Pathophysiology of Hypertension Flashcards
What is systemic arterial hypertension?
the condition of persistent non-physiologic elevation of system blood pressure
What figures suggest hypertension?
- systolic >140 mmHg
- diastolic >90 mmHg
What are the risk factors for hypertension?
- age (under 60s more prevalent in males, over 60s more prevalent in females)
- weight
- sex
- race (African Americans disproportionally affected)
- education status
- diet
Stage 1 hypertension
- clinical BP 140/90 or higher
- ABPM/HBPM daytime average of 135/85 or higher
Stage 2 hypertension
- clinic BP 160/100 or higher
- ABPM/HBPM daytime average of 150/95 or higher
Severe hypertension
- clinical systolic BP 180 or higher
- clinic diastolic BP 110 or higher
Contributing factors of primary hypertension
- weight
- lifestyle (Na intake, lack of exercise, smoking, alcohol)
- genetics
- organ systems
Components in controlling blood pressure
- cardiac output (SV x HR)
- TPR
- effective circulating volume (by the kidneys)
Contributors to systemic hypertension
- increased sympathetic activity/sensitivity
- RAAS
- circulating factors
Sympathetic neutrotransmission in ANS
in kidneys:
- preganglionic fibre synapses in adrenal medulla on chromaffin cell on a and B receptors
- releases ACH
- releases adrenaline
in smooth muscle, glands and cardiac muscle:
- preganglionic fibe synapses on post-ganglionic fibre near organ on a and b receptors
- releases ACH
- releases noradrenaline
What binds to a and b-receptors?
- adrenaline
- noradrenaline
- isoprenaline
What are the affinities of the catecholamines for the a-receptors?
NA = A»_space; ISO
What are the affinities for the catecholamines for b-receptors?
ISO > A > NA
Sympathetic activity contribution to hypertension
- increased signalling to vascular smooth muscle in blood vessels (a1)
- increased vasoconstriction and TPR
- increased signalling to pacemaker and contractile cells in heart (b1)
- increased HR, contraction and CO
- adrenaline and renin secretion
- increased angiotensin II, vasoconstriction and TPR
- increased ECV
What receptors does angiotensin II act on?
AT1 receptors
What structures are affected by angiotensin II?
vascular smooth muscle cells of blood vessels:
- increased vasoconstriction
- increased TPR
Hypothalamus:
- increased release of ADH
- increased reabsorption of water in kidneys
- increase in ECV
Zona Glomerulosa of adrenal glands:
- increased secretion of aldosterone
- increased Na+ reabsorption by kidney
- increased ECV
What is secondary low renin hypertension known as?
Conn’s Syndrome
What is low renin hypertension?
- plasma aldosterone : renin ratio
- low renin, normal aldosterone
Higher risk patients of low renin hypertension?
- older
- Afro-caribbean descent
What circulating factors affect hypertension?
- endothelin
- nitrous oxide
- reactive oxygen species
Endothelin in hypertension
- vasoconstrictor
- circulating concentrations not increased in hypertension but locally can be
- can bind ETa receptors on vascular smooth muscle cells to cause vasoconstriction
- can also bind ETa receptors in cardiomyocytes to increase contractility
Contradictions of endothelin in hypertension
- can bind to ETb receptors to produce NO causing vasodilation
- promotes salt and water excretion in kidneys
Difference in secondary to primary hypertension
secondary hypertension has an identifiable underlying cause whereas primary hypertension does not
Secondary hypertension caused renally
Renal parenchymal disease:
- glomerularnephritis
- diabetic nephropathy
- lupus nephritis
- polycystic kidney disease
Renal vascular disease:
- renal artery stenosis
- vasculitis
- fibromuscular dysplasia
