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Medical Physiology > Exam #2: Cardiac Cycle > Flashcards

Exam #2: Cardiac Cycle Flashcards

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USMLE® Step 1 flashcards
1
Q

Outline the shortcut to axis determination on ECG.

A

Normal= + in I & aVF
Left= + I & - aVF
Right= -I & + aVF
Extreme Right= -I & -aVF

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2
Q

What is normal R-wave progression?

A

Positive R-wave in V1

Negative R-wave in V6

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3
Q

What is abnormal R-wave progression an indication of?

A

Hypertrophy

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4
Q

What is the cardiac cycle?

A

Cycle of one heartbeat to the next & all the associated events taking place

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5
Q

How are heart rate & cardiac cycle related? What are the units for cardiac cycle & HR?

A

Heart rate varies inversely with duration of the cardiac cycle:

Increase HR= Decrease CC
Decrease HR= Increase CC

HR= bpm/ min (60 bpm) 
CC= sec/ beat (1.33 sec/beat)
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6
Q

With a change in HR, is the change in CC uniform?

A

No

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7
Q

When there is a change in HR, what part of the cardiac cycle is affected more? What are the consequences?

A

Effects diastole more than systole i.e. there is reduced filling time with a faster heart rate

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8
Q

When is the heart perfused?

A

Diastole

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9
Q

What are the seven phases of the cardiac cycle? How are they grouped?

A

Ventricular systole=

1) Isovolumic contraction
2) Rapid ejection
3) Reduced ejection

Ventricular diastole=

1) Isovolumic relaxation
2) Rapid filling
3) Reduced filling
4) Atrial systole

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10
Q

Draw the atrial pressure curve & correlated the pressure curve to the ECG tracing.

A

N/A

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11
Q

What is the a-wave & what does it correspond to?

A

A-wave= atrial systole; atrial contraction against the large blood volume in the atria, causes an increase in pressure

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12
Q

What causes mitral & tricuspid valve closing?

A

Atrial pressure dropping below ventricular pressure

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13
Q

What is the C-wave?

A

Ventricular contraction causes the leaflets of the mitral & tricuspid valves to push against the atria, measured as a rise in atrial pressure

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14
Q

What is the V-wave?

A

Slow filling of the atria as the ventricular myocytes contract, corresponding to a steady increase in atrial pressure

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15
Q

Next wave?

A

Atrial pressure exceeds ventricular pressure, leading to an opening of the mitral & tricuspid valves, leading to a drop in atrial pressure

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16
Q

What is right external JVD a sign of?

A

Conditions that increase right atrial pressure

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17
Q

Draw the ventricular pressure curve with the atrial pressure curve. Relate both to the ECG.

A

N/A

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18
Q

What is atrial kick?

A

A small expulsion of blood into the ventricle at the end of atrial systole

*Contributes roughly 15% of volume

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19
Q

Why does isovolumic pressure develop?

A

Cardiac valves are closed while ventricular myocytes contract= increased tension/ pressure without a change in volume

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20
Q

When does the aortic valve open?

A

Ventricular pressure is greater than aortic pressure

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21
Q

Does the aorta distend?

A

Yes, need distensible aorta to accomodate rapid ejection

22
Q

What is reduced ejection?

A

Ventricles still in contracted state, but there has been a decrease in LV pressure & blood flows lower out

23
Q

When does the end of reduced ejection occur? What does this correspond to on the ECG?

A

Aortic valve closing

T-wave

24
Q

What is isovolumic relaxation?

A

LVP continues to fall due to relaxation of the ventricles (chambers are getting bigger)

25
Q

When do the mitral and tricuspid valves open?

A

Once ventricular pressure is lower than atrial pressure

26
Q

What is rapid filling?

A

Fast flow of blood from the atria into the ventricles, after the mitral & tricuspid valves have opened

27
Q

How long does rapid filling last?

A

As long as there is no increase in pressure from distention of the ventricular walls

28
Q

What is reduced filling?

A

Filling of the ventricles that “stretches” the walls of the ventricles, generating pressure in the ventricles, but keeping the differential such that the AV valves remain open

29
Q

Draw the aortic pressure curve superimposed on the other pressure curves.

A

N/A

30
Q

What are the two clinically relevant points of the aortic pressure curve?

A

Diastolic pressure= low pressure prior to opening of the aortic valve

Systolic pressure= just after the highest pressure in the LV (max pressure)

31
Q

What causes aortic valve opening?

A

Ventricular pressure greater than aortic pressure

Aorta has to expand to accommodate the huge rush of ventricular outflow & elastic recoil serves to push blood to the periphery

32
Q

After ventricular ejection, the pressure gradient favors closure of the aortic semilunar valve during reduced ejection. Why does it not close?

A

Kinetic energy from the forward momentum of blood. When the aortic semilunvar valve closes, reduced ejection ends & isovolumic relaxation begins.

33
Q

What is the diaortic notch/ incisura?

A

A slight uptick in aortic pressure after the aortic valve closes, which is due to the backward wave returning from the periphery

34
Q

Draw the pressure wave from the arota.

A

N/A

35
Q

How is the aortic pressure wave influences by compliance?

A

Longer time= more compliance

Shorter time= less compliance & higher magnification

36
Q

When does the opening of the AV valves occur?

A

Diastole

37
Q

When do the AV valves occur?

A

Systole

38
Q

When does opening of the semilunar valves occur?

A

Systole

39
Q

When does the closure of the semilunar valves occur?

A

Diastole

40
Q

Draw the ventricular volume curve for the cardiac cycle.

A

N/A

41
Q

What is stroke volume? What is a normal stroke volume?

A

LVEDV (130mL)- LVESV (60 mL)

Thus a normal SV is 70 mL

42
Q

What is the first heart sound?

A
  • Closure of the AV valves, which happens at the beginning of isovolumic contraction
  • “Lub”
43
Q

What is the second heart sound?

A

Closure of the semilunar valves

- “Dub”

44
Q

What is physiological splitting?

A

Splitting of S2 (Dub) that occurs during deep inspiration

  • delayed closure of pulmonic valve
  • early closure of aortic valve

BOTH= aortic before pulmonic

45
Q

What is an opening snap?

A

Abnormal sound
Snap after S2 that may be due:
- mitral valve stenosis “groaning” from fibrosis or calcification

46
Q

What is S3? Is this abnormal?

A
  • Ventricular filling during the middle third of disatole?

Sometimes abnormal

47
Q

What is S4?

A

Pathological sound of atrial sytole into a stiff (hypertrophic) ventricle

48
Q

What is a Diastolic Murmur? What is a diastolic murmur and indication of?

A

A sound heard after S2 that may be due to mitral valve stenosis

49
Q

What is a Systolic murmur?

A

A sound heard after S1 & before S2

E.g. mitral valve regurgitation

50
Q

What is paradoxical splitting of S2?

A

The opposite of physiological splitting–splitting of S2 occurs during EXHALATION. This is due to changes in conductance e.g. LBBB

Medical Physiology (74 decks)

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