Pathophysiology of hypertension Flashcards
Overview
• PRIMARY vs. SECONDARY HYPERTENSION
- POSSIBLE MECHANISMS OF PRIMARY HYPERTENSION
- SYMPATHETIC SYSTEM
- RAAS
- CIRCULATING FACTORS • GENETICS
- MECHANISMS OF SECONDARY HYPERTENSION
- CONSEQUENCES OF HYPERTENSION
- TREATING HYPERTENSION
Discuss pulmonary hypertension
• Increased blood pressure in the arteries of the lungs
- Cause often not known
- Can be due to hypoxia, endothelial dysfunction, genetics, blockage/damage to blood vessels, side effects of drugs, left-sided HF
- Right side of the heart has to work harder
- Rare
- More common in patients with another heart or lung condition
- Usually only diagnosed when severe and symptomatic
Discuss systemic arterial hypertension
• Systemic arterial hypertension is the condition of persistent non-physiologic elevation of system blood pressure
- Typically defined as:
- Systolic > 140 mmHg and/or
- Diastolic > 90mmHg
- Identified as one of the major causal risk factors for cardiovascular disease
Discuss risk factors for hypertension
- Hypertension is a complex phenotype
- Multiple genetic risk factors
- Multiple environmental risk factors
- Age
- Weight
- Sex
- < 60 years more prevalent in males
- > 60 years more prevalent in females
- Race
- African Americans disproportionally affected
- Education status
- Diet
Discuss measurement of blood pressure in hypertension
- All adults >40 years should have BP measured
- <40 years with family history of atherosclerosis
• Minimum of 3-4 pairs of readings gathered over 3-4 months (unless severe HT)
RECOMMENEDED TO CONFIRM HT:
- Ambulatory blood pressure monitoring (ABPM)
- Measured twice per hour during waking hours
- At least 14 measurements to calculate average
- Home blood pressure monitoring (HBPM)
- Monitored twice daily (day/night, sitting)
- 2 recordings, 1min apart for 7 days (at least 4)
- All recordings after 1st to calculate average
Discuss classification of systemic hypertension
Stage 1 hypertension
• Clinic BP is 140/90 mmHg or higher and subsequent ambulatory or home blood pressure monitoring (ABPM or HBPM) daytime average is 135/85 mmHg or higher
Stage 2 Hypertension
• Clinic BP is 160/100 mmHg or higher and subsequent ABPM or
HBPM daytime average is 150/95 mmHg or higher
Severe Hypertension
• Clinic systolic BP is 180 mmHg or higher
• OR clinic diastolic BP is 110 mmHg or higher
Discuss systemic arterial hypertension
Also known as primary hypertension
- Also known as “essential” or “idiopathic” hypertension
- Accounts for ~90 % of human hypertension
- No apparent underlying cause
- Weight
- Lifestyle
- Dietary sodium intake, lack of exercise, alcohol, smoking
- Genetic factors
- Multiple organ systems
What is the way to calculate blood pressure from cardiovascular states
BP = CO x TPR
CO = Stroke volume (SV) x Heart Rate (HR)
Discuss blood pressure control
- Complex interactions of neurohormonal and local control systems that regulate BP and local tissue flow
- BUT it also involves additional systems that regulate circulatory volume in relation to vascular capacitance
(?) Short term: Cardiac output (CO) Total peripheral resistance (TPR) Long term: Effective circulating volume (ECV)
What are possible contributors to systemic hypertension
- INCREASED SYMPATHETIC ACTIVITY / SENSITIVITY
- RENIN-ANGIOTENSIN-ALDOSTERONE SYSTEM (RAAS)
- CIRCULATING FACTORS
How does the autonomic nervous system influence BP control
• Blood vessel tone • Heart rate and force of contraction • Adrenal gland secretion of adrenaline
Discuss neurotransmission in the ANS
• SyNS and PaNS are the two major EFFERENT pathways controlling targets other than skeletal muscle
• Involves a two-synapse pathway
• SyNS and PaNS work SYNERGISTICALLY to control visceral activity (often working in opposite ways)
Sympathetic releases noradrenaline and adrenaline at postganglionic neuron
Parasympathetic releases ACh at postganglionic neuron
Discuss adrenergic receptors (adrenoceptors)
• Catecholamines bind adrenoceptors to elicit their actions
Adrenaline (A)
Noradrenaline (NA)
Isoprenaline (ISO) Synthetic b-agonist
- Demonstrate different affinities to each receptor
- Intracellular action of a specific catecholamine is determined by the complement of receptors expressed on the cell surface
- Catecholamines bind adrenoceptors to elicit their actions
Discuss sympathetic contribution to hypertension
Increased blood pressure due to:
• Increased signalling to vascular smooth muscle cells of blood vessels (a1) so increase vasoconstriction so increaseTPR
• Increased signalling to pacemaker
and contractile cells in heart (b1) so increase HR and contraction so increase CO
• Adrenal gland secretion of adrenaline
• Renin secretion (b1 receptors) so increase Ang II so increase vasoconstriction so increase TPR
Ang II also increases Na+ and H2O absorption and so increase ECV
Discuss a quick overview of the kidneys
- Functional unit of kidney is a nephron
- Filters blood and produces urine
- Filter ~ 180 L blood/day
- REABSORPTION
• Na+ is predominant cation in ECF
• Movement of Na+ established osmotic
gradients for H2O movement • Na+ is freely filtered across
glomerulus, 99% will be reabsorbed
• The kidneys must balance Na+ intake with Na+ excretion
• This maintains ECF volume and therefore long-term BP
• Critical target for anti-hypertensives