Author's Affiliation: United Medical & Dental College, Karachi, Pakistan. Preamble: Cardiac Cycle is one of the complex topic of the heart for the students of basic years of medicine. Author has taken material from various sources and animated the individual pressure, volume, electrical & acoustic curves related with the events of cardiac cycles for better understanding.

1. 1Prof. Dr. Muhammad Abdul Azeem, UMDC
Prof. Dr. Muhammad Abdul Azeem,
United Medical & Dental College, Karachi, Pakistan

2. Definition of Cardiac Cycle
Events from the beginning of one
heart beat to the beginning of the next
beat is called cardiac cycle.
2Prof. Dr. Muhammad Abdul Azeem, UMDC

3. • Before the detailed study of Cardiac Cycle. It is
better to understand the relation between
electrical and mechanical activity that occurs
during cardiac cycle.
• Electrical activity: Represents generation and
propagation of electrical current from pacemaker
towards all parts of heart.
• Mechanical activity: Represents activation of
cardiac muscle fibers by electrical activity to
generate force for pumping of blood into
circulation.
3Prof. Dr. Muhammad Abdul Azeem, UMDC

4. Relation of Cardiac Muscle Contraction with Its
Action Potential
• Cardiac muscle begins to
contract a few mS after
the action potential
begins.
• They continues to
contract until a few mS
after the action potential
ends.
• Therefore, duration of
their contraction is a
function of duration of
their action potential, 0.2
second in atrial muscle
and 0.3 second in
ventricular muscle.
4Prof. Dr. Muhammad Abdul Azeem, UMDC

5. Cardiac
Cycle
5Prof. Dr. Muhammad Abdul Azeem, UMDC

6. Cardiac
Cycle
6Prof. Dr. Muhammad Abdul Azeem, UMDC

7. Atrial
Pressure
Curve
• a wave = atrial contraction as primer pump.
– Right atrial pressure = 4 to 6 mm Hg .
– Left atrial pressure = 7 to 8 mm Hg.
• c wave = ventricles begin to contract;
– bulging of the A-V valves backward toward the atria.
• v wave = end of ventricular contraction;
– slow flow of blood into the atria from the veins.
• v wave disappear when blood flow rapidly into
the ventricles. 7Prof. Dr. Muhammad Abdul Azeem, UMDC

8. Ventricular Pressure Curve
in Cardiac Cycle
8Prof. Dr. Muhammad Abdul Azeem, UMDC

9. Aortic Pressure Curve • Isovolumetric
Contraction of left
ventricle.
• Increase in ventricular
pressure
• Opening of Aortic
Valve.
• Contraction of
Ventricle.
• Entry of blood in aorta,
pressure 120mmHg.
• Aortic valve closes.
Appearance of Dicortic
notch.
• Incisura appears due
to Backward flow
Aortic
Valve
Open
Ejection wave
Systolic Phase
Reflected wave
Diastolic Phase
Incisura
Dicortic Notch
Aortic Valve Closes
9Prof. Dr. Muhammad Abdul Azeem, UMDC

10. Systolic intervals (0.27 Sec)
Isometric Contraction (Isovolumic; IVC) 0.05 (Sec)
Ejection Period 0.22 (Sec)
Diastolic intervals (0.53 Sec)
Proto-diastole (Reduced Ejection) 0.04 Sec
Isometric Relaxation (Isovolumic; IVR) 0.08 Sec
Rapid Filling 0.11 Sec
Slow Filling 0.19 Sec
Atrial Systole 0.11 Sec
http://www.slideshare.net/gopikrishnarayidi/cardiac-cycle-ppt-2 Dr. Gopi Krishna
TOTAL TIME OF CARDIAC CYCLE INCLUDING
SEVEN INTERVALS (0.8 Seconds)
10Prof. Dr. Muhammad Abdul Azeem, UMDC

11. End-Diastolic Volume, End-Systolic Volume, and Stroke Volume
Output
• During diastole, blood volume increases in
each ventricle to about 110 to 120 ml. This
volume is called end-diastolic volume.
• Ventricular emptying during systole decreases
70 ml from this volume. It is called stroke
volume output.
• The remaining volume in each ventricle is 40
to 50 ml (end-systolic volume).
11Prof. Dr. Muhammad Abdul Azeem, UMDC

12. VENTRICULAR VOLUME CURVE
12Prof. Dr. Muhammad Abdul Azeem, UMDC

13. Ejection Fraction & Ventricular
Volume
• The fraction of the end-diastolic volume that is ejected is called
the ejection fraction (about 60 percent of the total blood).
• During strong contraction of heart, the end-systolic volume is
reduced to only 10 to 20 ml.
• Conversely, when large amounts of blood flow into the
ventricles during diastole, the ventricular end-diastolic
volumes can become as great as 150 to 180 ml in the healthy
heart.
13Prof. Dr. Muhammad Abdul Azeem, UMDC

14. Left Ventricular Rotation During Systole In Cardiac
Cycle:
• Beneficial Effects of LV Rotation
–Maximizes intra-cavity pressures.
–Increases stroke volume.
–Minimizes myocardial oxygen demand.
14Prof. Dr. Muhammad Abdul Azeem, UMDC

15. Relation of ECG with Cardiac Cycle
• P wave appears
before atrial
systole.
• QRS complex
appear before
Isovolumetric
contraction of
ventricle.
• T wave appears
before iso-
volumetric
relaxation and
ends before actual
relaxation of
ventricles. 15Prof. Dr. Muhammad Abdul Azeem, UMDC

16. Recent Research (2013)
Detection of Heart Blocks by Cardiac Cycle Extraction
using Time- Scale Analysis
http://ijetsp.info/article/IJETSPV1I302.pdf
OVERLAPS OF SINGULAR CC IN
NORMAL HEART
(Regular Rhythm)
OVERLAPS OF SINGULAR CC IN
ARHYTHMIC HEART WITH BLOCK
(Irregular Rhythm)
All the cardiac cycles taken individually from ECG recordings are overlapped to detect
abnormalities in the heart. PR interval of a normal ECG has a maximum duration of 0.2
seconds, a PR interval of 0.3 second is considered as worst case value. Similarly, a QT
interval value of 0.44 seconds is considered.
16Prof. Dr. Muhammad Abdul Azeem, UMDC

17. Heart Sounds & Cardiac Cycle
Phonocardiogram
• Opening of valve does not produce any sound because it is a
slow process.
• During closure of valves, their vanes and the surrounding fluids
vibrate under the influence of sudden pressure changes, giving
off sound that travels in all directions in the chest.
17Prof. Dr. Muhammad Abdul Azeem, UMDC

18. VALVES
POSITION AS
PER
INTERCOSTAL
SPACE
POSITION AS
PER STERNAL
BORDER
Aortic
valve (to aorta)
right
second intercos
tal space
upper right
sternal border
Pulmonary
valve (to pulmo
nary trunk)
left second
intercostal
space
upper left
sternal border
Erb's point
Left third
intercostal
space
left sternal
border
Tricuspid
valve (to right
ventricle)
left fourth, fifth
intercostal
spaces
lower left
sternal border
Mitral
valve (to left
ventricle)
left fifth
intercostal
space
left
midclavicular
line

19. 19Prof. Dr. Muhammad Abdul Azeem, UMDC
SOUNDS FOUND
IN
COMPONENTS EVENT OF CARDIAC
CYCLE
CONDITIONS
First heart
sound (S1 )
Normal
Persons
two component sound,
M1, T1.
ventricles contract with
closure of A-V valves
The vibration is low in
pitch and relatively long-
lasting.
Second heart
sound (S2 )
Normal
Persons
2 components, A2 and P2. When semilunar valves
close rapidly at the end
of systole.
a rapid snap heard.
Third heart
Sound (S3)
Children & young adults Early diastolic filling of
Ventricles
Rare extra heart sound
occurs soon after normal
S1 and S2.
Fourth heart
Sound (S4)
Normal Adults Late diastolic filling of
Ventricle
S3 & S4 Diseased States; heart failure &
cardiac diseases
Gallop Sound
S4 prior to S1,
where atrial
contraction does
not precede
ventricular
contraction
Pathological Condition Forceful atrial
contraction
Absent in Fibrillation
(rapid & irregular
beating),
However, in left bundle branch block (LBBB) allow the P2 sound to be heard before the A2 sound during
expiration. With LBBB, inhalation brings A2 and P2 closer together where they cannot be audibly
distinguished.

20. Referred from
• Text book of physiology by Guyton
• Physiology by Berne & Leve
• Clinical Physiology by Ashish Banerjee
• Internet Resources
• Updated 2015