SMP - Cardiopulmonary Exam 1 > Lecture 11 - The Cardiac Cycle > Flashcards

Lecture 11 - The Cardiac Cycle Flashcards

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1
Q

Combined pressure of ejection of RV and LV?

A

125 mmHg

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2
Q

Which ventricular wall is thicker/stronger?

A

The LV

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3
Q

Describe the action of the RV contraction.

A
  1. Compresses the wall of the RV in a bellows like fashion => wall of right ventricle moving inwards toward the IV septum
  2. Shortening of free wall towards the apex
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4
Q

Does the IV septum functionally belong to the right or left ventricle?

A

Left

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5
Q

Describe the shape of the RV vs LV.

A

RV: thinner and semilunar shape

LV: thick and circular shape

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6
Q

Describe the action of the LV contraction.

A
  1. Circular contraction (constriction) of the chamber causing traction on the right ventricular wall
  2. Shortening of the chamber
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7
Q

What is a Wiggers diagram?

A 
Simultaneous tracing of:
1. Aortic pressure
2. Ventricular pressure
3. Atrial pressure
4. Ventricular volume
5. Phonocardiogram
6. Electrocardiogram
during 1 cardiac cycle
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8
Q

What is a phonocardiogram?

A

Recording of heart sounds

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9
Q

How would a left Wiggers diagram differ from a right differ diagram?

A

Left one would have higher pressures and there is slight asynchrony between the right and left hearts due to difference in pressure/resistance in circulations

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10
Q

What do isometric contraction and isometric relaxation have in common?

A

All 4 heart valves are closed during these intervals

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11
Q

Duration of average cardiac cycle?

A

70 beats/min => 0.85 second cardiac cycle => 0.28 systole and 0.58 diastole

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12
Q

Other names for isometric contraction and isometric relaxation?

A

Isovolumic contraction and isovolumic relaxation

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13
Q

What is the LV pressure at the start of ventricular contraction? What is this pressure called?

A

Between 4 and 12 mmHg because the LV is filled with blood => LV end diastolic pressure (LVEDP)

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14
Q

Describe the LV pressure curve during systole and diastole.

A
  1. As soon as the ventricles begin to contract the mitral valve closes due to the rise in pressure = start of left heart isometric contraction
  2. Very rapid rise in LV pressure until 80 mmHg
  3. Aortic valve opens => start of ejection = end of isometric contraction
  4. Pressure continues to rises and peaks at 120 mmHg
  5. Pressure falls off as most of the SV has been ejected
  6. Aortic valve closes when LVP < Aortic P (105 mmHg) = start of left isometric relaxation
  7. Drop in LVP to around 10 mmHg
  8. Mitral valve opens when LVP falls below the atrial pressure (all the way to 0 mmHg) = end of isometric relaxation
  9. LVP slowly rises during diastole as it fills with blood
  10. Atrial contraction causes small bump in LVP at the end of diastole
  11. LVP exceeds LAP = mitral valve closing
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15
Q

What event of the cardiac cycle is responsible for for the first heart sound (S1) of the phonocardiogram? What portion of the cardiac cycle does this correspond to?

A

Closure of the AV valves = beginning of the isometric contraction (through it actually)

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16
Q

What is the aortic pressure during the isometric contraction of the LV?

A

80 mmHg

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17
Q

How does the aortic pressure fluctuate upon opening of the aortic valve?

A

Follows LVP very closely, remaining just below it until LVP starts falling after peaking

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18
Q

Does the aortic pressure ever exceed the LVP during systole?

A

Yes, for a short period of time right after the LVP has peaked because flow is maintained by the kinetic energy (inertia) related to blood ejection

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19
Q

How does the aortic pressure change upon closing? What is this called?

A

Closing produces a high frequency oscillation in the aortic pressure curve = dichrotic notch

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20
Q

What event of the cardiac cycle is responsible for for the second heart sound (S2) of the phonocardiogram? What portion of the cardiac cycle does this correspond to?

A

Closure of semilunar valves = beginning of isometric relaxation

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21
Q

What happens immediately preceding ventricular contraction?

A

The QRS complex of the EKG is initiated

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22
Q

Compare LVP and aortic pressure during diastole?

A

LVP < aortic pressure during diastole with a small rise during atrial contraction

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23
Q

Are heart valves opening/closing caused by muscle contraction?

A

NOPE - pressure gradients

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24
Q

What is the hangout interval?

A

Interval between when the aortic pressure exceeds the LVP during diastole and the closure of the aortic valve

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25
What is another name for hangout interval?
Protodiastole
26
What % of ventricular filling does atrial contraction account for AT REST?
20-25%
27
When is LV volume constant?
Isometric relaxation and contraction
28
What is LV EDV at rest?
140 mL
29
When does most of the blood ejection from the LV occur?
First third of systole
30
What proportion of blood has been ejected by the end of systole?
At least half of the LV EDV
31
What is the normal ejection fraction of a heart at rest?
0.5
32
What is the systolic reserve capacity?
Volume remaining in the heart which could be pumped during maximal contraction (some of the residual volume is theoretically never available to be pumped: 20-25 mL)
33
What are the 3 phases of ventricular filling? Describe each.
1. Rapid passive ventricular filling = rushing in of blood during diastole right when the mitral valve opens caused by the atrium/ventricle pressure gradient 2. Slow passive filling = filling slows down as the pressure gradient dissipates 3. Active ventricular filling = filling caused by atrial contraction
34
Other name for slow passive filling of the ventricle?
Diastasis
35
Is atrial contraction necessary for cardiac function? Why/Why not?
NOPE because patients with atrial fibrillation can live for many years, although with limited exercise capacity
36
What does the ventricular volume depend on?
Size of person and blood volume
37
Describe the LA pressure curve during systole and diastole.
1. LVP rises above LAP at the beginning of systole causing mitral valve closure = start of isometric contraction 2. Upward deflection in LAP caused by the bulging of the AV valve due to ventricular contraction during isometric contraction = start of c wave 3. Aortic valve opens at end of isometric contraction causing drop in LAP = fall from peak of c wave 4. During rest of systole LAP rises gradually as LA fills with pulmonary blood = v wave 5. End of isometric relaxation = LVP falls below LAP => mitral valve opens (v wave peak) and LAP falls but stays above LVP through diastole 6. LAP remains low until atrial contraction = a wave
38
What do we call the crossing of the LVP and LAP curves accounting for the closing of the mitral valve?
Z point
39
In what chamber and during what portion of the cardiac cycle is the c wave?
In LA Starts at the start if IC and peaks at the end of it (continues through systole)
40
Compare LAP and LVP during diastole.
LAP above LVP during diastole
41
How is the cardiac cycle affected by maximal aerobic exercise? What is the issue though?
BOTH HR and SV are increased to increase the CO Issue: as the heart rate goes higher, the heart has less time to fill
42
What is the CO during maximal aerobic exercise?
25 L/min
43
Max HR?
180 bpm
44
What is the SV during maximal aerobic exercise?
100-130 mL
45
List the 2 phases of the cardiac cycle including isometric phases and valves.
1. Systole starting with isometric contraction and AV valve closing 2. Isometric contraction ends with semilunar valve opening 3. Systole ends with semilunar valve closing 4. Diastole starting with isometric relaxation and semilunar valve closing 5. Isometric relaxation ends with AV valve opening 6. Diastole ends with AV valve closing
46
When does the T wave of the EKG occur during the cardiac cycle? What does it represent?
Later portion of systole right before isometric relaxation Represents ventricular repolarization
47
What factors affect systolic aortic pressure?
1. SV (aka HR) 2. Aortic distensibility 3. Ejection velocity
48
What factors affect diastolic aortic pressure?
1. Systolic pressure | 2. Peripheral resistance
49
If we increase heart rate, what part of the ventricular volume curve are we most going to impact first?
Slow passive filling phase
50
How can we increase the SV?
1. Filling more by using the diastolic reserve capacity by increasing the venous pressure 2. Emptying more by using the systolic reserve capacity
51
When does the P wave of the EKG occur during the cardiac cycle? What does it represent?
In diastole right before atrial contraction Atrial depolarization
52
When are heart sounds S3 and S4 in the cardiac cycle?
Diastole
53
Do both atrioventricular valves close/open at the same time?
NOPE, mitral closes slightly before and opens slightly after
54
Do both semilunar valves close/open at the same time?
NOPE, aortic closes slightly before and opens slight after
55
What is the correct sequence of valvular opening and closing? Start at beginning of systole.
Mitral valve closing => tricuspid valve closing => pulmonary valve opens => aortic valve opens => aortic valve closes => pulmonary valve closes => tricuspid valve opens => mitral valve opens => mitral valve closing => tricuspid valve closing => ...
56
Describe the aortic pressure curve as it progresses down the arterial system from proximal to distal.
1. MAP consistently falls from the aorta to the capillaries 2. Loss of high frequency components of the atrial pressure curve, specifically the dichrotic notch 3. Pulse pressure increases as systolic portion of the wave narrows and peaks (pressure curve morphology also changes)
57
Which are transmitted faster: pressure or volume/flow? What does this explain?
Pressure This explains the aortic pressure curve as it progresses down the arterial system
58
What theory explains why the systolic portion of the aortic pressure narrows as the aortic pressure progresses down the arterial system (causing an increase in pulse pressure)? Explain it.
Reflected wave theory = pressure pulses are transmitted rapidly downstream but are also reflected back from branch points in the circulation, and these reflected waves amplify pulse pressures resulting in higher systolic and lower diastolic pressures toward the periphery
59
Effect of increased SV on pulse pressure?
Increased systolic P => increased pulse pressure
60
Effect of decrease in aortic distensibility on pulse pressure?
Increased systolic P => increased pulse pressure
61
Effect of decrease in HR on pulse pressure?
Increased pulse pressure because more time for filling => increased SV
62
Effect of decreased peripheral resistance on pulse pressure?
Increased pulse pressure because increase in systolic pressure (more venous return) and decreased diastolic pressure
63
How does anaphylaxis affect peripheral resistance?
Decreases it
64
Effect of increased ejection velocity on pulse pressure?
Increased systolic P => increased pulse pressure
65
What diastolic pressure is considered HT?
Above 90 mmHg
66
Explain the mechanism of essential hypertension.
Increase in total peripheral resistance => increase in both systolic and diastolic pressures (no change in pulse pressure in early stages) and increase in overall MAP
67
What is arteriosclerosis? How does it affect pressure?
Thickening and loss of elasticity in arterial walls => increased peak systolic pressure and diastolic pressure is unchanged (MAP is also relatively normal or slightly elevated) => increased pulse pressure
68
What is aortic insufficiency? How does it affect pressure?
Imperfect closure of the aortic valve => rapid, retrograde runoff of blood to the heart during diastole => decreased diastolic pressure => increased peak systolic pressure because of large SV => increased pulse pressure
69
What does long term HT develop into?
Arteriosclerosis
70
Effect of increase in HR on pulse pressure?
Decreased SV => decreased systolic pressure => decreased pulse pressure
71
How does aortic stenosis affect aortic pressure?
Longer/harder to pump blood through => decreased systolic pressure => decreased pulse pressure
72
Relationship between HR and SV?
As HR increases, SV decreases in an artificial situation if everything else is controlled for
73
During what phase of the cardiac cycle does ventricular repolarization occur?
During the reduced ejection phase
74
During what phase of the cardiac cycle does ventricular depolarization occur?
Atrial systole and S wave in the IC phase
75
During what phase of the cardiac cycle does S3 happen?
Rapid ventricular filling right after IR
76
During what phase of the cardiac cycle does S4 happen?
Atrial systole
77
How does HR decrease SV but increases CO? When does HR decrease CO?
HR always decreases SV but because the heart is beating faster more blood OVERALL in 1 minute is being ejected. This means that when HR increases CO, it's only decreasing SV a little because it's cutting into the slow passive filling phase during which only a little blood enters the ventricle compared to during the rapid filling phase. Then when HR increases to the point where it's cutting into the rapid filling phase of the heart, it's effect on the SV is too large to be overcome by the increased number of systoles in a minute so CO decreases.
78
What is the peak of the c wave on the atrium pressure curve followed by?
X descent
79
What is the peak of the v wave on the atrium pressure curve followed by?
Y descent
80
What exactly causes the aortic valve to close since it exceeds LVP at the beginning of the hangout period - why doesn't it close then? Is the pressure gradient not large enough?
The aortic valve takes some time to close after its pressure has exceeded the LVP because flow is maintained by the kinetic energy (inertia) related to blood ejection
81
Are left heart valves open for a shorter amount of time than right heart valves? Is this due to the Purkinje fibers starting earlier in the septum on the left side of the heart?
YUP NOPE, due to difference in afterload between the 2 sides of the heart
82
Which is higher: the pressure in the LVP at the end of the IC or at the end of ejection?
Pressure at the end of ejection
83
Is there a dichrotic notch on the aortic pressure curve if there is aortic insufficiency?
NOPE
SMP - Cardiopulmonary Exam 1
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