vascular and ischeamic heart disease Flashcards
define hypertension
a disorder in which the level of sustained arterial pressure is higher than expected for the age, sex and race of the individual ie 140/90mmHg
what is the difference between primary and secondary hypertension
Primary has no obvious cause whereas secondary has an underlying disease implied eg renal disease, endocrine disease…
what are some underlying diseases of secondary hypertension
- renal disease (reduced renal blood flow, excess renin release, salt and water overload)
- endocrine disease
- aortic disease
- renal artery stenosis
- drug therapy
what is benign hypertension
- A cause of serious threatening morbidity
- Asymptomatic, incidental finding often heath checks
- Eventually causes left ventricular hypertrophy, congestive cardiac failure, increases atheroma…
what is left ventricular hypertrophy
Left ventricular hypertrophy is enlargement and thickening (hypertrophy) of the walls of your heart’s main pumping chamber (left ventricle)
- increased LV load
- poor perfusion
- interstitial fibrosis
- micro-infarcts
- diastolic dysfunction
- sudden cardiac death
- cardiac failure
- affects outcome of other diseases
what is malignant hypertension
Can develop from either benign primary of secondary hypertension or arise denovo. Needs urgent treatment to prevent death
- causes cerebral oedema - seen as papilloedema
- acute renal failure
- acute heart failure
- ## headache and cerebral haemorrhage
where do the right and left coronary arteries arise
base of the aorta
where does most coronary venous blood drain via
drains via the coronary sinus into the right atrium
what are special adaptation of coronary circulation
- High capillary density
- High basal blood flow
- High oxygen extraction (75% compared to 25% whole body average) under resting conditions
- This means extra O2 cannot be supplied by increasing O2 extraction
- Can only be supplied by increasing coronary blood floe
what are the intrinsic mechanisms that influence coronary blood flow
- A decrease in P02 causes vasodilation of the coronary arteries
- Metabolic hyperaemia matches flow to demand
- Adenosine (from ATP) is a potent vasodilator
what are extrinsic mechanisms that influence coronary blood flow
- Coronary arterioles supplied by sympathetic vasoconstrictor nerves but are overridden by metabolic hyperaemia as a result of increased heart rate and stroke volume
- So sympathetic stimulation of the heart results in coronary vasodilation despite direct vasoconstriction effect
- Circulating adrenaline activates Beta 2 adrenergic receptors, which cause vasodilation.
why does most of coronary blood flow and myocardial perfusion occur during diastole
the subendocardial vessels from the left coronary artery aren’t compressed
what vessels supply the brain with blood
internal carotid and vertebral arteries which unite to form the basal arteries
what is the circle of willis
basilar (formed by 2 vertebral arteries) and carotid arteries anastomose to form the circle of willis
- major cerebral arteries arise from the circle of willis
- cerebral perfusion should be maintained even if one carotid artery gets obstructed
- obstruction of a smaller branch of a main artery would deprive a region of the brain of its blood supply
what is the auto regulation of cerebral blood flow
- if MABP rises the resistance vessels automatically constrict to limit blood flow
- if MABP falls the resistance vessels dilate to maintain blood flow
- autoregulation fails if MABP falls below 60mmHg or rises above 160mmHg
- a MABP below 50mmHg results in confusion, fainting and brain damage if not quickly corrected
what does an increase and decrease in PCO2 cause in cerebral blood flow
increase = vasodilation decrease = vasoconstriction
what is the normal inter cranial pressure within the skull
8-13mmHg