hypertension Flashcards
what is hyoertension
when you have bp higher than the ideal
the level of bp where investigation can do more harm than good
affects 50% of people
describe the bp distribution
unimodal
any distinction between normal and abnormal is arbitrary
hat we accept as normal is lower than what we used to
how have the guidelines for bp been updated
ambulatory and home bp (recorded by a machine at any interval that you like) compared to ‘office’ bp
ambulatory is 5-1mmHg lower than Bp in surgeries
what is the current practice
lower bp to less than 120mmHg
not always tolerated
problem with treating hypertension
30-40% people have hypertension
need to know which ones to treat
when people’s bp is lowered - feel v ill - you need to treat the patient not the condition
relationship of bp with age
in advanced countries, the systolic bp rises with age
diastolic stays flat, in v old age it decreases
therefore gap between systolic and diastolic increases with age - this is the pulse pressure
>60 majority people hypertensive
>80 almost everyone is
exception when ou’re very old
hypertension is good
if heart strong enough to maintain a high bp it is good enough to work normally
younger though, reducing hypertension reduces strokes - it is important to treat
what does the word ‘normal’ mean when describing hypertension in elderly
common
NOT right
what is the threshold for bp risk
no reliable threshold
at risk if >110
issue woth the fact that bp is continuous
if reduce - risk doesn’t disappear - people with low bp still have attributable DALYs
what is secondary hypertension
when there are identifiable causes
how much of the hypertension is secondary - %
5% older
15% loung
causes of secondary hypertension
renal disease (inc renal artery stenosis)
Conn’s syndrome - tumour secreting aldosterone
phaeochromocytoma - tumour secreting catecholamines - rare
the pill
pre-eclampsia/pregnancu associated hypertension
genetic casues - liddie’s syndrome
aetiology of primery hypertension
single genes - involved in Na handling in the kidney monogenic rare polygenic common dietary salt obestity alchohol birthweight pregnancy
relationship between bp and genes
30-40% bp variation due to genes
try to find cause in the majority of the population
SNPs only 4% of this
monogenic disease accounts for <1% population - Liddie’s and apparent mineralocorticoid excess
complex polygenic casues - multiple genes with small effects, interaction with sex, other genes and the env
lot of genes but they have a small effect on bp
what is associated with hypertension, haemodynamically
increased TPR decreased arterial compliance normal CO normal blood vol central shift in volume small effect in venous circulation
what causes elevated TPR in hypertension
vasoconstriction of arteries and arterioles
growth and remodelling - lumen smaller, wall thicker - don’t know if this is an adaption to hypertension or the cause
rarefraction - capillary loss = reduced area for blood flow = increased TPR
Describe isolated systolic hypertension
Systolic >140mmHg
Diastolic <90
Increasing stiffness of medium and large arteries
Piles wave reflected - greater by the time it reaches the brachial artery than when it left the heart
TPR doesn’t increase
How does the kidney cause primary hypertension
It is involved in no regulation - exciretion of na, regulation of water and ECF
Best evidence in relation to salt intake
Impaired renal function and blood flow is the commonest 2nd cause of hypertension - parenchyma disease Andy stenosis
Almost all monogenic causes affect na excretion
Population size with no salt have low population bp Andy no rise with age
Animals with reduced na handling have high bp
In rats - hypertension translated with a kidney transplantation
How do endocrine and paracrine factors cause primary hypertension
Inconsistant evidence
How does the SNS cause primary hypertension
High sympathetic activity drives high bp
Activity deminishes woth age but no is still high
what does hypertension increase your risk of
CHD
stroke
peripheral vascular disease/atheramotous disease
heart failure
atrial fibrillation
dementia/cognitive impairment - slow deterioration
retinopathy
how does hypertension affect the heart
large heart - thick walls
more likely to fail and cause sudden death
arrhythmia and abnormality of heart rhythm
how is hypertension related to congestive heart failure
1st and 2nd cause of heart failure
prevalence increasing in contrast to other things
hypertension increases risk 2-3 fold, accounts for 25% of cases
hypertension precedes CHF in 90% of cases, most CHF in elderly is due to hypertension
people live with a bad heart and then get congestive heart failure
how is hypertension associated with large arteries
hypertension causes large arteries
intima media thickness 2-3x larger than normal
may cause aneurysms - lead to thrombosis or haemorrhage (weakness in wall, rupture - can happen in the brain)
85% of hypertension related strokes is due to clotting and thrombosis not bursting
how is hypertension linked with the eye
retina
swelling of the optic disk- papilledema
extrudates - leakage of blood or plasma into retina = white patches
damage illustrates microvasculature damage
thickening of wall
arteriolar narrowing
vasospasm,
impaired perfusion
increased leakage to surrounding tissue
this mainly happens when people have been on treatment and stop it
how is hypertension linked with the microcirculation
reduction in capillary density = impaired perfusion in organ that is affected, increased PVR
elevated capillary pressure = damage and leakage
how does hypertension affect the kidney
granular capsular surface cortical thinning = renal atrophy renal disfunction - albuminuria extreme hypertension is rare but leads to rapid progression of renal failure subcapsular haemorrhages
how is microalbuminuria caused
hypertension causes increased albumin in the urine
reduced GFR
GFR decreases with age anyway
action of angiotensin receptor blockers
block receptor stops bad effect in kidney
action of ACE inhibitors
reduce ANG 2 production
but it is not completely blocked - made through different pathways
do you use ARBs or ACE inhibitors
people generally respond to 1 and not the other
action of diuretics
chlorothiazide
only used if in crisis
used when there is a large fluid overload
thiazide diuretics don’t reduce BP by diuresis, lower the PVR but we don’t know how
action of B blockers
block B1 receptors in the heart - reduce rate of contraction, reduced CO
block B1 receptors in kidney - reduced secretion of renin, reduced activity of RAAS
not favoured, other drugs better at stopping strokes
action of Ca channel blockers
major effect in vascular smooth muscle (block V gated channels) - reduce Ca influx = less myosin actin cross bridging
minor effect in heart - inhibition of Ca influx = reduces contractility, and rate of contraction - negative dermotropy (reduce flow of blood through heart, can be used in atrial fibrillation to slow the heart down)
low salt environment and hypertension
lwo salt of env- bp doesn’t rise with age
not common because most people eat a lot of salt
