S3 L1 Hypertension and Heart Failure Flashcards
What is blood pressure?
Driving force to perfuse organ with blood (force per unit area acting on vessels)
- Pressure needed to drive blood out of the heart- requires a pressure gradient
What are some of the features of BP?
Not uniform throughout the body - Gravity has an impact Measure systolic and diastolic pressure Cyclical Physiologically regulated variable → changes
What affect the BP?
Mean Arterial Pressure (MAP)= Cardiac output (CO) x total peripheral resistance (TPR)
TRP also called systemic vascular resistance
How can the mean arterial pressure be calculated?
Diastolic blood pressure + ((systolic blood pressure - diastolic blood pressure)/ 3)
Time in systolic blood pressure is much smaller
How is the blood pressure regulated?
Autonomic sympathetic pathway and renin angiotensin-aldosterone system (RAAS)
Plus autacoid including bradykinin and NO (vasodilation)- action from the endothelium on vascular smooth muscle
How does the sympathetic activity regulate BP?
Decrease in BP
- ↑Activation of β1 adrenoreceptors on the heart → CO
- ↑ Activation of α1 adreno receptors on smooth muscle → ↑venous return
- ↑ Activation of β1 adrenoreceptor on kidney → ↑peripheral resistance and ↑renin release
Increase in Blood pressure
How does the renal blood flow regulate BP?
Decrease BP
↓ Renal blood flow → ↓ GFR → ↑Na+, H2O retention → ↑Blood volume → ↑CO → ↑BP
AND
↓ Renal blood flow→ ↑Renin → ↑Angiotensin II → ↑Aldosterone → ↑Sodium, water retention → ↑BV → ↑CO → ↑BP
How are resistance and increased mean arterial pressure related?
Resistance to flow = 8nL / πr^4
Radius of vessel main determinant of flow
Small change in radius = big change in resistance
How does the radius change?
Smooth muscle tone changes total peripheral resistance
Vasoconstriction causes ↑peripheral resistance require ↑BP to drive blood through systemic circulation to maintain CO
What is the pathophysiology of hypertension?
- Elevated blood pressure (essential/primary/idiopathic) still not completely understood
- Leads to vascular changes including remodelling, thickening and hypertrophy
- Increased vasoactive substances including ET-1 (endothelin-1), NA (noradrenaline) and AngII (angiotensin II)
- Vascular remodelling also occurs as a direct result of local salt sensitivity
- Hyperinsulinemia and hyperglycaemia lead to endothelial dysfunction and increased ROS - NO signalling reduced
What is the end results of hypertension?
- Permanent and maintained medial hypertrophy of vasculature with ↑↑TPR and ↓Compliance of vessels
- Results in end organ damage (renal, peripheral vascular disease, aneurysm, vascular dementia and retinal disease)
- Hypertensive heart disease- LVH → dilated cardiac failure
- Increased morbidity and mortality
Why should we treat hypertension?
Silent killer- often asymptomatic
Increases the risk of other diseases such a coronary heart disease, stroke
How is hypertension defined?
Labile, age, sex and population differences make it difficult to define
Elevation in blood pressure that is associated with an increase in risk of some harm
Significant to cause end organ damage
An elevated blood pressure that treated will do more good than harm
What is the NICE definition of hypertension?
140/90 mmHg= hypertension
Approx >40% population in England
What are the different types of hypertension?
Essential/ primary/ idiopathic - 90% of cases
Other 10%
- Secondary hypertension (secondary to another disease)
- Pre hypertension
- Isolated systolic/diastolic hypertension
- White coat/ clinic (real phenomenon- elevated BP in GP or hospital settings)
How is hypertension diagnosed?
- Screening the at risk population
- Increasing public awareness of risk factors
- Appropriate lifestyle changes to limit risk- no immediate gain presence a challenge- don’t see or feel change so difficult to believe changes are working
- Reliable measurements based on clinical guidelines
- Regular monitoring and refinement of medication
- SILENT KILLER
How should a BP be obtained?
- Sitting, relaxed and arm is supported
- Both arms >15mmHg difference repeat measurement and use arm with higher reading
- Measurements over period of visits +/- Ambulatory BP measurement (ABPM) or Home BP measurement (HBPM)
- Emergency treatment required (>180 SBP or 120 DBP + clinical signs)
- CVD risk and end organ damage should be assessed whilst waiting for hypertension confirmation
- Aim- target BP and reduced CVD risk
What is the target BP?
140/90 <80 year old including type II diabetes
150/90 >80 year old
135/85 type 1 diabetes
What are the different stages of hypertension?
120/80 mmHg 'desired' minimise CVD risk Stage 1 - Clinical BP 140/90 - 159/99 mmHg and subsequent ABPM daytime/ HBPM average blood pressure ranging from 135/85 mmHg to 149/94 mmHg Stage 2 - Clinical BP 160/100 - 180/120 mmHg - ABPM/HBPM 150/95mmHg or higher Stage 3 - Clinical systolic BP of 180mmHg or higher OR clinical diastolic BP of 120mmHg or higher
What is prehypertension?
Slippery slop to hypertension >120/80 <140/90 mmHg
How can you prevent progression of hypertension?
- Promotion of regular exercise
- Modified healthy/balance diet
- Reduction in stress and increased relaxation
- Limited/ reduced alcohol intake
- Discourage excessive caffeine consumption
- Smoking cessation
- Reduction in dietary sodium
- All contribute to CVD risk reduction
These should be promoted to all patient groups not just pre pharmacological groups
What are the classes of drugs that are used to treat hypertension?
Angiotensin converting enzyme inhibitors (ACEi)
Angiotensin (AT1) receptor blockers (ARBs)
Calcium channel blockers (CCBs)
Diuretics- thiazide and thiazide-like
Other agents
What is ACE?
Angiotensin converting enzyme
Found on the luminal surface of capillary endothelial cells, predominantly in the lungs
Catalyses the conversion of AngI to AngII (active vasoconstrictor)
What is angiotensin II?
Afford action through AT1 (and AT2 receptors)
AT1 receptor subtype typical of classic angiotensin II action
- Vasoconstriction
- Stimulation of aldosterone (DCT)
- Cardiac and vascular muscle cell growth
- Vasopressin (ADH) release from posterior pituitary
BP↑ through combination of vasoconstriction and ↑circulating blood volume
What do ACEi do?
Limit the conversion of AngI to AngII by inhibiting ACE
Reduction in AngII activity
- Vasodilation ↓peripheral resistance → ↓afterload
- Reduction in aldosterone release ↑Na+ and H2O excretion
- Reduce vasopressin (ADH) release (↑H2O excretion)
- Reduce cell growth and proliferation
All can contribute to antihypertensive effects
AngII can also be produced from AngI independently of ACE via Chymases (additional pathway)
What are some of the common ACEi?
‘-pril’
- Lisinopril
- Ramipril
What are the adverse effects of ACEi?
Hypotension
Dry cough (10-15% bradykinin association)
Hyperkalaemia (low aldosterone ↑K+)
Cause or worsen renal failure (especially renal artery stenosis where constriction of efferent arterioles are needed)
Angioedema (more common in Afro-Caribbean patients)
What are the warning/contraindications of using ACEi?
- Renal artery stenosis
- AKD
- Pregnancy
- CKD- cation
- Idiopathic angioedema
What are the important drug interactions of ACEi?
↑K+ drugs
NSAIDs
Other antihypertensive agents
How do ACEi affect bradykinin?
ACE also needed for bradykinin breakdown into peptide fragments
Use of ACEi potentiate bradykinin
- Vasodilation via NOS/NO and PGI2
→ ACEi vasodilation in low-renin hypertensives
What are the Angiotensin receptors blockers (ARB)?
‘-sartan’
Candesartan
Losartan
Where are the main mechanisms of action of ARBs?
AT1 and AT2 receptors
AT1 are important in relation to cardiovascular regulation
Confusing nomenclature- AngII blockers - block angiotensin II, AT1-receptors blockers- act at T1 receptor or ARBs
No affect on bradykinin as act further down in the pathway - less effective in low-renin hypertensive patients dry cough and angioedema much less likely
What are the adverse effects of ARBs?
Hypotension
Hyperkalaemia (low aldosterone ↑K+)
Cause or worsen renal failure