CVS Item 2.pdf

Cardiovascular system
Dr. Raihana zannat

Item (2)
• Cardiac cycle: (definition, events)
Pressure change
Volume change
• Heart sound( types, characteristics,
significance)
• ECG(definition, principles,
interpretation)

Cardiac cycle
Definition:
The cyclical repetition of various changes
in the heart from beat to beat is called
cardiac cycle.

Cardiac cycle time:
It is the time required for one complete
cardiac cycle.
Cardiac cycle time= time/ heart rate
Cardiac cycle time is 0.8 sec when heart rate
is 75 /min.
❑ 60sec(time)/75 beat (heart beat)
= 0.8 sec

Q. If heart rate is 85 beats/min, what will be the
cardiac cycle time?

If HR ↑ which one is more compromised?
Diastole

Consists of
• Diastole - a period of relaxation during which
the heart fills with blood
• Systole - a period of contraction

Changes occur during cardiac cycle
1. Pressure changes in ventricle, atria, aorta,
pulmonary artery, jugular vein.
2. Changes in volume of ventricle and atria.
3. Production of heart sound & apex beat.
4. Production of pulse & appearance of pulse
wave.
5. Electrical changes in the heart recorded as
electrocardiogram (ECG)

Events of cardiac cycle
1. Atrial events:
a. Atrial systole ( 0.1 sec)
b. Atrial diastole ( 0.7 sec)
2. Ventricular events:
a. Ventricular systole(0.3 sec)
b. Ventricular diastole( 0.5 sec)

Ventricular systole( 0.3 sec)
l. Isometric contraction phase(0.05 sec)
ll. Maximum ejection phase( 0.11 sec)
lll. Reduced ejection phase( 0.14 sec)

Ventricular diastole( 0.5 sec)
l. Protodiastolic phase( 0.04 sec)
ll. Isometric relaxation phase( 0.08 sec)
lll. 1st rapid filling phase(0.113 sec)
lV. Slow filling phase or Diastasis( 0.167 sec)
V. Last rapid filling phase ( 0.1 sec)

Atrial systole:(0.1 sec)
➢It is the first event ( 0.1 sec).
➢It initiates the cardiac cycle, because the
pace maker SA node is situated here.
➢10% blood ejected to ventricle.
➢Pressure change:Intraatrial pressure increase
➢4th heart sound is produce.

Atrial diastole (0.7 sec)
➢It begins after atrial systole.
➢first half of the atrial diastole:
• Rt Atria collect blood from superior & inferior venacava
• Lt atria from pulmonary veins.
• AV valves remain close.
• Coincide with ventriular diastole.
➢ During second half :
• AV valves open and blood passes from the atria to
the ventricle.
• About 80% of the ventricular filling occurs passively
during atrial diastole.(v. dias.)

Ventricular systole(0.3 )
It begins after atrial systole. It has 3 phases.
1. Isometric contraction phase( 0.05 sec)
➢ It is the interval between the closure of the AV valves and
the opening of the semilunar valves.
➢ 1st heart sound produce due to closure of AV valve.
➢ Intraventricular pressure rises sharply.
➢ When Intraventeicular pressure exceed the pressure in
aorta(80 mm Hg) & pulmonary artery(10 mm Hg), the
semilunar valves open & the phase ends.

2. Maximum ejection phase( 0.11 sec)
➢the outflow is very rapid.
➢Ventricles pump about 70% of the blood.
3. Reduced ejection phase( 0.14 sec)
➢ out flow rate is slow .
➢Ventricles pump about 30% of the blood.

Note---------
• End systolic volume:60-80 ml/ventricle
• Ejection fraction: fraction of end diastolic
volume that is ejected by each ventricle in
each beat.

Ventricular diastole( 0.5 sec)
It starts at the end of ventricular systole. It has five phases.
1. Protodiastolic phase(0.04 sec)
➢ It is the interval between onset of diastole & closure of
semilunar valves.
➢ Here ventricles relax so intraventricular pressure falls.
➢ 2nd heart sound produce.

2. Isometric relaxation phase(0.08 sec)
➢ It is the interval between the closure of the semi lunar
valves & opening of the AV valves.
➢ The ventricles relaxes as a close cavity so no blood get in or
out of it.
➢ The intraventricular pressure falls sharply.
➢ When intraventricular pressure falls below the atrial
pressure then AV valves open & the phase ends.

3 . 1 st rapid filling phase(0.113 sec)
➢It begins with the opening of the AV valves.
➢Blood rushes rapidly from the atria in to the ventricles
➢Produces 3rd heart sound.
4. Slow filling phase or Diastasis(0.167 sec)
➢This phase is longest but the amount of filling is
minimum.
5.Last rapid filling phase(0.1 sec)
➢Ventricular diastole coincides with atrial systole.
➢Due to atrial contraction rushes of blood in to the
ventricle
➢Produces 4th heart sound.

Note----
• End diastolic volume: 130-150 ml

Blood flows because of pressure
difference
Systolic pressure
(mm Hg)
Diastolic
pressure
Rt. Atria 4-6 0
Lt. Atria 7-8 0
Rt. ventricle 25(15-30) <5
Lt. Ventricle 120(90-140) 4-12
Aorta 120(90-140) 60-90
Pulmonary
artery
25(15-30) 8(5-15)

Atrial Pressure change
LEFT ATRIAL PRESSURES -
Systolic : 7 – 8 mm Hg
Diastolic : 0 mm Hg
RIGHT ATRIAL PRESSURES
Systolic : 4 – 6 mm Hg
Diastolic : 0 mm Hg

Pressure Changes in the Atria
• a wave -caused by atrial contraction. right atrial
pressure ↑ 4 to 6 mm Hg during atrial contraction,
and the left atrial pressure ↑ 7 to 8 mm Hg.
• The c wave occurs when the ventricles begin to
contract- partly by slight backflow of blood &
mainly by bulging of A-V valves toward atria.
• The v wave occurs toward the end of ventricular
contraction; it results from slow flow of blood into
the atria from the veins while the A-V valves are
closed

ATRIAL PRESSURE WAVES
❖The "a" wave - atrial
contraction.
❖“c” wave - at the onset of
ventricular contraction.
❖“v” wave - towards the
end of ventricular
contraction due to
accumulation of blood in
the atria.
Fig: Pressure waves during
Atrial systole.
(http://freedownload.is/ppt/cardiac-cycle)

Ventricular Pressure change
Right ventricle:
during systole: 15-30 mm Hg
during diastole: 0- 5 mm Hg
Left ventricle:
during systole: 90-140 mm Hg
during diastole: 4-12 mm Hg

Aorta :
During systole : 90- 140 mm Hg
During diastole : 60 – 90 mm Hg
Pulmonary artery:
During systole : 15 - 30 mm Hg
During diastole : 5-15 mm Hg

Volume Changes in the Ventricles
END DIASTOLIC VOLUME –It is the volume of blood
in each ventricle at the end of the diastole. (110 –
130 ml)
END SYSTOLIC VOLUME – It is the volume of blood
remains in each ventricle at the end of systole. (40 –
60 ml)
STROKE VOLUME - It is the amount of blood pumped
out by each ventricle in each beat. It is about 70 ml.

Preload
• The degree of tension on the muscle when it begins
to contract, which is called the preload.
For cardiac contraction :
• The preload is - end-diastolic pressure when the
ventricle has become filled.

afterload
• The load against which the muscle exerts its
contractile force is called the afterload.
• The afterload of the ventricle is the pressure
in the artery leading from the ventricle

❑
At rest,----- the heart pumps 4 to 6 L /min
Exercise------- four to seven times i.e.20 to 35 L/min

Heart sound
Definition:
The vibratory motion of the heart produced during
different events of the cardiac cycle which conducts
through the structures surrounding the heart &
produces special audible sound called heart sound.
Types:
• 1st heart sound
• 2nd heart sound stethoscope
• 3rd heart sound is heard in many young
• 4th heart sound not heard by Stethoscope
All sounds can recorded by phonocardiogram.

Heart
sound
Causes Character Duration
1st •Closure of A-V
valve
•Just after the
onset of
ventricular
systole
•Isometric
contraction
•Low
frequency
(25-45 Hz)
•Dull &
prolonged
( L-U-B-B)
0.14-0.15
sec

Heart
sound
2nd At the onset of
ventricular
diastole.
Vibrations
associated with
closure of SLV.
Protodiastolic
period.
•High
frequency
(50 Hz)
•Short &
sharp like
the word
DUB
0.11-0.12
sec

Heart
sound
3rd Rapid rush of
blood during
rapid ventricular
filling stage
Soft, low
pitched
0.1 sec
4th Rapid rush of
blood in last
rapid filling
phase.
Rarely
heard in
normal
individual
.02 sec

Significance of heart sound
1st heart sound:
i. It indicates the clinical onset of ventricular systole.
ii. It indicates the proper closure of AV valve.
iii. The duration & intensity indicates the condition of
the myocardium.
Clinical identification
• Comes after prolong pause
• Coincide with apex beat & carotid pulse
• Just before radial pulse

2nd heart sound:
❖It indicates the end of systole & beginning of
diastole.
❖Clear 2nd heart sound indicates proper closure of
semilunar valves.
3rd heart sound:
❖ it indicates the beginning of ventricular filling.
4th heart sound:
❖It indicates the end of the ventricular filling

Splitting of 2nd heart sound
• Aortic valve close before pulmonary valve.
• During inspiration, interval widens.

Murmurs :
Abnormal sound heard over the heart is called
murmurs.
cause:
1. when the orifice of a valve is
narrowed(stenosis).
2. when a valve is incompetent
(regurgitation or insufficiency)

Bruit:
Murmurs arising from a peripheral artery due to
arterial stenosis.

Apex beat:
it is the out ward thrust, felt at the fifth
intercostal space about 1.27 cm inside the
midclavicular line. It coinside with 1st heart
sound.

ECG(Electrocardiogram)
The electrical activities of heart can be
recorded by placing electrodes on the skin on
opposite sides of the heart by
electrocardiograph machine is known as
Electrocardiogram.
The machine by which the electrocardiogram is
recorded is known as Electrocardiograph.
(Einthoven Willium – Father of ECG)

Clinical use of ECG
• 1. To elucidate cardiac arrhythmias
• 2.To elucidate cardiac conduction defect
• 3. To diagnose myocardial hypertrophy,
ischemia & infarction
• 4. To find information about electrolyte
imbalance( hyper & hypokalaemia)
• 5. To see toxicity of certain drugs.

• Electrode- The metallic plate through which the
electrical potential can be recorded
• Leads –the specific point of electrical contact on the
limb or on chest in front of the heart.
Leads 3 types
1. Bipolar or standard limb lead (Lead I, II, III)
Lead I - Rt arm & Lt arm
Lead II - Rt arm & Lt leg
Lead III - Lt arm & Lt leg

2. Augmented Unipolar limb lead
aVL – left arm
aVF - left leg
aVR – Right arm
3. Unipolar chest leads :
V1 – 4th intercostal space at Rt border of sternum
V2 - 4th intercostal space at Lt border of sternum
V3 - At midpoint between V2 & V4
V4 – 5th intercostal space at Lt midclavicular line
V5 - 5th intercostal space at Lt anterior axillary line
V6 - 5th intercostal space at Lt mid axillary line

The normal ECG composed of
• P wave: is produced by atrial depolarization
• QRS complex : is produced by ventricular
depolarization
• T wave : is produced by ventricular
repolarization

Time callibration & voltage is ECG
In the horizontal calibration lines----
• 10 small divisions represent 1 millivolt
• Positivity in the upward direction
• Negativity in the downward direction.

• The vertical lines are time calibration lines.
• Each inch in the horizontal direction is 1
second
• Each inch is usually broken into five segments
by dark vertical lines.
• the intervals between these dark lines
represent 0.20 second.
• The 0.20 second intervals are then broken
into five smaller intervals by thin lines
• Each of which represents 0.04 second

Speed of paper =25mm/sec
• Each large( 5mm) square = 0.2 sec
• Each small ( 1mm) square = 0.04 sec
• Heart rate = 1500/ P-R interval(mm)
• If P-R interval = 5mm, HR = 300/min
• If P-R interval = 25mm, HR = 60/min

Calculation of heart rate
0.04 sec = 1 small square
60 sec = 1500 small square
Number of R –R interval in 1500 square 20
(suppose)
20 squire= 1 cardiac cycle
Number of heart beat = 1500/20=75 beats/min

Normal ECG
composed of
❑ P wave
❑QRS complex
❑T wave

P wave :
❖ It is a positive wave & the first wave in ECG.
❖ Produced by atrial depolarization before atrial
contraction.
❖ duration 0.1 sec.
❖ Amplitude 0.1- 0.12 mV.
Clinical signification:
➢ Right atrial hypertrophy: tall ‘P’ wave.
➢Left atrial hypertrophy: it is tall & broad based like
‘M’
➢Hyperkalemia & atrial fibrilation: ‘P’ wave absent.
➢Sinoatrial block: ‘P’ wave is inverted or absent.

QRS complex:
❖ it is complex because it has small negative ‘Q’ then
continued as positive tall ‘R’ wave followed by small
negative ‘S’ wave.
❖Produced by ventricular depolarization before
ventricular contraction.
❖Duration is 0.08 – 0.1 sec
❖Amplitude - ‘Q’ wave- 0.1 – 0.2 mV
‘R’ wave- 1 mV
‘S’ wave- 0.4 mV

Clinical significance:
➢Bundle branch block: QRS is prolonged or deformed
➢Hyperkalemia : QRS is prolonged.

T wave:
❖ it is last positive wave seen in ECG
❖Produced by ventricular repolarization
❖Duration: 0.2 sec
❖Amplitude : 0.3 mV

Clinical significance:
➢ Acute MI : ‘T’ wave tall & broad based
➢ Old age, hyper ventilation, MI, Left ventricular
hypertrophy : flat or inverted ‘T’ wave
➢Hypokalemia: small, flat or inverted ‘T’ wave
➢Hyperkalemia: ‘T’ wave is tall

Intervals Normal
duration
Events in heart
PR interval(
begining of P to
that of QRS )
0.12sec –
0.20 sec
Atrial depolarization &
conduction through AV node
QRS duration 0.8 sec Ventricular depolarization &
atrial repolarization
QT interval( onset
of Q wave to end of
T wave)
0.04 sec Ventricular depolarization
plus ventricular repolarization
ST segment(end of 0.32 sec Ventricular repolarization
ECG Intervals

Changes of ECG
• Anterior MI( early changes) :
ST elevation in I, avL & V3 – V6
ST depression in II, III & avF
First degree heart block : PR interval is abnormally
prolonged
Hypokalaemia : ST segment depression , PR interval
prolonged, T wave inverted
Hyperkalaemia : Tall, peaked T wave, widen QRS
complex
Hypocalcaemia : ST segment prolonged

WHY ATRIAL REPOLARIZATION WAVE IS
ABSENT?
• In the normal ECG, the atrial T wave
appears at about the same time that the
QRS complex of the ventricles appears.
• So it is obscured by the large ventricular
QRS complex

Einthoven's Triangle
• It is an equilateral triangle drawn arbitrarily
around the area of the heart. It represents the
bipolar lead.
• This illustrates that the two arms and the left
leg form apices of a triangle surrounding the
heart.

Heart block
• It is the blockage of impulse generated by SA
node in the conductive system.
• Types:
1. 1st degree heart block
2. 2nd degree heart block
3. 3rd degree heart block

1st degree heart block
• Conduction of impulse through the AV node is
slow.
• Prolonged P-R interval.

2nd degree heart block
• Some of impulse fail to pass in the ventricle.
• 1 ventricular contraction for 2 to 3 atrial
contraction.
• QRS complex missing in ECG

3rd degree heart block
• Impulse produce by SA node cannot reach the
ventricle.

Review of cardiac cycle
Ventricular Diastole:
1.Isovolumetric relaxation- valve closed
2.First rapid filling - by the accumulated blood in
atria
3. Slow filling -middle 3rd of diastole, small
amount of blood normally flows
4. Last rapid filling -atria contract. 20% filling.

Ventricular Systole
1. Isovolumetric contraction- no myocardial
shortening. when ventricular pressure >80
mm(Hg), aortic valve opens
2. Rapid ejection
3. Slow ejection continues upto aortic pressure
120 mm (Hg)

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