15. Hypertension Flashcards
What is abnormal blood pressure?
140/90 mmHg
Describe the way systolic blood pressure changes with age
Rises in a linear way
Describe the way diastolic blood pressure changes with age
It plateaus and declines in old age
Describe the difference in blood pressure with increasing age
It the gap between systolic and diastolic BP increases
What is the relationship between BP and risk of stroke?
Exponential
What is the relationship between BP and myocaridal infarction?
Exponential
Define primary hypertension
There is no identifiable cause
Define secondary hypertension
There is an identifiable cause
What is the proportion of primary and secondary hypertension?
Primary = 90-95% Secondary = <5%
List the causes of secondary hypertension
Renal disease
Tumours secreting aldosterone (Conn’s syndrome)
Tumours secreting catecholamines
Oral contraceptive pill
Pre-eclampsia/pregnancy associated hypertension
Rare genetic diseases (e.g Liddle’s syndrome)
What is the most common cause of secondary hypertension?
Renal disease
What are two types of genetic causes of primary hypertension?
Monogenic (rare) Complex Polygenic (common)
List the environmental causes of primary hypertension
o Dietary Salt o Obesity/Overweight/Lack of Exercise o Alcohol o Pre-natal Environment (underweight babies have a higher risk of cardiovascular disease and diabetes) o Pregnancy (pre-eclampsia)
What is Liddle’s syndrome?
Monogenic - mutation in amiloride-sensitive tubular epithelial Na channel
What is Apparent mineralocorticoid excess?
Monogenic - mutation in 11beta-hydroxysteroid dehydrogenase
What is typically established hypertension associated with?
- Increased TPR
- Reduced arterial compliance (higher pulse pressure) - distensibility of larger arteries is reduced
- Normal cardiac output
- Normal blood volume/extracellular volume
- Central shift in blood volume - secondary to reduced venous compliance
What are the causes of an increased TPR in hypertension?
1) Active narrowing of arteries - vasocontriction
2) Structural narrowing of Arteries - vasocontriction is accompanied by remodelling of arteries. The lumen gets smaller
3) Loss of capillaries - rarefaction
Define rarefaction
Reduction in capillary density which means that resistance increased
Define isolated systolic hypertension
Systolic BP > 140 and a Diastolic BP < 90. Characterised by the divergence of the SBP and DBP
What is isolated systolic hypertension caused by?
Increased stiffness of the arteries so that the pulse wave is reflected and amplified by the time it reaches the brachial artery
How do you treat isolated systolic hypertension?
You can’t treat it with drugs since it would just decrease DBP further
What are the possible causes of primary hypertension?
Kidney
Sympathetic nervous system
Endocrine/Paracrine factors
Discuss the effects of the kidney on hypertension
Impaired renal function or blood flow is the commonest cause of hypertension. Renal sodium excretion and salt intake issues greatly affect BP
List the major risks attributable to increased BP?
- Coronary heart disease
- Stroke
- Peripheral vascular disease/atheromatous disease
- Heart failure
- Atrial fibrillation
- Dementia/cognitive impairment
- Retinopathy
What structural changes in the heart are caused by hypertension?
Hypertrophy of the left ventricle and change in ventricular volume (remodelling)
Define heart failure
The inability of the heart to adequately pump blood at normal filling pressure
By how much does hypertension increase the risk of CHF?
2-3 folds
How many cases of CHF does hypertension account for?
25%
What is the majority of hypertension in the elderly attributed to?
Ageing
What is hypertension associated with in terms of arteries?
Hypertrophy, acceleration of atherosclerosis, dilation of the large arteries (aneurysm) which can lead to thrombosis or haemorrhage
Describe Charcot-Bouchard aneurysms
Aneurysms of the brain vasculature which occur in small blood vessels - they are commonly associated with chronic hypertension and are a common cause of cerebral haemorrhage
List the features caused by hypertension seen in the retina
o Thickening of the wall of small arteries
o Arteriolar narrowing
o Vasospasm
o Impaired perfusion
o Increased leakage into surrounding tissue (exudates)
In the microvasculature what is hypertension associated with?
Reduction in capillary density
Elevated capillary pressure
What does reduction in capillary density cause?
Impaired perfusion and an increase in peripheral vascular resistance
What does elevated capillary pressure cause?
Damage and leakage
What is a manifestation of renal dysfunction?
Loss of albumin in the urine (microalbuminuria and macroalbuminuria)
What is lost in renal dysfunction?
The kidney gradually loses nephrons and their function deteriorates
What is micoalbuminuria a sign of?
Renal dysfunction = glomerular damage
How does hypertension affect the GFR (glomerular filtration rate)
Decreases the GFR with rate
In terms of albumin, the higher your BP the more…
Albumin you will leak
