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Chapter: Medicine Study Notes : Cardiovascular


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)



·        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:


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