Introducing how the cardiovascular system fails Flashcards
What is a stroke?
Rapid loss of brain function due to loss of perfusion to parts of the brain
Give another name for a stroke
Cerebrovascular accident
List the two types of stroke
Ischemic
Haemorrhagic
Define an ischemic stroke
Cerebral blood vessels become blocked
Define haemorrhagic stroke
Cerebral blood vessels rupture
List some stresses which may cause a blood vessel to burst
High blood pressure
High wall tension/Large diameter
Low elasticity
Turbulent flow
List some damages which may cause blood vessels to burst
Diabetes
Trauma eg. PCI
Atherosclerosis
Define aneurysm
A pathological, localized, blood-filled balloon-like bulge in the wall of a blood vessel
Define ruptured aneurysm
When the aneurysm bursts and blood leaks out
What is tension in a cylinder?
The force tangential to the circumference of the cross section that is trying to rip the wall apart
What is the wall tension like in a larger vessel?
Greater
Give the equation for wall tension in a cylinder
Wall tension = pressure x radius
What is compliance?
The change in volume caused by a change in pressure
Stretchiness
What happens if there is low compliance
A change in pressure results in a very little change in volume
What reduces arterial blood pressure?
Age
Disease
Build up of connective tissue
Atherosclerosis
Do veins or arteries have more compliance?
Veins
Describe the two characteristics of laminar flow
All molecules travel in the same direction
Slower speed at the edges
Describe the causes of turbulent flow
When the low viscosity molecules flow at high speeds in random directions passing junctions and mixing
List the activities of the endothelium
Angiogenesis Haemostasis White cell recruitment Hormone trafficking Blood vessel tone Fluid filtration
Describe the symptoms of acute myocardial infarction
Extremely painful chest pain
However some women present atypically where there is an absence of chest pain but they experience jaw, back, neck or head pain followed by symptoms of nausea, cough, dyspnoea or weakness
When can an AMI become fatal?
When it leads to arrhythmia or heart failure after many AMIs
What does an AMI cause?
Reduced capacity of the heart to pump
Give the symptoms of atherosclerosis
Asymptomatic however causes other diseases which possess symptoms
List the main causes of atherosclerosis
Immune action
Hyperlipidemia
Unknown aetiology
What is coronary artery disease?
Narrowing/obstruction of the arteries supplying the heart
Give the 2 causes of CAD
Atherosclerosis
Coronary vasospasm
What is a plaque rupture?
When a fibrous plaque bursts open
How safe are atheromas?
Quite safe even if they occlude 50% of the vessel.
What happens if a plaque rupture occurs in a coronary artery, thrombus or embolism?
A myocardial infarction occurs
Describe the ways the sympathetic nervous system responds to an MI
Release of noradrenaline and adrenaline in response to haemodynamic abnormalities and pain
Describe the ways the sympathetic nervous system responds to heart failure
Increase heart rate
Increase contractility
Increase peripheral resistance
Increased risk of arrhythmia
Give the equation for net pressure
Net pressure = hydrostatic pressure + osmotic pressure
What is pulmonary oedema and explain its cause?
Fluid accumulation in the lungs caused by left heart failure. Damming of the blood leads to increase in hydrostatic pressure in pulmonary circulation
List the symptoms of pulmonary oedema
Dyspnoea
Orthopnoea
Hypoxia
What is ascites?
The accumulation of fluids in the peritoneal canal
What is the main cause of ascites?
Heart failure
What is peripheral oedema?
The swelling of tissues especially in the ankles
State the main cause of peripheral oedema
Chronic low output heart failure
What is compensation?
Maintaining homeostasis of a physiological function despite stressors/malfunctions. Happens via endogenous physiological feedback using starling’s law
What is decompensation?
A medical emergency where the heart fails to maintain adequate circulation after long standing previously compensated vascular disease
Describe cardiac remodelling
The growth of cardiac muscle leading to changes in shape, size and function caused by injury such as MI, hypertension or valve disease. The result is hypertrophy or dilation. May become pathological
Name the treatments that inhibit cardiac remodelling
ACE inhibitors
Spironolactone
Name the two types of ventricular hypertrophy
Eccentric
Concentric
Describe eccentric ventricular hypertrophy
Dilation due to volume overload
Describe concentric ventricular hypertrophy
Thicken due to pressure overload
What does ADH do?
Decreases diuresis (loss of water as urine) Causes kidneys to reabsorb more water
Where is ADH released from?
Posterior pituitary gland
What does aldosterone do?
Increases the reabsorption of NaCl in the kidneys thus decreases diuresis
Where is aldosterone released from?
The adrenal cortex
What effect does decreased diuresis have on blood pressure?
Increases blood pressure
What do diuretic drugs do?
Antagonise the hormones ADH and aldosterone leading to fluid loss and an increase in blood pressure
What does angiotensin 2 do?
Increases blood pressure by stimulating the release of ADH and Aldosterone, causes vasoconstriction and hypertrophy and cardiac remodelling
Describe the sequence of the renin-angiotensin- aldosterone system
Angiotensinogen- renin enzyme- angiotensin I- ACE enzyme- Angiotensin II- aldosterone
What do thiazide and thiazide like diuretics do?
Block reabsorption at the DCT
Give an example of a thiazide and thiazide like diuretic
Indapamide
What do loop diuretics do?
Block reabsorption at the loop of henle
Give an example of a loop diuretic
Furosemide
What do K+sparing diuretics do?
Inhibit aldosterone receptors at the cortical collecting duct
Give an example of a K+ sparing diuretic
Spironolactone
Define heart failure
The cardiac output does not meet the needs of the lungs and body
Describe chronic low output heart failure
There is a low cardiac output usually due to accumulated heart damage
Chronic condition with poor 5 year survival rate
Describe decompensated heart failure and how the body responds.
Medical emergency which can lead to death if not treated.
Kidney increases plasma volume to compensate for poor perfusion and leads to fluid overload. The heart is unable to pump the extra fluid so fluid damming leads to increased venous hydrostatic pressures. Increased back pressure further damages the heart. Capillaries become leaky and gas exchange can not occur
What symptoms are present in left heart failure and why?
Respiratory symptoms
Right heart pumps into lungs but left atrium is too full therefore there is an increased hydrostatic pressure in pulmonary circulation
Describe congestive heart failure
The pulmonary vasculature becomes congested and in extreme cases the lungs fill with fluid from blood vessels
Describe right heart failure
This causes systemic symptoms. Increase in central venous pressure causes peripheral oedema and ascites
How does the body respond to heart failure?
Loss of cardiac output stimulates sympathetic nervous system to compensate by increasing heart rate and peripheral resistance
List the symptoms of heart failure
Oedema
Fatigue
Dyspnoea- orthopnoea and paroxysmal nocturnal dyspnoea
Define in terms of blood pressure cardiogenic shock
Systolic blood pressure less than 90 mmHg
How does cardiogenic shock progress?
Positive feedback
Describe the treatment for shock
Aggressive IV fluid and oxygen while monitoring airways
List 3 chronic heart failure treatments
ACE inhibitors
Diuretics
Beta blockers
Describe the homeostatic mechanisms for low cardiac output
Increase sympathetic activity- increase HR, increase heart contractility and vasoconstriction
Kidneys accumulate fluid- Decrease glomerular filtrate rate, increase venous return and preload and increase central venous pressure
List the low output heart failure treatment goals
Prevent acute decompensated heart failure
Counteract cardiac remodelling
Minimize symptoms
