CVS 14 - Hypertension Flashcards
Above which blood pressure is it considered abnormal?
140/90 mmHg
Describe how blood pressure may change with age.
- Systolic BP rises in a linear fashion.
- Diastolic BP plateaus and declines into old age
- ^This causes gap between systolic and diastolic BP to increase.
- Exponential risk between BP and stroke risk
How is hypertension classified?
- Identifiable causes - Secondary Hypertension (<5%). e.g. renal disease, tumours secreting aldosterone, oral contraceptive, etc
- Unidentifiable - Primary / essential (90-95%)
What is the most common cause of secondary hypertension?
Renal disease
Explain how genetics and environmental influences can contribute to high BP.
Genetics -
- Monogenic (rare - < 1%) -
- Complex polygenic
Environment -
- Dietary salt
- Obesity/overweight
- Alcohol
- Pre-natal environment
- Pregnancy
Give 2 monogenic causes of hypertension.
- Liddles Syndrome - mutation in amiloride-sensitive tubular epithelial Na channel
- Apparent mineralocorticoid excess - mutation in 11B-hydroxysteroid dehydrogenase
5 things that hypertension can be associated with.
- Increased TPR
- Reduced arterial compliance (higher pulse pressure) - reduced distensibility of larger arteries.
- Normal CO
- Normal blood volume/extracellular volume
- Central shift in blood volume
What are the causes of increased TPR in hypertension?
- Active narrowing of arteries (vasoconstriction)
- Structural narrowing of arteries (vasoconstriction followed by remodelling of arteries). Lumen of arteries gets smaller.
- Loss of capillaries. Rarefaction = reduction in capillary density - resistance is increased.
What is isolated systolic hypertension?
- Systolic BP > 140, Diastolic BP < 90.
- Typically occurs in people over 60, as systolic and diastolic pressures diverge.
- Pulse wave is reflected - it bounces off the walls of the stiffened blood vessels. The wave is greater when it reaches the brachial artery.
What are 3 possible causes of primary hypertension
- Kidney
- Sympathetic Nervous System
- Endocrine/paracrine factors
How may the kidney be the cause of hypertension?
The kidney exerts a major role on BP by regulating Na/H2O/ECF volume
- Impaired renal function / blood flow is the commonest 2dary cause of hypertension (e.g. renal parenchymal disease)
- Most monogenic causes of hypertension affects renal Na excretion.
What consequential risks can hypertension cause
- CHD
- Stroke
- Peripheral Vascular Disease
- Heart failure
- Atrial fibrillation
- Dementia/cognitive impairment
- Retinopathy
Hypertension can cause structural changes in the heart. How?
LV wall may thicken (hypertrophy) and ventricular volume may change (remodelling)
Describe the relationship between hypertension and congestive heart failure?
- Heart Failure = inability to adequately pump out blood at normal filling pressures.
- Increases risk of CHF 2/3 fold
- Precedes heart failure in 90% of cases.
Hypertension is associated with large artery hypertrophy. What else is is associated with?
Accelerated atherosclerosis.
Can also cause an aneurysm, which may cause a thrombosis or haemorrhage is aneurysm ruptures.
What are Charcot-Bouchard Aneurysms?
Brain vasculature aneurysms occurring in small blood vessels. Commonly associated with chronic hypertension and a common cause of cerebral haemorrhage.
What features of microvascular damage are present on the retina in hypertensive patients?
- Thickening of wall of small arteries.
- Arteriolar narrowing
- Vasospasm
- Impaired perfusion
- Increased leakage into surrounding tissue
Hypertension is associated with reduced capillary density and elevated capillary pressure. What can these cause.
Reduced capillary density = impaired perfusion and increased in PVR
Elevated capillary pressure = damage and leakage
Renal dysfunction is common from hypertension. How can it manifest?
Loss of albumin in the urine (microalbuminuria and macroalbuminuria).
Kidney loses nephrons and deteriorates in function.
What is microalbuminuria a sign of?
Glomerular damage
How does GFR change with age in hypertensive patients?
Decline in GFR