Aneurysms, hypertension and stroke Flashcards
What is hypertension?
Sustained elevation of systolic and diastolic blood pressure (> 140/90mmHg)
What are primary and secondary causes of hypertension?
- No identifiable primary cause - idiopathic
- Secondary - renal disease, adrenal tumours, aortic coarctation, steorid Rx
How can hypertension cause organ damage? (vessels, heart, lungs, kidney, eye, brain) [brief]
- Vessels - atheroma, aneurysm, elastic reduplication
- Heart - left ventricular hyeprtrophy, LHF
- Lungs - pulmonary oedema due to LHF
- Kidney - nephroscelerosis, renal failure
- Eye - retinal capillary damage, haemorrhages, exudates
- Brain - microaneurysms, stroke, ischaemic cortical atrophy
What is hypertensive heart disease?
When increased load causes concentric left ventricular hypertrophy. This can lead to heart failure.
What happens in hypertensive nephropathy?
Granular cortical atrophy due to nephrosclerosis - loss of a glomerulus causes atrophy of the nephron.
What happens in hypertensive retinopathy as it gets worse?
- Early - nicking of retinal veins by overlying arterioles, normally they run alongside.
- Moderate - straightened, wider capillaries, flame shaped haemorrhages, ‘cotton wool’ spots, hard exudates around macula
- Late chronic/malignant - Papilloedema, haemorrhage
What change in parameter of an arteriole can alter the systemic arterial blood pressure, thus causing hypertension?
Luminal diameter - resistance of flow is equiv to the fourth power of the diameter.
What is the difference between atherosclerosis and arteriosclerosis?
Atherosclerosis is the narrowing of the artery because of plaque build-up, a disease of the intima.
Arteriosclerosis refers to the general hardening/thickening of the artery walls, so atherosclerosis is a type of it.
Does atheroma cause hypertension?
Atheroma tends to affect larger blood vessels so does not increase TPR, so unlikely to cause hypertension. The two diseases are often encountered together though.
What happens to blood vessels (arterioles) in hypertension? What is hyaline arteriosclerosis?
Resistance arterioles show elastic duplication in hypertension.
Plasma exudes into the intima and deeper layers of the wall (media), causing hardening and a ‘pink glassy’ structure. This is ‘hyaline arteriosclerosis’.
The endothelium in hypertension is subject to damage by shearing forces applied by high cardiac output: atheroma is likely to develop at sites of endothelial damage due to hypertension.
What 3 things stimuate renin release by the kidney juxtaglomerular complex?
- Low renal blood flow/pressure
- Low blood Na+
- Sympathetic NS
How do you get from renin to angiotensin II?
- Angiotensinogen cleaved to angiotensin I
- By enzyme renin
- Angiotensin I activated to angiotensin II
- by ACE (from lung)
How does angiotensin II increase blood pressure?
- Vasoconstriction of resistance vessels
- ALDOSTERONE -> inc water reabsorption
- ADH -> inc water reabsorption
- thirst -> inc blood volume
- cardiac hypertrophy
- SNS -> noradrenaline inc
What signals negative feedback in the renin-angiotensin-aldosterone system?
Natriuretic peptides (ANP, BNP) released by the heart
How can ACE inhibitors (-pril) result in a dry cough as a side-effect?
As ACE is released from the lung surfaces, ACE inhibitors result in bradykinin build up within the lung and cause irritation resulting in a dry cough.
What is an aneurysm?
A bulge in the wall of a blood vessel
What is the difference between a ‘true’ and ‘false’ aneurysm?
True anuerysm is when all 3 layers of the blood vessel are affected, a false aneurysm is when not all 3 are affected, eg. it might be a punctured wall causing the bulge/expansion.
Describe ‘berry’ (saccular) aneurysms
- Typically occur at bifurcations of arteries - circle of willis
- Rupture -> subarachnoid haemorrhage