Physiology of cardiac cycle

1. Cardiac Cycle
Prof. Dr. Rashid Mahmood

2. Cardiac Cycle| Prof. Dr. Rashid Mahmood 2

3. CourtesyCardiac Cycle| Prof. Dr. Rashid Mahmood 3
Cardiac Cycle

4. Cardiac Cycle| Prof. Dr. Rashid Mahmood 4

5. DEFINITION
•All the events taking place in the Heart from one
systole to another systole or from one Diastole to
another Diastole.
Mainly Comprised of:
Electrical Events
Mechanical events

6. Electrical & Mechanical events
Electrical Events
• ECG
Mechanical events
• Pressure Changes
• Volume Changes
• Production of Heart Sounds
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8. Phases of cardiac cycle (Mechanical events)
SYSTOLE
1. Isovolumetric
Contraction
2. Rapid Ejection
Phase
3. Slow Ejection Phase
DIASTOLE
1. Isovolumetric
Relaxation
2. Rapid Filling phase
3. Slow filling phase
(Diastasis)
4. Atrial systoleCardiac Cycle| Prof. Dr. Rashid Mahmood 8

9. Q.1
• What is the name of this
diagram?
A. Cardiac Cycle Diagram
B. Volume-Pressure
Diagram
C. Pressure-Volume
Diagram
D. Ejection work diagram
E. Left-ventricular
diagramCardiac Cycle| Prof. Dr. Rashid Mahmood 9B

10. ISOVOLUMETRIC CONTRACTION
The Beginning of systole
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11. ISOVOLUMETRIC CONTRACTION
Heart
• Which valves close at the
beginning of this phase
• atrioventricular (AV) valves
• Ventricular systole is defined
as the interval between the
closing of the AV valves and
the opening of ?
• the semilunar valves (aortic
and pulmonary valves).
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12. ISOVOLUMETRIC CONTRACTION (Pressures & Volumes)
• The AV valves close when the
pressure in the ventricles (red)
exceeds the pressure in the atria
(yellow).
• As the ventricles contract
isovolumetrically -- their volume does
not change (white) -- the pressure
inside increases, approaching the
pressure in the aorta and pulmonary
arteries (green).
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13. Q. 2
1. What happens at Point
A?
2. What volume is
represented at Point A?
3. What period is
represented by AB?
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1. Mitral valve opens
2. End-Systolic Volume
3. Period of filling

14. RAPID EJECTION
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15. RAPID EJECTION
Heart
•The semilunar (aortic and
pulmonary) valves open at
the beginning of this
phase.
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16. RAPID EJECTION
Pressures & Volumes
• While the ventricles continue
contracting, the pressure in the
ventricles (red) exceeds the
pressure in the aorta and
pulmonary arteries (green); the
semilunar valves open, blood exits
the ventricles, and the volume in
the ventricles decreases rapidly
(white).
• As more blood enters the arteries,
pressure there builds until the
flow of blood reaches a peak.
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17. REDUCED EJECTION
The end of systole
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18. REDUCED EJECTION
Heart
•At the end of this phase
the semilunar (aortic
and pulmonary) valves
close.
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19. REDUCED EJECTION
Pressures & Volumes
• After the peak in ventricular and
arterial pressures (red and green),
blood flow out of the ventricles
decreases and ventricular volume
decreases more slowly (white).
• When the pressure in the ventricles
falls below the pressure in the
arteries, blood in the arteries
begins to flow back toward the
ventricles and causes the semilunar
valves to close. This marks the end
of ventricular systole mechanically.
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20. Q. 3
1. What happens at Point
B?
2. What volume is
represented at Point B?
3. What period is
represented by BC?
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1. Mitral valve closes
2. End-Diastolic Volume
3. Isovolumic contraction

21. ISOVOLUMETRIC RELAXATION
The beginning of Diastole
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22. ISOVOLUMETRIC RELAXATION
Heart
•At the beginning of this
phase the AV valves are
closed.
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23. ISOVOLUMETRIC RELAXATION
Pressures & Volumes
• Throughout this and the previous two
phases, the atrium in diastole has
been filling with blood on top of the
closed AV valve, causing atrial
pressure to rise gradually (yellow).
• The pressure in the ventricles (red)
continues to drop.
• Ventricular volume (white) is at a
minimum and is ready to be filled
again with blood.
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24. RAPID VENTRICULAR FILLING
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25. RAPID VENTRICULAR FILLING
Heart
•Once the AV valves open,
blood that has
accumulated in the atria
flows rapidly into the
ventricles.
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26. RAPID VENTRICULAR FILLING Pressures & Volumes
•Ventricular volume (white)
increases rapidly as blood flows
from the atria into the ventricles.
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27. Q. 4
1. What happens at Point
C?
2. What volume is
represented at Point C?
3. What period is
represented by CD?
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1. Aortic valve opens
2. End-Diastolic Volume
3. Period of Ejection

28. REDUCED VENTRICULAR FILLING
(Diastasis)
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29. REDUCED VENTRICULAR FILLING
Heart
•Rest of blood that has
accumulated in the atria
flows slowly into the
ventricles.
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30. REDUCED VENTRICULAR FILLING Pressures
& Volumes
•Ventricular volume
(white) increases more
slowly now.
•The ventricles continue
to fill with blood until
they are nearly full.
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31. ATRIAL SYSTOLE
The end of diastole
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32. ATRIAL SYSTOLE - Heart
• Prior to atrial systole, blood has been
flowing passively from the atrium into
the ventricle through the open AV valve.
• During atrial systole the atrium contracts
and tops off the volume in the ventricle
with only a small amount of blood.
• Atrial contraction is complete before the
ventricle begins to contract.
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33. Pressure Changes in
the Atria
. ‘a Wave: Produced due to atrial contraction
Rt. Atrial Pressure ( 4-6mmHg <
Lt Atrial Pressure (7-8mmHg)
. ‘C’ Wave. Mainly due to bulging of A-V valve in to the
atrium during ventricular contraction.
. ‘V’ Wave: produced due to slow flow of blood into the
atrium when the A-V valves are still closed during
ventricular contraction
a c v
Atrial Pressure Curve (Blue)

34. Q. 5
1. What happens at Point
D?
2. What volume is
represented at Point C?
3. What period is
represented by DA?
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1. Aortic valve closes
2. End-Systolic Volume
3. Isovolumic relaxation

35. Applied aspects
Stroke Volume
•Volume of blood pumped
by each ventricular
contraction
•Normal value
• 70 ml
Ejection Fraction
•Fraction of end-
diastolic volume that is
ejected
•Normal value
•60% (0.6)
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36. Q. 6
1. Which arrows represent
Stroke Volume?
2. If EDV= 140 ml, ESV= 70
ml, then SV= ?
3. How much is the Ejection
Fraction in above case?
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1. Black arrows
2. 70 ml
3. 50% (0.5)

37. THE COMPLETE
PICTURE
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41. Assessment Q 7 (Part 1-4) (Yes/ No)
1. AV valves open and close passively
2. Stroke vol can be doubled by increasing ESV &
decreasing EDV
3. Calculations of ejection fraction
4. Increasing HR decreases heart filling
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All: Yes

42. Assessment Q. 8 (Part 1-4)
(Aortic & pulmonary artery valves )
1. Which is snap closed?
2. Which closes softly?
3. Velocity of ejection in these valves is greater than
A-V Valves (True / False )
4. These valves are supported by chordae tendineae
(True / False )
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1. Aortic
2. Pulmonary
3. True
4. False

43. Summary (Slide ½)
•Events that occur from the beginning of one heartbeat
to next are called the Cardiac Cycle
•Cardiac cycle consists of a period of contraction
(Systole) followed by relaxation (Diastole)
•Systole consists of isovolumic contraction, followed by
period of rapid & then slow ejection.
•Diastole consists of isovolumic relaxation, followed by
Rapid Filling phase, Slow filling phase (Diastasis), &
then Atrial systole
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44. Summary (Slide 2/2)
•Normally ESV is 40-50 ml, EDV is 110-120 ml, and
stroke volume output 40-50 ml; with an ejection
fraction of 60% (0.6)
•Left ventricular pressure during rapid filling stage is 2-
3 mmHg, at the end of isovolumic contraction 80
mmHg, and 120 mmHg at the peak of the Ejection
Phase.
•‘a’ wave of Atrial systole is due to Atrial contraction, ‘c’
wave due to bulging of A-V valves backwards, and ‘v’
wave due to slow flow of blood from veins to atria.Cardiac Cycle| Prof. Dr. Rashid Mahmood 44

45. Thank You
ppt available on slideshare.com
Questions/ Comments:
drrashid62@gmail.com
rashid.mahmood@rmi.edu.pk
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