Download General Principles Cardiac Cycle

12/13/2010
Cardiovascular Physiology
At end of this lecture you should be able to know:
 General principles of cardiac cycle
 Different events of cardiac cycle
 Mechanical events’ phases of cardiac cycle

Correlation with ECG & heart sounds
 Volume changes in cardiac cycle
Dr. Abeer A. AlMasri
 Pressure changes in cardiac cycle
 Complete picture correlating cardiac cycle events
MBBS, MSc, PhD
Assistant Professor
Consultant Cardiovascular Physiologist
College of Medicine, KSU
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General Principles
Cardiac Cycle
Describing sequence of events (electrical &
mechanical) that take place in the heart in
each beat
 Blood flows from an area of high pressure
to an area of low pressure
 Events on Rt & Lt sides of the heart are the
Cardiac cycle duration = 0.8 sec …
same, but pressures are lower on Rt side
■ When HR 75/min
■ Shortened when HR 
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Definitions
Definitions … (Cont.)
Systole = Phase of contraction
Diastole = Phase of relaxation

 End-diastolic volume (EDV):

 Volume of blood in ventricle at end of diastole
  110-120 ml
o
o
 Stroke volume (SV):
Ventricular systole = 0.3 sec
Ventricular diastole = 0.5 sec
o
 Amt of blood ejected from each ventricle
during systole
  70 ml/beat
o
Atrial systole = 0.1 sec
Atrial diastole = 0.7 sec
 Importance of ventricular diastole:
1. Coronary blood flow
2. Ventricular filling
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 Normally diastole is longer > systole
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Dr. Abeer AlMasri, Faculty of Medicine,
KSU
12/13/2010
Cardiovascular Physiology
Intra-cardiac Pressures
Right Side
Definitions … (Cont.)
Left Side
 Right ventricle:
 End-systolic volume (ESV):
 Amt of blood left in each ventricle at end of
systole
  40-50 ml
 Left ventricular:
25-30/2-8 mmHg
100-120/3-12 mmHg
 Pulmonary artery:
 Aorta:
15-30/4-12 mmHg
 Ejection fraction (EF):
120/80 mmHg
(mean press 9-18 mmHg)
 Right atrium:
 Fraction of end-diastolic volume that is
ejected
  60 %
 Left atrium:
2-10 mmHg
2-8 mmHg
(pulmonary wedge press)
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To study cardiac cycle:
Mechanical Events:
I:
II:
Ventricular
Ventricular
in
diastole repeated
systole
next beat
Volume changes
III:
Pressure changes
IV:
Heart sounds
V:
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Mechanical events
Electrical events (ECG)
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Mechanical Events:
Phases of the cardiac cycle
Cardiac cycle consists of 8 phases
■ Early ventricular diastole:
1. Protodiastole
2. Isometric relaxation phase
3. Rapid filling phase
■ Mid ventricular diastole:
4. Reduced filling phase
■ Late ventricular diastole:
5. Atrial systole
Ventricular
diastole
■ Ventricular systole:
1. Isometric
contraction phase
Ventricular
systole
2. Rapid ejection
phase
3. Reduced ejection
phase
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Dr. Abeer AlMasri, Faculty of Medicine,
KSU
12/13/2010
Cardiovascular Physiology
Phases of cardiac cycle:
1. Atrial systole:
 At end of ventricular
diastole

AV-vs open, (semilunarvs closed)

Tops off last 27-30% of
ventricular filling

Blood arriving heart can’t
enter atrium, it flows back
up jugular vein
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Atrial Pressure Curve
- Atrial Systole -
ECG
- Atrial Systole -
"a" wave occurs, due to ↑ atrial press during atrial
contraction
 P wave occurs, due to atrial depolarization
In jugular venous pulse, " first wave" occurs due to
back regurgitation of blood to jugular vein
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Pressure & Volume Curve
- Atrial Systole -
Heart Sounds
- Atrial Systole 
Associated with fourth heart sound (S4)

S4 is abnormal
 ? Normal in elderly
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Dr. Abeer AlMasri, Faculty of Medicine,
KSU
12/13/2010
Cardiovascular Physiology
Phases of cardiac cycle:
Atrial Pressure Curve
- Isometric Contraction Phase -
2. Isometric contraction phase:
 At beginning of systole
 Period b/w closure of AV-vs &
opening of semilunar- vs
 Lasts 0.04 sec
 Ventricle is a closed chamber,
contract w/out change in volume
 Volume in ventricle is EDV
Ascending limb (+ve) of“c" wave occurs:
o ↑ atrial press as a result of RV contraction
o Pushes TV into atrium (bulging of cusps)
 Ventricular press < aortic press
 Aortic v opens at end of this
phase (when LV = 80mmHg)
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Heart Sounds
- Isometric Contraction Phase -
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ECG
- Isometric Contraction Phase -
 QRS complex occurs, due to ventricular
 First heart sound (S1, "lub") occurs, due to
depolarization
closure of AV vs & associated blood turbulence
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Phases of cardiac cycle:
3. Maximum (rapid) ejection phase:
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Pressure & Volume Curve
- Isovolumetric Contraction Phase -
 Contraction of ventricle
causes ventricular press to 
> aortic press
 Semilunar-vs open at
beginning of this phase
 Volume of blood ejected =
SV
 Ventricular volume  rapidly
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Dr. Abeer AlMasri, Faculty of Medicine,
KSU
12/13/2010
Cardiovascular Physiology
Atrial Pressure Curve
- Maximum (rapid) Ejection Phase -
ECG
- Maximum (rapid) Ejection Phase -
Descending limb (–ve) of "c" wave occurs:
o due to  atrial press as a result of pulling down of AV
 No Deflections
cusps by fibrous AV ring & ventricular contraction
N.B. Atrial press gradually  due to continuous VR
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Pressure & Volume Curve
- Maximum (rapid) Ejection Phase -
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Heart Sounds
- Maximum (rapid) Ejection Phase -
 None
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Phases of cardiac cycle:
ECG
- Reduced Ejection Phase -
4. Reduced ejection phase:
 At end of systole
 Ventricular volume 
more slowly
 semilunar v close at end
of this phase
 T wave occurs, due to ventricular
 Ventricular press  <
repolarization
aortic press
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Dr. Abeer AlMasri, Faculty of Medicine,
KSU
12/13/2010
Cardiovascular Physiology
Pressure & Volume Curve
- Reduced Ejection Phase -
Heart Sounds
- Reduced Ejection Phase -
 None
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Phases of cardiac cycle:
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Phases of cardiac cycle:
6. Isometric relaxation phase:
5. Protodiastolic phase:
 At beginning of diastole

Period b/w end of ventricular cont action &
aortic v closure

Lasts 0.04 sec

 ventricular press < aortic press

Aortic v closes by end of this phase as a result of
back press (when LV press 110 mmHg)

Atrial press still , due to continuous VR
 Period b/w closure of semilunar-
vs & opening of AV-vs
 Lasts 0.04 sec
 LV is a closed chamber, i.e. relax
w/out change in volume
 Volume of bl in ventricle = ESV
 LV relaxes w   press
 AV-vs open at end of this phase
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Atrial Pressure Curve
- Isometric Relaxation Phase -
ECG
- Isometric Relaxation Phase -
"v" wave occurs, due to back flow of blood hitting
closed AV v
 No Deflections
Ventricular press continues 
Atrial press  gradually due to continuous VR on top
of closed AV v
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Dr. Abeer AlMasri, Faculty of Medicine,
KSU
12/13/2010
Cardiovascular Physiology
Pressure & Volume Curve
- Isometric Relaxation Phase -
Heart Sounds
- Isometric Relaxation Phase -
 Second heart sound (S2, "dup") occurs
when semilunar (aortic & pulmonary) vs close
 S2 normally splits, as aortic v closes slightly
earlier than pulmonary v
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Phases of cardiac cycle:
ECG
- Rapid Filling Phase -
7. Rapid filling phase:
 Atrial press > ventricular
press
 AV-vs open
  60-70% of blood passes
passively to ventricles
along press gradient
 No Deflections
 Ventricular volume 
rapidly
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Pressure & Volume Curve
- Rapid Filling Phase -
Heart Sounds
- Rapid Filling Phase -

Third heart sound (S3) occur, due to
rapid passive ventricular filling
 S3 is usually abnormal
 ? Normal in children
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Dr. Abeer AlMasri, Faculty of Medicine,
KSU
12/13/2010
Cardiovascular Physiology
ECG
- Reduced Filling Phase -
Phases of cardiac cycle:
8. Reduced filling phase (Diastasis):
 Remaining atrial
blood flows slowly
into ventricles
 AV-vs still open
 LV volume  > slowly
 No Deflections
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Pressure & Volume Curve
- Reduced Filling Phase -
Heart Sounds
- Reduced Filling Phase -
 None
Aortic
closes
Aortic
opens
Mitral
opens
Mitral
Closes
S4 S1
S2
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Atrial Systole
Reduced Ventricular
Filling
Isovolumic Relax.
Rapid Ventricular
Filling
Reduced Ejection
Rapid Ejection
Atrial Systole
Isovolumic contract.
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The Complete Picture
Correlation of events in
cardiac cycle
S3
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Dr. Abeer AlMasri, Faculty of Medicine,
KSU
12/13/2010
Cardiovascular Physiology
Correlation of events in cardiac cycle
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Phase
Ventricular volume
1.
2.
3.
4.
Atrial systole
Isometric contraction phase
Rapid ejection phase
Reduced ejection phase
5.
6.
7.
8.
Protodiastole
Isometric relaxation phase
Rapid filling phase
Reduced filling phase

Constant
 rapidly
 slowly
Constant
Constant
 rapidly
 slowly
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Cardiac Cycle
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
Aortic pressure

Arterial pressure waves

Pulmonary artery pressure

Atrial pressure

Jugular venous pulse wave
Cardiac Cycle
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Dr. Abeer AlMasri, Faculty of Medicine,
KSU
12/13/2010
Cardiovascular Physiology
Pressure changes:
1. Aortic pressure changes … 120/80
a. Ascending or anacrotic
limb:
= diastolic P + 1/3 (systolic P - diastolic P)

with max ejection phase
 Aortic press  up to 120 mmHg
b. Descending or catacrotic
limb:
 with reduced ejection phase
 Passes in 4 stages
Pressure changes:
1. Aortic pressure changes … 120/80
Pulse pressure = Systolic P – Diastolic P
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Clinical significant of aortic pressure changes:
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Descending or catacrotic limb:
Passes through 4 stages
♥
Aortic Stenosis
1.  Aortic press:
■ Amt of blood enters aorta < leaves
♥
Shock or dehydration
2. Dicrotic notch (incisura):
= Sudden drop in aortic press
♥
Aortic Regurgitation
♥
Hypertension
♥
Pregnancy
■ Due to sudden closure of aortic v
■ At end of protodiastole phase
3. Dicrotic wave:
= Slight  in aortic press
■ Due to elastic recoil of aorta
4. Slow  aortic press: up to 80
mmHg
■ Due to continued flow of blood from
aorta  systemic circulation
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Pressure changes:
3. Pulmonary artery pressure changes … 21-25/5-10
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Pressure changes:
2. Arterial pressure changes … 110-130/70-90
Similar to aortic press changes but with
difference in magnitude
Similar to aortic press waves but sharper
Reflects a systolic peak press of 110-130 mmHg
& a diastolic press of 70-90 mmHg
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Dr. Abeer AlMasri, Faculty of Medicine,
KSU
12/13/2010
Cardiovascular Physiology
Pressure changes:
4. Atrial pressure changes:
Causes of atrial pressure waves:
‘a’ wave: Atraial systole
x
‘c’ wave: Ventricular sytole
o +ve  bulging of TV into RA during
isovolumetric contraction phase
o -ve  pulling of atrial ms during ventricular
contraction
y
Results in:
 3 upward deflection  a, c, & v
o 2 components in each wave: +ve ( press), -ve
‘v’ wave: Atrial diastole or  VR
… RA press due to filling of atrium w
blood
( press)
 2 downward deflection  x & y
The 3 wave (a, c, & v) are equal to ONE cardiac
cycle = 0.8 sec
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Pressure changes:
5. Jugular venous pulse changes:
x
Causes of atrial pressure waves … (Cont.)
‘x’ descent: Downward displacement of TV
during rapid ejection phase
y
‘y’ descent: Rapid blood flow from RA to RV
‘a-c’ interval:
■ Measured from the start of ‘a’ wave to start of
‘c’ wave
Also results in:
■ Indicates time of conduction of excitation waves
■ 3 upward waves: a, c, & v
■ 2 downward waves: x & y
through AV node & bundle
■ Corresponds to P-R interval of ECG
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 Detected over anterior chest wall by:
■ Stethoscope, (auscultation)
Cardiac Cycle
■ Phonocardiography, (sound recording device)
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Dr. Abeer AlMasri, Faculty of Medicine,
KSU
12/13/2010
Cardiovascular Physiology
Different Heart Sounds
Cause
C-cycle
Duration
Frequency
S1
S2
S3
S4
Sudden closure
of AV-vs
Sudden closure of
semilunar vs
Rush of bl
during rapid
vent filling 
vibration of
vent ms.
Vibration produced
by cont of atrial
ms (attributed to
vent filling)
Marks
beginning of
vent systole
(Isovolumetric
cont)
0.15 sec
(Longer)
0.11-0.125 sec
(Shorter)
25-35 Hz
50 Hz
Low pitch (LUB)
Character
Best
heard
Marks beginning of
vent diastole (When
vent press fall
below arterial
press)
(Louder)
M& T
Max vent filling
phase of
diastole
0.05 sec
‘4’ heart sounds:
Atrial systole
(just before 1st
HS)
0.04 sec
Important for diagnosis of valvular heart
diseases (murmurs)
High pitch (DUB)
(Softer, sharper)
Split into 2 sounds
during inspiration =
Physiological splitting
(due to delay closure of
pulm v).
A & P
Usually not
audible
Usually not audible
(Rarely heard)
M
M
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Thank You
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■ 1st & 2nd ht sounds … (usually heard)
■ 3rd & 4th ht sounds … (sometimes detected)
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Dr. Abeer AlMasri, Faculty of Medicine,
KSU