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Cardiology > Cardiac Cycle Mechanical and Electrical Events I and II > Flashcards

Cardiac Cycle Mechanical and Electrical Events I and II Flashcards

1
Q

How much of the body’s basal metabolic energy expenditure is used by a healthy CV system?

A

10%

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2
Q

3 reasons appropriate pressure is necessary within a vessel or cardiac chamber.

A
  1. to achieve proper flow rates to different organs/regions
  2. to permit appropriate fluid/solute exchange
  3. to ensure appropriate stress and workload for heart and vessel
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3
Q

How is pressure generally measured?

A

as a difference between two pressures

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4
Q

What is the normal force exerted by a fluid or gas on the wall of the vessel that contains it?

A

pressure

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5
Q

What characterizes the movement of a fluid/gas from one place to another

A

flow

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6
Q

What is the difference between flow rate and flow velocity?

A

flow rate = volume/time (L/min)

flow velocity = distance/time (cm/s)

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7
Q

Total blood flow to the body is _____ cardiac output

A

systemic

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8
Q

Which principle describes the pressure gradient associated with flow velocity and what kind of disorders is it used to understand?

A

bernoulli –> basis of quantifying burdens caused by valave disorders

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9
Q

Which principle describes the chamber wall force/tension associated with chamber cavity pressure dimension and wall thickness and what kind of forces is it used to understand?

A

laplace –> determines wall forces required to pump blood and forces distending chambers and vessels

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10
Q

Per Bernoulli principle, pressure gradient is associated with what order of velocity?

A

v^2

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11
Q

What parameter describes chamber wall tension/stress per the laplace relationship?

A

sigma (= pressure * radius/(2*thickness))

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12
Q

What happens to chamber pressure during systole and why?

A

chamber pressure increases because chamber muscle shortens in order to decrease chamber volume to propel blood to immediately downstream chamber

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13
Q

When does the most of cardiac myocardial activity occur?

A

systole

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14
Q

What happens to chamber pressure during diastole and why?

A

chamber pressure decreases because chamber muscle lengthens in order to increase chamber volume for filling

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15
Q

Does diastole require metabolic activity?

A

yes –> it is an active process –> need energy to release actin/myosin crossbridges (e.g. during infarct can get a heart stuck in systole b/c can’t engage diastole)

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16
Q

T/F systole and diastole occur at the same time in the atria and in the ventricles.

A

F

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17
Q

What does the wiggers diagram demonstrate?

A

pressure waveforms in left heart/right heart/Ao and PA

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18
Q

What are the features of the cardiac cycle: isovolumetric relaxation?

A

12-16 msec between closure of semilunar valves and opening of AV valves –> rapid ventricular pressure decline due to termination of ventricular myocardial active state

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19
Q

What are the features of the cardiac cycle: diastolic filling?

A

150-800 msec between opening and closing of AV valves –> progressive filling of ventricles from atria finished by contribution of atrial contraction

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20
Q

What are the features of the cardiac cycle: isovolumetric contraction?

A

10msec between closure of AV valves and opening of semilunar valves –> rapid ventricular pressure increase due to development of ventricular active state

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21
Q

What are the features of the cardiac cycle: systolic ejection?

A

250-800msec between opening and closing of semilunar valves due to shortening of ventricular muscle

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22
Q

When do atrial and ventricular systole occur in relation to one another?

A

atrial systole occurs first (120-160msec before) and finishes faster (b/c of shorter AP) –> there is a small amount of overlap but generally you want the atrium to be in diastole/filling while the ventricle is in systole/emptying

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23
Q

The duration of atrial systole is longer/shorter than ventricular systole. Why?

A

shorter –> majority of atrial inflow from venous systems occurs during ventricular systole

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24
Q

How is the timing relationship between atrium and ventricle achieved?

A

delay of passage of activation wavefront through the AV node

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25
Q

The ventricles normally cycle between what two pressures?

A

pressure equilibrium with atria and pressure equilibrium with great vessels

26
Q

T/F valves are active flexible structures that move in response to hemodynamic forces

A

F –> passive

27
Q

What energy expenditure occurs during termination of contraction?

A

scavenging of calcium from cytosol by SR –> modulated by phospholamban

28
Q

What is the consequence of relaxation failure during diastole?

A

failure makes cardiac chambers less compliant/stiffer during diastole –> requires elevated systemic and pulmonary venous pressure AKA diastolic heart failure

29
Q

4 components of AV valves

A
  1. valve annulus
  2. valve leaflets
  3. chordae tendinae
  4. papillary muscles
30
Q

4 requirements for proper closure of AV valves

A
  1. passive movements of leaflets toward atria driven by ventricle pressure
  2. contraction of valve annulus
  3. contraction of papillary muscle
  4. appropriate contraction and geometry of ventricle that anchors the papillary muscle
31
Q

Are semilunar valves more or less complex than AV valves?

A

less complex –> passive opening/closing, leaflets don’t need additional support

32
Q

2 requirements for semilunar valve closure

A
  1. appropriate valve annulus diameter

2. appropriate leaflet geometry

33
Q

Closure of semilunar valves is an active/passive process and closure of AV valves is an active/passive process.

A

passive, active

34
Q

2 consequences of valve dysfunction

A

regurgitation (failure to close properly), stenosis (failure to open properly)

35
Q

What pressure difference does the aortic valve ensure during systole and diastole?

A

systole: LV = Ao
diastole: Ao > Lv

36
Q

What pressure difference does the mitral valve ensure during systole and diastole?

A

systole: LV > LA
diastole: LV = LA

37
Q

3 phases of arterial pressure waveform

A
  1. rapid upstroke at onset of ventricular systole –> high velocity ventricular ejection
  2. rounded peak in mid/late systole –> decay of ventricular ejection ends with dicrotic notch due to semilunar valve closure
  3. gradual decay of pressure in diastole –> progressive runoff of blood out of arterial system into peripheral vasculature
38
Q

Difference between peak systolic pressure and end diastolic pressure

A

pulse pressure

39
Q

Positive deflection due to atrial contraction (pressure waveform)

A

A wave –> occurs just before the end of ventricular diastole

40
Q

Positive deflection due to atrial filling (pressure waveform)

A

V wave –> majority of atrial filling occurs during ventricular systole/atrial diastole

41
Q

Negative deflection due to atrial diastolic relaxation (pressure waveform)

A

X descent –> occurs at the onset of ventricular systole

42
Q

Negative deflection due to rapid atrial emptying (pressure waveform)

A

Y descent –> occurs at end of ventricular diastole

43
Q

Early diastolic emptying of atria is passive/active

A

passive

44
Q

Pressure in the left ventricle at the end of ventricular diastole (at onset of ventricular systole)

A

left ventricular end diastolic pressure (LVEDP)

45
Q

What is the principle determinant of ventricular end diastolic dimension?

A

LVEDP

46
Q

Distal large arteries have higher/lower systolic pressure and larger/smaller pulse pressure than those closer to the heart?

A

higher and larger

47
Q

2 functions of systemic arteries

A
  1. conduit

2. cushion cardiac pulsations so that capillary blood flow is continuous rather than pulsatile

48
Q

What is the source of the dicrotic notch

A

pressure wave reflection –> the systemic arterial pressure wave is reflected ~80cm from the the aortic valve and returns to the heart just at the beginning of diastole –> augments ascending aortic pressure during diastole and contributes to dampening of arterial pulsations

49
Q

Why are distal arterial systolic pressures greater than proximal arterial systolic pressures?

A

pressure wave reflections return to distal arteries faster than to the heart so their pressure waveforms are added to the systolic pressure at those points generating taller pressure waveforms vs. they come to the heart after the peak of systolic pressure so they appear as a second wave (Dicrotic notch)

50
Q

What is the effect of age on pulse wave velocity?

A

reduced vascular compliance –> faster pressure wave reflection/higher velocity –> higher arterial pressure at the aortic valve (because the systolic pressure and the reflection wave add together rather than forming a dicrotic notch) –> LV has to match this higher pressure on each systole AKA the reflected wave competes with systolic ejection

51
Q

Peak aortic systolic pressure

A

120

52
Q

Peak pulmonary artery systolic pressure

A

25

53
Q

Mean left atrial pressure

A

12

54
Q

Mean right atrial pressure

A

5

55
Q

What accounts for the difference in right and left side systolic pressures?

A

LV has to pump higher pressure to reach head than RV has to pump to reach lungs

56
Q

What accounts for the difference in right and left ventricle diastolic compliance?

A

LV has more muscle and is less compliant so pressure requirement for expansion to diastolic volume increases

57
Q

What determines the myocardial fiber length at onset of systole?

A

LVEDP

58
Q

What is the pressure that pulmonary capillaries are exposed to?

A

mean left atrial pressure

59
Q

What is the pressure that generates LVEDP?

A

mean left atrial pressure

60
Q

What is the pressure that is the overall measure of the individual’s intravascular volume and hydration state?

A

right atrial pressure

61
Q

What is the pressure that the left ventricle has to support?

A

aortic pressure

62
Q

What is a clinical consequence of high left atrial pressure?

A

pulmonary edema –> too much pressure for lung capillaries

Cardiology (41 decks)

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