Electrocardiography - Wikipedia, The Free Encyclopedia

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https://en.wikipedia.org/wiki/Electrocardiography

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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https://en.wikipedia.org/wiki/Electrocardiography 2

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
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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.png


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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.png


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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.svg


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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.svg


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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.svg


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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.jpg


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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/Fetus


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1. ^ "ECG- s implified. Aswini Kumar M.D." (http://www.lifehugger.com/doc/120/ecg-100-steps). LifeHugger.

Retrieved 2010-02-11.

2. ^ Braunwald E. (Editor),Heart Disease: A Textbook of Cardiovascular Medicine, Fifth Edition, p. 108,

Philadelphia, W.B. Saunders Co., 1997. ISBN 0-7216-5666-8.

3. ^ Van Mieghem, C; Sabbe, M; Knockaert, D (2004). "The clinical value of the ECG in noncardiac conditions".

Chest125 (4): 156176. doi:10.1378/chest.125.4.1561 (http://dx.doi.org/10.1378%2Fchest.125.4.1561).

PMID 15078775 (//www.ncbi.nlm.nih.gov/pubmed/15078775).

4. ^ "2005 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascula

Care Part 8: Stabilization of the Patient With Acute Coronary Syndromes". Circulation112: IV89 IV110.2005. doi:10.1161/CIRCULATIONAHA.105.166561

(http://dx.doi.org/10.1161%2FCIRCULATIONAHA.105.166561). PMID 16314375

(//www.ncbi.nlm.nih.gov/pubmed/16314375).

5. ^ Ronald M. Birse, rev. Patricia E. Knowlden (http://www.oxforddnb.com/view/article/37794) Oxford Dictionary

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.)

6. ^ Burdon Sanderson J; Page, F. J. M. (1878). "Experimental results relating to the rhythmical and excitatory

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


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).


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


11. ^ Cooper J (1986). "Electrocardiography 100 years ago. Origins, pioneers, and contributors".N Engl J Med315

(7): 4614. doi:10.1056/NEJM198608143150721 (http://dx.doi.org/10.1056%2FNEJM198608143150721).


12. ^ Mark, Jonathan B. (1998).Atlas of cardiovascular monitoring. New York: Churchill Livingstone. ISBN 0-443-

08891-8.

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


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


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.php


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6/17/13 Electrocardiography - Wikipedia, the free encyclopedia.

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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