The cardiac cycle refers to the repeating sequence of heart contraction and relaxation as the heart pumps blood throughout the body. It begins with atrial contraction which pumps blood into the ventricles, followed by ventricular contraction which pumps blood out of the heart and into the arteries. The cycle is monitored by an electrocardiogram (ECG) which detects and graphs the electrical activity of the heart muscles. Key waves in the ECG correspond to atrial and ventricular contraction and relaxation phases. Heart sounds are also produced during closure of the valves and provide information about heart function.

1. CARDIAC CYCLE , ECG
AND HEART SOUNDS.
BY
MRS.WINCY THIRUMURUGAN
professor

3. DEFINITION OF CARDIAC CYCLE
The cardiac cycle is defined as a sequence of
alternating contraction and relaxation of
the atria and ventricles in order to
pump blood throughout the body.
OR
“Cardiac cycle refers to the series of events
that take place when the heart beats.”

4. • Each cycle is initiated by spontaneous contraction in
the SA node and then transmit through the A-V
bundle and branches into the ventricles results
completion of one cycle.

5. • Cardiac cycle begins
at 4th gestational
week when
the heart first
begins contracting.
• when the atria are
in diastole, the
ventricles are in
systole and vice
versa.

6. EVENTS OR PHASES OF CARDIAC CYCLE:
Two Major events of cardiac cycle
Diastolic phase (Diastole) in this phase the heart chamber are
in the state of relaxation and fills with blood that receives from
the veins [IVC,SVC,PULMONARY VEINS]
Systolic phase (Systole) in this the heart chambers are
contracting and pumps the blood towards the periphery via the
arteries.[ Pulmonary artery and aorta]

7. PHASES OF THE CARDIAC CYCLE
The different phases of the cardiac cycle involve:
1. Atrial diastole - Atrial relaxation
2. Atrial systole -Atrial contraction
3. Isovolumic relaxation -ventricular relaxation in the early
phase but blood will not move and the Atrio ventricular valves will
be closed
4. Ventricular filling - ventricular relaxation , the Atrio
ventricular valves will be open allows filling blood in the
ventricles
5. Isovolumic contraction of ventricle – ventricular systole in the early
phase but no movement of the blood.The semilunar valves will be
closed.

8. Iso means Equal
systole-contraction
Diastole-relaxation

9. Cardiac Cycle Phases:
Following are the different phases that occur in a cardiac cycle:
1. Atrial Diastole: In this stage, chambers of the heart are calmed. That
is when the aortic valve and pulmonary artery valve and
atrioventricular valves close, thus causing chambers of the heart to
relax.
2. Atrial Systole: At this phase, atrium contracts and blood flow from
atrium to ventricle .

10. 3.Isovolumic Contraction of ventricle:(EARLY PHASE)
At this phase,the ventricles begin to contract [ early systole]. The
atrioventricular valves, aortic and pulmonary artery valves closed , but
there won’t be any transformation in volume and no volume change
occurs.
4.Ventricular Ejection:( END PHASE)
Here ventricles contract and emptying. Pulmonary valve and aortic
valve[semilunar valves] open and blood moves into aorta and into the
pulmonary trunk.

11. 5.Isovolumic Relaxation of the ventricle: (Early PHASE)
 In this phase, no blood enters the ventricles
[ early diastole] and pressure decreases, ventricles stop contracting
and begin to relax.
 When the ventricular pressure drop below the aortic and pulmonary
artery pressure – pulmonary artery and aortic valve close.

12. 6. Ventricular Filling Stage: second phase.
In this stage, blood flows from atria into the ventricles by
three stages.
1.Rapid Filling.
When AV valves are opened, there is a sudden rush of
blood from atria into ventricles. So this period is called the
first rapid filling period.
Filling during this period occurs without atrial systole. About
70% of filling takes place during this phase which lasts for
0.11 second.

13. 2.Slow Filling
After the sudden rush of blood, the ventricular filling becomes slow.
Now, it is called the slow filling. It is also called diastasis. Filling during
this phase also occurs without atrial systole. About 20% of filling occurs
in this phase. Duration of slow filling phase is 0.19 second.
3. Last Rapid Filling [atrial kick]
This occurs because of atrial systole. After slow filling period, the
atria contract and push a small amount of blood into the
ventricles. About 10% of ventricular filling takes place during this
period. Duration is 0.11 seconds.

14. Duration of Cardiac Cycle:
In a normal person, a heartbeat is 72 beats/minute.
So, the duration of one cardiac cycle can be calculated as:
1/72 beats/minute=.0139 minutes/beat
is equal to .834 seconds. [ 60sec/72 beats =.834 seconds]
At a heartbeat 72 beats/minute, duration of each cardiac cycle will be 0.8 seconds.
Duration of different stages of the cardiac cycle is given below:
•Atrial systole: continues for about 0.1 seconds
•Ventricular systole: continues for about 0.3 seconds [0.27]
•Complete cardiac diastole: continues for about 0.4seconds [ average of atrial and ventricular
relaxation]

15. DURATION OF VENTICULAR
Venticular Systole ( 0.27 )
1. Isometric contraction 0.05
2. Period of Ejection 0.22
DURATION OF Venticular Diastole
( 0.53 )
1. Diastole 0.04
2. Isometric
Relaxation 0.08
3. Rapid filling 0.11
4. Slow filling 0.19
5. Last rapid filling 0.11
The total duration of ventricular events is 0.27 + 0.53 = 0.8
Hence,the duration of each cardiac cycle is 0.8 second.
Atrial Events
1. Atrial Systole - 0.11/ 0.1 sec
2. Arterial Diastole- 0.69 i.e. 0.7 sec
The duration of arterial events is 0.8sec. 0.1 + 0.7 = 0.8 sec

17. ECG

18. ECG –ELECTRO CARDIO GRAM AND
EVENTS OF CARDIAC CYCLE.

21. • Willem Einthoven was a Dutch doctor and physiologist.
• He invented the first practical electrocardiograph (ECG or EKG) in
1895
• An Electrocardiogram (ECG) is a medical test that
detects cardiac (heart) abnormalities by measuring the
electrical activity generated by the heart as it contracts.
• The machine that records the patient’s ECG is called
an electrocardiograph.
• The electrocardiograph records the electrical activity of
the heart muscle and displays this data as a trace on a
screen or on paper.
• ECGs from healthy hearts have a characteristic shape
and a normal ECG wave is called sinus rhythm.
• Any irregularity in the heart rhythm or damage to the
heart muscle can change the electrical activity of the
heart so that the shape of the ECG is changed.

25. Electrode (E.C.G) Gel will
improve conductivity
between the skin and the
heart rate monitor
electrodes.

27. PLACEMENT OF ECG LEADS

28. U - repolarization of the Purkinje fibers
Depolarization – Contraction of ventricles
Repolarization –Relaxation of ventricles

30. ECG WAVES:
• The P wave is caused by spread of depolarization through the atria [ atrial
systole]
• After the onset of the P wave, The QRS waves Occurs as a result of
electrical depolarization of the ventricles, [ventricular systole]
• Finally, the ventricular T wave represents the stage of repolarization of
the ventricles[ ventricular diastole]
• The 'U' wave is a wave comes after the T wave of ventricular
repolarization and may not always be observed as a result of its small
size. 'U' waves are thought to represent repolarization of the Purkinje
fibers.

32. Measured in millivolts (mv). It means
A unit of measure for low voltage levels .

33. HEART
SOUNDS

34. Heart sounds

36. First Heart Sound (S1)
• The first heart sound results from the
closing of the mitral and tricuspid valves.
• The sound produced by the closure of
mitral valve is termed M1, and the sound
produced by closure of the tricuspid
valve is termed T1.
• The M1 sound is much louder than the
T1 sound due to higher pressures in the
left side of the heart.

37. Second Heart Sound (S2):
• The second heart sound is produced by the
closure of the aortic and pulmonic valves.
• The sound produced by the closure of the
aortic valve is termed A2, and the sound
produced by the closure of the pulmonic valve
is termed P2.
• The A2 sound is normally much louder than
the P2 due to higher pressures in the left side

38. Third Heart Sound (S3):
• The third heart sound, also known as the
“ventricular gallop,” occurs just after S2 when
when the mitral valve opens, allowing passive
filling of the left ventricle.
• The S3 sound is actually produced by the
large amount of blood striking a very
compliant LV.
[Compliance heart means how easily the chamber of
heart or the lumen of blood vessels expands when it is

39. Fourth Heart Sound (S4):
The fourth heart sound, also known as
the “atrial gallop,” occurs just before S1
when the atria contract to force blood
into the LV.
If the LV is noncompliant, and atrial
contraction forces blood through the
atrioventricular valves, a S4 is produced