15. Hypertension Flashcards
What is hypertension?
- Blood pressure at which intervention does more good than harm
- Above 140/90 mmHg
- Causes more deaths than any other single cause
How does Systolic and Diastolic blood pressure change with age?
- Systolic BP rises in a linear way
- Diastolic BP rises into old age, then declines
- The gap between SBP and DBP (pulse pressure) increases
What is the relationship between blood pressure and the risk of stroke?
Exponential
When do most strokes (and MIs) occur in hypertensive people?
When their BP is well controlled
Give 6 causes of secondary hypertension (5% of hypertension - identifiable causes)?
- Renal disease (most common)
- Tumours secreting aldosterone (Conn’s syndrome)
- Tumours secreting catecholamines (pheochromocytoma)
- Oral contraceptive pill
- Pre-eclampsia/pregnancy associated hypertension
- Rare genetic causes
Give 2 examples of monogenic conditions (rare) in hypertension
- Liddle’s Syndrome - mutation in amiloride-sensitive tubular epithelial Na channel
- Apparent mineralocorticoid excess - mutation in 11b-hydroxysteroid dehydrogenase
How do complex polygenic conditions play a part in hypertension?
- Multiple genes can have small effects (positive and negative)
- Interactions with sex, other genes and environment
- Common
How does the environment have an impact on hypertension?
- Dietary salt
- Obesity
- Alcohol
- Pre-natal environment (underweight babies)
- Pregnancy (pre-eclampsia)
What are the haemodynamics of hypertension?
- Increased total peripheral resistance
- Reduced arterial compliance
- Normal cardiac output
- Normal blood volume
- Central shift in blood volume (reduced venous compliance)
Why does total peripheral resistance increase in hypertension?
- Active narrowing of arteries (vasoconstriction)
- Structural narrowing of arteries (remodelling - thicker walls and smaller lumen)
- Loss of capillaries (rarefraction - reduction in capillary density)
What is Isolated Systolic Hypertension?
- Systolic BP > 140
- Diastolic BP < 90
- Tends to occur in people over 60 - increasing pulse pressure
- Pulse wave is reflected - bounces off the walls of stiffened vessels
- Greater by the time it reaches the brachial artery
- No specific drugs as the normal diastolic blood pressure would be unnecessarily reduced
What are 3 possible causes of primary hypertension?
- Kidney - regulates sodium/water/extracellular fluid volume
- Sympathetic Nervous System - high activity
- Endocrine/paracrine factors - inconsistent evidence
What are major risks, attributable to increased BP?
- Coronary heart disease
- Stroke
- Peripheral vascular disease
- Heart failure
- Atrial fibrillation
- Dementia/cognitive impairment
- Retinopathy
What changes to the heart can hypertension cause?
- Wall of left ventricle could thicken (hypertrophy)
* Change in ventricular volume (remodelling)
What is heart failure?
Inability of the heart to adequately pump blood at normal filling pressures
What is the relation between the large arteries and hypertension?
- Hypertension associated with hypertrophy of large arteries
- Associated with the acceleration of atherosclerosis
- May cause dilation of the large arteries (aneurysm)
- Can lead to thrombosis or haemorrhage if the aneurysm ruptures
What are Charcot-Bouchard Aneurysms?
- Aneurysms of the brain vasculature
- Small blood vessels
- Associated with chronic hypertension
- Cerebral haemorrhage
What changes occur in the retina in hypertension?
• Microvascular damage
- thickening of the wall of small arteries
- arteriolar narrowing
- vasospasm
- impaired perfusion
- increased leakage into surrounding tissue (exudates)
What changes occur in the kidneys in hypertension?
- Renal dysfunction - loss of albumin in urine (micro/macroalbuminuria)
- Glomerular damage
- Decline in Glomerular Filtration Rate with age
- Kidney gradually loses nephrons and their function deteriorates
- Diabetes can accelerate this process
