This Presentation is all about the Cardiac cycle. The cardiac cycle is the performance of the human heart from the ending of one heartbeat to the beginning of the next. It consists of two periods: one during which the heart muscle relaxes and refills with blood, called diastole, following a period of robust contraction and pumping of blood, dubbed systole.

1. Cardiac Cycle
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2. Cardiac Cycle
• succession of (sequence of) coordinated events taking place in the
heart during each beat.
• Each heartbeat consists of two major periods called systole and
diastole.
• During systole, heart contracts and pumps the blood through
arteries.
• During diastole, heart relaxes and blood is filled in the heart.
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3. EVENTS OF
CARDIAC CYCLE
Atrial Events
Atrial systole
0.11 sec
Atrial diastole
0.69 sec
Ventricular
Events
Ventricular
systole 0.27 sec
Ventricular
diastole 0.53
sec
Ventricular Systole
0.27 sec
• Isometric
contraction 0.05
sec
• Ejection period
0.22 sec
Ventricular Diastole
0.53 sec
• Protodiastole 0.04
• Isometric
relaxation 0.08
• Rapid filling 0.11
• Slow filling 0.19
• Last rapid filling
0.11
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4. Atrial Systole
• also known as last rapid filling phase or presystole.
• considered as the last phase of ventricular diastole.
• a small amount, i.e. 10% of blood is forced from atria into
ventricles
• not essential for the maintenance of circulation
• During atrial systole, the intra-atrial pressure increases, Intra-
ventricular pressure and ventricular volume also slightly increase
• Contraction of atrial musculature causes the production of fourth heart
sound
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5. Atrial Diastole
• After atrial systole, the atrial diastole starts. Simultaneously,
ventricular systole also starts
• This long atrial (0.69 sec) diastole is necessary because, this is the
period during which atrial filling takes place
• Right atrium receives deoxygenated blood from all over the body via
…
• Left atrium receives oxygenated blood from lungs via…
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6. • Out of 0.69 sec of atrial
diastole, first 0.27 sec
coincides with ventricular
systole.
• Later part of atrial
diastole coincides with
ventricular diastole for
about 0.4 sec
• So, the heart relaxes as a
whole for 0.4 sec
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7. Isometric Contraction Period
• the first phase of ventricular systole. It lasts for 0.05
• Isometric contraction is the type of muscular contraction
characterized by increase in tension, without any change in the
length of muscle fibers
• also called isovolumetric contraction.
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8. • after atrial systole, the atrioventricular valves are closed due
to increase in ventricular pressure.
• Semilunar valves are already closed.
• ventricles contract as closed cavities in such a way that there
is no change in the volume of ventricular chambers or in
the length of muscle fibers
• Only the tension increases in ventricular musculature
• Closure of atrioventricular valves at the beginning of this
phase produces first heart sound
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9. Significance of Isometric Contraction
• during this phase, the pressure increases sharply inside the ventricles
• When the pressure increases above the pressure in the aorta and
pulmonary artery, the semilunar valves open
• This phase is responsible for the opening of semilunar valves, leading
to ejection of blood from the ventricles into aorta and pulmonary
artery
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10. Ejection Period 0.22 sec
• Due to the opening of semilunar valves and isotonic contraction of
ventricles, blood is ejected out of both the ventricles.
• Ejection period is of two stages:
1. First Stage or Rapid Ejection Period 0.13 sec
• starts immediately after the opening of semilunar valves
• a large amount of blood is rapidly ejected from both the ventricles.
2. Second Stage or Slow Ejection Period 0.09 sec
• the blood is ejected slowly with much less force.
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11. End-systolic Volume
• Ventricles are not emptied at the end of ejection period
• some amount of blood remains in each ventricle
• Amount of blood remaining in ventricles at the end of ejection
period is called end systolic volume.
• 60 to 80 mL per ventricle
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12. Protodiastole 0.04 second
• first stage of ventricular diastole
• Due to the ejection of blood, the pressure in aorta and pulmonary
artery increases and pressure in ventricles drops
• intraventricular pressure becomes less than the pressure in aorta and
pulmonary artery, the semilunar valves close.
• Second Heart Sound
• Closure of semilunar valves during this phase produces second heart
sound
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13. Isometric Relaxation Period 0.08 sec
• Isometric relaxation is the type of muscular relaxation, characterized
by decrease in tension without any change in the length of muscle
fibers
• also called isovolumetric relaxation.
• all the valves of the heart are closed
• both the ventricles relax as closed cavities without any change in
volume or length of the muscle fiber
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14. Significance of Isometric Relaxation
• the ventricular pressure decreases
• When the ventricular pressure becomes less than the pressure in the
atria, the atrioventricular valves open
• opening of atrioventricular valves, resulting in filling of ventricles
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15. Rapid Filling Phase 0.11 sec
• Atrioventricular valves are opened, there is a sudden rush of blood
from atria into ventricles
• which is accumulated in atria during atrial diastole
• About 70% of filling takes place during this phase
• Rushing of blood into ventricles during this phase causes production
of third heart sound
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16. Slow Filling Phase 0.19 sec
• It is also called diastasis.
• about 20% of filling occurs in this phase
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17. Last Rapid Filling Phase 0.11 sec
• Last rapid filling phase occurs because of atrial systole.
• After slow filling period the atria contract and push a small amount of
blood into ventricles
• About 10% of ventricular filling takes place during this period
• Flow of additional amount of blood into ventricle due to atrial systole
is called atrial kick.
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18. End-diastolic Volume
• the amount of blood remaining in each ventricle at the end of
diastole
• It is about 130 to 150 mL per ventricle.
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19. Harshit Jadav 19

20. • End-systolic Volume: 60 to 80 mL per ventricle
• End-diastolic Volume: 130 to150 mL per ventricle.
• From 130 to 150 mL of end-diastolic volume, 70 mL is ejected out by
each ventricle. Stroke Volume
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21. Ejection fraction
• Normal ejection
fraction is 60% to
65%.
• Ejection fraction is
the measure of left
ventricular function
• Why left???
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22. Stroke Volume
• Stroke volume is the amount of blood pumped out by each ventricle
during each beat
• Normal value: 70 mL (60 to 80 mL) when the heart rate is normal
(72/minute
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23. Cardiac Output / Minute Volume
• Minute volume is the amount of blood pumped out by each ventricle
in one minute
• Minute volume = Stroke volume × Heart rate
• Normal value: 5 L/ventricle/minute.
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