113 - Syncope

Question 1

What is syncope?

Answer 1

A transient loss of consciousness (TLoC)

due to: transient global cerebral hypoperfusion

Characterised by: rapid onset, short duration, spontaneous complete recovery

Question 2

What is pre-syncope?

Answer 2

Nearly syncope

Question 3

What differentials are there for syncope?

Answer 3

Epilepsy, Metabolic disorders, hypoxia, hypoglycaemia, vertebro-basilar TIA, psychogenic?

Question 4

What other names are there for vasovagal syncope?

Answer 4

Reflex syncope

Neuronaly mediated syncope

Question 5

What is vasovagal syncope?

Answer 5

History of syncopy with an absence of cardiac disease

Occurs after standing, noxious stimulus, nausea and vomitting, after exertion, after heat.

Question 6

What is cardiac syncope?

Answer 6

Known history of cardiac disease.
Evidence of structural abnormalities
Chest pain, palpitations
During exercise

Question 7

What investigations could you do in syncope?

Answer 7

History
ECG
Echocardiogram
Tilt test
CXR

Question 8

What is an ECG

Answer 8

Records electrical activity of the heart

Looks at sum total of electrical signals at a moment in time - coming towards the electrode

Question 9

What leads does a 12 lead ECG have?

Answer 9

3 Bipolar limb leads (I, II, III)
3 unipolar augmented lumb leads (aVr, aVl, aVf)
Chest leads (V1-6)

Question 10

Which leads do you get a horizontal view of the heart?

Answer 10

Chest leads V1-6

Question 11

Which leads are prominent if the heart is orientated correctly?

Answer 11

If lead I and II are prominently positive in QRS - probably normal

Question 12

What is occuring at each stage of the ECG wave?

Answer 12

p = atrium depolarising
PR = gap while signal delayed in AV node
QRS = ventricles depolarising
t = ventricles repolarising

Question 13

What is the cardiovascular system?

Answer 13

A convective transport system - driven by pressure difference in systemic system
In cells/microvessels = diffusion transport system

Question 14

How do you measure blood presure?

Answer 14

sphygmomanometry

Question 15

What does the systolic pressure represent?

Answer 15

Ventricles contracting, mitral + tricuspid contract

Question 16

What does diastolic pressure represent?

Answer 16

Atrium contracting, aortic and pulmonary valves shut, aorta relaxes

Question 17

What is the pulse pressure?

Answer 17

The difference between systolic and diastolic pressure

Question 18

How do you calculate mean arterial pressure?

Answer 18

Diastolic + 1/3 pulse pressure

or

Pa = CO x total peripheral resistance

Question 19

What is central venous pressure?

Answer 19

LOW - around 2 mmHg

Question 20

What is darcy’s law?

Answer 20

Flow = pressure change / resistance

Question 21

What is compliance?

Answer 21

Measure of expandability - veins -> high->flexible

Arteries -> low -> stiff

Question 22

Which arteries are elastic? What effect does this have?

Answer 22

Aorta/Large arteries

Windkessel effect - smooths out wave, by storing elastic energy, increasing efficiency

Question 23

Which arteries are conduit arteries? What are their characteristics?

Answer 23

large/medium arteries

Muscle prevents collapse
Less elastin
Smaller tunica media

Question 24

Which vessels are resistance vessels?

Answer 24

Small arteries and arterioles
Muscle tone regulates blood flow
Thick walls compared to lumen

Question 25

Which vessels are exchange vessels?

Answer 25

Capilleries

Question 26

Which vessels are capitance vessels?

Answer 26

Veins

Provide a resevoir of blood
can collapse
60-70% of blood stored in them

Question 27

What are the 3 blood pumps of the body?

Answer 27

Heart
Skeletal muscle pump
Respiratory pump

Question 28

How is blood flow distributed through organs?

Answer 28

By resistance

Question 29

How are the pulmonary and systemic systems arranged?

Answer 29

In series

Question 30

How are organs in the systemic system arranged?

Answer 30

In parallel

Question 31

How is blood pressure regulated in the short term? Where are receptors located?

Answer 31

Baroreceptor reflex:

Baroreceptor -> medulla -> ANS -> SA node

• Atrial stretch receptors
• L ventrical/coronary artery stretch receptor
• Aortic arch baroreceptors
• Carotid sinuses

Question 32

Which nerves nerves take the impusles from the baroreceptors to the ANS?

Answer 32

Vagus nerve

Glossopharangeal nerve

Question 33

What happens when arterial pressure increases in the baroreceptor reflex?

Answer 33

Increase impulses, Increase stimulation, Increase PARASYMPATHETIC NS -> decrease HR at SA node and vasodilate

Question 34

What happens when arterial pressure decreases in the baroreceptor reflex?

Answer 34

Reduce impulses, reduce stimulation, increase SYMPATHETIC, increase HR, contractibility + vasoconstriction

Question 35

What are the long term ways BP is regulated?

Answer 35

Osmoregulation
Pressure Natriuresis
Renin-Angiotensin-Aldesterone