15 When the cardiovascular system goes wrong Flashcards
Why can it be difficult for GPs to determine whether you need treatment for hypertension?
You’re nervous when you go to the GP so your blood pressure goes up
What happens as you get older CV system
hypertension increases
What is considered and unhealthy blood pressure
More than 140/90mmHg
What are the two types of hypertension?
- Essentil/idiopathic
- Secondary
What is secondary hypertension?
Hypertension arising from a known medical source - an underlying medical condition
What is idiopathic hypertension
Essential
Arises from an unknown medical cause e.g. obesity, lack of exercise, alcohol intake, genetic predisposition
What causes secondary hypertension?
- kidney disease - increase in angiotensin II or expansions of extracellular fluid
- endocrine disorders
- adrenal medulla disease (phaeochromocytoma - excessive adrenalin secretion)
What does angiotensin II do?
narrows vessels by acting on aldosterone production
What does the adrenal gland produce?
Cortex - steroid hormones
medulla -adrenalin
How do we treat hypertension?
Try to reduce CO by:
- Beta blockers
- ACE inhibitors
- Inhibit membrane depolarisation and therefore the CO
- Reduce total periphery resistance
What do beta blockers do and what are they used to treat?
used to treat hypertension:
reduce sympathetic activity, reduce renin, lower renin angiotensin cycle
What to ACE inhibitors do and what are they used to treat?
Angiotensin converting enzyme inhibitors: decrease angiotensin II effect on aldosterone production inhibit vasoconstriction (by angiotensin II)
How is total periphery resistance reduced?
inhibiting the action of noradrenaline
What can hypertension increase the risk of?
Stroke Atherosclerosis Renal failure Heart failure Aneurysms
What happens during arteriosclerosis?
Blood vessel walls harden and thicken
loss of elasticity comes naturally with ageing
clinically significant if caused by atherosclerosis
What happens in atheroscleosis?
- damage to endothelium
- Fatty plagues (atheromas) form under epithelial layer
- turbulent blood flow slows flow causing clots formation
- vessel lumen narrows
- arterial remodelling and subsequent expansion of neovessels can lead to aneurysms formation and rupture
- fragments of plaques become lodged and stuck in vessel causing thrombosis
Treatments of atherosclerosis:
- Change the levels of lipids in the body
- Statins decrease cholesterol synthesis an reduce LDLs
- Bile acid binding resins reduce LDLs
- Fibrates lower LDLs and increase HDLs
Ischaemic heart disease
Also known as coronary artery disease
- blockade of coronary vessels causes insufficient blood supply to the myocardium
- causes cell death
- causes angina pectoris (lactate molecules released in cell death bind to nociceptors (responsible for sensation of pain)
- tissue death can start within 20 minutes
- most common in left ventricle and anterior ventricular artery
Treatments for ischaemic heart disease:
Balloon angioplasty and stenting - restructure damaged vessels
Ca channel blockers - increases vasodilation
Organic nitrates - increase vasodilation
Beta-adrenoceptor antagonists -reduce CO
What ate the two types of valve defects?
Regurgitation
Stenosis
What happens in regurgitation (valve defect)
The valves don’t close properly causing back flow of blood, turbulence and decreased CO
What happens in stenosis?
-inadequate opening of the valves obstructs flow
caused by thickening of the valve, papillary muscles or chordae tendinae following disease
-In rheumatic fever white blood cells continue attacking the tissues after infection and cause cumulative damage after 20 yrs.
-severe occlusion can cause left atria hypertrophy (enlargement of cells) which puts more pressure on the right atrium and and pulmonary circulation
this can cause increased CHP and so pulmonary oedema and left ventricular hypertrophy
–> failiure
Types of arrhythmia
- tachycardia
- bradychardia
What is arrhythmia and what does it arise from?
Deviations from the normal beating of the heart caused by disruptions in the flow of blood due to changes in electrical conditions.
-arise from abnormal electrical conductions (myogenic tissues?)
What do arrhythmias cause?
Not many problems associated with arrhythmias but sustained can cause dizziness and palpitations
What is bradycardia? and how does it arise?
HR under 60 bpm (untrained individual)
- Slowed impulse form the SAN (sinus bradycardia)
- Pause in normal SAN activity (sinus arrest)
- Tissue damage from injury which blocks electrical impulses from the SAN (from car crashes where sternum hits the steering wheel)
What are the treatments for bradycardia?
pacemaker
What is tachycardia and what are the different types?
-sinus
-non sinus
HR above 100 bpm
What are the causes of sinus tachycardia?
- overexposure to caffein, amphetamines
- overactive thyroid glands
What happens in sinus tachycardia?
SAN beating faster than it should
How do you treat sinus tachycardia?
Beta blockers
Ca channel blockers
What is non sinus tachycardia?
Abnormal beating of the heart caused by a problem in the conduction pathway or with muscle cells (not SAN)
With regard to non sinus tachycardia, what is ventricular fibrillation and what causes it?
chaotic contractions within the ventricles caused by:
- congenital heart disease
- electrocution accidents or heart injury
- heart surgery
- ischaemia
What causes non sinus tachycardia?
- triggered beats
- automaticity
- re-entry (circus movement?)
- ventricular fibrillation
With regard to non sinus tachycardia, what is automaticity and what causes it?
when the heart muscle cells contract on their own, ectopically.
-automaticity is increased by a
SNS and hypoxia
With regard to non sinus tachycardia, what is triggered beats and what causes it?
- Defects in the ion channels of individual cells cause multiple spontaneous depolarisations leading to arrhythmia
- leads to substained abnormal rhythm so ventricles can become out of sync with atrial filling
- rare but prevalent in youths (Long QT syndrome)
- can be lethal
With regard to non sinus tachycardia, what is re-entry and what causes it?
Electrical impulses travel in small circular circuits rather than down the heart
- caused by conduction block or heart damage
- causes atrial flutter and paroxysmal supraventricular tachycardia which is potentially lethal
What causes chronic heart failure?
caused by damage to cardiac muscle or hypertension or valve defects
What happens in chronic heart failure?
- cardiac output is inadequate despite venous return due to decline in contractility
- can cause oedema in lungs and body tissues due to build up of venous return
- causes breathlessness and fatigue
How do you treat chronic heart failure?
- ACE inhibitors
- AGII blockers
- Aldosterone blockers
