see Hypertensive Retinopathy(Topic)

·        Classified as:

o   Primary/essential (what most people have – but a diagnosis of exclusion): contributing factors include hereditary, obesity, alcohol intake, salt intake (60% of patients respond to ¯salt intake – but compliance difficult)

o   Secondary causes: renal disease (eg renal artery stenosis, diabetic kidney disease, etc), endocrine (eg ­cortisol, ­aldosterone, acromegaly, oral contraceptives), neurogenic (eg psychogenic), sleep apnoea (major changes in baroreceptor reflexes)

·        Epidemiology:

o   Prevalence ­ with age. Older people at greater risk at any given blood pressure compared with young

o   Strong risk factor for stroke, congestive heart failure, coronary artery disease and renal failure

o   Probably 10 – 20% of older adults require treatment (ie have essential hypertension with diastolic pressure > 95 mmHg)

o   Treatment reduces related complications. Stroke risk reduces in line with BP, MI risk doesn‟t reduce as much for a given drop in BP

·        History:

o   How accurate is the diagnosis?

o   Usually symptomless

o   Possibly related symptoms: palpitation, flushing, headache

o   Related risk factors: history of renal, cardiac or neurological disease

o   Asthma, diabetes, gout, renal disease: complications with drug treatment

o   Occupational

o   Diet: salt, fat

o   Smoking and alcohol

o   Family History

·        Detection and assessment:

o   Blood pressure more labile in older adults Þ measure 2 to 3 times (in same arm). Measure standing and sitting

o   In primary hypertension usually ­ on standing.  In secondary hypertension, usually ¯ on standing

o   Basic workup:

§  Urine for protein, blood and glucose ® DM, renal disease

§  FBC for polycythaemia, renal disease, alcohol

§  Electrolytes (especially K): exclude odd endocrine causes

§  ECG: any end organ damage

o   Additional tests if indicated:

§  Microscopic analysis of urine (for casts)

§  Plasma lipids

§  Blood glucose: need to modify drug treatment

§  Serum Ca, PO4, uric acid (gout – associated with hypertension, may also ­ due to drugs)

§  Echocardiogram or CXR

§  Special tests for secondary causes if indicated: eg renal imaging, 24 hour urine for catecholamine metabolites (phaeochromocytoma)

·        Pathology:

o  Pathophysiology: poorly understood. Older people have ¯renin, and are more responsive to Na depletion. „Hardening‟ of arteries ®­systolic pressure. ¯Responsiveness to b-mediated vascular relaxation

o  Leads to hypertensive heart disease: left ventricular hypertrophy ® relative myocardial ischaemia. Aortic valvular disease also ® LV hypertrophy

o  Malignant hypertension (accelerated hypertension): hypertension leading to rapidly progressive vascular compromise. Blood vessels show fibrinoid necrosis or concentric hyperplasia („onion skin‟ changes)

Non-drug treatment

·        Remove/substitute drugs: eg NSAIDs, OCP, Prednisone

·        Always attempt lifestyle changes first:

o  Stop smoking (little effect on BP, but biggest impact on risk factors)

o  Weight loss

o  ¯Alcohol (max 2 drinks per day)

o  ¯Salt intake (max 70 mmol/day)

o  ­exercise

o  ¯Saturated fats

Drug Treatment

·        When to treat:

o  Given it is such a strong risk factor, consider hypertension above systolic 140 mmHg

o  Always treat > 170 systolic or > 110 diastolic

o  Hardly ever treat < 140 and < 90 diastolic 

o  In between, controversial. Consider other risks. If over 65 no other risk factors needed (eg diabetes, etc). Give considerable attention to non-pharmacological approaches for 3 – 6 months. Long term follow up necessary 

o  Treat 72 older adults for 5 years to prevent 1 death, treat 43 for 5 years to prevent one cerebrovascular event 

o  Aim of treatment: diastolic < 90

·        Rules of thumb:

o  Use low doses of several agents, rather than increasing doses of one drug (especially thiazides) 

o  First line: thiazides (with or without a potassium sparing agent) and/or b-blocker (atenolol most used in trials). If tolerate them both then add them together 

o  ACE inhibitors: not so effective but rated best quality of life

o  Don‟t take diuretic, ACE inhibitor and NSAIDS together (renal side effects)

o  Introduce slowly, monitor for symptoms and postural hypotension

o  Aim for 140/90, and then attempt back titration 3 monthly

·        Individualise depending on co-morbid conditions: