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Electrocardiography
Intervention
Image showing a patient connected to the 10
electrodes necessary for a 12-lead ECG
ICD-9-CM 89.52
MeSH D004562
MedlinePlus 003868
Example of Modern PC Based AME ECG
ElectrocardiographyFrom Wikipedia, the free encyclopedia
Electrocardiography (ECG orEKG from Greek: kardia,
meaning heart) is a transthoracic (across the thorax or chest)
interpretation ofthe electrical activity of the heart over a
period of time, as detected by electrodes attached to the
surface of the skin and recorded by a device external to the
body.[1] The recording produced by this noninvasive
procedure is termed an electrocardiogram (also ECG or
EKG).
An ECG is used to measure the rate and regularity of
heartbeats, as well as the size and position of the chambers,
the presence of any damage to the heart, and the effects of
drugs or devices used to regulate the heart, such as a
pacemaker.
Most ECGs are performed for diagnostic or research
purposes on human hearts, but may also be performed on
animals, usually for diagnosis of heart abnormalities or
research.
Contents
1 Function
2 History3 ECG graph paper
3.1 Layout
4 Leads
4.1 Placement of
electrodes
4.1.1 Additional
electrodes
4.2 Limb leads
4.3 Unipolar vs. bipolar
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Twelve-lead EKG of a 26-year-old male
leads
4.4 Augmented limb leads
4.5 Precordial leads
5 Waves and intervals
6 Vectors and views
6.1 Axis
6.2 Clinical lead groups
7 Filter selection8 Indications
8.1 Myocardial infarction
8.2 Pulmonary embolism
9 Some pathological patterns
which can be seen on the ECG
9.1 Electrocardiogram
heterogeneity
9.2 Rhythm Strip
10 Fetal electrocardiography
11 See also
12 References
13 External links
Function
An ECG is a way to measure and diagnose abnormal rhythms of the heart, [2] particularly abnormal rhythms cause
by damage to the conductive tissue that carries electrical signals, or abnormal rhythms caused by electrolyte
imbalances.[3] In a myocardial infarction (MI), the ECG can identify if the heart muscle has been damaged in
specific areas, though not all areas of the heart are covered.[4] The ECG cannot reliably measure the pumping
ability of the heart, for which ultrasound-based (echocardiography) or nuclear medicine tests are used. It is possibl
for a human or other animal to be in cardiac arrest, but still have a normal ECG signal (a condition known as
pulseless electrical activity).
The ECG device detects and amplifies the tiny electrical changes on the skin that are caused when the heart muscl
depolarizes during each heartbeat. At rest, each heart muscle cell has a negative charge, called the membrane
potential, across its cell membrane. Decreasing this negative charge towards zero, via the influx of the positive
cations, Na+ and Ca++, is called depolarization, which activates the mechanisms in the cell that cause it to contract
During each heartbeat, a healthy heart will have an orderly progression of a wave of depolarisation that is triggered
by the cells in the sinoatrial node, spreads out through the atrium, passes through the atrioventricular node and then
spreads all over the ventricles. This is detected as tiny rises and falls in the voltage between two electrodes placed
either side of the heart which is displayed as a wavy line either on a screen or on paper. This display indicates the
overall rhythm of the heart and weaknesses in different parts of the heart muscle.
Usually, more than two electrodes are used, and they can be combined into a number of pairs (For example: left
arm (LA), right arm (RA) and left leg (LL) electrodes form the three pairs LA+RA, LA+LL, and RA+LL). The
output from each pair is known as a lead. Each lead looks at the heart from a different angle. Different types of
ECGs can be referred to by the number of leads that are recorded, for example 3-lead, 5-lead or 12-lead ECGs
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An early commercial ECG device
(1911)
(sometimes simply "a 12-lead"). A 12-lead ECG is one in which 12 different electrical signals are recorded at
approximately the same time and will often be used as a one-off recording of an ECG, traditionally printed out as a
paper copy. Three- and 5-lead ECGs tend to be monitored continuously and viewed only on the screen of an
appropriate monitoring device, for example during an operation or whilst being transported in an ambulance. There
may or may not be any permanent record of a 3- or 5-lead ECG, depending on the equipment used.
History
The etymology of the word is derived from the Greekelectro, because it is related to electrical activity, kardio,
Greek for heart, andgraph, a Greek root meaning "to write".
Alexander Muirhead is reported to have attached wires to a feverish patient's wrist to obtain a record of the
patient's heartbeat while studying for his Doctor of Science (in electricity) in 1872 at St Bartholomew's Hospital.[5
This activity was directly recorded and visualized using a Lippmann capillary electrometer by the British physiologi
John Burdon Sanderson.[6] The first to systematically approach the heart from an electrical point-of-view was
Augustus Waller, working in St Mary's Hospital in Paddington, London.[7] His electrocardiograph machine
consisted of a Lippmann capillary electrometer fixed to a projector. The trace from the heartbeat was projected
onto a photographic plate which was itself fixed to a toy train. This allowed a heartbeat to be recorded in real timeIn 1911 he still saw little clinical application for his work.
An initial breakthrough came when Willem Einthoven, working in Leiden
the Netherlands, used the string galvanometer he invented in 1901.[8]
This device was much more sensitive than both the capillary electromete
Waller used and the string galvanometer that had been invented
separately in 1897 by the French engineer Clment Ader.[9] Rather than
using today's self-adhesive electrodes Einthoven's subjects would
immerse each of their limbs into containers of salt solutions from which
the EKG was recorded.
Einthoven assigned the letters P, Q, R, S and T to the various
deflections,[10] and described the electrocardiographic features of a
number of cardiovascular disorders. In 1924, he was awarded the Nob
Prize in Medicine for his discovery.[11]
Though the basic principles of that era are still in use today, many advances in electrocardiography have been mad
over the years. The instrumentation, for example, has evolved from a cumbersome laboratory apparatus to compa
electronic systems that often include computerized interpretation of the electrocardiogram.[12]
ECG graph paper
The output of an ECG recorder is a graph (or sometimes several graphs, representing each of the leads) with time
represented on thex-axis and voltage represented on they-axis. A dedicated ECG machine would usually print
onto graph paper which has a background pattern of 1mm squares (often in red or green), with bold divisions eve
5 mm in both vertical and horizontal directions.
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One second of ECG graph paper
It is possible to change the output of most ECG devices but it is standard to represent each mV on the y axis as
1 cm and each second as 25 mm on thex-axis (that is a paper speed of 25 mm/s). Faster paper speeds can be
used, for example, to resolve finer detail in the ECG. At a paper speed of 25 mm/s, one small block of ECG pape
translates into 40 ms. Five small blocks make up one large block, which translates into 200 ms. Hence, there are
five large blocks per second. A calibration signal may be included with a record. A standard signal of 1 mV must
move the stylus vertically 1 cm, that is, two large squares on ECG paper.
Layout
By definition, a 12-lead ECG will show a short segment of the recording
of each of the 12-leads. This is often arranged in a grid of four columns
by three rows, the first column being the limb leads (I,II and III), the
second column the augmented limb leads (aVR, aVL and aVF) and the
last two columns being the chest leads (V1-V6). It is usually possible to
change this layout, so it is vital to check the labels to see which lead is
represented. Each column will usually record the same moment in time
for the three leads and then the recording will switch to the next column,
which will record the heart beats after that point. It is possible for the heart rhythm to change between the columns
of leads.
Each of these segments is short, perhaps one to three heart beats only, depending on the heart rate, and it can be
difficult to analyse any heart rhythm that shows changes between heart beats. To help with the analysis, it is
common to print one or two "rhythm strips", as well. This will usually be lead II (which shows the electrical signal
from the atrium, the P-wave, well) and shows the rhythm for the whole time the ECG was recorded (usually 56
sec). Some ECG machines will print a second lead II along the very bottom of the paper in addition to the output
described above. This printing of lead II is continuous from start to finish of the process.
The term "rhythm strip" may also refer to the whole printout from a continuous monitoring system, which may showonly one lead and is either initiated by a clinician or in response to an alarm or event.
Leads
The term "lead" in electrocardiography causes much confusion because it is used to refer to two different things. In
accordance with common parlance, the word lead may be used to refer to the electrical cable attaching the
electrodes to the ECG recorder. As such, it may be acceptable to refer to the "left arm lead" as the electrode (and
its cable) that should be attached at or near the left arm. Usually, 10 of these electrodes are standard in a "12-lead
ECG.
Alternatively (and some would say properly, in the context of electrocardiography), the word lead may refer to the
tracing of the voltage difference between two of the electrodes and is what is actually produced by the ECG
recorder. Each will have a specific name. For example "lead I" is the voltage between the right arm electrode and
the left arm electrode, whereas "Lead II" is the voltage between the right arm and the left leg. (This rapidly become
more complex as one of the "electrodes" may in fact be a composite of the electrical signal from a combination of
the other electrodes). Twelve of this type of lead form a "12-lead" ECG.
To cause additional confusion, the term "limb leads" usually refers to the tracings from leads I, II and III rather tha
the electrodes attached to the limbs.
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Proper placement of the limb
electrodes, color-coded as
recommended by the American Heart
Association (a different colour
scheme is used in Europe): The limb
electrodes can be far down on the
limbs or close to the hips/shoulders,
but they must be even (left vs
right).[16]
* When exercise stress tests are
performed, limb leads may be placed
on the trunk to avoid artifacts while
ambulatory (arm leads moved
subclavicularly and leg leads medial to
and above the iliac crest).
Placement of electrodes
Ten electrodes are used for a 12-lead ECG. The electrodes usually consist of a conducting gel, embedded in the
middle of a self-adhesive pad onto which cables clip. Sometimes the gel also forms the adhesive.[13] They are
labeled and placed on the patient's body as follows:[14][15]
Electrode label
(in the USA)Electrode placement
RA On the right arm, avoiding thick muscle.
LAIn the same location where RA was placed, but on
the left arm.
RL On the right leg, lateral calf muscle.
LLIn the same location where RL was placed, but on the
left leg.
V1
In the fourth intercostal space (between ribs 4 and 5)
just to the right of the sternum (breastbone).
V2In the fourth intercostal space (between ribs 4 and 5)
just to the left of the sternum.
V3 Between leads V2 and V4.
V4In the fifth intercostal space (between ribs 5 and 6) in
the mid-clavicular line.
V5Horizontally even with V4, in the left anterior axillary
line.
V6Horizontally even with V4 and V5 in the midaxillary
line.
Additional electrodes
The classical 12-lead ECG can be extended in a number of ways in an attempt to improve its sensitivity in detectin
myocardial infarction involving territories not normally "seen" well. This includes an rV4 lead, which uses the
equivalent landmarks to the V4 but on the right side of the chest wall and extending the chest leads onto the back
with a V7, V8 and V9.
The Lewis lead or S5 has the LA electrode placed in the second intercostal space to the right of the sternum with
the RA at the fourth intercostal space. It is read as lead I and is supposed to demonstrate atrial activity much bette
to aid in identification of atrial flutter or broad-complex tachycardia.
A posterior ECG can aid in the diagnosis of a posterior myocardial infarction. This is performed by the addition of
leads V7, V8 and V9 extending around the left chest wall toward the back.
Limb leads
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Placement of the precordial leads
12 leads
In both the 5- and 12-lead configurations, leads I, II and III are called
limb leads. The electrodes that form these signals are located on the limbs
one on each arm and one on the left leg.[17][18][19] The limb leads form
the points of what is known as Einthoven's triangle.[20]
Lead I is the voltage between the (positive) left arm (LA)
electrode and right arm (RA) electrode:
Lead II is the voltage between the (positive) left leg (LL) electrode
and the right arm (RA) electrode:
Lead III is the voltage between the (positive) left leg (LL)
electrode and the left arm (LA) electrode:
Simplified electrocardiograph sensors designed for teaching purposes,
e.g. at high school level, are generally limited to three arm electrodes
serving similar purposes.[21]
Unipolar vs. bipolar leads
The two types of leads are unipolar and bipolar. Bipolar leads have one positive and one negative pole.[22] In a 12
lead ECG, the limb leads (I, II and III) are bipolar leads. Unipolar leads also have two poles, as a voltage is
measured; however, the negative pole is a composite pole (Wilson's central terminal, or WCT) made up of signals
from multiple other electrodes.[23] In a 12-lead ECG, all leads except the limb leads are unipolar (aVR, aVL, aVF
V1, V2, V3, V4, V5, and V6).
Wilson's central terminal VW is produced by connecting the electrodes RA, LA, and LL together, via a simple
resistive network, to give an average potential across the body, which approximates the potential at infinity (i.e.
zero):
Augmented limb leads
Leads aVR, aVL, and aVF are augmented limb leads (after their inventor Dr. Emanuel Goldberger known
collectively as the Goldberger's leads). They are derived from the same three electrodes as leads I, II, and III.
However, they view the heart from different angles (or vectors) because the negative electrode for these leads is a
modification of Wilson's central terminal. This zeroes out the negative electrode and allows the positive electrode t
become the "exploring electrode". This is possible because Einthoven's Law states that I + (II) + III = 0. The
equation can also be written I + III = II. It is written this way (instead of I II + III = 0) because Einthoven
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reversed the polarity of lead II in Einthoven's triangle, possibly because he liked to view upright QRS complexes.
Wilson's central terminal paved the way for the development of the augmented limb leads aVR, aVL, aVF and the
precordial leads V1, V2, V3, V4, V5 and V6.
Lead augmented vector right (aVR)' has the positive electrode (white) on the right arm. The negative
electrode is a combination of the left arm (black) electrode and the left leg (red) electrode, which "augments
the signal strength of the positive electrode on the right arm:
Lead augmented vector left (aVL) has the positive (black) electrode on the left arm. The negative electrode
is a combination of the right arm (white) electrode and the left leg (red) electrode, which "augments" the
signal strength of the positive electrode on the left arm:
Lead augmented vector foot (aVF) has the positive (red) electrode on the left leg. The negative electrode is
combination of the right arm (white) electrode and the left arm (black) electrode, which "augments" the sign
of the positive electrode on the left leg:
The augmented limb leads aVR, aVL, and aVF are amplified in this way because the signal is too small to be usefu
when the negative electrode is Wilson's central terminal. Together with leads I, II, and III, augmented limb leads
aVR, aVL, and aVF form the basis of the hexaxial reference system, which is used to calculate the heart's electrica
axis in the frontal plane. The aVR, aVL, and aVF leads can also be represented using the I and II limb leads:
Precordial leads
The electrodes for the precordial leads (V1, V2, V3, V4, V5 and V6) are placed directly on the chest. Because of
their close proximity to the heart, they do not require augmentation. Wilson's central terminal is used for the negativ
electrode, and these leads are considered to be unipolar (recall that Wilson's central terminal is the average of the
three limb leads. This approximates common, or average, potential over the body). The precordial leads view the
heart's electrical activity in the so-called horizontal plane. The heart's electrical axis in the horizontal plane is referre
to as the Z axis.
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Schematic representation of normal
ECG
Animation of a normal ECG wave
Waves and intervals
A typical ECG tracing of the cardiac cycle (heartbeat) consists of a P
wave, a QRS complex, a T wave, and a U wave, which is normally
invisible in 50 to 75% of ECGs because it is hidden by the T wave and
upcoming new P wave.[27] The baseline of the electrocardiogram (the flat
horizontal segments) is measured as the portion of the tracing following
the T wave and preceding the next P wave and the segment between theP wave and the following QRS complex (PR segment). In a normal
healthy heart, the baseline is equivalent to the isoelectric line (0mV) and
represents the periods in the cardiac cycle when there are no currents
flowing towards either the positive or negative ends of the ECG leads.
However, in a diseased heart the baseline may be elevated (e.g. cardiac
ischaemia) or depressed (e.g. myocardial infarction) relative to the
isoelectric line due to injury currents flowing during the TP and PR
intervals when the ventricles are at rest. The ST segment typically remains
close to the isoelectric line as this is the period when the ventricles are
fully depolarised and thus no currents can flow in the ECG leads. Sincemost ECG recordings do not indicate where the 0mV line is, baseline
depression often gives the appearance of an elevation of the ST segment
and conversely baseline elevation gives the appearance of depression of
the ST segment.[28]
Feature Description Duration
RR
interval
The interval between an R wave and the next R
wave: Normal resting heart rate is between 60 and
100 bpm.
0.6 to
1.2s
P wave
During normal atrial depolarization, the main
electrical vector is directed from the SA node
towards the AV node, and spreads from the right
atrium to the left atrium. This turns into the P wave
on the ECG.
80ms
PR
interval
The PR interval is measured from the beginning of
the P wave to the beginning of the QRS complex.
The PR interval reflects the time the electrical
impulse takes to travel from the sinus node throughthe AV node and entering the ventricles. The PR
interval is, therefore, a good estimate of AV node
function.
120 to
200ms
PR
segment
The PR segment connects the P wave and the
QRS complex. The impulse vector is from the AV
node to the bundle of His to the bundle branches
and then to the Purkinje fibers. This electrical
activity does not produce a contraction directly50 to
120ms
https://en.wikipedia.org/wiki/PR_intervalhttps://en.wikipedia.org/wiki/Atrium_(anatomy)https://en.wikipedia.org/wiki/Atrium_(anatomy)https://en.wikipedia.org/wiki/P_wave_(electrocardiography)https://en.wikipedia.org/wiki/Beats_per_minutehttps://en.wikipedia.org/wiki/R_wavehttps://en.wikipedia.org/wiki/RR_intervalhttps://en.wikipedia.org/wiki/Electrocardiography#cite_note-28https://en.wikipedia.org/wiki/Electrocardiography#cite_note-27https://en.wikipedia.org/wiki/File:ECG_principle_slow.gifhttps://en.wikipedia.org/wiki/File:SinusRhythmLabels.svg7/28/2019 Electrocardiography - Wikipedia, The Free Encyclopedia
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Detail of the QRS complex, showing
ventricular activation time (VAT) and
amplitude
and is merely traveling down towards the
ventricles, and this shows up flat on the ECG. The
PR interval is more clinically relevant.
QRS
complex
The QRS complex reflects the rapid depolarization
of the right and left ventricles. They have a large
muscle mass compared to the atria, so the QRS
complex usually has a much larger amplitude than
the P-wave.
80 to
120ms
J-point
The point at which the QRS complex finishes and
the ST segment begins, it is used to measure the
degree of ST elevation or depression present.
N/A
ST
segment
The ST segment connects the QRS complex and
the T wave. The ST segment represents the period
when the ventricles are depolarized. It is
isoelectric.
80 to
120ms
T wave
The T wave represents the repolarization (orrecovery) of the ventricles. The interval from the
beginning of the QRS complex to the apex of the T
wave is referred to as the absolute refractory
period. The last half of the T wave is referred to as
the relative refractory period (or vulnerable
period).
160ms
ST
interval
The ST interval is measured from the J point to the
end of the T wave.320ms
QT
interval
The QT interval is measured from the beginning ofthe QRS complex to the end of the T wave. A
prolonged QT interval is a risk factor for
ventricular tachyarrhythmias and sudden death. It
varies with heart rate and for clinical relevance
requires a correction for this, giving the QTc.
Up to
420ms in
heart rate
of 60
bpm
U wave
The U wave is hypothesized to be caused by the
repolarization of the interventricular septum. They
normally have a low amplitude, and even more
often completely absent. They always follow the T
wave and also follow the same direction in
amplitude. If they are too prominent, suspect
hypokalemia, hypercalcemia or hyperthyroidism
usually.[29]
J wave
The J wave, elevated J-point or Osborn wave
appears as a late delta wave following the QRS or
as a small secondary R wave. It is considered
pathognomonic of hypothermia or
https://en.wikipedia.org/wiki/Hypothermiahttps://en.wikipedia.org/wiki/Pathognomonichttps://en.wikipedia.org/wiki/Osborn_wavehttps://en.wikipedia.org/wiki/Electrocardiography#cite_note-29https://en.wikipedia.org/wiki/U_wavehttps://en.wikipedia.org/wiki/QT_intervalhttps://en.wikipedia.org/wiki/ST_intervalhttps://en.wikipedia.org/wiki/T_wavehttps://en.wikipedia.org/wiki/ST_segmenthttps://en.wikipedia.org/wiki/J-pointhttps://en.wikipedia.org/wiki/QRS_complexhttps://en.wikipedia.org/wiki/Ventricular_activation_timehttps://en.wikipedia.org/wiki/QRS_complexhttps://en.wikipedia.org/wiki/File:QRS_complex.png7/28/2019 Electrocardiography - Wikipedia, The Free Encyclopedia
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Upper limit of normal QT interval,corrected for heart rate according to
Bazett's formula,[24] Fridericia's
formula[25] and subtracting 0.02s
from QT for every 10bpm increase in
heart rate.[26] Up to 0.42s (420ms)
is chosen as normal QTc of QTB and
QTF in this diagram.
Graphic showing the relationshipbetween positive electrodes,
depolarization wavefronts (or mean
electrical vectors), and complexes
displayed on the ECG
hypocalcemia.[30]
Originally, four deflections were noted, but after the mathematical correction for artifacts introduced by early
amplifiers, a fifth deflection was discovered. Einthoven chose the letters P, Q, R, S, and T to identify the tracing
which was superimposed over the uncorrected labeled A, B, C, and D.[10]
In intracardiac electrocardiograms, such as can be acquired from pacemaker sensors, an additional wave can be
seen, the H deflection, which reflects the depolarization of the bundle ofHis.[31] The H-V interval, in turn, is the duration from the beginning of the
H deflection to the earliest onset of ventricular depolarization recorded in
any lead.[32]
Vectors and views
Interpretation of the ECG
relies on the idea that different
leads (meaning the ECG leads
I, II, III, aVR, aVL, aVF and
the chest leads) "view" the
heart from different angles.
This has two benefits. Firstly,
leads which are showing
problems (for example ST
segment elevation) can be used
to infer which region of the
heart is affected. Secondly, the
overall direction of travel of the wave of depolarisation can also be
inferred which can reveal other problems. This is termed the cardiac axi. Determination of the cardiac axis relies on the concept of a vector
which describes the motion of the depolarisation wave. This vector can
then be described in terms of its components in relation to the direction o
the lead considered. One component will be in the direction of the lead
and this will be revealed in the behaviour of the QRS complex and one
component will be at 90 to this (which will not). Any net positive deflection of the QRS complex (i.e. height of th
R-wave minus depth of the S-wave) suggests the wave of depolarisation is spreading through the heart in a
direction that has some component (of the vector) in the same direction as the lead in question.
Axis
The heart's electrical axis refers to the general direction of the heart's depolarization wavefront (or mean electrical
vector) in the frontal plane. With a healthy conducting system, the cardiac axis is related to where the major muscl
bulk of the heart lies. Normally, this is the left ventricle, with some contribution from the right ventricle. It is usually
oriented in a right shoulder to left leg direction, which corresponds to the left inferior quadrant of the hexaxial
reference system, although 30 to +90 is considered to be normal. If the left ventricle increases its activity or
bulk, then there is said to be "left axis deviation" as the axis swings round to the left beyond 30; alternatively, in
conditions where the right ventricle is strained or hypertrophied, then the axis swings round beyond +90 and "righ
axis deviation" is said to exist. Disorders of the conduction system of the heart can disturb the electrical axis withou
https://en.wikipedia.org/wiki/Hexaxial_reference_systemhttps://en.wikipedia.org/wiki/Euclidean_vectorshttps://en.wikipedia.org/wiki/Electrocardiography#cite_note-32https://en.wikipedia.org/wiki/Electrocardiography#cite_note-31https://en.wikipedia.org/wiki/Bundle_of_Hishttps://en.wikipedia.org/wiki/Electrocardiography#cite_note-naming-10https://en.wikipedia.org/wiki/Electrocardiography#cite_note-30https://en.wikipedia.org/wiki/Hypocalcemiahttps://en.wikipedia.org/wiki/File:ECG_Vector.svghttps://en.wikipedia.org/wiki/Electrocardiography#cite_note-Yanowitz-26https://en.wikipedia.org/wiki/Electrocardiography#cite_note-Fridericia-1920-25https://en.wikipedia.org/wiki/Electrocardiography#cite_note-Bazett-1920-24https://en.wikipedia.org/wiki/File:QT_interval_corrected_for_heart_rate.png7/28/2019 Electrocardiography - Wikipedia, The Free Encyclopedia
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Diagram showing how the polarity of
the QRS complex in leads I, II, and
III can be used to estimate the heart'selectrical axis in the frontal plane
The hexaxial reference system showing the orientation
of each lead: For example, if the bulk of heart muscle is
oriented at +60 degrees with respect to the SA node,
lead II will show the greatest deflection and aVL the
least.
necessarily reflecting changes in muscle bulk.
Normal30
to 90Normal Normal
Left axis
deviation
30
to
90
May indicate left anterior
fascicular block or Q waves
from inferior MI.
Left axis deviation is
considered normal in
pregnant women and
those with emphysema.
Right
axis
deviation
+90
to
+180
May indicate left posterior
fascicular block, Q waves
from high lateral MI, or a
right ventricular strain pattern
Right deviation is
considered normal in
children and is a
standard effect of
dextrocardia.
Extreme
right axis
deviation
+180
to
90
Is rare, and considered an
'electrical no-man's land'
In the setting of right bundle branch block, right or left
axis deviation may indicate bifascicular block.
Clinical lead groups
Of the 12 leads in total, each records the electrical
activity of the heart from a different perspective, which
also correlates to different anatomical areas of the heart
for the purpose of identifying acute coronary ischemia
or injury. Two leads that look at neighbouring
anatomical areas of the heart are said to be contiguous.
The relevance of this is in determining whether an
abnormality on the ECG is likely to represent true
disease or a spurious finding.
https://en.wikipedia.org/wiki/Bifascicular_blockhttps://en.wikipedia.org/wiki/Right_bundle_branch_blockhttps://en.wikipedia.org/wiki/Dextrocardiahttps://en.wikipedia.org/wiki/Myocardial_infarctionhttps://en.wikipedia.org/wiki/Right_axis_deviationhttps://en.wikipedia.org/wiki/Emphysemahttps://en.wikipedia.org/wiki/Myocardial_infarctionhttps://en.wikipedia.org/wiki/Left_axis_deviationhttps://en.wikipedia.org/wiki/Hexaxial_reference_systemhttps://en.wikipedia.org/wiki/File:Hexaxial_reference_system.svghttps://en.wikipedia.org/wiki/File:Rapid_Axis_Vector.svg7/28/2019 Electrocardiography - Wikipedia, The Free Encyclopedia
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Diagram showing the contiguous
leads in the same color
Category
Color
on
chart
Leads Activity
Inferior
leads'Yellow
Leads
II, III
and
aVF
Look at electrical activity from the vantage
point of the inferior surface (diaphragmatic
surface of heart)
Lateral
leadsGreen
I,
aVL,
V5and
V6
Look at the electrical activity from the
vantage point of the lateral wall of left
ventricle
The positive electrode for leads I
and aVL should be located distally
on the left arm and because of
which, leads I and aVL are
sometimes referred to as the high
lateral leads.Because the positive electrodes for
leads V5 and V6 are on the patient's
chest, they are sometimes referred to
as the low lateral leads.
Septal
leadsOrange
V1and
V2
Look at electrical activity from the vantage
point of the septal surface of the heart
(interventricular septum)
Anterior
leadsBlue
V3and
V4
Look at electrical activity from the vantagepoint of the anterior wall of the right and left
ventricles (sternocostal surface of the heart)
In addition, any two precordial leads next to one another are considered to be contiguous. For example, though V
is an anterior lead and V5 is a lateral lead, they are contiguous because they are next to one another. A common
saying to remember the contiguous leads is "I see all leads" (inferior, septal, anterior and lateral).
Lead aVR offers no specific view of the left ventricle. Rather, it views the inside of the endocardial wall to the
surface of the right atrium, from its perspective on the right shoulder.
Filter selection
Modern ECG monitors offer multiple filters for signal processing. The most common settings are monitor mode an
diagnostic mode. In monitor mode, the low-frequency filter (also called the high-pass filter because signals above
the threshold are allowed to pass) is set at either 0.5 Hz or 1 Hz and the high-frequency filter (also called the low-
pass filter because signals below the threshold are allowed to pass) is set at 40 Hz. This limits artifacts for routine
cardiac rhythm monitoring. The high-pass filter helps reduce wandering baseline and the low-pass filter helps reduc
50- or 60-Hz power line noise (the power line network frequency differs between 50 and 60 Hz in different
https://en.wikipedia.org/wiki/Mains_power_systemshttps://en.wikipedia.org/wiki/Low-pass_filterhttps://en.wikipedia.org/wiki/High-pass_filterhttps://en.wikipedia.org/w/index.php?title=Sternocostal_surface_of_the_heart&action=edit&redlink=1https://en.wikipedia.org/wiki/Anteriorhttps://en.wikipedia.org/wiki/Interventricular_septumhttps://en.wikipedia.org/wiki/Septalhttps://en.wikipedia.org/wiki/Ventricle_(heart)https://en.wikipedia.org/wiki/Laterallyhttps://en.wikipedia.org/wiki/Diaphragmatic_surface_of_hearthttps://en.wiktionary.org/wiki/inferiorhttps://en.wikipedia.org/wiki/File:Contiguous_leads.svg7/28/2019 Electrocardiography - Wikipedia, The Free Encyclopedia
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Wiggers diagram, showing a normal
ECG curve synchronized with other
major events during the cardiac cycle
countries). In diagnostic mode, the high-pass filter is set at 0.05 Hz,
which allows accurate ST segments to be recorded. The low-pass filter is
set to 40, 100, or 150 Hz. Consequently, the monitor mode ECG display
is more filtered than diagnostic mode, because its passband is
narrower.[33]
Indications
Medical societies do not recommend either the ECG or any other
cardiac imaging procedure as a routine screening procedure in patients
without symptoms and who are at low risk for coronary heart disease.[34]
This is because overuse of the procedure is more likely to supply
incorrect supporting evidence for a nonexistent problem than to detect a
true problem.[34] Tests which falsely indicate the existence of a problem
are likely to lead to misdiagnosis, the recommendation of invasive procedures, or overtreatment, and the risks
associated with managing false information are usually more troublesome than not using ECG results to make a
health recommendation in low-risk individuals.[34]
Symptoms generally indicating use of electrocardiography include:
Symptoms of myocardial infarction
Symptoms of pulmonary embolism
Cardiac murmurs[35]
Syncope or collapse[35]
Seizures[35]
Perceived cardiac dysrhythmias[35]
It is also used to assess patients with systemic disease, as well as monitoring during anesthesia and critically ill
patients.[35]
Myocardial infarction
Main article: Electrocardiography in myocardial infarction
Characteristic changes seen on electrocardiography in myocardial infarction is included in the WHO criteria as
revised in 2000.[36] According to these, a cardiac troponin rise accompanied by either typical symptoms,
pathological Q waves, ST elevation or depression or coronary intervention are diagnostic of myocardial infarction
Pulmonary embolism
In pulmonary embolism, an ECG may show signs of right heart strain or acute cor pulmonale in cases of large PEs
the classic signs are a large S wave in lead I, a large Q wave in lead III and an inverted T wave in lead III
(S1Q3T3).[37] This is occasionally (up to 20%) present, but may also occur in other acute lung conditions and has
therefore limited diagnostic value. This S1Q3T3 pattern from acute right heart strain is termed the "McGinn-White
sign" after the initial describers. The most commonly seen signs in the ECG is sinus tachycardia, right axis deviation
and right bundle branch block.[38] Sinus tachycardia was however still only found in 869% of people with PE. [39
https://en.wikipedia.org/wiki/Electrocardiography#cite_note-39https://en.wikipedia.org/wiki/Electrocardiography#cite_note-38https://en.wikipedia.org/wiki/Right_bundle_branch_blockhttps://en.wikipedia.org/wiki/Sinus_tachycardiahttps://en.wikipedia.org/wiki/Electrocardiography#cite_note-37https://en.wikipedia.org/wiki/T_wavehttps://en.wikipedia.org/wiki/Cor_pulmonalehttps://en.wikipedia.org/wiki/Pulmonary_embolismhttps://en.wikipedia.org/wiki/Troponinhttps://en.wikipedia.org/wiki/Electrocardiography#cite_note-Alpert-2000-36https://en.wikipedia.org/wiki/Electrocardiography_in_myocardial_infarctionhttps://en.wikipedia.org/wiki/Electrocardiography_in_myocardial_infarctionhttps://en.wikipedia.org/wiki/Electrocardiography#cite_note-masters-35https://en.wikipedia.org/wiki/Anesthesiahttps://en.wikipedia.org/wiki/Electrocardiography#cite_note-masters-35https://en.wikipedia.org/wiki/Cardiac_dysrhythmiahttps://en.wikipedia.org/wiki/Electrocardiography#cite_note-masters-35https://en.wikipedia.org/wiki/Seizurehttps://en.wikipedia.org/wiki/Electrocardiography#cite_note-masters-35https://en.wikipedia.org/wiki/Syncope_(medicine)https://en.wikipedia.org/wiki/Electrocardiography#cite_note-masters-35https://en.wikipedia.org/wiki/Cardiac_murmurhttps://en.wikipedia.org/wiki/Pulmonary_embolismhttps://en.wikipedia.org/wiki/Myocardial_infarctionhttps://en.wikipedia.org/wiki/Electrocardiography#cite_note-whenyouneedEKGs-34https://en.wikipedia.org/wiki/Electrocardiography#cite_note-whenyouneedEKGs-34https://en.wikipedia.org/wiki/Electrocardiography#cite_note-whenyouneedEKGs-34https://en.wikipedia.org/wiki/Coronary_heart_diseasehttps://en.wikipedia.org/wiki/Electrocardiography#cite_note-Atlas_Cardio_Monitor_130-33https://en.wikipedia.org/wiki/Cardiac_cyclehttps://en.wikipedia.org/wiki/Wiggers_diagramhttps://en.wikipedia.org/wiki/File:Wiggers_Diagram.svg7/28/2019 Electrocardiography - Wikipedia, The Free Encyclopedia
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Electrocardiogram of a patient with
pulmonary embolism showing sinus
tachycardia of approximately 150beats per minute and right bundle
branch block.
Some pathological patterns which can be seen on the ECG
The following table mentions some pathological patterns that can be seen on electrocardiography, followed by
possible causes.
Shortened QT interval Hypercalcemia, some drugs, certain genetic abnormalities, hyperkalemia
Prolonged QT interval Hypocalcemia, some drugs, certain genetic abnormalities
Flattened or inverted T wavesCoronary ischemia, hypokalemia, left ventricular hypertrophy, digoxin effect,
some drugs
Hyperacute T wavesPossibly the first manifestation of acute myocardial infarction, where T waves
become more prominent, symmetrical, and pointed
Peaked T wave, QRS wide,
prolonged PR, QT shortHyperkalemia, treat with calcium chloride, glucose and insulin or dialysis
Prominent U waves Hypokalemia
Electrocardiogram heterogeneity
ECG heterogeneity is a measurement of the amount of variance between one ECG waveform and the next. This
heterogeneity can be measured by placing multiple ECG electrodes on the chest and then computing the variance iwaveform morphology across the signals obtained from these electrodes. Recent research suggests ECG
heterogeneity often precedes dangerous cardiac arrhythmias.
In the future, implantable devices may be programmed to measure and track heterogeneity. These devices could
potentially help ward off arrhythmias by stimulating nerves such as the vagus nerve, delivering drugs such as beta-
blockers, and if necessary, defibrillating the heart.[40]
Rhythm Strip
https://en.wikipedia.org/wiki/Electrocardiography#cite_note-40https://en.wikipedia.org/wiki/Defibrillationhttps://en.wikipedia.org/wiki/Beta-blockershttps://en.wikipedia.org/wiki/Vagus_nervehttps://en.wikipedia.org/wiki/Cardiac_arrhythmiashttps://en.wikipedia.org/wiki/Shapehttps://en.wikipedia.org/wiki/Electrodeshttps://en.wikipedia.org/wiki/Heterogeneityhttps://en.wikipedia.org/wiki/Waveformhttps://en.wikipedia.org/wiki/Variancehttps://en.wikipedia.org/wiki/Hypokalemiahttps://en.wikipedia.org/wiki/Hyperkalemiahttps://en.wikipedia.org/wiki/Myocardial_infarctionhttps://en.wikipedia.org/wiki/Digoxinhttps://en.wikipedia.org/wiki/Left_ventricular_hypertrophyhttps://en.wikipedia.org/wiki/Hypokalemiahttps://en.wikipedia.org/wiki/Coronary_ischemiahttps://en.wikipedia.org/wiki/Long_QT_syndromehttps://en.wikipedia.org/wiki/Hypocalcemiahttps://en.wikipedia.org/wiki/Hyperkalemiahttps://en.wikipedia.org/wiki/Short_QT_syndromehttps://en.wikipedia.org/wiki/Hypercalcemiahttps://en.wikipedia.org/wiki/Right_bundle_branch_blockhttps://en.wikipedia.org/wiki/Sinus_tachycardiahttps://en.wikipedia.org/wiki/File:Pulmonary_embolism_ECG.jpg7/28/2019 Electrocardiography - Wikipedia, The Free Encyclopedia
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Although multiple leads, and thus multiple electrical vectors, are commonly used in unison to gain diagnostic and
therapeutic insight into cardiac status monitoring one lead, referred to as a rhythm strip, can be useful to trend
cardiac function in terms of heart rate, regularity, pauses, and basic rhythm.
Fetal electrocardiography
Fetal electrocardiography records the electrical activity of a fetus, and when performed as a part of monitoring in
childbirth, involves a single electrode being passed through the woman's cervix and attached to the baby's scalp. [4According to a Cochrane review, monitoring the fetus using ECG plus cardiotocography (CTG) resulted in fewer
instances of fetal scalp blood testing, and less surgical assistance with the birth, compared to CTG alone. [41] There
was no difference in the number of Caesarean deliveries and little to suggest the babies were in better condition at
birth.[41]
See also
Advanced cardiac life support (ACLS)
Angiogram
Automated ECG interpretation
HEART scan
Ballistocardiograph
Bundle branch block
Cardiac cycle
Cardiac stress test
Echocardiogram
Edgar Hull
Electrical conduction system of the heartElectrocardiogram technician
Electroencephalography
Electrogastrogram
Electropalatograph
Electroretinography
Human heart
Heart rate monitor
Holter monitor
Intrinsicoid deflection
Magnetic field imaging
Magnetocardiography
Myocardial infarction
Rapid Interpretation of EKG's
Treacherous technician syndrome
References
https://en.wikipedia.org/wiki/Treacherous_technician_syndromehttps://en.wikipedia.org/wiki/Rapid_Interpretation_of_EKG%27shttps://en.wikipedia.org/wiki/Myocardial_infarctionhttps://en.wikipedia.org/wiki/Magnetocardiographyhttps://en.wikipedia.org/wiki/Magnetic_field_imaginghttps://en.wikipedia.org/wiki/Intrinsicoid_deflectionhttps://en.wikipedia.org/wiki/Holter_monitorhttps://en.wikipedia.org/wiki/Heart_rate_monitorhttps://en.wikipedia.org/wiki/Human_hearthttps://en.wikipedia.org/wiki/Electroretinographyhttps://en.wikipedia.org/wiki/Electropalatographhttps://en.wikipedia.org/wiki/Electrogastrogramhttps://en.wikipedia.org/wiki/Electroencephalographyhttps://en.wikipedia.org/wiki/Electrocardiogram_technicianhttps://en.wikipedia.org/wiki/Electrical_conduction_system_of_the_hearthttps://en.wikipedia.org/wiki/Edgar_Hullhttps://en.wikipedia.org/wiki/Echocardiogramhttps://en.wikipedia.org/wiki/Cardiac_stress_testhttps://en.wikipedia.org/wiki/Cardiac_cyclehttps://en.wikipedia.org/wiki/Bundle_branch_blockhttps://en.wikipedia.org/wiki/Ballistocardiographhttps://en.wikipedia.org/wiki/HEART_scanhttps://en.wikipedia.org/wiki/Automated_ECG_interpretationhttps://en.wikipedia.org/wiki/Angiogramhttps://en.wikipedia.org/wiki/Advanced_cardiac_life_supporthttps://en.wikipedia.org/wiki/Electrocardiography#cite_note-Neilson2012-41https://en.wikipedia.org/wiki/Electrocardiography#cite_note-Neilson2012-41https://en.wikipedia.org/wiki/Fetal_scalp_blood_testinghttps://en.wikipedia.org/wiki/Cardiotocographyhttps://en.wikipedia.org/wiki/Cochrane_reviewhttps://en.wikipedia.org/wiki/Electrocardiography#cite_note-Neilson2012-41https://en.wikipedia.org/wiki/Scalphttps://en.wikipedia.org/wiki/Cervixhttps://en.wikipedia.org/wiki/Monitoring_in_childbirthhttps://en.wikipedia.org/wiki/Fetus7/28/2019 Electrocardiography - Wikipedia, The Free Encyclopedia
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of National Biography 2004 (Subscription required) (original source is his biography written by his wife
Elizabeth Muirhead. Alexandernn Muirhead 1848 1920. Oxford, Blackwell: privately printed 1926.)
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motions of the ventricle of the frog heart".Proc Roy Soc Lond27 (185189): 41014. doi:10.1098/rspl.1878.006
(http://dx.doi.org/10.1098%2Frspl.1878.0068).
7. ^ Waller AD (1887). "A demonstration on man of electromotive changes accompanying the heart's beat"
(http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1485094).J Physiol (Lond)8 (5): 22934. PMC 1485094(//www.ncbi.nlm.nih.gov/pmc/articles/PMC1485094). PMID 16991463
(//www.ncbi.nlm.nih.gov/pubmed/16991463).
8. ^ Rivera-Ruiz, M; Cajavilca, C; Varon, J (1927-09-29). "Einthoven's String Galvanometer: The First
Electrocardiograph" (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2435435). Texas Heart Institute journal /
from the Texas Heart Institute of St. Luke's Episcopal Hospital, Texas Children's Hospital
(Pubmedcentral.nih.gov) 35 (2): 1748. PMC 2435435 (//www.ncbi.nlm.nih.gov/pmc/articles/PMC2435435).
PMID 18612490 (//www.ncbi.nlm.nih.gov/pubmed/18612490).
9. ^ Interwoven W (1901). "Un nouveau galvanometre". Arch Neerl Sc Ex Nat6: 625.
10. ^ ab Hurst, J. Willis (1998-11-03). "Naming of the Waves in the ECG, With a Brief Account of Their Genesis".
Circulation98 (18): 193742. doi:10.1161/01.CIR.98.18.1937 (http://dx.doi.org/10.1161%2F01.CIR.98.18.1937
PMID 9799216 (//www.ncbi.nlm.nih.gov/pubmed/9799216).
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(7): 4614. doi:10.1056/NEJM198608143150721 (http://dx.doi.org/10.1056%2FNEJM198608143150721).
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13. ^ See images of ECG electrodes [1] (http://www.superboverseas.com/show_product.asp?id=104) [2]
(http://images.google.com/images?q=ecg+electrode&oe=UTF-8&rls=org.mozilla:en-US:official&client=firefox-
a&um=1&ie=UTF-
8&sa=N&tab=wi&ei=IOEHSqCELp3ItgeY8_2HBw&oi=property_suggestions&resnum=0&ct=property-
revision&cd=1)
14. ^ "Einthoven's Triangle" (http://library.med.utah.edu/kw/ecg/ecg_outline/Lesson1/lead_dia.html).
Library.med.utah.edu. Retrieved 2009-08-15.
15. ^ AHA Diagnostic ECG Electrode Placement
(http://www.welchallyn.com/documents/Cardiopulmonary/Electrocardiographs/PC-
Based%20Exercise%20Stress%20ECG/poster_110807_pcexerecg.pdf). WelchAllyn
16. ^ RESTING 12-LEAD ECG ELECTRODE PLACEMENT AND ASSOCIATED PROBLEMS
(http://www.scst.org.uk/coleman/resting.htm). scs t.org.uk
17. ^ "Lead Placement"
(http://web.archive.org/web/20110720090219/http://davidge2.umaryland.edu/~emig/ekgtu03.html). Univ. of
Maryland School of Medicine Emergency Medicine Interest Group. Retrieved 2009-08-15.
18. ^ "Limb Leads ECG Lead Placement Normal Function of the Heart Cardiology Teaching Package Practice
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Learning Division of Nursing The University of Nottingham"
(http://www.nottingham.ac.uk/nursing/practice/resources/cardiology/function/limb_leads.php). Nottingham.ac.uk
Retrieved 2009-08-15.
19. ^ "Lesson 1: The Standard 12 Lead ECG"
(http://library.med.utah.edu/kw/ecg/ecg_outline/Lesson1/index.html#orientation). Library.med.utah.edu. Retrieved
2009-08-15.
20. ^ Electrocardiogram explanation image (http://nobelprize.org/medicine/educational/ecg/images/triangle.gif).
nobelprize.org
21. ^ e.g. Pasco Pasport EKG Sensor PS-2111, Sciencescope ECG Sensor, etc.
22. ^ Fay Johnson ECG presentation (http://academic.cuesta.edu/fjohnson/PowerPoint_PDF/12leadecg.pdf). Cuesta
College Home Page
23. ^ "Electrocardiogram Leads" (http://www.cvphysiology.com/Arrhythmias/A013.htm). CV Physiology. 2007-03-
26. Retrieved 2009-08-15.
24. ^ Bazett HC. (1920). "An analysis of the time-relations of electrocardiograms". Heart(7): 353370.
25. ^ Fridericia LS (1920). "The duration of systole in the electrocardiogram of normal subjects and of patients with
heart disease".Acta Medica Scandinavica (53): 469486.
26. ^ Lesson III. Characteristics of the Normal ECG
(http://library.med.utah.edu/kw/ecg/ecg_outline/Lesson3/index.html) Frank G. Yanowitz, MD. Professor of
Medicine. University of Utah School of Medicine. Retrieved on Mars 23, 2010
27. ^ A movie by the National Heart Lung and Blood Institute explaining the connection between an ECG and theelectricity in heart: What Is the Heart? (http://www.nhlbi.nih.gov/health/dci/Diseases/hhw/hhw_electrical.html)
28. ^ Electrophysiological Changes During Cardiac Ischemia (http://www.cvphysiology.com/CAD/CAD012.htm)
29. ^ Andrew R Houghton; David Gray (27 January 2012). Making Sense of the ECG, Third Edition
(http://books.google.com/books?id=8s4TQ6yYHRkC). Hodder Education. p. 214. ISBN 978-1-4441-6654-5.
Retrieved 20 May 2012.
30. ^Cellular Basis for the Electrocardiographic J Wave. doi:10.1161/01.CIR.93.2.372
(http://dx.doi.org/10.1161%2F01.CIR.93.2.372).
31. ^ H deflection (http://medical-dictionary.thefreedictionary.com/H+deflection). thefreedictionary.com citing:
Mosby's Medical Dictionary, 8th edition. 2009
32. ^ H-V interval (http://medical-dictionary.thefreedictionary.com/H-V+interval). thefreedictionary.com citing:
McGraw-Hill Concise Dictionary of Modern Medicine. 200233. ^ Mark JB "Atlas of Cardiovascular Monitoring." p. 130. New York: Churchill Livingstone, 1998. ISBN 0-443-
08891-8.
34. ^ abc Consumer Reports; American Academy of Family Physicians (April 2012), "EKGs and exercise stress test
When you need them for heart disease and when you don't" (http://consumerhealthchoices.org/wp-
content/uploads/2012/04/ChoosingWiselyEKGAAFP2.pdf), Choosing Wisely: an initiative of the ABIM
Foundation (Consumer Reports), retrieved August 14, 2012
35. ^ abcde Masters, Jo; Bowden, Carole; Martin, Carole (2003). Textbook of veterinary medical nursing. Oxford:
Butterworth-Heinemann. p. 244. ISBN 0-7506-5171-7.
36. ^ Alpert JS, Thygesen K, Antman E, Bassand JP. (2000). "Myocardial infarction redefined--a consensus docume
of The Joint European Society of Cardiology/American College of Cardiology Committee for the redefinition of
myocardial infarction".J Am Coll Cardiol36 (3): 95969. doi:10.1016/S0735-1097(00)00804-4(http://dx.doi.org/10.1016%2FS0735-1097%2800%2900804-4). PMID 10987628
(//www.ncbi.nlm.nih.gov/pubmed/10987628).
37. ^ McGinn S, White PD (1935). "Acute cor pulmonale resulting from pulmonary embolism". J Am Med Assoc104
(17): 147380. doi:10.1001/jama.1935.02760170011004
(http://dx.doi.org/10.1001%2Fjama.1935.02760170011004).
38. ^ Rodger M, Makropoulos D, Turek M, et al. (October 2000). "Diagnostic value of the electrocardiogram in
suspected pulmonary embolism". Am. J. Cardiol.86 (7): 8079, A10. doi:10.1016/S0002-9149(00)01090-0
(http://dx.doi.org/10.1016%2FS0002-9149%2800%2901090-0). PMID 11018210
(//www.ncbi.nlm.nih.gov/pubmed/11018210).
39. ^ Amal Mattu; Deepi Goyal; Barrett, Jeffrey W.; Joshua Broder; DeAngelis, Michael; Peter Deblieux; Gus M.
'
http://www.nottingham.ac.uk/nursing/practice/resources/cardiology/function/limb_leads.phphttps://en.wikipedia.org/wiki/Electrocardiography#cite_ref-39https://www.ncbi.nlm.nih.gov/pubmed/11018210https://en.wikipedia.org/wiki/PubMed_Identifierhttp://dx.doi.org/10.1016%2FS0002-9149%2800%2901090-0https://en.wikipedia.org/wiki/Digital_object_identifierhttps://en.wikipedia.org/wiki/Electrocardiography#cite_ref-38http://dx.doi.org/10.1001%2Fjama.1935.02760170011004https://en.wikipedia.org/wiki/Digital_object_identifierhttps://en.wikipedia.org/wiki/Paul_Dudley_Whitehttps://en.wikipedia.org/wiki/Electrocardiography#cite_ref-37https://www.ncbi.nlm.nih.gov/pubmed/10987628https://en.wikipedia.org/wiki/PubMed_Identifierhttp://dx.doi.org/10.1016%2FS0735-1097%2800%2900804-4https://en.wikipedia.org/wiki/Digital_object_identifierhttps://en.wikipedia.org/wiki/Electrocardiography#cite_ref-Alpert-2000_36-0https://en.wikipedia.org/wiki/Special:BookSources/0-7506-5171-7https://en.wikipedia.org/wiki/International_Standard_Book_Numberhttps://en.wikipedia.org/wiki/Electrocardiography#cite_ref-masters_35-4https://en.wikipedia.org/wiki/Electrocardiography#cite_ref-masters_35-3https://en.wikipedia.org/wiki/Electrocardiography#cite_ref-masters_35-2https://en.wikipedia.org/wiki/Electrocardiography#cite_ref-masters_35-1https://en.wikipedia.org/wiki/Electrocardiography#cite_ref-masters_35-0https://en.wikipedia.org/wiki/Consumer_Reportshttps://en.wikipedia.org/wiki/ABIM_Foundationhttp://consumerhealthchoices.org/wp-content/uploads/2012/04/ChoosingWiselyEKGAAFP2.pdfhttps://en.wikipedia.org/wiki/American_Academy_of_Family_Physicianshttps://en.wikipedia.org/wiki/Consumer_Reportshttps://en.wikipedia.org/wiki/Electrocardiography#cite_ref-whenyouneedEKGs_34-2https://en.wikipedia.org/wiki/Electrocardiography#cite_ref-whenyouneedEKGs_34-1https://en.wikipedia.org/wiki/Electrocardiography#cite_ref-whenyouneedEKGs_34-0https://en.wikipedia.org/wiki/Special:BookSources/0443088918https://en.wikipedia.org/wiki/Electrocardiography#cite_ref-Atlas_Cardio_Monitor_130_33-0http://medical-dictionary.thefreedictionary.com/H-V+intervalhttps://en.wikipedia.org/wiki/Electrocardiography#cite_ref-32http://medical-dictionary.thefreedictionary.com/H+deflectionhttps://en.wikipedia.org/wiki/Electrocardiography#cite_ref-31http://dx.doi.org/10.1161%2F01.CIR.93.2.372https://en.wikipedia.org/wiki/Digital_object_identifierhttps://en.wikipedia.org/wiki/Electrocardiography#cite_ref-30https://en.wikipedia.org/wiki/Special:BookSources/978-1-4441-6654-5https://en.wikipedia.org/wiki/International_Standard_Book_Numberhttp://books.google.com/books?id=8s4TQ6yYHRkChttps://en.wikipedia.org/wiki/Electrocardiography#cite_ref-29http://www.cvphysiology.com/CAD/CAD012.htmhttps://en.wikipedia.org/wiki/Electrocardiography#cite_ref-28http://www.nhlbi.nih.gov/health/dci/Diseases/hhw/hhw_electrical.htmlhttps://en.wikipedia.org/wiki/Electrocardiography#cite_ref-27http://library.med.utah.edu/kw/ecg/ecg_outline/Lesson3/index.htmlhttps://en.wikipedia.org/wiki/Electrocardiography#cite_ref-Yanowitz_26-0https://en.wikipedia.org/wiki/Electrocardiography#cite_ref-Fridericia-1920_25-0https://en.wikipedia.org/wiki/Electrocardiography#cite_ref-Bazett-1920_24-0http://www.cvphysiology.com/Arrhythmias/A013.htmhttps://en.wikipedia.org/wiki/Electrocardiography#cite_ref-23http://academic.cuesta.edu/fjohnson/PowerPoint_PDF/12leadecg.pdfhttps://en.wikipedia.org/wiki/Electrocardiography#cite_ref-22https://en.wikipedia.org/wiki/Electrocardiography#cite_ref-21http://nobelprize.org/medicine/educational/ecg/images/triangle.gifhttps://en.wikipedia.org/wiki/Electrocardiography#cite_ref-20http://library.med.utah.edu/kw/ecg/ecg_outline/Lesson1/index.html#orientationhttps://en.wikipedia.org/wiki/Electrocardiography#cite_ref-19http://www.nottingham.ac.uk/nursing/practice/resources/cardiology/function/limb_leads.php7/28/2019 Electrocardiography - Wikipedia, The Free Encyclopedia
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pitfalls and improving the outcomes. Malden, Mass: Blackwell Pub./BMJ Books. p. 10. ISBN 1-4051-4166-2.
40. ^ Verrier, Richard L. Dynamic Tracking of ECG Heterogeneity to Estimate Risk of Life-threatening Arrhythmias.
(http://www.cimit.org/forum/forum-cardio-09.25.07.Verrier.html) CIMIT Forum. September 25, 2007.
41. ^ abc Neilson, J. P. (2012). "Fetal electrocardiogram (ECG) for fetal monitoring during labour". In Neilson, Jame
P. Cochrane Database of Systematic Reviews. doi:10.1002/14651858.CD000116.pub3
(http://dx.doi.org/10.1002%2F14651858.CD000116.pub3).
External links
LearnTheHeart.com - Basic explanation of the ECG and tutorial on how to interpret an electrocardiogram.
Hundreds of examples. (http://www.learntheheart.com/EKGBasics.html)
Electrocardiogram, EKG, or ECG (http://www.nhlbi.nih.gov/health/dci/Diseases/ekg/ekg_what.html)
Explanation of what an ECG is, who needs one, what to expect during one, etc. Written by the National
Heart Lung and Blood Institute (a division of the NIH)
Free ECG tutorial videos (http://ecgteacher.com/)
12-lead ECG library (http://www.ecglibrary.com)
ECG in 100 steps a PowerPoint presentation (http://www.lifehugger.com/doc/120/ecg-100-steps)
ECGpedia: Course for interpretation of ECG (http://en.ecgpedia.org)
Photographic guide to 12-lead ECG electrode placement on males & females
(http://www.instamedic.co.uk/osce/ecg/)
ECG Lead Placement
(https://www.nottingham.ac.uk/nursing/practice/resources/cardiology/function/placement_of_leads.php) A
teaching guide "designed for student nurses who know nothing at all about Cardiology"
ECGsim (http://www.ecgsim.org) - A simulation tool to demonstrate and study the relation between the
electric activity of the heart and the ECG
Minnesota ECG Code (http://www.sph.umn.edu/epi/ecg/)
EKG Review: Arrhythmias (http://www.gwc.maricopa.edu/class/bio202/cyberheart/ekgqzr0.htm) A guidto reading ECGs not written for a university biology (anatomy and physiology) course.
Retrieved from "http://en.wikipedia.org/w/index.php?title=Electrocardiography&oldid=558878190"
Categories: Cardiac procedures Electrodiagnosis Cardiac electrophysiology Electrophysiology
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