The cardiac cycle describes the mechanical and electrical events of the heart during one complete heartbeat. It includes atrial and ventricular relaxation and filling followed by contraction and ejection. The normal cardiac cycle is approximately 0.8 seconds long and divided into systole which is 1/3 of the cycle and diastole which is 2/3. It involves phases such as isovolumetric contraction, ejection, isovolumetric relaxation and filling. Events in the cardiac cycle produce the four characteristic heart sounds.

2. Topic: Cardiac cycle
Supervisor; Dr Kelaash Kumar
Presantator ; Dr Abdul Qadeer

3. • DEFINATION
• EVENTS
• DURATION & DIVISION
• SUB-DIVISION
• HEART SOUNDS

4. Definition
• Cardiac cycle is the period from beginning of one
heart beat to begnning of other heart beat in which
atrial and ventricle change pressure and changes in
volume occurs in different phases.
• OR
• Mechanical and electrical events that causes cardiac
contraction or ejection (ventricular systole ) , and
relaxtion or filling (ventricular diastole) and pressure
gradient develop between chambers which leads to
ejection of stroke volume and farward flow of blood
through body

5. EVENTS
• Atrial and ventrical diastole(relaxation)
• Filling phase
• Atrial and venticle systole (contraction)
• Ejection phase
• Pump blood

6. Duration
• > Normally heart beats rate 72bpm and
• > cardiac cycle duration is 0.8 sec
• Cardiac cycle inversely proportional to heart rate.
• >Duration of
• Diastole 2/3rd
• Systole 1/3rd

7. Division cardiac cycle phase
1-Atrial systole
• atrial systole is also known as last rapid filling or pre-
systole
• It is usually consider as last phase of ventricle
diastole
• Duration is 0.11sec
• During this period only 10% of blood is forced from
atria into ventricle
• Intra atrial pressure increase
• Contraction of atria musculature cause production
4th heart sound

8. Atrial diastole
Atrial diastole start after atrial systole sumitaniously
ventricular systole also start.
Atrial diastole last for about 0.7sec
The long atrial diastole is necessory because ,this is
period during which atrial filling take place

9. Ventricle Events
• CONTRACTION(SYSTOLE)
• ISOVOLUMETRIC CONTRACTION PERIOD
• EJECTION PERIOD
• PROTO-DIASTOLE
• RELAXTION (DIASTOLE)
• ISOVOLUMETRIC RELAXTION PERIOD
• RAPID FILLING
• SLOW FILLING
• LAST RAPID FILLING

10. ISOVOLUMETRIC CONTRACTION
• First phase of ventricle systole
• It last for 0.05sec
• This is a type of muscle contraction characterized by increase in
tension without any change n length of muscle fiber
• Immediately after atrial contracion ,the atrioventriculoVavle are
closed due to increase n ventricular pressure
• Semilunar valve already closed
• Now ventricle contract as closed cavities
• In such way no change in the ventricle chamber or the length of
fiber
• Only the tension increase in ventricle musculture
• Closure of AV-valve begnining of this phase produce 1st Heart sound

11. Ejection period
• Due to opening of the semilunar valves and
isotonic contraction ventricles blood is ejected
out of both ventricle
• Duration of ejection period =0.22sec
• FIRST STAGE (RAPID EJECTION)
• SECOND STAGE ( SLOW EJECTION)

12. 1ST STAGE RAPID EJECTION
• Start immeditely after the opening of
semilunar valves
• During this stage large amount of blood is
rapidly ejected from both ventricle
• It last for 0.13sec

13. 2nd stage Slow ejection
• During this stage the blood is ejected slowly
with much less force
• Duration of this period is 0.09sec

14. Proto diastolic
• first sage of ventricle diastole hence the name
protodiastole
• Duration of this phase is 0.04sec
• Due to the ejection of blood ,the pressure is aorta
and pulmonary artry increased and pressure in
ventricle drops
• When intraventricle pressure become less than
the pressure in aorta &pulmonary artery
,semilunar valve closed
• Cosure of semilunar valve during this phase
produce 2nd heart sound

15. ISOVOLUMETRIC RELAXTION PERIOD
• It is stage of muscular relaxtion characterized
by decrease in tension without any change in
length of muscle fiber
• During this period once again all the valve of
the heart are closed
• Intraventricle pressure decreases
• Duration is 0.08sec

16. RAPID FILLING PHASE
• When AV valves are opened there is sudden
rush of blood from atria into ventricle
• So this period is called first rapid filingperiod
• Ventricles are also relaxed isotonically about
70% of filling take place during this phase
which last for 0.11sec.
• Rushing of blood into ventricle during this
phase cause production of 3rd heart sound

17. Slow filling phase
• After sudden rush of blood , ventricle filling
become slow, now it is called slow filling
• It is also called as diastsis
• About 20% of filling occur in this phase
• Durration last for 0.19 sec

18. LAST-RAPID FILLING
• Last rapid filling phase occur because of atrial
systole
• After slow filling period the atria contract and
push a small ammount of blood into ventricle
• About 10%ventricle filling take place during
this period
• Flow of additional amount of blood into
ventricles due to the atrial systole is atrial kick