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Cardiovascular Biology 311 > Lecture 2: Cardiac and Vascular Function: > Flashcards

Lecture 2: Cardiac and Vascular Function: Flashcards

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1
Q

Wiggers Diagram

A

Learn

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2
Q

What happens to ventricular volume at the VE/IVR time period and why?

A

Ventricular volume becomes negative as their is negative flow (backwards) because E aorta is less than E ventricle. (some back flow)

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3
Q

How can the phases filling and ejection be divided in the wiggers diagram?

A

Into rapid and reduced time periods.

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4
Q

What does an echocardiogram show in terms of ventricular wall thickness during the cardiac cycle?

A

Ventricular wall thickness varies between systole and diastole.

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5
Q

What sort of motion do the atrioventricular valves reform during ejection?

A

A ripple like effect as blood is ejected.

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6
Q

What is the general difference between left and right ventricles in terms of pressures and valve sequences?

A

Pressure is lower in the right ventricle therefore timing is slightly different.

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7
Q

What does the RV pump blood through?

A

The low resistance lungs

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8
Q

What does the LV pump blood through?

A

The entire system circuit

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9
Q

Describe the timing of the mitral and tricuspid valves

A

The tricuspid valve opens before the mitral

The mitral valve closes just before the mitral valve

i.e LV has less filling time

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10
Q

Describe the timing of the aortic and pulmonary valve

A

The pulmonary valve opens before the aortic valve

Aortic closes before the pulmonary valve

i.e LV has less ejection time

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11
Q

Why do the AV and semilunar valves have different timings between the left and right sides of the heart?

A

RV valves open sooner and close later because:

  • Differences in electrical activation and pressures (takes less time to generate pressure in the RV.)
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12
Q

Describe the pressure of the RA

A

~3mmHg

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13
Q

Describe RV pressures

A

(s) 18mmHg

d) 0mmHg (i.v.r

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14
Q

Describe PA pressures

A

(s) 18mmHg

(d) 12mmHg

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15
Q

Describe PA wedge pressures (cap)

A

8mmHg average

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16
Q

Describe LA pressures

A

8 mmHg average

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17
Q

Describe LV pressures

A

(s) 130 mmHg

(d) 0 mmHg

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18
Q

Describe the systemic aortic pressure

A

(s) 130 mmHg

(d) 75 mmHg

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19
Q

Whats the components of CO?

A

CO = HR x SV

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20
Q

What are the determinants of SV?

A
  • Preload
  • Afterload
  • Ionotropy
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21
Q

How does HR affect CO?

A

HR directly influences CO and also indirectly acts via the determinants of SV particularly preload and inotropic state.

22
Q

Describe the main factors of CO;

A

CO = SV x HR

SV = EDV - ESV

EDV influenced by Preload
ESV influenced by Afterload and Inotropic state

HR influences preload and Inotropic state

23
Q

How does HR influence preload?

A

Reduced preload by reducing the time of ventricular filling therefore redoing SV

24
Q

How does HR influence inotropic star?

A

HR relates to the force frequency relationship that plays a minor role in ionotropy.

25
Q

What are the relaxants graphs for ventricular performance?

A 
PV loop
Ejection Fraction
Peak dP/dT
Ventricular function curve
CO/VR MRAP curve a.k.a guyton VP graph
26
Q

What does the linear line on the P-V graph represent?

A

Potential pressure of the chamber

This is never achieved as the valves open once threshold pressure is reached

27
Q

Potential pressure increases linearly with and represents what relationship?

A

EDV

This clearly reflects the force-sarcomere length relationship.

28
Q

When is the length tension relationship for sarcomeres exhibited?

A

During isometric or fixed length muscle contraction

29
Q

Why can sarcomeres generate varying levels of tension at a fixed resting length?

A

Inotropic state accounts for this and means that sarcomeres can generate more force from an unchanged resting length

30
Q

What can be obtained from a P-V loop?

A

The ventricular work performed each cardiac cycle (stroke work)

SW = SV x TPR (P xV)

31
Q

What are the four determinants of cardiac performance?

A

Preload
Afterload
Inotropic state
Chronotropic state

32
Q

What is preload?

A

The tension produced by the degree of stretch of myocyte filaments

  • L-T relationship
  • Length dependant activation
    (a) - Increased stretch increases troponin C sensitivity to Ca
    (b) - Increased stretch increases the activation of stretch sensitive Ca channels
33
Q

What is Afterload?

A

The pressure of which the ventricle must pump against

Increased in hypertension.

34
Q

What is inotropic state?

A

The degree of activation of contractile proteins by Ca in the myocyte sarcomere.

35
Q

What influences ionotropy?

A
  • AP plateau phase (excitation contraction coupling)
  • External ion gradient (NCX and Na/K ATP ase transporters)
  • Force frequency relationship
  • ANS
  • Drugs
    \ Caffiene, inhibits PDE prevents cAMP breakdown
    \ Digoxin, cardiac glycoside inhibits Na/K ATPase, NCX reverses
    \ Verapamil, Ca channel inhibitor
  • Heart failure
36
Q

How does chonrotropic state influence CO?

A
  • HR increases, CO increases
  • Force frequency relationship
  • High HR reduces SV, decreasing CO
37
Q

What does the equilibrium between CO and VR represent on the venous return/ CO curve?

A

This is the steady state equilibrium at which the heart works with some transient deviations.

The MRAP at this point = mean systemic filling pressure

38
Q

What are normal values for Ejection Fraction?

A 
Rest = ~50%
Exercise = ~85%
39
Q

What are the two types of ventricular function curves?

A

Stroke volume vs preload

Stroke Work vs preload

40
Q

Why is stroke volume vs preload not used?

A

Stroke volume is difficult to measure and not independent of afterload

41
Q

Why is stroke work vs preload good?

A

Not susceptible to changes in after load

If MAP increases, SV decreases keeping SW constant.

42
Q

What does a ventricular function curve represent?

A

Summery of the P-V and frank-starling relations

43
Q

A family of curves on the ventricular function curve represents?

A

Different inotropic states

44
Q

What does a ventricular function curve account for?

A

Preload
After load
Inotropic state

45
Q

Describe how LA pressure is obtained?

A

A fluid filled catheter with a ballon tip is passed through the femoral vein via the heart into the PA. Ballon inflates and measures the pre-capillary pressure which is representative of the LA pressure mostly…

This can measure both pulmonary artery pressure and pulmonary wedge pressure.

46
Q

What are two methods of CO measurement?

A

Ficks Method

Thermodilution

47
Q

What is Ficks method?

A

Based on conservation of mass.

Using a known quantity of bolus i.e O2 injected prior to the heart and over time the concentration is measured down stream. The rate of dilution is representative of CO

48
Q

What are the prerequisite of ficks method?

A

1) Mixed venous blood (whole body average of O2 concentration
2) All the measured substance must be collected, none lost
3) Steady state must exist, Ventilation and CO

49
Q

What is thermodilution?

A

Using this indicator dilution technique.

  • Cold saline is used as indicator
  • Measured downstream temperature change to indicate the rate of dilution and thus CO
50
Q

What are the advantages of thermodilution?

A
  • No arterial puncture needed
  • No toxicity
  • Recirculation is negligible / ignored
51
Q

Check 205 notes

A

Now

Cardiovascular Biology 311 (18 decks)

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