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CVB by Minnie (Madeleine) > SM 111a - Pressure-Volume Loops and the Cardiac Cycle > Flashcards

SM 111a - Pressure-Volume Loops and the Cardiac Cycle Flashcards

1
Q

Which event of the cardiac cycle occurs at #4?

A

The mitral valve opens

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2
Q

Which law explains why LV thickening is an adaptation to chronic hypertension?

A

Laplace’s law

Thickening of the LV is a response to increased pressure that will keep the wall stress on each individual myocyte constant

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3
Q

Between which two numbers does isovolumic relaxation occur?

What is happening physiologically?

A

Betwen #3 and #4 (F and A)

The LV is in diastole. It is relaxing, but pressure has not yet fallen below LA pressure. Both the aortic and mitral valves are closed

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4
Q

During which phases is blood flowing from the right atrium to the right ventricle?

A

From the beginning of the y descent (marked by v) to the closure of the tricuspid valve (end of atrial systole)

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5
Q

Which curve represents heart failure?

A

2

Lower stroke volume at every end diastolic pressure

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6
Q

What is wall stress?

How is it calculated?

A

Wall stress is the circumfrential force per unit area that must be exerted to maintain a particular pressure inside the left ventricle

A myocyte will fail above a certain level of stress; therefore, thickening of the LV (increasing h) is an adaptive mechanism that decreases the stress on each individual myocyte

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7
Q

Which event of the cardiac cycle occurs at #3?

A

The aortic valve closes

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8
Q

What event happens at #1?

A

The mitral valve closes

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9
Q

What does the a wave represent?

A

Right atrial systole, latter part of ventricular filling

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10
Q

What event happens at #4?

A

The mitral valve opens

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11
Q

Between which numbers does isovolumic contraction occur?

What is happening physiologically?

A

Between #1 and #2 (C and D)

The left ventricle is in systole; it is contracting, but pressure in the LV has not yet overcome the aortic pressure. Both the mitral and aortic valves are closed

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12
Q

Which event of the cardiac cycle occurs at #1?

A

Mitral valve closes

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13
Q

What is the physiologic basis of a split S2?

When are we most likely to hear it?

A

Split S2 results when the aortic valve closes slightly before the pulmonary valve

We are most likely to hear it upon inspiration. Inspiration creates negative pressure in the lungs, futher decreasing the pressure in the pulmonary trunk (compared to pressure in the aorta)

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14
Q

What is Laplace’s Law?

Give the equation and explain

A

Laplace’s law gives the equation for wall stress

Wall stress is proportional to pressure and radius, and inversely proportional to the thickness of the wall (h)

This explains why LV hypertropy is an adaptive mechanism to chronic hypertension

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15
Q

At which number/letter would we hear S1?

A

1/C

The mitral valve closes

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16
Q

What does the v wave respresent?

A

Right atrial filling

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17
Q

Which event of the cardiac cycle occurs at #2?

A

The aortic valve opens

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18
Q

Isovolumic contraction happens between which two numbers?

A

1 and 2

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19
Q

When is the left ventricle in systole?

A

From just before #1 through just before #3

The mitral valve closes (#1) when the LV pressure becomes greater than the LA pressure, due to LV contraction (systole)

The aortic valve closes when the LV pressure drops below the aortic pressure, due to LV relaxation (diastole)

20
Q

How does increasing preload affect the cardiac cycle?

A

Increased preload ->

  • Increased LV end diastolic volume (actually, increasing EDV usually results in increased preload)
  • Increased stroke volume
  • May be a small increase in LV end diastolic pressure
21
Q

At which number should we hear S1?

At which nubmer should we hear S2?

A

S1: At #1, when the mitral valve closes

S2: at #3, when the aortic valve closes

22
Q

How does increasing contractility affect the cardiac cycle?

A

Increased contractility ->

  • Increased maximum systolic pressure
  • Longer ejection time
  • Increased stroke volume
    • Due to decreased end systolic volume (more blood is squeezed out)
  • No change in end diastolic volume
23
Q

Isovolumic relaxation happens between which two numbers?

24
Q

What does the y descent represent?

A

The y descent begins wehn pressure in the RA exceeds that of the RV

The tricuspid valve opens, and blood flows from the RA to the RV. The y descent ends when the RA contracts to squeeze the last bit of blood into the RV

25
Which valves are open betwen D and F?
The aortic valve is open The mitral valve is closed
26
Purple = normal pressure-volume loop Which of the follwing changes created the red pressure-volume loop? a) Increased contractility b) Increased preload c) Increased afterload
c) Increased afterload
27
What is the physologic basis of S1?
The tricuspid and bicuspid valves closing
28
What is the physiologic or pathologic basis of S3?
S3 occurs due to rapid deceleration of blood against a distended or incompliant left ventricle This happens **Physiologic basis:** Athletes and young children. Left ventricle fills almost to its maximum, and it cannot streth further to accomodate a "soft landing" of inflowing blood **Pathologic basis:** Enlarged or weak heart
29
What value is represented by #5?
Stroke volume
30
Between which numbers/letters is the LV in systole?
Just before #1 (C) to just before #3 (F)
31
At which number/letter woudl we hear S2?
#3/F The aortic valve closes
32
When in the cardiac cycle are we likely to hear S4, if it is present?
Late in diastole, right before S1
33
What is the Frank-Starling relationship?
Increased myocyte stretch -\> Stronger contraction The LV pressure increase resulting from **increased end diastolic volume** and therefore increased preload, results in **increased contractile force** generated by the heart, **and increased systolic blood pressure**
34
Which valves are open between A and C?
The mitral valve is open The aortic valve is closed
35
Purple = normal pressure-volume loop Which of the follwing changes created the red pressure-volume loop? a) Increased contractility b) Increased preload c) Increased afterload
b) Increased preload
36
When in the cardiac cycle are we likely to hear S3, if it is present?
Early in diastole, after the aortic and pulmonary valves close
37
Which curve represents increased intropy?
1 Increased intropy = increased contractility Greater stroke volume for every end distolic volume
38
What event happens at #3?
The aortic valve closes
39
When is the left ventricle in diastole?
From just before #3 to just before #1 LV relaxation causes the aortic valve to close (3) When it begins to contract at the end of systole, the mitral valve closes (1) in response
40
How does increasing afterload affect the cardiac cycle?
Increased afterload -\> * Increased maximum systolic pressure * Decreased stroke volume * Due to increased end systolic volume * No change in end diastolic volume
41
Between which numbers/letters is the LV in diasole?
From just before #3 (F) to just before #1 (C)
42
What event happens at #2?
The aortic valve opens
43
What factors will increase myocardial O2 consumption?
Anything that causes the heart to work harder (ex: pumping more blood or overcoming some pathology), will increase myocardial O2 consumption * Increased preload * Increased afterload * Increased contractility * Increased HR * Decreased pulmonary vascular resistance * More return to LA, which goes to LV, which LV has to pump out * Increased time in systole
44
What is the physiologic or pathologic basis of S4?
S4 is always pathologic Occurs when forceful atrial contraction ejects blood into a stiff left ventricle
45
What does the x wave represent? What interrupts the x wave?
The x wave represents relaxation of the atrium after atrial systole It is interrupted by the c wave, when the tricuspid closes to create a brief pressure increase in right atrial pressure
46
Purple = normal pressure-volume loop **Which of the follwing changes created the red pressure-volume loop?** a) Increased contractility b) Increased preload c) Increased afterload
a) Increased contractility
47
What is the physiologic basis of S2?
The aortic and pulmonary valves closing Note: it is normal for the aortic valve to close slightly beofore the pulmonary valve, causing a **split S2**

CVB by Minnie (Madeleine) (43 decks)

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