Cardiac Cycle Flashcards by Sara Russell

What is responsible for the closing and opening of the AV and semilunar valves?

Passive process due to the pressure difference across the valve
(Atrial pressure > ventricular pressure) - AV
(Ventricular pressure > aortic/pulmonary pressure) - Semilunar

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Define the cardiac cycle and types of events.

One complete set of cardiac contraction and relaxation. 
Consists of the mechanical events (volume and pressure changes) 
Electrical events (ECG)
Valvular events (heart sounds)

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Describe how the time is spent in either diastole/systole.

Normally 2/3 diastole, 1/3 systole

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What happens to the time in diastole and systole when the heart rate increases?

With an increase in heart rate, diastole will be cut down and therefore the heart spends less time in the filling phase.

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Name the phases involved in diastole.

Isovolumetric/Isometric Ventricular Relaxation (0.05s)

Passive Ventricular Filling (0.5s)

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Describe isovolumetric/isometric ventricular relaxation.

After ventricular contraction, there is a reduction in pressure. ALL VALVES ARE SHUT.
Ventricular volume is at a minimum (ESV - end systolic volume)
No change in the volume of blood in the ventricles
Atria are filling with blood returning to the heart, atrial pressure < ventricular pressure

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Describe ventricular filling (0.5s)

Atrial pressure is greater than ventricular pressure
AV valves open causing atrial accumulation to move passively into the ventricles
Volume in ventricles is at a max = EDV (130ml)

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Name the two phases of systole.

Isovolumetric (Isometric) Contraction (0.05s) 
Ventricular Ejection (0.3s)

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Describe Isovolumetric (Isometric) Contraction

Ventricle pressure > atrial pressure, but less than aortic/pulmonary pressure
AV valves snap shut = S1 sound
Tension builds in fibres to increase pressure
Takes 0.05s

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Describe Ventricular Ejection

LVP > AP 
RVP > PAP 
SL valves open 
Blood is ejected
Lasts about 0.3s

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Describe what happens after ventricular ejection.

Pressure in ventricles decreases to be less than aortic and pulmonary pressure. SL valves close = S2 sound.
Goes back to ESV, starts isovolumetric/isometric ventricular relaxation.

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What are the phases of diastole?

Isovolumetric (isometric) relaxation and ventricular filling

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What are the phases of systole?

Isovolumetric contraction and ventricular ejection

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When is ventricular volume at a max and a min?

Maximum at EDV

Minimum at ESV

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Name the two phases which the cardiac cycle is divided into.

Ventricular diastole: ventricles are relaxed

Ventricular systole: ventricles are contracting

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How long is isovolumetric ventricular relaxation?

0.05s

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How long is ventricular filling?

0.5s

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How long is isovolumetric ventricular contraction?

0.05s

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How long is isovolumetric ventricular relaxation?

0.05s

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How long is ventricular ejection?

0.3s

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Name the events taking place in the cardiac cycle.

Electrical events (ECG) 
Mechanical events (volume and pressure changes) 
Valvular events (opening and closing - heart sides)

Describe what happens to ventricular volume.

Maximum at end of diastole (EDV)
Constant during isometric ventricular contraction
Falls rapidly during ventricular ejection
Minimum at the end of ventricular systole (ESV)
Constant during isometric ventricular relaxation

When is ventricular pressure at a minimum?

Beginning of diastole

Describe what happens to ventricular pressure during ventricular filling and after atrial contraction?

Ventricular pressure rises a little

When does ventricular pressure rise dramatically?

During isometric contraction (systole)

Describe what happens to ventricular pressure during the ejection phase of systole.

Continues to rise to a maximum during the ejection phase then falls during late systole

What happens in isovolumetric relaxation with regards to ventricular pressure?

Falls dramatically to a minimum valve

When is arterial pressure at a minimum?

End of diastole (diastolic pressure)

When does arterial pressure rise to a maximum?

During the ejection phase (systolic pressure)

What happens when the ventricular pressure falls below the arterial pressure?

Aortic valve closes (S2)

How do we calculate arterial pulse pressure?

SP - DP

How do we calculate SV?

EDV - ESV

What are the differences between the right side of the heart and the left side of the hear

Right ventricular volumes = left ventricular volumes Pulmonary resistance is lower than total peripheral resistance (systemic circulation) Right ventricular and pulmonary artery pressures are lower than the left ventricular pressure and aortic pressure

Name the three waves of right atrial pressure.

A C V

Describe the importance of knowing that there are no valves between the right atrium and vena cavae.

Pressure changes in the right atrium are transmitted back into the large veins - jugular venous column. Can see the A C and V waves in the jugular venous column.

What do we use the JVP for?

To assess right atrial pressure

What is the normal HR and cardiac cycle duration at rest?

Heart rate - 60bpm | Cardiac cycle duration - 1s (2/3 diastole, 1/3 systole)

What happens to diastole and systole as HR increases?

Both diastole and systole duration decrease | But diastole decreases more than systole to preserve systolic time

What does the P wave indicate about the cardiac cycle?

Atrial depolarization - precedes atrial contraction

What does the QRS complex indicate about the cardiac cycle?

Ventricular depolarization - precedes ventricular contraction

What does the T wave show?

Ventricular repolarization

Which events occur first?

Electrical events precede mechanical events

What causes the first heart sound?

Closure of the mitral and tricuspid valves | M1 before T1

What does the first heart sound sound like?

Lubb

Which AV valve closes first?

Mitral before tricuspid

What causes the second heart sound?

Closure of semilunar valves Aortic closes before pulmonary Dubb

What causes the third heart sound?

Rapid ventricular filling early diastole

When may the third heart sound be heard?

In the young or those with LVF

What causes S4?

Ventricular filling in atrial top up indicates reduced ventricular compliance Gallop rhythm

What causes murmurs?

Turbulent blood flow Narrowing of a valve - stenosis Reversal of flow through a valve - valve insuffiency or incompetence Murmurs are an important sign of valve lesions

When does the murmur occur in aortic stenosis?

Between S1 and S2

When does the murmur occur in mitral incompetence?

Throughout systole