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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
LV pressure wave form and ECG?
Image attached
26
What are the typical values on an LA pressure wave form?
a-wave = 4-16 mmHg v-wave = 6-21 mmHg MAP = 2-12 mmHg
27
Define the pressure waves on LAP wave form?
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
Causes of prominent C & V wave on LAP wave form?
- Incompetent AV valves - X-wave is abolished
29
Draw the frank-sterling relationship?
The strength of cardiac muscle contraction is dependent on initial length
30
What is ANP?
- Brain natriuretic peptide - Cytokines natriuretic peptide
31
Characteristic of ANP?
- 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
What is BNP?
- 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
What is the formula for SVR ?
SVR = MAP - MRAP / CO x 80 MAP = Mean arterial pressure MRAP = Mean right arterial pressure CO = Cardiac output
34
What is the formula for PVR?
PVR = MPAP - PCWP / CO x 80 MPAP = Mean pulmonary arterial pressure PCWP = Pulmonary capillary wedge pressure CO = Cardiac output
35
What is the normal PVR & SVR value ?
PVR = 50-150 dyne/sec/cm-5 SVR = 700-1500 dyne/sec/cm-5
36
What is the normal value for EDV (End diastolic volume)?
120mls
37
What is the normal value for diastolic aortic pressure?
80 mmHg
38
What is the normal SV?
70 mls
39
Draw a cardiac pressure volume loop?
See attached image both vertical lines represents IVC & IVR
40
Calculate work of ventricle?
work = pressure x volume
41
What is the formula for calculating ejection fraction ?
EF = EDV - ESV / EDV x 100 EDV - ESV = SV
42
Demonstrate the effect of increased pre-load by diagram?
- Increasing preload increases SV
43
Demonstrate the effect of increased after-load by diagram?
See image
44
Demonstrate CCF on a pressure volume loop?
See image attached
45
Factors affecting the pressure volume loop and thus diastolic function/
- Compliance - Distensibility - Relaxation
46
Describe the valsalva manoeuvre ?
Blowing against a closed glottis for 10s
47
Describe the phases of valsalva manoeuvre?
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
What are the innervation of the receptors of the valsalva manoeuvre?
Aortic arch baroreceptor - Vagus nerves Carotid baroreceptors - Glossopharyngeal
49
Response to sudden drop in BP?
- Baroreceptor reflex activation - Redistribution of cardiac output - Activation of renin-angiotensin aldosteron - Increased ADH secretion
50
What are starling forces?
- Movement of fluid into the IV compartment - Decreased hydrostatic pressure - Increased oncotic pressures
51
What is the Bain Bridge reflex ?
Atrial baroreceptor activation in response to hypovolaemia
52
Sensitivity and specificity of the cardiac stress test ?
Specificity = 90% Sensitivity = 65%
53
What are the factors associated with severe cardiac disease?
- 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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