153 - Hypertension Flashcards
Proportion of Australians over 18 who are hypertensive
~30%
Arbitrary definition of hypertension
Systolic over 140mmHg and diastolic over 90mmHg
Primary/essential hypertension
No specific identifiable cause.
Responsible for 90-95% of hypertension
Secondary hypertension
Identifiable pathology that is causing hypertension
5-10% of hypertension
Benign hypertension
Blood pressure rises gradually, over a long period.
Majority of cases.
Malignant hypertension
Blood pressure rises rapidly, over a short period.
Minority of cases.
Two forces that leads to blood pressure
Cardiac output (stroke volume, heart rate, blood volume) and resistance in arteiroles.
Aortic changes from age
1
2
3
Aorta: loss of elasticity, hardening i.e. ‘arteriosclerosis’
Media: fragmentation of elastin, increased collagen
Intima: increased collagen
What effect does hypertension have on blood vessels?
Exacerbates age-related changes.
Aorta: loss of elasticity, hardening i.e. ‘arteriosclerosis’
Media: fragmentation of elastin, increased collagen
Intima: increased collagen
Age-related arterial changes in small and medium arteries
1
2
– Media: fragmentation of elastin, increased collagen, sometimes calcification
– Intima: increased collagen -> thickening
Age-related arteriolar changes 1 2 3 4
Arteriolar hyalinosis/hyaline arteriolosclerosis
– Deposition of plasma proteins in wall
– Increased collagen
– Smooth muscle atrophy
–Arteriole wall becomes thickened by homogenous eosinophilic glassy material (‘hyaline’) and the lumen narrowed
Arteriolar change in hypertension, or with age
Arteriolar hyalinosis/hyaline arteriosclerosis
What can hyaline arteirolosclerosis lead to?
Can slightly increase diastolic blood pressure with age.
Genetic predispositions to primary hypertension 1 2 3 4 5 6
– Polygenic genetic influences. Genetic polymorphisms may influence for example
• Sympathetic responses
• Transport of ions across cell membranes in vessels or kidney
• Arteriolar responses to local regulatory factors
• Activity of components of the renin-angiotensin-aldosterone system and secretion of renin
• Genetic determinants may also influence target organ damage
Lifestyle factors contributing to primary hypertension 1 2 3 4
- Amount of salt in diet
- Alcohol intake
- Levels of physical activity
- Abdominal obesity and metabolic syndrome (can influence e.g. renal sodium retention, increased sympathetic activity, ion transport across cell membranes)
Age, gener, race predispositions to primary hypertension
1
2
- Prevalence lower in premenopausal females than in age-matched males and in postmenopausal women
- Higher in those of African descent
Broad divisions of primary hypertension
High plasma renin and low plasma renin.
Possibly correlate with vasoconstrictor and volume-dependent forms of hypertension.
Systolic hypertension with wide pulse pressure
1
2
Several groups:
• Decreased compliance of aorta (arteriosclerosis).
Age related changes –> loss of elasticity -> elevation of the systolic pressure and widening of the pulse pressure. If excessive -> isolated systolic hypertension
• Increased stroke volume e.g. aortic regurgitation, hyperthyroidism, fever (can treat some of these causes)
Most common pathology leading to secondary hypertension
Renal disease
EG: diabetic glomerulosclerosis, certain glomerulonephritides, polycystic renal disease, chronic renal diseas
Examples of non-renal causes of secondary hypertension 1 2 3 4
– Endocrine e.g. adrenocortical adenoma producing cortisol or aldosterone, phaeochromocytoma, pituitary adenoma producing ACTH
– Vascular e.g. coarctation of aorta, renal artery stenosis
– Medications e.g. corticosteroids, oestrogen
– Other e.g. neurogenic/cerebral, hypercalcemia, toxaemia of pregnancy, obstructive sleep apnoea, cocaine use
Coarctation of the aorta
Congenital narrowing of aorta
Does atherosclerosis cause hypertension
Under certain circumstances.
EG when it is stenosing renal arteries.
Effects of essential hypertension
Causes complications by causing concentric left ventricular hypertrophy and by predisposing to pathology in arteries and arterioles.
Examples of arterial and arteriolar effects of hypertension
1
2
3
• Large and medium sized arteries
- Atherosclerosis
- Aortic dissection
•Medium arteries: berry aneurysm (Circle of Willis)
•Arterioles: hyaline arteriolosclerosis/arteriolar hyalinosis
What is an aneurysm most directly related to?
Weakening of media.
Arterial wall can normally withstand increased pressure from hypertension, but will only dilate if media is weakened.
Where is the blood in an aortic dissection?
Between inner 2/3 and outer 1/3 of media
What causes the majority of myocardial infarcts?
Atherosclerosis with thrombosis of a coronary vessel
Effect of hypertension on heart function
Can predispose to myocardial infarcts from coronary vessel atherosclerosis
Effect of concentric hypertrophy on LV chamber size
Doesn’t actually change it that much. The chamber walls can stretch to accommodate blood.
Effects of concentric hypertrophy on LV
1
2
3
1) Impairing diastolic filling (pressure is too high)
2) Increasing the myocardial oxygen demand
3) Reducing the coronary perfusion (increased pressure in wall increases capillary pressure, which reduces the pressure gradient between coronary arteries and capillaries
What are individuals with concentric hypertrophy at increased risk of? 1 2 3 4 5
1) Angina
2) Myocardial infarction
3) Congestive cardiac failure
4) Atrial fibrillation
5) Sudden cardiac death
How is hypertension a risk factor for renal injury?
1
2
Two theories (neither might be the case):
• Transmission of elevated pressures to glomeruli –> sclerosis
•Hyaline arteriolosclserosis -> chronic ischaemia
Proteinuria is a marker of the severity of chronic kidney disease and is a predictor of its progression
Benign nephrosclerosis 1 2 3 4
Age-related.
Rough surface of kidney.
Atrophy of nephrons.
Because of arteriolosclerosis
How can hypertension exacerbate age-related benign nephrosclerosis?
Can lead to arteriolosclerosis.
Histological features of benign nephrosclerosis
1
2
3
1) Interstitial scarring
2) Chronic inflammation
3) Atrophic glomeruli and tubules
4) Sclerosed glomeruli
What does chronic injury of a glomerulus lead to?
Sclerosis of the glomerulus
Characteristic histological feature of thrombo-emoli
Cholesterol crystal plaques
Most common cause of cerebral infarctions
Thrombo-emboli
Biggest risk factor for cerebral haemorrhages
Hypertension (leads to arteriolosclerosis)
Lacunar infarctions
Small infarctions in the brain, from hyalinised vessels occluding flow.
Effects of hypertension on the retina
AV nipping.
Exudates.
Haemorrhages.
These changes are caused by hyaline arteriolosclerosis
How to assess a hypertensive patient 1 2 3 4 5 6
• Complete history and physical examination to:
– Confirm diagnosis: guidelines for measuring BP and confirming diagnosis
– Seek other cardiovascular risk factors and assess absolute cardiovascular risk (risk of a cardiovascular event occurring within the next 5 years)
– Seek secondary causes of HT
– Identify end-organ damage
– Seek comorbidities
– Determine the potential for intervention, including lifestyle modification
Malignant hypertension or hypertensive emergency development
May develop de novo in those with normal BP or in those with pre-existing essential HT
Complications of malignant hypertension
1
2
- Hyperplastic arteriolosclerosis
* Fibrinoid necrosis and thrombosis
Differences in vascular changes between benign and malignant hypertension
Benign has hyaline arteriolosclerosis.
Malignant has hyperplastic arteriolosclerosis
Hyperplastic arteriolosclerosis
Onion-skin appearance, with increased layers of media.
Can have fibrinoid necrosis
Effect of hyperplastic arteirolosclerosis on kidney
Deteriorating renal function
Effect of hyperplastic arteirolosclerosis on the retina
Retinopathy (arteriolar spasm, haemorrhages, exudates, papilledema)
Effect of hyperplastic arteirolosclerosis on brain
Encephalopathy. Failure of autoregulation of cerebral blood flow, hyperperfusion and cerebral oedema
Effect of hyperplastic arteirolosclerosis on blood
Microangiopathic haemolytic anaemia
