13- Hypertension Flashcards
What are the top 3 leading causes of death
High BP
Tobacco
High cholesterol
What is hypertension
the level of blood pressure above which investigation and treatment do more good than harm
E.g.>140/90 in the uk
How are BP measured at home different
Threshold 5-10 mm Hg lower
What happens to BP with age
Mean BP rise with age
Pulse pressure rises with age
The majority of people >60y would be expected to be hypertensive by current definitions, almost everyone hypertensive by >80y
Although in populations with low salt intake the increase is less
What are some causes of secondary HT
Renal disease, including renal artery stenosis, • Tumours secreting aldosterone (Conn’s syndrome) • Tumours secreting catecholamines (pheochromocytoma) • Oral contraceptive pill • Pre-eclampsia/pregnancy associated hypertension • Rare genetic causes (e.g. Liddle’s syndrome)
What can influence risk of primary HT
Genetics –Monogenic (rare) –Complex polygenic (common) •Environment –Dietary salt (sodium) –Obesity / overweight, lack of exercise –Alcohol –Pre-natal environment (~birthweight) –Pregnancy (pre-eclampsia) –Other dietary factors and environmental exposures?
Give 2 examples of mono genetic disease causing HT
Liddle’s syndrome
•Mutation in amiloride-sensitive tubular epithelial Na channel
–Apparent mineralocorticoid excess
•Mutation in 11b-hydroxysteroid dehydrogenase
What is HT associated with
Increased total peripheral resistance
• Reduced arterial compliance (higher pulse pressure)
• Normal cardiac output
• Normal blood volume/extracellular volume
• Central shift in blood volume
– secondary to reduced venous compliance
What accounts for increased peripheral vascular resistance
Active narrowing of arteries – vasoconstriction (probably short-term) •Structural narrowing of arteries –growth and remodelling (adaptive?) •Loss of capillaries –rarefaction (adaptive/damage?)
How is BP calculated from CO
BP= COx PVR
How does increasing artery stiffness influence the pulse wave
Pulse wave reflected and is greater by the time it reaches brachial artery
What are possible causes of primary HT
Kidney
–Key role in BP regulation (Guyton)
–Best evidence especially in relation to salt intake
•Sympathetic nervous system
–Evidence linking high sympathetic activity to the development of hypertension
•Endocrine/paracrine factors
–Inconsistent evidence
Give evidence for the kidney being a cause of HT
The kidney exerts a major influence on BP through regulationof sodium/water/extracellular fluid volume1
•Impaired renal function or blood flow is the commonest 2º cause of hypertension (e.g. renal parenchymal disease, renal artery stenosis),
•Almost all monogenic causes of hypertension affect renal Na+ excretion
•Salt intake is strongly linked with blood pressures of human populations. Populations with low salt have low population blood pressures and no rise in BP with age.
•Animals with reduced renal Na+ handling (genetic or experimental) develop hypertension. Excess salt intake in many animals results in elevated blood pressure
•In rats hypertension can be ‘transplanted’ with the kidney, there is similar, though incomplete data, in man
What does high BP increase your risk of
coronary heart disease •stroke •peripheral vascular disease/atheromatous disease •heart failure •atrial fibrillation •dementia /cognitive impairment •retinopathy
How much does HT increase the risk of CHF
2-3 times
How does HT affect the heart
increase in left ventricular wall mass
How does HT affect the retina
There is thickening of the wall of small arteries, arteriolar narrowing, vasospasm, impaired perfusion and increased leakage into the surrounding tissue
What does renal dysfunction due to HT cause
increased albumin loss in the urine
- decline in GFR with age - glomerular filtration rate
Both indicative of renal damage
What happens to systolic and diastolic BP separately with age
Systolic blood pressure rises more
or less in a linear way
• Diastolic blood pressure plateaus
and as you get into really old age, the diastolic blood pressure begins to decline
How does HT affect large arteries
Hypertension is associated with hypertrophy of large arteries
• It is also associated with the acceleration of atherosclerosis
• Hypertension may also cause dilation of the large arteries (aneurysm)
• This can lead to thrombosis or haemorrhage if the aneurysm ruptures
