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Cardiac cycle
 There is a similar cycle on both sides of
the heart, but the pressures in the right
ventricle and pulmonary arteries are less
than those in the left ventricle and aorta.
 The cycle starts with depolarisation at the
sinoatrial node leading to atrial
contraction.
 Until this time blood flow into the ventricles
has been passive, but the atrial
contraction increases filling by 20-30%.
Cardiac cycle
 A single cycle of cardiac activity can be divided
into two basic stages.
 The first stage is diastole, which represents
ventricular filling and a brief period just prior to
filling at which time the ventricles are relaxing.
 The second stage is systole, which represents
the time of contraction and ejection of blood from
the ventricles.
Cardiac cycle
 To analyze these two stages in more detail,
it is convenient to divide the cardiac cycle into
seven phases.
 The first phase begins with the p-wave in the
electrocardiogram, which represents atrial
depolarization.
 The last phase of the cardiac cycle ends with
the appearance of the next p-wave.
Cardiac Cycle - Atrial Contraction (Phase 1)
A-V Valves Open; Semilunar Valves Closed
1
2
3
Phase
4
5
6
Aortic
Pressure
120
Press 80
(mmHg)
A
RA
7
LV Press
40
LA
PA
a
c
LA Press
v
0
LVEDV
120
LV
RV
LV
Vol
(ml)
80
LVESV
40
ECG
Phase 1
Atrial Contraction
IV
Heart
Sounds
0
I
II
III
0.4
Time (sec)
0.8
Cardiac Cycle - Isovolumetric Contraction
(Phase 2) All Valves Closed
1
2
3
Phase
5
4
6
Aortic
Pressure
120
Press 80
(mmHg)
A
RA
7
LV Press
40
LA
PA
a
c
LA Press
v
0
P
P
LV
RV
LVEDV
120
LV
Vol
(ml)
80
LVESV
40
ECG
Phase 2
Isovolumetric
Contraction
IV
Heart
Sounds
0
I
II
III
0.4
Time (sec)
0.8
Cardiac Cycle - Rapid Ejection (Phase 3)
Aortic and Pulmonic Valves Open; AV Valves Remain Closed
1
2
3
Phase
4
5
6
Aortic
Pressure
120
Press 80
(mmHg)
A
RA
7
LV Press
40
LA
PA
a
c
LA Press
v
0
LVEDV
120
LV
RV
LV
Vol
(ml)
80
LVESV
40
ECG
Phase 3
Rapid Ejection
IV
Heart
Sounds
0
I
II
III
0.4
Time (sec)
0.8
Cardiac Cycle - Reduced Ejection (Phase 4)
Aortic and Pulmonic Valves Open; AV Valves Remain Closed
1
2
3
Phase
4
5
6
Aortic
Pressure
120
Press 80
(mmHg)
A
RA
7
LV Press
40
LA
PA
a
c
LA Press
v
0
LVEDV
120
LV
RV
LV
Vol
(ml)
80
LVESV
40
ECG
Phase 4
Reduced Ejection
IV
Heart
Sounds
0
I
II
III
0.4
Time (sec)
0.8
Cardiac Cycle - Isovolumetric Relaxation
(Phase 5) All Valves Closed
1
2
3
Phase
4
5
6
Aortic
Pressure
120
Press 80
(mmHg)
A
RA
7
LV Press
40
LA
PA
a
c
LA Press
v
0
P
P
LV
RV
LVEDV
120
LV
Vol
(ml)
80
LVESV
40
ECG
Phase 5
Isovolumetric
Relaxation
IV
Heart
Sounds
0
I
II
III
0.4
Time (sec)
0.8
Cardiac Cycle - Rapid Filling (Phase 6)
A-V Valves Open
1
2
3
Phase
4
5
6
Aortic
Pressure
120
Press 80
(mmHg)
A
RA
7
LV Press
40
LA
PA
a
c
LA Press
v
0
LVEDV
120
LV
RV
LV
Vol
(ml)
80
LVESV
40
ECG
Phase 6
Rapid Filling
IV
Heart
Sounds
0
I
II
III
0.4
Time (sec)
0.8
Cardiac Cycle - Reduced Filling (Phase 7)
A-V Valves Open
1
2
3
Phase
4
5
6
Aortic
Pressure
120
Press 80
(mmHg)
A
RA
7
LV Press
40
LA
PA
a
c
LA Press
v
0
LVEDV
120
LV
RV
LV
Vol
(ml)
80
LVESV
40
ECG
Phase 7
Reduced Filling
IV
Heart
Sounds
0
I
II
III
0.4
Time (sec)
0.8