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BLOCK C - CIRCULATION > The Heart Pump > Flashcards

The Heart Pump Flashcards

1
Q

In terms of pressures, what causes the atrioventricular valve to close at the start of isovolumetric contraction?

A

When the contraction of the left ventricle causes ventricular pressure to exceed atrial pressure, the AV valve closes.

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2
Q

In terms of pressures, what causes the aortic valve to open?

A

When isovolumetric contraction of the left ventricle causes the ventricular pressure to exceed the pressure in the aorta (~80mmHg).

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3
Q

When are both the AV valves and semilunar valves closed?

A

Isovolumetric contraction
Isovolumetric relaxation

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4
Q

What is the peak systolic blood pressure?

A

~120mmHg
When the LV and aortic pressures reach a maximum (during the ejection phase).

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5
Q

When does the aortic valve close?

A

When the aortic pressure exceeds the ventricular pressure, the aortic valve closes.

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6
Q

Closure of the aortic valve marks the start of…

A

Isovolumetric relaxation

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7
Q

Closure of the atrioventricular valve marks the start of…

A

Isovolmetric contraction

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8
Q

What is the dicrotic notch?

A

It is a brief dip in the aortic pressure caused by the closure of the aortic valve. When this valve closes, it exposes the sinuses of Valsalva and the forward flow of blood is briefly interrupted (blood flows backwards to fill these sinuses, resulting in the dicrotic notch).
The blood then bounces off of the valve, creating a brief spike in aortic pressure, which then proceeds to steadily decrease as blood moves out of the aorta and into the systemic circulation.

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9
Q

What is another name for the dicrotic notch?

A

Incisura

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10
Q

Diastole begins after the closure of…

A

the aortic valve

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11
Q

When does the ventricle reach its minimum end-systolic volume?

A

At the time of the aortic valve closure (ie. at the beginning of diastole).

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12
Q

Proper filling of the ventricle (ventricular diastole) depends on 3 conditions….

A
  1. The filling pressure of blood returning to the heart and atria
  2. The ability of the atrioventricular valve to open fully (no stenosis)
  3. The ability of the ventricular wall to expand passively with little resistance (i.e. high compliance).
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13
Q

The healthy heart is … so that filling occurs with only small increases in diastolic pressure.
a) highly compliant
b) non-compliant

A

a) highly compliant

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14
Q

A healthy heart is compliant and easy to fill, whereas a stiff heat requires more… to fill.

A

pressure

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15
Q

Atrial contraction is initiated near the end of…

A

ventricular diastole (P-wave of ECG)

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16
Q

When is the LV at its fullest?

A

End-diastolic volume (i.e. right after atrial contraction, before aortic valve opens).

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17
Q

When is the LV at its emptiest?

A

End-systolic volume (i.e. right after the closure of the aortic valve)

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18
Q

Summarize the a, c, v waves and x, x’ and y descents.

A

a: Atrial systole (contraction)
x: Atrial relaxation
c: AV valve bulges into the atrium
x’: Atrial relaxation (ctd.)
v: Atrial filling
y: Passive atrial emptying

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19
Q

In the atrial pressure curve, the x descent may be interrupted by…

A

a small upward deflection (c wave), caused by the bulging of the AV valve into the atrium during isovolumetric contraction.

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20
Q

Explain why the pressure increases in the a wave and v wave of the atrial pressure curve.

A

a wave: Atrium contracts, which causes an increase in pressure
v wave: Atrium is filled with returning blood, causing an increase in pressure

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21
Q

During the x’ descent, downward movement of the … during systole leads to a fall in atrial pressure.

A

atrioventricular annulus

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22
Q

Since the 2 sides of the heart are arranged in series with another, it stands to reason that both have identical…

A

stroke volumes

23
Q

The right heart pump generates less pressure than the left because…

A

the pulmonary vessels provide less resistance than the systemic vessels.

24
Q

What is a normal pulmonary artery pressure (systolic/diastolic)

A

24/8 mmHg

25
Q

What is the ejection fraction?

A

Stroke volume/End-diastolic volume * 100
Percentage of blood pumped out of a ventricle with each heartbeat

26
Q

The highest arterial blood pressure is called… and occurs at…

A

The highest arterial blood pressure is called systolic BP and occurs at peak ventricular contraction.

27
Q

The lowest blood pressure is called… and occurs at…

A

The lowest blood pressure is called diastolic BP and occurs at the end og diastole.

28
Q

What is pulse pressure?

A

Systolic BP - Diastolic BP
Reflects the force generated by the heart with each heartbeat.

29
Q

A high pulse pressure indicates…

A

Stiff or damaged arteries:
* aging
* atherosclerosis
* hypertension
Higher SBP relative to DBP

30
Q

A low pulse pressure indicates…

A

Heart failure, blood loss, aortic stenosis (aortic valve is narrowed)
Lower SBP relative to DBP

31
Q

Define mean arterial pressure (MAP)

A

Average blood pressure throughout the cardiac cycle.

Not simply the average of SBP and DBP, because the heart spends 2/3 of the cardiac cycle in diastole and 1/3 in systole.

MAP=((2xDBP)+SBP)/3
MAP=DBP+(1/3 pulse pressure)

32
Q

What is the S1 heart sound?

A

Closure of atrioventricular valves at the start of systole

33
Q

What is the S2 heart sound

A

Closure of the semilunar valves at the end of systole

34
Q

What is the S3 heart sound?

A

Extra heart sound heard in early diastole when there is early diastolic filling (can sometimes be normal).

35
Q

What is the S4 heart sound?

A

Extra heart sound heard when there is atrial contraction into a stiff, non-compliant ventricle (usually abnormal).

36
Q

The pressure-volume loop is a graphical representation of…

A

changes in intraventricular pressure during the cardiac cycle

x-axis: intraventricular volume
y-axis: intraventricular pressure

37
Q

What is the EDPVR and what does it depict?

A

The EDPVR is the end-diastolic pressure volume relation. It is a curve depicting the change in left ventricular pressure as the end-diastolic volume is increased.

38
Q

As we increase end-diastolic volume, how does the EDPVR curve change?
What does this mean.

A

It remains relatively flat until abnormally elevated end-diastolic volumes, at which point it curves upwards.

This means a healthy left ventricle is highly compliant (large increase in volume yields little increase in pressure).

39
Q

If a pathological process makes the left ventricle less compliant, how will the EDPVR curve change?

A

It will shift upwards (for the same volume, the pressure in the ventricle will now be greater).

40
Q

What is the ESPVR?

A

The ESPVR is the end-systolic pressure volume relation. It is a curve depicting changes in ventricular pressure as a function of intraventricular volume in a maximally contracted ventricle.

41
Q

As we increase the volume of blood in a heart that is fully contracted (as it would be at the end of systole), how does the ESPVR curve change?

A

The greater the volume of blood, the greater the pressure in the left ventricle (and vice versa: the more blood we remove from a maximally contracted ventricle, the smaller the pressure).

In other words, the ESPVR curve is linear.

42
Q

The ESPVR curve is also called…

A

contractility curve

43
Q

The ESPVR curve demonstrates that as the heart fills with more blood, it can…

A

generate a higher pressure.

44
Q

A steeper ESPVR slope indicates…

A

increased contractility of the heart (e.g. with sympathetic stimulation)

45
Q

A flatter ESPVR slope indicates…

A

decreased contractility of the heart (e.g. during heart failure)

46
Q

As you fill the heart with blood, the muscle fibres become…

A

longer, i.e. more stretched

47
Q

Active tension is equal to…
Define active tension vs resting tension.

A

Active tension is equal to peak isometric tension minus resting tension.

Active tension is the force generated by cross-bridge cycling between actin and myosin (because muscle is actively trying to contract).
Resting tension is the force generated simply by stretching the muscle fibre (passive).

48
Q

When a muscle is over-stretched, peak isometric tension is higher than a moderately stretched muscle. Explain why, despite this, active tension is higher in a moderately stretched muscle.

A

In an overstretched muscle, the resting tension is higher than in a moderately stretched muscle. Therefore, a greater proportion of the total tension generated can be attributed to resting tension rather than active tension in an overstretched muscle.

The proportion of tension attributed to active tension is highest in a moderately stretched muscle.

49
Q

When is active tension the highest?

A

In a moderately stretched muscle fibre.

50
Q

What are the 3 determinants of the stroke volume?

A
  1. Ventricular preload (i.e. end-diastolic volume)
  2. Ventricular afterload (the pressure against which the heart contracts during ejection, i.e. MAP)
  3. Ventricular contractility (inherent strength of the heart’s contraction during systole).
51
Q

Based on Frank-Starling’s law, how does an increase in cardiac filling (i.e. preload i.e. end-diastolic volume) affect stroke volume?

A

Greater filling = greater stroke volume

52
Q

Define afterload

A

Afterload is the force against which the ventricle contracts during ejection.
* Left ventricular wall stress
* Proportional to left ventricular systolic pressure
* Used interchangeably with mean arterial pressure

53
Q

How will an increase in mean arterial blood pressure affect the point at which the aortic valve opens?

A

The aortic valve opens once the let ventricular pressure exceeds the aortic pressure.

If the aortic pressure increases, then the left ventricular pressure will also have to be higher before the aortic valve opens.

In other words, to open the aortic valve in these conditions, the ventricle will have to generate a higher pressure.

BLOCK C - CIRCULATION (10 decks)

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