Understanding the Cardiac Cycle: Phases and Events Explained

 
CARDIOVASCULAR
 
SYSTEM
CARDIAC
 
CYCLE
 
Dr Syed 
Shahid
 
Habib
Professor 
& 
Consultant 
Clinical 
Neurophysiology
Dept. 
of
 
Physiology
College 
of 
Medicine 
& 
KKUH
King Saud
 
University
 
PROF. 
HABIB
 
2018
 
O
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At the end 
of 
the lecture 
you should be
able 
to
 
…..
 
PROF. 
HABIB
 
2018
 
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PROF. 
HABIB
 
2018
 
CARDIAC
 
CYCLE
 
Definition:
 
Cardiac 
Cycle is 
the time 
duration
comprising all the 
events from 
beginning 
of
one 
heart 
contraction 
to 
the 
beginning 
of
next 
heart
 
contraction.
 
At 
heart 
rate 
of 75 
beats per 
minute
duration of 
one 
Cardiac 
cycle is 
0.8
 
second.
 
What are 
the
 
Events?
 
PROF. 
HABIB
 
2018
 
Mechanical
 
changes:
1.
Phases 
of cardiac
 
cycle
2.
Heart
 
sounds
3.
Pressure 
changes during 
cardiac
 
cycle
4.
Volume 
changes during 
cardiac 
cycle
Electrical
 
Changes
5.
Electrocardiogram
 
(ECG)
 
EVENTS 
OF 
CARDIAC
 
CYCLE
 
PROF. 
HABIB
 
2018
 
The 
Events 
of 
the Cardiac
 
Cycle
 
PROF. 
HABIB
 
2018
 
Atrial 
systole: 
0.1
 
second
Atrial 
diastole 
: 
0.7
 
seconds
Ventricular
 
Events
Ventricular 
systole 
: 
0.3
 
seconds
Ventricular 
diastole 
: 
0.5
 
seconds
 
PHASES 
OF 
CARDIAC
 
CYCLE
Atrial
 
Events
 
CARDIAC
 
CYCLE
0.8
 
SECONDS
 
PROF. 
HABIB
 
2018
 
V
E
N
T
RICU
L
A
R
SYSTOLE
0.3
 
SECONDS
 
V
E
N
T
RICU
L
A
R
DIASTOLE
0.5
 
SECONDS
 
ATRIAL
SYS
T
O
L
E
0.1
 
SEC
 
ATRIAL
 
DIASTOLE
0.7
 
SECONDS
 
CARDIAC
 
CYCLE
0.8
 
SECONDS
 
PROF. 
HABIB
 
2018
 
PROF. 
HABIB
 
2018
 
Ventricular systole
1.
Isovolumetric 
contraction
2.
Ejection
 
phase
Rapid
 
ejection
Slow 
ejection
Ventricular
 
Diastole
1.
Isovolumetric 
relaxation
 
phase
2.
Filling
 
phase
Rapid
 
filling
Slow 
filling (Continued
 
filling)
Last 
rapid 
filling 
(Atrial
 
Systole)
 
VENTRICULAR
 
EVENTS
 
PROF. 
HABIB
 
2018
 
PHASES 
OF 
CARDIAC
 
CYCLE
 
PROF. 
HABIB
 
2018
 
Importance of the long 
ventricular 
diastole? 
This 
is 
important
 
for:
 
Coronary blood 
flow & 
Ventricular
 
filling
 
PROF. 
HABIB
 
2018
 
PROF. 
HABIB
 
2018
 
PROF. 
HABIB
 
2018
 
PRESSURE
 
CHANGES
 
VARIOUS 
PRESSURE
 
VALUES
 
PROF. 
HABIB
 
2018
 
VOLUME
 
CHANGES
 
End 
Diastolic 
Volume:
 
Volume 
of blood in 
each
ventricle 
at 
the 
end 
of
 
diastole.
 
It 
is about 110 
120
 
ml.
End 
Systolic 
Volume:
 
Volume 
of blood in 
each
ventricle 
at 
the 
end 
of 
Systole. 
It 
is about 
40 
to 
50
ml
Stroke 
Volume:
 
It 
is 
a 
volume 
of blood 
pumped
out 
by 
each ventricle per 
beat.
 
It 
is about 
70 
ml.
Stroke 
volume 
(SV) 
= 
EDV 
 
ESV
 
PROF. 
HABIB
 
2018
 
EJECTION FRACTION
 
(EF) is 
the 
percentage 
of
ventricular 
end 
diastolic volume 
(EDV) 
which 
is
ejected 
with each
 
stroke.
 
SV 
or 
(EDV 
 
ESV)
 
X
 
100
 
EDV
 
75
X 
100 
=
 
62.5%
120
Normal ejection 
fraction 
is 
about 
60 – 65
 
%.
Ejection 
fraction 
is 
good 
index 
of 
ventricular
 
function.
 
PROF. 
HABIB
 
2018
 
EF
 
=
 
ATRIAL
 
SYSTOLE
 
Atrial
 
Depolarization
Atrial
 
contraction
Atrial 
pressures
 
rise
Blood flows 
across 
AV
 
valves
 
ATRIA 
= PRIMER PUMPS
 
.
Ventricular 
filling
 
:
80% 
- 
direct flow 
from 
SVC 
&
 
IVC
20% 
- 
atrial
 
contraction.
 
PROF. 
HABIB
 
2018
 
PROF. 
HABIB
 
2018
 
Increase 
in 
ventricular 
pressure
 
>
atrial 
pressure 
AV 
valves
 
close
After 
0.02s, 
semilunar 
valves
 
open
Period between 
AV 
valve 
closure
and semilunar 
valve 
opening 
heart 
prepares 
for 
contraction
without 
shortening→ occurs
without
 
emptying
Tension 
develops 
without 
change 
in
muscle
 
length
 
ISOVOLUMETRIC
 
CONTRACTION
 
PROF. 
HABIB
 
2018
 
When
  
LV
pres 
> 80 
mm Hg  
RV
pres 
> 8 
mm
 
Hg,
The 
semilunar 
valves
 
open.
Rapid 
Ejection – 70% 
emptying
 
in
first 
1/3
 
duration
Slow 
Ejection – 30% in 
last 
2/3
 
time
The 
pressure 
in the 
ventricle
 
keeps
decreasing until 
it 
becomes lower
than 
that 
of the 
great
 vessels
 
EJECTION
 
PROF. 
HABIB
 
2018
 
When 
ventricle 
pressure 
< 
arterial
pressure→ 
backflow of blood →
forces 
semilunar 
valves 
to
 close.
For 
0.03-0.06 s, 
ventricle
 
relaxes
despite 
no 
change 
in its
 
volume
AV 
and Semilunar 
valves 
are
 
closed
Meanwhile, 
atria 
fill up 
and 
atrial
pressure 
gradually
 
rises
Pressures 
in 
ventricle 
keep 
falling 
till
it is < 
atrial
 
pressure
 
ISOVOULUMETRIC
 
RELAXATION
 
PROF. 
HABIB
 
2018
 
Begins 
with 
the 
opening
 
of
AV
 
valves
Rapid filling 
first 
1/3
 
of
diastole 
(60-70%
 
blood)
Reduced 
filling 
(Diastasis)
 
middle 
1/3 
of
 
diastole
Atrial contraction 
last
 
1/3
of 
diastole 
(27-30%
 
blood)
 
VENTRICULAR
 
FILLING
 
As 
the 
atrial pressures 
fall, 
the 
AV 
valves 
close 
and 
left 
ventricular volume
is 
now 
maximum → 
EDV 
(120 
ml 
in
 
LV)
 
PROF. 
HABIB
 
2018
 
Aortic 
Pressure
 
Curve
 
a.
Ascending 
or 
anacrotic
 
limb:
 
This coincides with
 
the
‘rapid 
ejection
 
phase’
 
The 
amount 
of
 
blood
enters 
aorta 
>
 
leaves
 
Aortic 
pressure 
↑ up
 
to
120
 
mmHg
b.
Descending 
or
 
catacrotic
limb: 
(Has 
4
 
stages)
 
Pulmonary artery 
pressure changes
are 
similar 
to 
the aortic 
pressure
changes but 
with 
difference 
in
magnitude. Normal 
pulmonary
artery 
pressure during 
the 
cardiac
cycle 
25-30/4-12
 
mmHg
 
Descending / 
catacrotic 
limb - 4
 
STAGES
 
1.
Aortic
 
pressure:
 
This coincides 
with the 
‘reduced
ejection
 
phase’
 
The 
amount 
of 
blood 
enters 
aorta 
<
leaves
 
2.
Dicrotic 
notch (incisura):  
Due
to 
closure 
of aortic
 
valve
 
There 
is sudden 
drop 
in aortic
pressure
 
This 
notch 
is 
seen 
in the aortic
pressure curve 
at 
end of 
ventricular
systole
 
3.
Dicrotic
 
wave:
Due 
to 
elastic recoil 
of the
 
aorta
 
Slight 
in aortic
 
pressure
 
4.
Slow 
aortic press: up 
to 
80 
mmHg
Due 
to 
continued 
flow of 
blood
 
from
aorta 
systemic
 
circulation
 
PROF. 
HABIB
 
2018
 
Atrial pressure 
changes during 
the 
cardiac 
cycle
THE 
JUGULAR 
VENOUS 
PULSE
 
(JVP)
 
PROF. 
HABIB
 
2018
 
OF. HABIB
 
2018
 
The 3 
wave 
(a, c, 
& 
v) 
are 
equal
to 
ONE 
cardiac cycle 
= 
0.8
 
sec
 
Atrial pressure 
changes during 
the
cardiac
 
cycle
 
3 
upward
 
waves:
 
a, 
c, & v
 
waves
 
2 
components 
in
 
each
wave: 
+ve 
(↑ pr), 
-ve
(↓
 
pr)
 
2 
downward
 
deflection
(waves):
 
x & y
 
waves
 
PROF. 
HABIB
 
2018
 
 
‘a’ wave: 
Atrial systole: 
atrial pressure during atrial
 
contraction
 
 
‘c’ 
wave: Ventricular
 
systole
 
+ve 
as a 
result 
of 
bulging 
of 
AV 
valve into 
the 
atria during
‘isovolumetric 
contraction
 
phase’
 
-ve 
as a 
result 
of 
pulling 
of the 
atrial muscle 
& 
AV 
cusps
down 
during 
‘rapid 
ejection 
phase’, 
resulting 
in 
atrial
pressure
 
 
‘v’ 
wave: 
Atrial diastole 
or 
venous 
return
 
(VR)
 
+ve: 
atrial pressure 
gradually due 
to continuous
 
VR
 
-ve 
as a 
result 
of 
atrial pressure during 
‘rapid 
filling
 
phase’
 
 
‘x’
 
descent:
 
Downward 
displacement 
of 
AV 
valves 
during ‘reduced
ejection
 
phase’
 
‘y’
 
descent:
 
atrial pressure during ‘reduced filling
 
phase’
 
Atrial pressure
 
waves
 
PROF. 
HABIB
 
2018
 
CORRELATING 
EVENTS
 
TOGETHER
 
2
6
 
PROF. 
HABIB
 
2018
 
JVP 
‘a’
 
wave
ECG 
– P 
wave 
precedes the 
atrial 
systole. 
PR 
interval 
depolarization
proceeds 
to 
the 
AVN. 
The 
brief 
pause 
allows 
complete ventricular
 
filling
Heart sounds 
- 
S 
4 
pathological. 
Vibration 
of the 
ventricular 
wall 
during
atrial contraction. Heard in ‘stiff’ 
ventricle 
like 
in 
hypertrophy 
and 
in 
elderly.
Also heard in 
massive 
pulmonary embolism, cor pulmonale,
 
TR
 
A
T
R
I
A
L
S
Y
S
T
O
L
E
 
PROF. 
HABIB
 
2018
 
JVP 
‘c’ 
wave 
→ due 
to 
the 
bulging 
of the 
Tricuspid 
valve 
into
RA secondary 
to 
increased pressure 
in the
 
ventricle.
ECG 
– End of 
QRS
 
complex
Heart
 
Sounds
 
 
S
1 
: 
closure 
of the 
AV
 
valves.
 
I
S
O
V
O
L
U
M
E
T
R
I
C
C
O
N
T
R
A
C
T
I
O
N
Volume 
does not 
change
All 
valves 
are
 
closed
 
PROF. 
HABIB
 
2018
 
JVP 
– no
 
waves
ECG 
– T
 
wave
Heart 
sounds 
 
none
Aortic
 
pressure
 
-
 
Rapid 
rise 
in 
the 
pressure 
= 120 
mm
Hg. 
Even 
at 
the end of 
systole 
pressure 
in 
the 
aorta 
is
maintained 
at 
90 
mm Hg 
because 
of the 
elastic
 
recoil
 
E
J
E
C
T
I
O
N
R
a
p
i
d
S
l
o
w
 
PROF. 
HABIB
 
2018
 
JVP: 
‘v’ 
wave 
– due 
to venous return to 
the 
atria 
from 
SVC 
and
 
IVC
ECG: 
End of T
 
wave
Heart 
sounds: 
S
2 
: 
closure 
of the 
semilunar 
valves 
coincides with
this
 
phase.
Aortic 
pressure curve: 
INCISURA 
- 
when 
the 
aortic 
valve 
closes.
Caused 
by 
a short 
period 
of 
backflow 
before 
the 
valve 
closes
followed by 
sudden cessation 
of the 
backflow when the 
valve
closes.
 
I
S
O
V
O
L
U
M
E
T
R
I
C
R
E
L
A
X
A
T
I
O
N
Volume 
does not 
change
All 
valves 
are
 
closed
 
PROF. 
HABIB
 
2018
 
V
E
N
T
R
I
C
U
L
A
R
F
I
L
L
I
N
G
 
PROF. 
HABIB
 
2018
 
Rapid
 
filling
Reduced
 
filling
Atrial
 
contraction
 
 
JVP 
‘y’ 
descent in 
first 
2/3 
& 
‘a’ wave 
in 
last
 
1/3
ECG 
P 
wave 
before 
atrial
 
systole
Heart sounds 
-
 
S
3
 
-
 
Pathological 
in adults. 
Seen
 
in
dilated 
congestive 
heart 
failure, 
MI, 
MR, 
severe
hypertension. 
Normal in
 
children.
 
PROF. 
HABIB
 
2018
 
A
B
N
O
R
M
A
L
I
T
I
E
S
 
O
F
 
a
 
W
A
V
E
 
PROF. 
HABIB
 
2018
 
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t
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PROF. 
HABIB
 
2018
 
Both ventricular 
systole 
& 
diastole 
can 
be
 
divided
into 
early 
& 
late
 
phases.
 
Systole:
Early
 
systole
 
=
 
‘Isovolumetric
 
Contraction’.
Late
 
systole
 
=
 
Isotonic 
Contraction
 ‘EjectionPhase’.
 
Diastole:
Early 
diastole 
=
 
‘IsovolumetricRelaxation’.
Late
 
diastole
 
=
 
Isotonic
 
Relaxation
 
‘Filling
 
Phase’.
 
PROF. 
HABIB
 
2018
 
B
A
S
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C
 
M
Y
O
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A
R
D
I
A
L
 
M
U
S
C
L
E
 
M
E
C
H
A
N
I
C
S
:
 
LateDiastole
(Filling
 
phase)
 
VENTRICULAR 
PRESSURE - 
VOLUME
 
LOOP
 
Plots 
LV 
pressure
 
against
LV 
volume 
through 
one
complete
 
cardiaccycle
 
Systole: 
divided
 
into
Early 
systole
 
Late
systole
Diastole: 
divided
 
into
Early 
diastole 
Late
diastole
 
PROF. 
HABIB
 
2018
undefined
 
SV 
= 
EDV 
-
 
ESV
 
Systolic
 
BP
 
D
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s
t
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lic
BP
 
B
e
g
i
nn
i
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g
of
 
Systole
 
ESV
 
EDV
 
End of
S
ys
t
o
le
C
ontr
act
ili
t
y
Area 
=
 
Work
Compliance
 
VENTRICULAR 
PRESSURE - 
VOLUME
 
LOOP
 
a
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EFFECT 
OF 
ATRIAL 
CONTRACTION 
ON 
VENTRICLE
 
FILLING
 
 
At 
rest, 
atrial
contraction 
adds little
extra 
blood 
to 
the
ventricles.
 
 
When 
the 
heart 
rate 
is
high, 
ventricle 
filling
time 
is
 
reduced.
 
 
During 
exercise, 
atrial
contraction 
adds a
MORE 
amount 
of
blood 
to 
the
ventricles
.
 
PROF. 
HABIB
 
2018
 
A
t
 
R
e
s
t
 
 
A
f
t
e
r
E
x
e
r
c
i
s
e
 
Hear 
Rate 
&
Cardiac
 
Cycle
 
PROF. 
HABIB
 
2018
 
Hear 
Rate 
& 
Cardiac
 
Cycle
 
PROF. 
HABIB
 
2018
 
Higher 
the 
rate 
lesser 
is 
duration 
of 
Cardiac
 
cycle.
 
However, 
the 
duration 
of 
systole 
is much 
more 
fixed 
than 
that
 
of
diastole.
 
When 
the 
heart 
rate 
is 
increased, diastole 
is 
shortened to 
a
much 
greater 
degree. 
For example, 
at 
a 
heart 
rate 
of 
65
beats/min, 
the 
duration 
of 
diastole 
is 0.62 
s, 
whereas 
at 
a
 
heart
rate 
of 
200 
beats/min, 
it is 
only 
0.14
 
s.
Up 
to 
about 
180/min, 
filling 
is 
adequate 
as
long 
as 
there 
is enough 
venous
 
return,
and 
cardiac output 
per 
minute 
is 
increased 
by
an 
increase 
in 
rate. 
However, 
at 
very 
high
heart 
rates, 
filling may 
be 
compromised 
to
such 
a 
degree 
that cardiac output 
per 
minute
falls.
Physiologic 
and 
clinical implications 
of
shortened diastole: 
The heart 
muscle
rests during diastole. Coronary blood
flows 
to 
the 
subendocardial portions
of the 
left 
ventricle 
only during
diastole. Furthermore, most 
of the
ventricular 
filling 
occurs 
in
 
diastole.
 
T
H
A
N
K
S
 
PROF. 
HABIB
 
2018
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Explore the intricate workings of the cardiac cycle, from the mechanical and electrical changes to the phases in both atria and ventricles. Learn about the time duration of a cardiac cycle, the impact of heart rate on systole and diastole, and various pressure, volume, and sound changes occurring during this vital process. Delve into fascinating facts about the heart and discover its incredible capabilities.


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  1. CARDIOVASCULAR SYSTEM CARDIAC CYCLE Dr Syed ShahidHabib Professor & Consultant Clinical Neurophysiology Dept. of Physiology College of Medicine & KKUH King Saud University PROF. HABIB 2018

  2. OBJECTIVES At the end of the lecture you should be able to .. 1. 2. 3. Enumerate the phases of cardiac cycle Explain the effect of heart rate on duration of systole and diastole Recognize the pressure, electrical, sound and volume changes during cardiac cycle Correlate different phases of cardiac cycle with various changes in events. Compare and contrast left and right ventricular pressures and volumes during the normal cardiac cycle. Describe atrial pressure waves & their relationship to cardiac cycle Describe the use of the pressure-volume loop in describing the phases of the cardiac cycle 4. 5. 6. 7. SOURCE GUYTON 13TH ED. CHAPTER9: PAGE:113-119 PROF. HABIB 2018

  3. FACTS ABOUT OUR HEART Size of a fist and weighing about 250 grams In lifetime beats 2,500 million times and pumps 110 million gallons of blood. Every day, your heart creates enough energy to drive a truck for 20 miles (32 km). In a lifetime, that is equivalent to driving to the moon and back Our heart has its own electrical impulse, it can continue to beat even when separated from the body, as long as it has an adequate supply of oxygen PROF. HABIB 2018

  4. CARDIAC CYCLE Definition: Cardiac Cycle is the time duration comprising all the events from beginning of one heart contraction to the beginning of next heart contraction. At heart rate of 75 beats per minute duration of one Cardiac cycle is 0.8 second. What are the Events? PROF. HABIB 2018

  5. EVENTS OF CARDIAC CYCLE Mechanical changes: 1.Phases of cardiac cycle 2.Heart sounds 3.Pressure changes during cardiac cycle 4.Volume changes during cardiac cycle Electrical Changes 5.Electrocardiogram (ECG) PROF. HABIB 2018

  6. The Events of the Cardiac Cycle PROF. HABIB 2018

  7. PHASES OF CARDIAC CYCLE Atrial Events Atrial systole: 0.1 second Atrial diastole : 0.7 seconds Ventricular Events Ventricular systole : 0.3 seconds Ventricular diastole : 0.5 seconds CARDIAC CYCLE 0.8 SECONDS PROF. HABIB 2018

  8. ATRIAL SYSTOLE 0.1 SEC ATRIALDIASTOLE 0.7 SECONDS VENTRICULAR SYSTOLE 0.3 SECONDS VENTRICULAR DIASTOLE 0.5 SECONDS CARDIAC CYCLE 0.8 SECONDS PROF. HABIB 2018

  9. PROF. HABIB 2018

  10. VENTRICULAR EVENTS Ventricular systole 1.Isovolumetric contraction 2.Ejection phase Rapid ejection Slow ejection Ventricular Diastole 1. Isovolumetric relaxation phase 2. Filling phase Rapid filling Slow filling (Continued filling) Last rapid filling (Atrial Systole) PROF. HABIB 2018

  11. PHASES OF CARDIAC CYCLE PROF. HABIB 2018

  12. VENTRICULAR SYSTOLE (Peak of R wave of QRS complex to the end of T wave) 0.31 sec ISO-VOLUMETRIC CONTRACTION 0.06 sec MAXIMUM EJECTION (2/3, 70%) 0.11 sec REDUCED EJECTION (1/3, 30%) 0.14 sec VENTRICULAR DIASTOLE (End of T wave to the peak of R wave of QRS complex) 0.52 sec ISO-VOLUMETRIC RELAXATION 0.06 sec RAPID INFLOW 0.11 sec SLOW INFLOW / DIASTASIS 0.2 sec ATRIAL SYSTOLE (after P wave) 0.11 sec 7 Phases of CARDIACCYCLE 0.8 sec Importance of the long ventricular diastole? This is important for: Coronary blood flow & Ventricular filling PROF. HABIB 2018

  13. PROF. HABIB 2018

  14. PROF. HABIB 2018

  15. PRESSURE CHANGES

  16. VARIOUS PRESSURE VALUES CHAMBERS NORMAL RANGE (mm ofHg) Right Atrium 2 8 Right Ventricle ( systolic) 15 25 (diastolic) 2 -8 Pulmonary Artery (systolic) 15 25 (diastolic) 8 - 15 Left Atrium 2-10 Left Ventricle (systolic) 100 120 (diastolic) 2 10 PROF. HABIB 2018

  17. VOLUME CHANGES

  18. End Diastolic Volume: Volume of blood in each ventricle at the end of diastole. It is about 110 120 ml. End Systolic Volume: Volume of blood in each ventricle at the end of Systole. It is about 40 to 50 ml Stroke Volume: It is a volume of blood pumped out by each ventricle per beat. It is about 70 ml. Stroke volume (SV) = EDV ESV PROF. HABIB 2018

  19. EJECTION FRACTION (EF) is the percentage of ventricular end diastolic volume (EDV) which is ejected with each stroke. SV or (EDV ESV) EF = X100 EDV 75 X 100 = 62.5% 120 Normal ejection fraction is about 60 65%. Ejection fraction is good index of ventricular function. PROF. HABIB 2018

  20. ATRIAL SYSTOLE Atrial Depolarization Atrial contraction Atrial pressures rise Blood flows across AV valves ATRIA = PRIMER PUMPS . Ventricular filling : 80% - direct flow from SVC & IVC 20% - atrial contraction. PROF. HABIB 2018

  21. PROF. HABIB 2018

  22. ISOVOLUMETRIC CONTRACTION Increase in ventricular pressure> atrial pressure AV valves close After 0.02s, semilunar valves open Period between AV valve closure and semilunar valve opening heart prepares for contraction without shortening occurs without emptying Tension develops without change in musclelength PROF. HABIB 2018

  23. EJECTION When LV pres > 80 mm Hg RV pres > 8 mmHg, The semilunar valvesopen. Rapid Ejection 70% emptyingin first 1/3duration Slow Ejection 30% in last 2/3time The pressure in the ventriclekeeps decreasing until it becomes lower than that of the great vessels PROF. HABIB 2018

  24. ISOVOULUMETRIC RELAXATION When ventricle pressure < arterial pressure backflow of blood forces semilunar valves to close. For 0.03-0.06 s, ventriclerelaxes despite no change in its volume AV and Semilunar valves are closed Meanwhile, atria fill up and atrial pressure graduallyrises Pressures in ventricle keep falling till it is < atrial pressure PROF. HABIB 2018

  25. VENTRICULAR FILLING Begins with the openingof AV valves Rapid filling first 1/3of diastole (60-70%blood) Reduced filling (Diastasis) middle 1/3 ofdiastole Atrial contraction last1/3 of diastole (27-30%blood) As the atrial pressures fall, the AV valves close and left ventricular volume is now maximum EDV (120 ml in LV) PROF. HABIB 2018

  26. Aortic Pressure Curve a.Ascending or anacroticlimb: This coincides withthe rapid ejectionphase The amount ofblood enters aorta > leaves Aortic pressure upto 120 mmHg b.Descending orcatacrotic limb: (Has 4 stages) Pulmonary artery pressure changes are similar to the aortic pressure changes but with difference in magnitude. Normal pulmonary artery pressure during the cardiac cycle 25-30/4-12 mmHg

  27. Descending / catacrotic limb - 4STAGES 1. Aortic pressure: This coincides with the reduced ejectionphase The amount of blood enters aorta < leaves 2. Dicrotic notch (incisura): Due to closure of aortic valve There is sudden drop in aortic pressure This notch is seen in the aortic pressure curve at end of ventricular systole 3. Dicrotic wave: Due to elastic recoil of the aorta Slight in aortic pressure 4. Slow aortic press: up to 80 mmHg Due to continued flow of blood from aorta systemiccirculation PROF. HABIB 2018

  28. Atrial pressure changes during the cardiac cycle THE JUGULAR VENOUS PULSE (JVP) PROF. HABIB 2018

  29. OF. HABIB 2018

  30. Atrial pressure changes during the cardiac cycle The 3 wave (a, c, & v) are equal to ONE cardiac cycle = 0.8sec 3 upwardwaves: a, c, & v waves 2 components ineach wave: +ve ( pr), -ve ( pr) 2 downwarddeflection (waves): x & ywaves PROF. HABIB 2018

  31. Atrial pressure waves a wave: Atrial systole: atrial pressure during atrial contraction c wave: Ventricular systole +ve as a result of bulging of AV valve into the atria during isovolumetric contraction phase -ve as a result of pulling of the atrial muscle & AV cusps down during rapid ejection phase , resulting in atrial pressure v wave: Atrial diastole or venous return (VR) +ve: atrial pressure gradually due to continuous VR -ve as a result of atrial pressure during rapid filling phase x descent: Downward displacement of AV valves during reduced ejectionphase y descent: atrial pressure during reduced filling phase PROF. HABIB 2018

  32. CORRELATING EVENTS TOGETHER 26 PROF. HABIB 2018

  33. ATRIAL SYSTOLE JVP a wave ECG P wave precedes the atrial systole. PR interval depolarization proceeds to the AVN. The brief pause allows complete ventricular filling Heart sounds - S 4 pathological. Vibration of the ventricular wall during atrial contraction. Heard in stiff ventricle like in hypertrophy and in elderly. Also heard in massive pulmonary embolism, cor pulmonale, TR PROF. HABIB 2018

  34. ISOVOLUMETRIC CONTRACTION Volume does not change All valves are closed JVP c wave due to the bulging of the Tricuspid valve into RA secondary to increased pressure in theventricle. ECG End of QRS complex Heart Sounds S1 : closure of the AVvalves. PROF. HABIB 2018

  35. EJECTION Rapid Slow JVP no waves ECG T wave Heart sounds none Aortic pressure - Rapid rise in the pressure = 120 mm Hg. Even at the end of systole pressure in the aorta is maintained at 90 mm Hg because of the elastic recoil PROF. HABIB 2018

  36. ISOVOLUMETRIC RELAXATION Volume does not change All valves are closed JVP: v wave due to venous return to the atria from SVC and IVC ECG: End of T wave Heart sounds: S2 : closure of the semilunar valves coincides with this phase. Aortic pressure curve: INCISURA - when the aortic valve closes. Caused by a short period of backflow before the valve closes followed by sudden cessation of the backflow when the valve closes. PROF. HABIB 2018

  37. VENTRICULAR FILLING Rapid filling Reduced filling Atrial contraction JVP y descent in first 2/3 & a wave in last1/3 ECG P wave before atrial systole Heart sounds - S3- Pathological in adults. Seen in dilated congestive heart failure, MI, MR, severe hypertension. Normal inchildren. PROF. HABIB 2018

  38. PROF. HABIB 2018

  39. ABNORMALITIES OF a WAVE Elevated a wave Tricuspid stenosis Decreased ventricular compliance (ventricular failure, pulmonic valve stenosis, or pulmonary hypertension) Cannon a wave Atrial-ventricular asynchrony (atria contract against a closed tricuspid valve) complete heart block, following premature ventricular contraction, during ventricular tachycardia, with ventricular pacemaker Absent a wave Atrial fibrillation or atrial standstill Atrial flutter PROF. HABIB 2018

  40. Volume-Pressure Diagram During the Cardiac Cycle; Cardiac Work Output. PROF. HABIB 2018

  41. BASIC MYOCARDIAL MUSCLEMECHANICS: Both ventricular systole & diastole can bedivided into early & latephases. Systole: Earlysystole= IsovolumetricContraction . Late systole= Isotonic Contraction EjectionPhase . Diastole: Early diastole = IsovolumetricRelaxation . Late diastole= IsotonicRelaxation FillingPhase . PROF. HABIB 2018

  42. VENTRICULAR PRESSURE - VOLUMELOOP Plots LV pressureagainst LV volume through one complete cardiaccycle Systole: divided into Early systole Late systole Diastole: dividedinto Early diastole Late diastole LateDiastole (Fillingphase) PROF. HABIB 2018

  43. VENTRICULAR PRESSURE - VOLUMELOOP Systolic BP End of Systole Diastolic BP Contractility Area = Work Compliance Beginning of Systole EDV ESV SV = EDV - ESV

  44. b. Increased afterload refers to an increase in aortic pressure. n The ventricle must eject blood against a higher pressure, resulting in a decrease in stroke volume .is reflected in decreased width of the pressure volume loop. The decrease in stroke volume results in an increase in end-systolic volume. a. Increased preload: n refers to an increase in end-diastolic volume and is the result of increased venous return. causes an increase in stroke volume based on the Frank Starling relationship .reflected in increased widthof the pressure volume loop.

  45. EFFECT OF ATRIAL CONTRACTION ON VENTRICLE FILLING At rest, atrial contraction adds little extra blood to the ventricles. When the heart rate is high, ventricle filling time is reduced. During exercise, atrial contraction adds a MORE amount of blood to the ventricles. PROF. HABIB 2018

  46. Hear Rate & Cardiac Cycle At Rest After Exercise PROF. HABIB 2018

  47. Hear Rate & Cardiac Cycle Higher the rate lesser is duration of Cardiaccycle. However, the duration of systole is much more fixed than thatof diastole. When the heart rate is increased, diastole is shortened to a much greater degree. For example, at a heart rate of 65 beats/min, the duration of diastole is 0.62 s, whereas at aheart rate of 200 beats/min, it is only 0.14s. Up to about 180/min, filling is adequate as long as there is enough venous return, and cardiac output per minute is increased by an increase in rate. However, at very high heart rates, filling may be compromised to such a degree that cardiac output per minute falls. Physiologic and clinical implications of shortened diastole: The heart muscle rests during diastole. Coronary blood flows to the subendocardial portions of the left ventricle only during diastole. Furthermore, most of the ventricular filling occurs in diastole. PROF. HABIB 2018

  48. THANKS PROF. HABIB 2018

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