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Cardiovascular & Respiratory Medicine > Cardiac Cycle > Flashcards

Cardiac Cycle Flashcards

1
Q

Contrast diastole and systole

A

Diastole:

  • lasts approximately 2/3 of each beat
  • ventricular relaxation
  • split into 4 distinct phases

Systole:

  • lasts approximately 1/3 of each beat
  • ventricular contraction
  • split into 3 distinct phases
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2
Q

What are the 7 phases of the cardiac cycle in order?

A
  • atrial systole
  • isovolumetric contraction
  • rapid ejection
  • slow ejection
  • isovolumetric relaxation
  • rapid passive filling
  • slow passive filling
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3
Q

Which phase gives the end-diastolic volume?

A

-isovolumetric contraction (just before blood is ejected)

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4
Q

Which phase gives the end-systolic volume?

A

-slow ejection (blood has been ejected)

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5
Q

How can you calculate the stroke volume?

A

end-diastolic volume - end-systolic volume

about 72ml

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6
Q

How do you calculate the ejection fraction?

A

(100 x stroke volume ) / end-diastolic volume

about 67%

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7
Q

Where is the mitral (bicuspid) valve?

A

-left atrioventricular valve

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8
Q

Where the tricuspid valve?

A

-right atrioventricular valve

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9
Q

What is the P-wave on ECG signifying and which heart sound is it associated with?

A
  • indicates atrial excitation
  • starte of atrial systole
  • ventricles contract to ‘top up’ the volume of blood in ventricle

-S4

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10
Q

What can cause abnormal S4 sound?

A

-congestive heart failure, pulmonary embolism or tricuspid incompetence

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11
Q

What does the QRS complex tell us and which sound is it associated with?

A
  • isovolumetric contraction
  • marks the start of ventricular depolarisation
  • this is the interval between AV valves (tricuspid and mitral) closing Q & semi-lunar vales (pulmonary & aortic) opening S
  • contraction of ventricles with no change in volume

S1 ‘lub’ due to closure of AV valves and associated vibrations

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12
Q

What happens during rapid ejection?

A
  • opening of the aortic and pulmonary valves mark the start of this phase
  • as ventricles contract pressure within them exceeds pressure in aorta and pulmonary arteries
  • semilunar valves open, blood pumped out and the volume of ventricles decreases
  • no heart sounds.
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13
Q

What type of contraction occurs in the rapid ejection phase?

A

-isotonic

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14
Q

What happens during slow/reduced ejection?

A
  • marks the end of systole
  • reduced pressure gradient means aortic and pulmonary valves begin to close
  • blood flow from ventricles decreases and ventricular volume decreases more slowly
  • as pressure in ventricles fall below that in arteries, blood begins to flow back causing semilunar valves to close

-T phase- repolarisation

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15
Q

What happens in the isovolumetric relaxation phase?

A
  • the aortic and pulmonary valves shut, but the AV valves remain closed until ventricular pressure drops below atrial pressure
  • atrial pressure continues to rise
  • dichrotic notch caused by rebound pressure against aortic valve as distended aortic wall relaxes
  • S2 ‘dub’ due to closure of semilunar valves and associated vibrations
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16
Q

What causes the dichotic notch?

A

-caused by rebound pressure against aortic valve as distended aortic wall relaxes

17
Q

What happens in rapid passive filling?

A
  • occurs during isoelectric (flat) ECG between cardiac cycles
  • once AV valves open, blood flows rapidly into the ventricles

-S3

18
Q

What may S3 sound signify?

A
  • turbulent ventricular filling

- can be due to severe hypertension or mitral incompetence

19
Q

What happens during reduced passive filling?

A
  • diastasis
  • ventricular volume fills more slowly
  • the ventricles are able to fill considerably without the contraction of the atria
20
Q

What is diastasis?

A

-reduced passive filling

21
Q

How do the patterns of pressure changes differ in the left side and right side of the heart?

A

-they don’t- identical

22
Q

Quantitatively, how do the pressures in the right heart and pulmonary circulation differ from the left?

A
  • much lower (peak of systole)
  • despite lower pressures, right ventricles ejects same volume of blood as left; it is simply pumping the same quantity of blood into a lower pressure circuit.
23
Q

What is the average pressure in the systemic circuit?

A

120/80 mmHg

24
Q

What is the average pressure in the pulmonary circuit?

A

25/5 mmHg

25
Q

Pressure volume loops

A

1 loop = 1 heartbeat

https://www.youtube.com/watch?v=AnwPH5yU8rY

26
Q

Increase in preload has what affect on the stroke volume?

A
  • increases stroke volume

- the Frank-Starling relationship

27
Q

Increase in after load has what affect on the stroke volume?

A
  • decreases stroke volume

- as after load increases, the amount of shortening that occurs decreases

28
Q

What is cardiac output?

A

cardiac output = heart rate x stroke volume

29
Q

What three things affect stroke volume?

A
  • preload
  • afterload
  • contractility (increases through engagement of the autonomic NS and stimulation primarily of the sympathetic NS, which then changes the amount of Ca inside the cell on excitation- change force production)
30
Q

What is contractility?

A
  • measure of the strength of contraction of the heart
  • ejection fraction
  • increased by sympathetic stimulation
31
Q

How would the PV loop differ when there is hardening of the aortic valve?

A
  • hardening and narrowing of the aortic valve reduces flow and increases afterload
  • pressure required greater and less shortening of muscle cells so smaller stroke volume
32
Q

How would the PV loops differ when there is acute blood loss?

A
  • loss of blood reduces venous return which decreases preload
  • less ventricular volume therefore smaller stroke volume
33
Q

How would the PV loop differ during exercise?

A

-venous return increases and skeletal muscle stimulation increased via sympathetic NS

34
Q

Which is the longest phase of the cardiac cycle?

A

-reduced passive filling

Cardiovascular & Respiratory Medicine (15 decks)

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