Cardiology - Hypertension Flashcards
Risk factors for hypertension?
Age (systolic increases)
- diastolic decreases over age 60rys
Obesity and weight gain
- esp centrally located fat
- for every 9.2kg reduction –> 6/3mmHg
High salt diet
Low potassium diet and calcium
- urine Na:K ratio is stronger correlate to BP than either serum Na or K
Alcohol >=3SD/day
Physical inactivity
Genetics
- family study inheritability 15-30%
- twin inheritability 60% male, 30% female
How is adrenergic activity mediated in the autonomic nervous system?
Mediated by G proteins stimulated by norad/adrealine and dopamine
What are the adrenergic receptors in the autonomic nervous system?
Alpha-1:
- On post-synaptic cells in smooth muscle. Result in vasoconstriction.
- On kidneys they increase renal sodium reabsorption
Alpha-2:
- On post-synaptic cells
- activation results in noradrenaline –> negative feedback
Beta-1:
- On myocardium stimulates cardiac contraction and rate
- in kidneys stimulates renin release
Beta-2:
- Activation by adrenaline stimulates relaxation of vascular smooth muscle and vasodilation
What do alpha-1 receptors do in the autonomic nervous system?
Alpha-1: activated by ad/norad/dopamine
- On post-synaptic cells in smooth muscle. Result in vasoconstriction.
- On kidneys they increase renal sodium reabsorption
What do alpha-2 receptors do in the autonomic nervous system?
Alpha-2: activated by ad/norad/dopamine
- On post-synaptic cells
- activation results in noradrenaline –> negative feedback
What do beta-1 receptors do in the autonomic nervous system?
Beta-1:
- On myocardium stimulates cardiac contraction and rate
- in kidneys stimulates renin release
What do beta-2 receptors do in the autonomic nervous system?
Beta-2:
- Activation by adrenaline stimulates relaxation of vascular smooth muscle and vasodilation
What is the baroreflex in autonomic nervous system?
Stretch-sensitive nerve endings in carotid sinus and aortic arch
Increased BP –> increased nerve firings –> decreased sympathetic activity
What stimulates renin synthesis in RAAS?
Renin is synthesised in renal afferent renal arteriole.
Stimulated by:
1) Decreased NaCl in distal thick ascending LOH at macula densa
2) Reduced pressure/stretch in renal afferent arteriole
3) sympathetic stimulation of renin-secreting cells via Beta-1 Adrenoceptors
4) Blockage of ACE or Angiotensin II Receptor
What inhibits renin secretion in RAAS?
1) Increased NaCl in macula densa
2) Increased pressure/stretch in renal afferent arteriole
3) Beta-1 blockade
4) Angiotensin II Type I Receptor on juxtaglomerular cells by angiotensin II
What does Angiotensin II Receptor Type 1 do?
- Stimulates secretion of aldosterone by zona glomerulosa
- Stimulates vascular smooth muscle cell and myocyte growth
- Inhibits renin secretion
What does Angiotensin II Receptor Type 2 do?
- Vasodilation
- Sodium excretion
- Inhibition of cell growth and matrix formulation
What does aldosterone do in RAAS?
- stimulates amiloride sensitive epithelial sodium channels (ENaC) on apical side of principle cells in renal cortical collecting duct to increase Na reabsorption
- binds to mineralocorticoid receptors
- – cardiac fibrosis
- – nephrosclerosis
- – left ventricular hypertrophy
- – vascular inflammation and remodelling
Complications of Hypertension in the Heart?
- LVH and heart failure
- coronary and microvascular disease
- cardiac arrythmias
Complications of Hypertension in the brain?
Elevated BP is the STRONGEST risk factor for stroke (as per Harrisons)
Associated with late life cognitive decline
Complications of Hypertension in the kidney?
1) Hypertension is a RF for kidney injury and ESRF
- systolic BP more strongly associated
- black men more at risk
2) Atherosclerotic hypertension related vascular damage in pre-glomerular arterioles
- and damage to glomerular capillaries secondary to hyperfiltration
- and loss of autoregulation of renal blood flow and GFR
3) Macroalbuminuria (random urine Alb:Cr > 300) or microalbuminuria (random urine Alb:Cr 30 - 300)
4) Proteinuria: micro 50-500mg/day, macro >500mg/day
Complications of Hypertension in the peripheral arteries?
Peripheral artery disease
- ABI <0.90 = PAD associated with 50% stenosis
- ABI <0.80 = assoc with hypertension
Secondary Causes of Hypertension:
Renovascular hypertension - how to diagnose/screen
Scren renal blood flow with DTPA scan before and after captopril
Doppler ultrasound
Confirm with angiography
Secondary Causes of Hypertension:
Primary aldosteronism - how to diagnose/screen
Ensure potassium replete!!!
Screen with plasma aldosterone: renin ratio
(ratio >30:1 has 90% sens+spec)
Needs to be done OFF:
- aldosterone antagonists (increase renin and may increase aldosterone)
- ACEi and ARBs (increase renin)
Confirm on FAILURE to suppress aldosterone <150 after 2L isotonic saline over 4 hours
Secondary Causes of Hypertension:
Cushings - how to screen
24hour urine free cortisol
overnight dexamethasone suppression test
late night salivary cortisol
Secondary Causes of Hypertension:
Pheochromocytoma - how to screen
24hr urinary metanephrines or plasma fractionated free metanephrines
Secondary Causes of Hypertension?
Renovascular hypertension
Primary aldosteronism
Cushings Syndrome
Pheochromocytoma
Obstructive Sleep apnoea
Coarctation of aorta
Renin secreting tumours
Polycystic kindey disease
Hyperthyroidism
Hypothyroidism causes DIASTOLIC HTN
Hypercalcaemia
Monogenic forms
What is glucocorticoid remediable hyperaldosteronism?
Causes secondary hypertension
Autosomal dominant
11beta hydroxylase/aldosterone gene on Ch8
What is 17alpha hydroxylase deficiency?
Causes secondary hypertension
Autosomal recessive
Mutation on CYP17 on Ch10
In males: pseudohermaphroditism
In females: primary amenorrhoea and absent sex characteristics
What is 11beta hydroxylase deficiency?
Causes secondary hypertension
Which hypertensive syndrome is associated with pregnancy?
Autosomal dominant missense mutation with substitution of leucine for serine at codon 10
At which alcohol consumption levels do you increase risk for hypertension?
> =2 SD/day in males
>=1 SD/day in females
When do you treat hypertension?
If patients with <10% 5-yr CVD risk: if BP>=160/100
If patients with 10-15% 5yr CVD risk: if SBP>=140 or DSP>=90
Then aim for BP <140/90
If patients >15% 5yr CVD risk: aim for SBP <=120
Effect on kidney function from the SPRINT Study?
SPRINT compared intensive (SBP <120) vs standard (SBP <140) in HIGH RISK >50yr old patients with BPs 130-180mmHg and risk >15% of 5yr CVD.
Increased AKI
Effect on hypotension from the SPRINT Study?
SPRINT compared intensive (SBP <120) vs standard (SBP <140) in HIGH RISK >50yr old patients with BPs 130-180mmHg and risk >15% of 5yr CVD.
Increased ED presentations for hypotension
DID NOT change postural hypotension
Effect on falls/syncope from the SPRINT Study?
SPRINT compared intensive (SBP <120) vs standard (SBP <140) in HIGH RISK >50yr old patients with BPs 130-180mmHg and risk >15% of 5yr CVD.
Increased ED presentations for syncope
DID NOT increase injurious falls
Treatment approach to hypertension?
Start either thiazide, beta blocker, ACEi/ARB, CCB
If target not reached at 3 months, start 2nd agent
If target not reached at 6 months, add 3rd agent
Comparing antihypertensives…which is better to prevent stroke or all-cause mortality from CCB or BB?
CCB is better than beta blocker
Comparing antihypertensives…which is better to prevent heart failure from diuretic vs BB?
Diuretics
Comparing hypertensives….which is better to prevent MI from ACEi or BB?
ACEi is better to prevent MI
What are the NICE guidelines for treatment of hypertension?
STAGE 1:
BP>140/90 and subsequent ABPM average >=135/85
–> if <55yrs give ACEi
–> if African American or >55yrs give CCB
STAGE 2:
BP>160/100 and ABPM average >150/95
–>give both ACEi and CCB
STAGE 3:
SBP>180 or DBP>110
–> give ACEi, CCB and Thiazide
Then add spironolactone
What is the pathology of malignant hypertension?
Associated with diffuse necrotising vasculitis, arteriolar thrombi and fibrin deposition in arteriolar walls
What are the clinical features of malignant hypertension?
Progressive retinopathy:
- arteriolar spasm
- haemorrhages
- exudates
- papilloedema
Deteriorating renal function with proteinuria
Microangiopathic haemolytic anaemia
Encephalopathy
Treatment of malignant hypertension WITH encephalopathy?
Aim to reduce BP by <25% within minutes-2 hours
OR aim for BP 160/100
Treatment options:
- IV nitroprusside
- labetolol
- nicardipine
Treatment of malignant hypertension WITHOUT encephalopathy
- frequent captopril, clonidine or labetolol
- reduce BP over hours or longer
- aim for <5-15% reduction of BP in every 24 hour period
