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EDAIC PART II > Physiology (CVS) > Flashcards

Physiology (CVS) Flashcards

1
Q

What are the factors affecting myocardial oxygen supply?

A
  • Coronary blood flow
  • Arterial oxygen content
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2
Q

What are the factors affecting coronary blood flow?

A
  • Coronary perfusion pressure
  • Coronary patency
  • Coronary diameter
  • Blood viscosity
  • HR
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3
Q

Factors affecting coronary diameter?

A
  • Autoregulation
  • local metabolites & arterial gas tension
  • Drugs
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4
Q

Factors affecting arterial oxygen content ?

A
  • Hb concentration
  • Arterial oxygen content
  • Oxygen saturation
  • Presence of abnormal Hb
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5
Q

Factors affecting myocardial oxygen demand ?

A
  • Contractility
  • Tissue mass (Increased with hypertrophy)
  • Temperature
  • Afterload
  • HR
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6
Q

How can you measure coronary blood flow and cardiac output ? (Invasive)

A
  • Fick’s principle
  • Coronary angiography
  • Thermodilution
  • Transoesophageal echo
  • Trans-thoracic echo
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7
Q

Describe the Fick’s principle?

A
  • It can be used to measure flow in all organs
  • It states that substance taken by an organ is equal to blood flow to that organ and the arterio-venous difference of the substance
  • Argon & oxygen can be used
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8
Q

What is the equation for coronary blood flow?

A

Coronary blood flow = Uptake of substance arterial - venous difference

CO = VO2 / PaO2 - PvO2

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9
Q

What is the doppler effect?

A

Changed in the frequency of sound if their transmitter or receiver is moving.

It can be used to measure cardiac output by knowing the cross-sectional area of the aortic arch

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10
Q

What are the different types of action potentials ?

A
  • Cardiac AP
  • Pacemaker AP
  • Peripheral nerves AP
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11
Q

Draw a diagram of the cardiac muscle AP?

A

See diagram

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12
Q

Describe the phases of cardiac muscle AP?

A

Phase (0)
- Rapid depolarization after TP reached
- Sodium influx
- Vertical gradient

Phase (1)
- Re-polarization
- Sodium channels closing
- Potassium channels opening
- Short phase

Phase (2)
- Plateau phase
- Opening of L-type Calcium channels
- Depolarization maintained
- No further depolarization if possible
- This is the absolute refractory period
- Repolarization is slowed but not stopped

Phase (3)
- L-type calcium channels close
- Potassium efflux & repolarization occurs
- Relative refractory period

Phase (4)
- Na/K pump restores ionic gradients
- 3Na out & 2K into the cell

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13
Q

Why is tetany not possible in myocardial muscles?

A
  • Phase (2) of cardiac muscle AP
  • Opening of L-type calcium channels
  • Off-set of the effect of potassium
  • No further depolarization is possible
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14
Q

When does the relative refractory period occur in cardiac muscles?

A

During phase 3 & 4

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15
Q

Phase of pacemaker AP?

A

Phase (0)
- TP achieved at -40mV
- Open L-type Ca channels + Depolarization
- Slow calcium influx

Phase (3)
- Repolarization + Closing of Ca channels
- Opening of Potassium channels + Efflux

Phase (4)
- Hyperpolarization
- Drift towards threshold potential (TP)
- Sodium leak
- Opening T-type Ca channels
- Activation of Na/Ca pumps

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16
Q

Factors affecting phase (4) of pacemaker AP?

A
  • Sympathetic stimulation - Increased gradient
  • Parasympathetic stimulus - Decreased gradient
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17
Q

Phases of nerve action potential ?

A

Phase (1)
- Crosses the y-axis at -70mV
- Reaches threshold potential at -55mV

Phase (2)
- Rapid rise of membrane potential to +30mV
- Opening of voltage-gated Na channels + influx of Na

Phase (3)
- Rapid repolarization + closure of Na channels
- Potassium channels open + efflux

Phase (4)
- Hyperpolarization
- Na/k pumps restore ionic balance

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18
Q

Review the diagram of all the combined action potentials

A

See image

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19
Q

Draw of graph of the cardiac cycle superimposed on the ECG

A

See attached image

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20
Q

What is the value of normal CVP?

A

5-10 mmHg

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21
Q

Components of CVP trace?

A

C-wave:
- Isovolumetric contraction
- Bulging of tricuspid valve to the RV

Y-wave:
- Occurs after isovolumetric relaxation
- Tricuspid valve opens

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22
Q

What is the explationation for dicrotic notch on ECG?

A
  • IVR
  • Closure of the aortic valve
  • Back flow of blood just before aortic closure
  • Bulging of the sinus of valsalva
23
Q

What do the heart sounds signify?

A

HS1
- Closure of mitral & tricuspid valves
- Occurs at the beginning of systole
- Matches IVC

HS2
- Closure of aortic and pulmonary valves
- Occurs at the start of diastole
- Matches IVR

24
Q

Cardiac cycle sequence?

A

Start of IVC:
- Depolarization + Contraction
- LV pressure rises above CVP
- Mitral valve closes (S1)

End of IVC:
- LV pressure rises above aortic pressure
- :Aortic valve opens

Start of IVR:
- LV pressure falls below aortic pressure
- Aortic valve closes (S2)

End of IVR:
- LV pressure falls below CVP
- Mitral valve opens
- Ventricular filling occurs

25
Q

LV pressure wave form and ECG?

A

Image attached

26
Q

What are the typical values on an LA pressure wave form?

A

a-wave = 4-16 mmHg
v-wave = 6-21 mmHg
MAP = 2-12 mmHg

27
Q

Define the pressure waves on LAP wave form?

A

A-wave
- Atrial systole

C-wave
- Coincides with ventricular contraction
- Caused by AV valve bulging into the atrium

V-wave
- Pressure build up due to venous return
- AV valve open

X-descent
- Decline in pressure between C & V waves
- Pulling down of the atrium + RV contraction

Y-wave
- Decline in atrial pressure as AV valve open

28
Q

Causes of prominent C & V wave on LAP wave form?

A
  • Incompetent AV valves
  • X-wave is abolished
29
Q

Draw the frank-sterling relationship?

A

The strength of cardiac muscle contraction is dependent on initial length

30
Q

What is ANP?

A
  • Brain natriuretic peptide
  • Cytokines natriuretic peptide
31
Q

Characteristic of ANP?

A
  • Produced by cardiac myocytes atrial wall
  • Triggered by increased volume & stretch
  • Increases Sodium excretion
  • Inhibits Na reabsorption from collecting duct
  • Induced diuresis & decrease ECV
  • Caused arterial vasodilation
32
Q

What is BNP?

A
  • Brain natriuretic peptide
  • Located in the brain ventricle
  • Secreted in response to increased ECF
  • It is usually 20% of the value of ANP
  • Elevated in CCF - > ANP
33
Q

What is the formula for SVR ?

A

SVR = MAP - MRAP / CO x 80

MAP = Mean arterial pressure
MRAP = Mean right arterial pressure
CO = Cardiac output

34
Q

What is the formula for PVR?

A

PVR = MPAP - PCWP / CO x 80

MPAP = Mean pulmonary arterial pressure
PCWP = Pulmonary capillary wedge pressure
CO = Cardiac output

35
Q

What is the normal PVR & SVR value ?

A

PVR = 50-150 dyne/sec/cm-5
SVR = 700-1500 dyne/sec/cm-5

36
Q

What is the normal value for EDV (End diastolic volume)?

A

120mls

37
Q

What is the normal value for diastolic aortic pressure?

A

80 mmHg

38
Q

What is the normal SV?

A

70 mls

39
Q

Draw a cardiac pressure volume loop?

A

See attached image
both vertical lines represents IVC & IVR

40
Q

Calculate work of ventricle?

A

work = pressure x volume

41
Q

What is the formula for calculating ejection fraction ?

A

EF = EDV - ESV / EDV x 100

EDV - ESV = SV

42
Q

Demonstrate the effect of increased pre-load by diagram?

A
  • Increasing preload increases SV
43
Q

Demonstrate the effect of increased after-load by diagram?

A

See image

44
Q

Demonstrate CCF on a pressure volume loop?

A

See image attached

45
Q

Factors affecting the pressure volume loop and thus diastolic function/

A
  • Compliance
  • Distensibility
  • Relaxation
46
Q

Describe the valsalva manoeuvre ?

A

Blowing against a closed glottis for 10s

47
Q

Describe the phases of valsalva manoeuvre?

A

Phase (1)
Onset & short in duration
Increased thoracoabdominal pressure
Increased venous return
Increased BP & decreased HR

Phase (2)
Continues until the end of manoeuvre
Sustained rise in intrathoracic pressure
Reduced venous return
Fall in SBP + Cmpensatory tachycardia

Phase (3)
Begins as soon as manoeuvre is completed
Release of pressure
Large venous return vaccum
Fall in BP + Sustained tachycardia

Phase (4)
Continues until restoration normal values
Tarchycardia + Restoration of BP / VR
Reflex bradycardia occurs

48
Q

What are the innervation of the receptors of the valsalva manoeuvre?

A

Aortic arch baroreceptor - Vagus nerves
Carotid baroreceptors - Glossopharyngeal

49
Q

Response to sudden drop in BP?

A
  • Baroreceptor reflex activation
  • Redistribution of cardiac output
  • Activation of renin-angiotensin aldosteron
  • Increased ADH secretion
50
Q

What are starling forces?

A
  • Movement of fluid into the IV compartment
  • Decreased hydrostatic pressure
  • Increased oncotic pressures
51
Q

What is the Bain Bridge reflex ?

A

Atrial baroreceptor activation in response to hypovolaemia

52
Q

Sensitivity and specificity of the cardiac stress test ?

A

Specificity = 90%
Sensitivity = 65%

53
Q

What are the factors associated with severe cardiac disease?

A
  • Early ST-segment depression > 2mm
  • ST-depression > 5mins
  • Decreased BP > 10% of baseline
  • Failure to increase HR > 70% of baseline
  • Ventricular arrhythmias

EDAIC PART II (15 decks)

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