Aetiology Pathophysiology of Hypertension Flashcards
What are the most common causes of death due to raised blood pressure?
Ischemic heart disease and stroke
What end organ damage is associated with hypertension?
Describe blood pressure throughout the day
Fluctuates widely -
Physcial stress and mental stress
What is the definintion of hypertension?
That blood pressure above which the benefits of treatment outweigh the risks in term of morbidity and mortality
What is the blood pressure distribution in a population?
Exhibits a normal bell shaped curve
Each population has its own bell shaped curvre
What is the relationship between increased blood pressure and stroke/cardiovascular disease?
•Risk however rises exponentially and not linearly with pressure
Age also plays a significant role
What is ‘optimal’ blood pressure in terms of american opinion?
Opt <120/<80
What blood pressure is hypertension diagnosed at?
Varies - roughly 140/90
What does ABPM stand for?
Ambulatory blood pressure monitor – measures blood pressure every half hour – inflates the cuff every half hour at night time?
What is defined as stage 1 hypertension?
Clinic blood pressure is about 140/90 mmHg or higher
ABPM daytime average 135/85 mmHg or higher
What is defined as stage 2 hypertension?
•Clinic blood pressure is 160/100 mmHg or higher
ABPM daytime average 150/95 mmHg or higher
What is defined as severe hypertension?
Clinic systolic blood pressure is 180 mmHg or higher or diastolic blood pressure is 110 mmHg or higher
What is more common, primary and secondary hypertension?
Primary - where no cause is found
90% of cases
What are some of the causes of secondary hypertension?
Chronic renal disease
Renal artery stenosis
Endocrine disease - cushing’s, conn’s syndrome and paechromocytoma, GRA
How many deaths worldwide is high blood pressure responsible for?
The number 1 medical cause of death world-wide
Directly and indirectly responsible for >20% of all deaths
Which factors increase risks associated with hypertension?
Cigarette smoking
Diabetes mellitus - –5-30 X increase MI
Renal disease
Male - 2 x risk
Hyperlipidaemia
Previous MI or stroke
Left ventricular hypertrophy - 2 x risk
What parts of the human body are responsible for blood pressure?
–Cardiac output
- Stroke volume
- Heart rate
–Peripheral vascular resistance
What is the effect of the sympathetic nervous system on:
Stroke volume
Heart rate
Total peripheral resistance?
–increased cardiac output - contractility increases
–reflex tachycardia
–vasoconstriction
These increase blood pressure.
•The actions of the sympathetic system are rapid and account for second to second blood pressure control
What type of bloo pressure control is RAAS responsible for?
Long term
What is RAAS responsible for?
Maintainance of sodium balance
Control of blood volume
Control of blood pressure
What is RAAS stimulated by?
–fall in BP
–fall in circulating volume
–sodium depletion
- Any of the above stimulate renin release from the juxtaglomerular apparatus
- Renin converts angiotensinogen to angiotensin I
- Angiotensin I is converted to angiotensin II by angiotensin converting enzyme (ACE)
Angiotensin is a potent?
Vasoconstrictor
Anti-natiuretic peptide
Stimulator of aldosterone release from the adrenal glands (aldosterone increases the reabsorption of sodium from the loop of henle - reduces diuresis)
What is the effect of angiotensin 2 on myocyte and smooth muscle?
Causes myocyte and smooth muscle hypertrophy in the arterioles - arteries eventually get small and narrow and the can’t dilate - •can’t respond appropriately to relaxation - highly susceptible to damage.
In general what are the aetiologies of hypertension?
–Polygenic
- Major genes
- Poly genes
–Polyfactorial
- Environment
- Individual and Shared
What are the likely causes?
•Increased reactivity of resistance vessels and resultant increase in peripheral resistance
–as a result of an hereditary defect of the smooth muscle lining arterioles
•A sodium homeostatic effect
In essential hypertension the kidneys are unable to excrete appropriate amounts of sodium for any given BP. As a result sodium and fluid are retained and the BP increases
Failure in sodium pumping mechanism in the kidney.
Abnormality in the kidney specifically the portion that secretes sodium and water – reset point is raised – kidney starts to respond to high blood volume at a later point.
Other factors
- Age
- Genetics and family history
- Environment – stressfulness brings about a high blood pressure
- Weight
- Alcohol intake – most common for young scotsmen
- Race – afrocarribean – hypertensive in western area – high salt diets
How does blood pressure vary with age?
BP tends to rise with age, possibly as a result of decreased arterial compliance
What are the dangers of treating the elederly for high blood pressure?
Lowering blood pressure too much can cause syncope - loss of confidence.
What are the benefits of hypertehypertension treatment in the elderly?
–treating both diastolic and systolic hypertension in the elderly significantly reduces stoke and MI.
Describe the trends in hypertension in the family
–A history of hypertension tends to run in families
–The closest correlation exists between sibs rather than parent and child - the children share same genes and environment
Environment plays a large influence in the development of hypertension
How much influence do individual genes have in the incidence of high blood pressure?
–To date >30 genes recognised as important but individually they account for at most 0.5mmHg each
What is the influence of stress?
–Mental and physical stress both increase blood pressure
–However removing stress does nor necessarily return blood pressure to normal values
–True stress responders who have very high BP when they attend their doctor but low normal pressures otherwise tend to be highly resistant to treatment
What is the effect of reducing salt intake?
–Reducing salt intake in hypertensive individuals does lower blood pressure
–However reducing salt intake in normotensives appears to have little effect
–However there are real difficulties in achieving this level of salt restriction (fast food)
What is the relationship between alcohol and blood pressure?
–Small amounts of alcohol tend to decrease BP
–Large amounts of alcohol tend to increase BP
–If alcohol consumption is reduced BP will fall over several days to weeks.
–Average fall is small 5/3 mmHg
What is the relationship between obesity and blood pressure?
Obese patients have a higher blood pressure
How much of hypertension is partly or completely attritable to obesity?
up to 30%
What happens when an obese person loses weight?
Blood pressure falls
–In untreated patients a weight loss of 9Kg has been reported to produce a fall in BP of 19/18 mmHg
–In treated patients a fall in BP of 30/21 mmHg has been reported
–Weight reduction is the most important non-pharmacological measure available
How does birth weight affect chances of developing hypertension?
The lower the birth weight the higher the likelihood of developing hypertension and heart disease
How does the blood pressure of caucasians and black populations compare when living in the same environment?
–Caucasians have a lower BP than black populations living in the same environment
–Black populations living in rural Africa have a lower BP than those living in towns
Why do caucasians generally have a lower blood pressure than black populations?
–Possibly black populations are more susceptible to stress when living in towns
–Respond in different ways to changes in diet
–Black populations are genetically selected to be salt retainers and so are more sensitive to an increase in dietary salt intake
What are the causes of secondary hypertension?
•Renal disease: 20% of resistant hypertension
–chronic pyelonephritis
–fibromuscular dysplasia
–renal artery stenosis – narrowing of arteries
polycystic kidneys – atheromas plaque
•Drug Induced
–NSAIDs
–Oral contraceptive
–Corticosteroids
•Pregnancy
–pre-eclampsia
•Endocrine
–Conn’s Syndrome
–Cushings disease
–Phaeochromocytoma – tumour on adrenal – increase in adrenaline release
–Hypo and hyperthyroidism
–Acromegaly
•Vascular
–Coarctation of the aorta
•Sleep Apnoea
What is the result of a stenosed kidney?
Produces a lot of renin - increases the bloods pressure
How can you look for coartication in the clinical environment?
Produces a differences between radial pulses – narrowing slows pulse rate down
