Cardiovascular system

Compiled By: Prof. G B Rathod
EC department-BVM College,
Email: ghansyam.rathod@bvmengineering.ac.in
The Cardiovascular System

TOPIC OUTLINES…
 THE HEARTANDTHE CARDIOVASCULAR SYSTEM
 THE HEART
 THE ECGWAVEFORM
 THE STANDARD LEAD SYSTEM
 OTHER ECG SIGNALS
 ECG MACHINESAND READ OUT DEVICES
 TOPIC OUTCOME
 QUESTIONS
 REFERENCES
2

THE HEART AND CARDIOVASCULAR
SYSTEM
3
 Two side of the heart with four chambers where the
circulatory path for blood flow through the lungs is called
the pulmonary circulation , and the circulatory system that
supplies oxygen and nutrients to the cells of the body is
called the systemic circulation.
 The left heart is know as a pressure pump and right part of
the heart is known as a volume pump.
 The muscle contraction of the left heart is stronger than that
of the right heart.
 The muscles of the heart receives their own blood supply
form the coronary arteries.

SYSTEM
4
 The coronary arterial system is a special branch of the
systemic circulation.
 The pipes, the arteries and the veins, are not rigid but
flexible.
 They are capable of helping and controlling blood circulation
by their own muscular action and their own valve and
receptor system.
 The actual physiological system for the heart and circulation
is illustrated in the upcoming diagram and also equivalent
engineering type of piping diagram is shown.

SYSTEM
5

SYSTEM
6

SYSTEM
7
 The heart pumping into two major parts: systol and diastol.
 Systole is defined as the period of contraction of the heart
muscles, specifically the ventricular muscle, at which time
blood is pumped into the pulmonary artery and the aorta.
 Diastole is the period of dilation of the heart cavities as they
fill with blood.
 Normal heart beat rate about 75 beats per minute.
 The range is around 60 to 85 normal.
 When person stand up it is higher and when a person sits
down its lesser.

SYSTEM
8
 In women, its generally higher. In infant is around 140
beat/min
 The heart pumps about 5 lit/min. Its change in different
situation.
 At any given time, about 75 to 80 percent of the blood is in
the veins, about 20 percent in the arteries, and remainder in
capillaries.

THE HEART
9
 The heart is located between the lungs behind the
sternum and above the diaphragm.
 It is surrounded by the pericardium.
 Its size is about that of a fist, and its weight is about
250-300 g.
 Its center is located about 1.5 cm to the left of the
midsagittal plane.

THE HEART
11
 The walls of the
heart are composed
of cardiac muscle,
called myocardium.
 It consists of four
compartments:
 the right and left atria
and ventricles

THE HEART
12
 The tricuspid valve regulates
blood flow between the right
atrium and right ventricle.
 The pulmonary valve controls
blood flow from the right
ventricle into the pulmonary
arteries
 The mitral valve lets oxygen-
rich blood from your lungs
pass from the left atrium into
the left ventricle.
 The aortic valve lets oxygen-
rich blood pass from the left
ventricle into the aorta, then
to the body

THE HEART
13
 Electrical signal begins in the sinoatrial
(SA) node: "natural pacemaker." causes the
atria to contract.
 The signal then passes through the
atrioventricular (AV) node. sends the signal
to the ventricles via the “bundle of His”
causes the ventricles to contract.

THE HEART
15
 The sinoatrial node in humans is in the shape
of a crescent and is about 15 mm long and 5
mm wide.
The SA nodal cells are self-excitatory,
pacemaker cells. They generate an action
potential at the rate of about 70 per minute.
From the sinus node, activation propagates
throughout the atria, but cannot propagate
directly across the boundary between atria and
ventricles.

THE HEART
16
 The atrioventricular node (AV node) is located at
the boundary between the atria and ventricles; it
has an intrinsic frequency of about 50 pulses/min.
 If the AV node is triggered with a higher pulse
frequency, it follows this higher frequency. In a
normal heart, the AV node provides the only
conducting path from the atria to the ventricles.
 Propagation from the AV node to the ventricles is
provided by a specialized conduction system.

THE HEART
17
 Proximally, this system is composed of a common
bundle, called the bundle of His (after German
physician Wilhelm His, Jr., 1863-1934).
 More distally, it separates into two bundle branches
propagating along each side of the septum,
constituting the right and left bundle branches. (The
left bundle subsequently divides into an anterior and
posterior branch.)
 Even more distally the bundles ramify into Purkinje
fibers (named after Jan Evangelista Purkinje (Czech;
1787-1869)) that diverge to the inner sides of the
ventricular walls.

THE HEART
18
 Propagation along the conduction system takes place
at a relatively high speed once it is within the
ventricular region, but prior to this (through the AV
node) the velocity is extremely slow.
 From the inner side of the ventricular wall, the many
activation sites cause the formation of a wavefrom,
which propagates through the ventricular mass toward
the outer wall.
 This process results from cell-to-cell activation.
 After each ventricular muscle region has depolarized,
repolarization occurs

THE ECG WAVEFORM
19
 Electrocardiography(ECG or EKG) is a graphic recording
or display of the time-variant voltage produced by the
myocardium during the cardiac cycle.
 The ECG is used clinically in diagnosing various diseases
and conditions associated with the heart.
 Here only measurement related concepts will be discussed.
 For analysis, the cardiologist looks critically at the various
time intervals, polarities and amplitudes of ECG.
 The ECG waveforms and its intervals of time and
amplitudes values are in upcoming slides.

THE ECG WAVEFORM
21
 As mentioned in earlier topics, an instrument used to
obtain and record the electrocardiogram is called an
electrocardiograph.
 The string galvanometer, which was introduced to
electrocardiography by Einthoven in 1903 and it was
used until 1920. After that the signal amplifier are used
to design the new instruments.
 Day by day improvements done in various ECG
measuring instruments and accuracy is also achieved
up to certain marks.

THE ECG WAVEFORM
22
WAVE AMPLITUDE
P 0.25 mV
R 1.6 mV
Q 25% of R wave
T 0.1 to 0.5 mV
INTERVAL TIME
P-R 0.12 to 0.20 sec
Q-T 0.35 to 0.44 sec
S-T 0.05 to 0.15
P 0.11 sec
QRS 0.09 sec
Table.6.1:Amplitude of various waves in ECG
Table.6.2:Time interval of various
Segments in ECG

THE ECG WAVEFORM
23
 Normal heart rate is lies between 60 to 100 beats per
minute.
 A slow rate than this is called BRADYCARDIA (SLOW
HEART) and a higher rate, TACHYCARDIA (FAST
HEART).
 If the heart cycles are not evenly spaced, an arrhythamia
may be indicated.
 If the P-R interval is greater than 0.2 second, it can suggest
blockage of the AV node.
 If one or more of the basic features of the ECG should be
missing, a heart block of some sort might be indicated.

THE STANDARD LEAD SYSTEM
24
 Electrodes and Leads:
 To record an electrocardiogram, a number of electrodes,
usually five, are affixed to the body of the patient. The
electrodes are connected to the ECG machine by the same
number of electrical wires known as leads.
 The electrode applied to the right leg of the patient, for
example, is called RL lead.
 To avoid ambiguity between electrodes and the measuring
techniques, we use lead term for the particular group of
electrodes taken for the measurements.

25
 For individual lead wire, as well as the physical connection
to the body of the patient, the term electrode will be used.
 When ECG recorded by using certain placement of the
electrode, may be some aspects of the waveform missed.
 To avoid this problem, usually 12 different leads techniques
are used so that no important detail of the waveform is
missed.
 Placement of electrodes and names and configurations of
the leads have become standardized and are used the same
way throughout the world.

27
 Electrodes: The placement of the electrodes, as well as
the color code use to identify each electrode, is shown
in Figure 6.3.
 Mr. Einthoven had found better results using the
electrodes placements at specific locations.
 As a ground reference, we can use right leg.(It can be
anywhere but it became convention to use right leg).
 Chest or precordial electrodes will be introduced later.

28
 Leads: The placement of the electrodes as shown in
figure 6.3.
 Because the input of the ECG recorder has only two
terminals, a selection must be made among the
available active electrodes.
 The 12 standard leads used most frequently are shown
in upcoming figure 6.4.
 The three bipolar limp lead selections first introduced
by Einthoven.

29
LEAD CONNECTIONS
LEAD-I LeftArm(LA) and RightArm (RA)
LEAD-II Left Leg (LL) and RightArm (RA)
LEAD-III Left leg (LL) and LeftArm (LA)
• These three leads are called bipolar because for
each lead the ECG is recorded from two electrodes
and third electrode is not connected.
•In each of these lead positions, the QRS of a
normal heart is such that the R wave is positive.

30
Figure.6.4.1.Three lead techniques for measurement of ECG

31
Figure.6.4.2: Limbleads

32
 Einthoven made few assumption related to the cardiac
activity and ECG.
 He said that at any given instant of the cardiac cycle,
the frontal plane representation of the electrical axis of
the heart is two dimensional vector.
 The ECG measured from any three limb lead
techniques is time variant single dimensional
component of that vector.
 He also said that the heart is near the center of an
equilateral triangle, the apexes of which are the right
and left shoulders and the crotch.

34
 The other leads are known as unipolar type, which was
introduced by Wilson in 1994.
 For unipolar leads, the ECG is recorded between single
exploratory electrode and the central terminal, which
has a potential corresponding to the center of the body.
Three active limb electrodes together through resistors
of equal size.
 In augmented unipolar limb leads, the electrode used
as an exploratory electrode is not used for the central
terminal. These leads are aVR, aVL and aVF.(see
upcoming figure)

36
 The remaining leads are unipolar chest leads.
 These chest positions are called the precordial unipolar
leads and are designated V1 through V6.
 All three active limb electrodes are used to obtain the
central terminal, while a separate chest electrode is
used as an exploratory electrode.
 We will see the connection type of the precordial
unipolar leads also we will see the various ECG wave
forms for the particular patient by using different leads
techniques in upcoming diagrams.

41
 Some special modified leads are also used for the ECG
measurements. The most widely used modification for
ongoing ECG monitoring is modified chest lead I
(MCL1) also called the marriott lead, named after its
inventor.
 For this lead technique, the placement of the electrodes
on the body is different.
 Recordings obtained in this techniques are very useful
in differentiating left ventricular ectopic rhythms from
aberrant right ventricular or super ventricular rhythms.

Other ECG Signals
42
 Interdigital ECG
 Between two index fingers of the hands. Specially for those
implanted pacemakers
 Esophageal ECG
 Electrodes placed in the esophagus close to the heart.
Specially to examine the artery activity of the heart.
 Toilet seat ECG
 Two electrodes placed on the either side of the toilet seat.To
check the cardiac activity during the defecation.

ECG Read Out Devices
44
 TwoTypes : Oscilloscope and Strip chart
 CRO or Digital Display Device
 Most Oscilloscope made for ECG display use a horizontal
sweep speed of 25 mm/s.
 Medical strip chart recorders offer the same speeds. Standard
ECG papers has a grid pattern that is 50 mm wide.The small
grid division are 1 mm apart, while the large grid divisions
are 5 mm apart.

ECG Machine Mechanism Circuit
45

BLOOD PRESSURE
46
 The blood pressure for the human is divided in two
parts. Systolic and the Diastolic,
 Systolic is a pressure when the systole cycle of the
heart is running. It means when the ventricular section
contracts at that time the blood pressure of arteries is
known as the systolic blood pressure. Which is higher
value compare to diastolic. Normal is 120 mmHg
 Diastolic is a pressure while heart is in the second
cycle call diastole at which the blood is poured in the
atrium section.

BLOOD PRESSURE
47
 The diastolic normal value is around 80 mmHg.
 The value of blood pressure at the different condition of the
body is different. E.g. , while eating, exercise, sleeping,
angry…
 The body having its own monitoring system by which it
can control the flow of the blood in the special section of
mind.
 More blood pressure can damage the arteries and also can
directly affect the heart.
 Majority heart attacks are due to high blood pressure.
 We will see the graphical representation of the blood
pressure.

BLOOD PRESSURE
49
 Normally the arteries handle the higher value of blood
pressure, so it requires a wall of the arteries thick and
compare to that the veins are not handling that much of
large values, so it requires a thin walls.
 The diameter of the veins is lager compare to the
diameter of the arteries and capillaries.
 Since about 75 to 80 percent of the blood volume is
contained in the venous system, the veins tend to serve
as a reservoir for the body’s blood supply.
 We will see the diagrams of major arteries of the body
and veins of the human body.

CHARACTERISTICS OF BLOOD FLOW
52
 The blood flow at any point in the circulatory system is the
volume of blood that passes that point during a unit of time.
 Measured in mmltr/min or ltr/min
 The blood flow is highest in the pulmonary artery and the
aorta, where these blood vessels leaves the heart.
 The flow at this point is known as the cardiac output, which
is in the range of 3.5 to 5 lit/min
 Blood flow is a function of the blood pressure and flow
resistance of the blood vessels in the same way electrical
current flow depends on voltage and resistance.

53
 When under the low temperatures or under the
influence of certain drugs(e.g., nicotine), the body
reduces the blood flow through the skin by
vasoconstriction (narrowing) of the capillaries.
 Heat, excitement, or local inflammation, among other
things, can cause vasodilation (widening) of the
capillaries, which increase the blood flow, at least
locally.
 The velocity of blood flowing through a vessel is not
constant throughout the cross section of the vessel but
is a function of the distance from the wall structures.

54

55
 When the blood flow in a certain vessel is completely
obstructed(e.g., by a blood clot or thrombus), the tissue in
the area supplies by this vessel may die.
 Such obstruction in brain is cause cerebrovascular
accident(CVA) or stroke.
 The coronary arteries that supply blood for the heart muscle
is called myocardial (or coronary) infract or heart attack,
whereas merely a reduced flow in the coronary vessels can
cause a severe chest pain called angina pectoris.
 The blood clot in a vessel in the lung is called an embolism.

HEART SOUNDS
56
 Medical professionals can diagnosis certain types of
heart disorders by the sounds and vibrations associated
with the beating of the heart and the pumping of blood.
 The techniques of listening to sounds produced by the
organs and vessels of the body is called auscultation.
 The heart sounds heard by the stethoscope actually
occur at the time closure of major valves in the heart.
 With each heartbeat, the normal heart produces two
distinct sounds that are audible in the stethoscope
called “lub-dub”.

HEART SOUNDS
57
 The lub is caused by the closure of the atrioventicular
valves, which permit flow of blood from the atria into
the ventricles but prevent flow in the reverse direction.
 Normally this is called the first heart sound, its occurs
approximately at the time of the QRS complex of the
electrocardiogram and just before ventricular systole.
 The dub part of the heart sounds is called the second
heart sound and caused by the closing of the semilunar
valves, which release blood into the pulmonary and
systemic circulation systems.

HEART SOUNDS
58
 The third heart sound is sometimes heard, especially in
adults.
 This sound, which occurs from 0.1 to 0.2 sec after the
second heart sound, is attributed to the rush of blood
from the atria into the ventricles, which causes
turbulence and some vibration of the ventricular walls.
 An atrial heart sound, which is not audible but may be
visible on graphic recording, occurs when the atria
actually do contract, squeezing the remainder of the
blood into the ventricles.
 Upcoming figure shows the all heart sounds.

HEART SOUNDS
60
 In abnormal hearts additional sounds, called murmurs,
are heard between the normal heart sounds.
 Murmurs are generally caused either by improper
opening of valves or by regurgitation, when the valves
do not close completely and allow some backward
flow of blood.
 Another cause of murmurs can be a small opening in
the septum, which separates the left and right sides of
the heart.
 The upcoming diagram shows the various types of
murmurs.

HEART SOUNDS
62
 The first heart sound primarily of energy in the 30 to 45 Hz
range.
 The second heart sound usually higher in pitch than the first
with maximum energy in the 50 to 70 Hz range.
 The third heart sound is and extremely weak vibration, with
most of its energy at or below 30 Hz.
 Murmurs are in the range of 100 to 600 Hz.
 A graphic recording of heart sounds known as
phonocardiogram.
 The vibrations of the side of the heart as its thumps against
hitting the chest wall form the vibrocardiogram.

HEART SOUNDS
63
 When an artery is partially occluded so that the blood
velocity through the constriction is increased
sufficiently, identifiable sounds can be heard
downstream through stethoscope. These sounds, called
korotkoff sounds, are used in the common method of
blood pressure measurements.
 “Ballistocardiogram”, is direct result of the dynamic
forces of the heart as it beats and pumps blood into the
major arteries.

OUTCOMES
64
 We also come to know various aspects related to heart
and its functioning.
 Overall we can say the overview of the cardiovascular
system that we can relate with the electronics
engineering and instrumentation side.
 The machines related to ECG measurement are also
understood.

REFERENCES
65
 Book: “Biomedical instrumentation and measurements
“ ,by L. Cromwell, F .Weibell, and E. Pfeiffer. PHI
publication 2nd Edition
 www.worldofteaching.com
 Introduction to Biomedical Equipment Technology by Joseph
J. Carr. and John M. Brown. Forth Edition Pearson
Publication- 2012

Cardiovascular system

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