113 - Syncope Flashcards
What is syncope?
A transient loss of consciousness (TLoC)
due to: transient global cerebral hypoperfusion
Characterised by: rapid onset, short duration, spontaneous complete recovery
What is pre-syncope?
Nearly syncope
What differentials are there for syncope?
Epilepsy, Metabolic disorders, hypoxia, hypoglycaemia, vertebro-basilar TIA, psychogenic?
What other names are there for vasovagal syncope?
Reflex syncope
Neuronaly mediated syncope
What is vasovagal syncope?
History of syncopy with an absence of cardiac disease
Occurs after standing, noxious stimulus, nausea and vomitting, after exertion, after heat.
What is cardiac syncope?
Known history of cardiac disease.
Evidence of structural abnormalities
Chest pain, palpitations
During exercise
What investigations could you do in syncope?
History ECG Echocardiogram Tilt test CXR
What is an ECG
Records electrical activity of the heart
Looks at sum total of electrical signals at a moment in time - coming towards the electrode
What leads does a 12 lead ECG have?
3 Bipolar limb leads (I, II, III)
3 unipolar augmented lumb leads (aVr, aVl, aVf)
Chest leads (V1-6)
Which leads do you get a horizontal view of the heart?
Chest leads V1-6
Which leads are prominent if the heart is orientated correctly?
If lead I and II are prominently positive in QRS - probably normal
What is occuring at each stage of the ECG wave?
p = atrium depolarising PR = gap while signal delayed in AV node QRS = ventricles depolarising t = ventricles repolarising
What is the cardiovascular system?
A convective transport system - driven by pressure difference in systemic system
In cells/microvessels = diffusion transport system
How do you measure blood presure?
sphygmomanometry
What does the systolic pressure represent?
Ventricles contracting, mitral + tricuspid contract
What does diastolic pressure represent?
Atrium contracting, aortic and pulmonary valves shut, aorta relaxes
What is the pulse pressure?
The difference between systolic and diastolic pressure
How do you calculate mean arterial pressure?
Diastolic + 1/3 pulse pressure
or
Pa = CO x total peripheral resistance
What is central venous pressure?
LOW - around 2 mmHg
What is darcy’s law?
Flow = pressure change / resistance
What is compliance?
Measure of expandability - veins -> high->flexible
Arteries -> low -> stiff
Which arteries are elastic? What effect does this have?
Aorta/Large arteries
Windkessel effect - smooths out wave, by storing elastic energy, increasing efficiency
Which arteries are conduit arteries? What are their characteristics?
large/medium arteries
Muscle prevents collapse
Less elastin
Smaller tunica media
Which vessels are resistance vessels?
Small arteries and arterioles
Muscle tone regulates blood flow
Thick walls compared to lumen
Which vessels are exchange vessels?
Capilleries
Which vessels are capitance vessels?
Veins
Provide a resevoir of blood
can collapse
60-70% of blood stored in them
What are the 3 blood pumps of the body?
Heart
Skeletal muscle pump
Respiratory pump
How is blood flow distributed through organs?
By resistance
How are the pulmonary and systemic systems arranged?
In series
How are organs in the systemic system arranged?
In parallel
How is blood pressure regulated in the short term? Where are receptors located?
Baroreceptor reflex:
Baroreceptor -> medulla -> ANS -> SA node
- Atrial stretch receptors
- L ventrical/coronary artery stretch receptor
- Aortic arch baroreceptors
- Carotid sinuses
Which nerves nerves take the impusles from the baroreceptors to the ANS?
Vagus nerve
Glossopharangeal nerve
What happens when arterial pressure increases in the baroreceptor reflex?
Increase impulses, Increase stimulation, Increase PARASYMPATHETIC NS -> decrease HR at SA node and vasodilate
What happens when arterial pressure decreases in the baroreceptor reflex?
Reduce impulses, reduce stimulation, increase SYMPATHETIC, increase HR, contractibility + vasoconstriction
What are the long term ways BP is regulated?
Osmoregulation
Pressure Natriuresis
Renin-Angiotensin-Aldesterone
