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LEARN ECG
Global institute of medical sciences – www.gims-org.com
Conquering the ECG
Besides the stethoscope, the electrocardiogram (ECG) is the

oldest and most enduring tool of the cardiologist. A basic
knowledge of the ECG will enhance the understanding of
cardiology (not to mention this book).
Electrocardiography
At every beat, the heart is depolarized to trigger its contraction.

This electrical activity is transmitted throughout the body and can
be picked up on the skin. This is the principle behind the ECG. An
ECG machine records this activity via electrodes on the skin and
displays it graphically. An ECG involves attaching 10 electrical
cables to the body: one to each limb and six across the chest.
ECG terminology has two meanings for the word "lead":
 the cable used to connect an electrode to the ECG recorder

 the electrical view of the heart obtained from any one
combination of electrodes
Carrying out an ECG
1. Ask the patient to undress down to the waist and lie down
2. Remove excess hair where necessary
3. Attach limb leads (anywhere on the limb)
Dr.G.Bhanu Prakash www.gims-org.com www.facebook.com/doctorbhanuprakash

Figure 1
Standard attachment sites for chest leads.
Figure 1
Standard attachment sites for chest leads.

Attach the chest leads (see Figure 1
) as follows:
oV1 and V2: either side of the sternum on the fourth rib
(count down from the sternal angle, the second rib
insertion)
o V4: on the apex of the heart (feel for it)
o V3: halfway between V2 and V4
o V5 and V6: horizontally laterally from V4 (not up
towards the axilla)
4. Ask the patient to relax
5. Press record

The standard ECG uses 10 cables to obtain 12 electrical views of
the heart. The different views reflect the angles at which
electrodes "look" at the heart and the direction of the heart's
electrical depolarization.
Limb leads
Three bipolar leads and three unipolar leads are obtained from
three electrodes attached to the left arm, the right arm, and the
left leg, respectively. (An electrode is also attached to the right
leg, but this is an earth electrode.) The bipolar limb leads reflect
the potential difference between two of the three limb electrodes:
 lead I: right arm–left arm

 lead II: right arm–left leg
 lead III: left leg–left arm
The unipolar leads reflect the potential difference between one of

the three limb electrodes and an estimate of zero potential –
derived from the remaining two limb electrodes. These leads are
known as augmented leads. The augmented leads and their
respective limb electrodes are:
 aVR lead: right arm

 aVL lead: left arm
 aVF lead: left leg
Chest leads
Another six electrodes, placed in standard positions on the chest

wall, give rise to a further six unipolar leads – the chest leads
(also known as precordial leads), V1–V6. The potential difference
of a chest lead is recorded between the relevant chest electrode
and an estimate of zero potential – derived from the average
potential recorded from the three limb leads.
Planes of view
Figure 2
The limb leads looking at the heart in a vertical (more...)

Figure 2
The limb leads looking at the heart in a vertical plane.
Table 1
ECG leads and their respective views of the heart
Table 1
ECG leads and their respective views of the heart

View Lead

View Lead
Inferior II, III, aVF
Anterior I, aVL, V1–V3
Septal V3, V4
Lateral V4–V6
The limb leads look at the heart in a vertical plane (see Figure 2
), whereas the
chest leads look at the heart in a horizontal plane. In this way, a
three-dimensional electrical picture of the heart is built up (see
Table 1).
Performing Dogs
British physiologist Augustus D Waller of St Mary's Medical

School, London, published the first human electrocardiogram in
the British Medical Journal in 1888. It was recorded from Thomas
Goswell, a technician in the laboratory, using a capillary
electrometer. After that, Waller used a more available subject for
his demonstrations – his dog Jimmy, who would patiently stand
with his paws in glass jars of saline.
Depolarization of the heart
Figure 3
The cardiac depolarization route. AVN: atrioventricular (more...)
Figure 3

The cardiac depolarization route. AVN: atrioventricular node;
SAN: sinoatrial node. Reproduced with permission from WB
Saunders (Guyton A, Hall J. Textbook of Medical Physiology.
Philadelphia: WB Saunders, 1996).
The route that the depolarization wave takes across the heart is
outlined in Figure 3
. The sinoatrial node (SAN) is the heart's pacemaker. From the

SAN, the wave of depolarization spreads across the atria to the
atrioventricular node (AVN). The impulse is delayed briefly at the
AVN and atrial contraction is completed.
The wave of depolarization then proceeds rapidly to the bundle of

His where it splits into two pathways and travels along the right
and left bundle branches. The impulse travels the length of the
bundles along the interventricular septum to the base of the heart,
where the bundles divide into the Purkinje system. From here, the
wave of depolarization is distributed to the ventricular walls and
initiates ventricular contraction.

The ECG trace
The ECG machine processes the signals picked up from the skin
by electrodes and produces a graphic representation of the
electrical activity of the patient's heart. The basic pattern of the
ECG is logical:
 electrical activity towards a lead causes an upward

deflection
 electrical activity away from a lead causes a downward
deflection
 depolarization and repolarization deflections occur in
opposite directions
Figure 4
The basic pattern of electrical activity across the (more...)

Figure 4
The basic pattern of electrical activity across the heart.
The basic pattern of this electrical activity was first discovered

over a hundred years ago. It comprises three waves, which have
been named P, QRS (a wave complex), and T (see Figure 4

).
P wave
The P wave is a small deflection wave that represents atrial

depolarization.
PR interval
The PR interval is the time between the first deflection of the P

wave and the first deflection of the QRS complex.
QRS wave complex
The three waves of the QRS complex represent ventricular

depolarization. For the inexperienced, one of the most confusing

aspects of ECG reading is the labeling of these waves. The rule
is: if the wave immediately after the P wave is an upward
deflection, it is an R wave; if it is a downward deflection, it is a Q
wave:
 small Q waves correspond to depolarization of the

interventricular septum. Q waves can also relate to breathing
and are generally small and thin. They can also signal an old
myocardial infarction (in which case they are big and wide)
 the R wave reflects depolarization of the main mass of the
ventricles –hence it is the largest wave
 the S wave signifies the final depolarization of the ventricles,
at the base of the heart
ST segment
The ST segment, which is also known as the ST interval, is the

time between the end of the QRS complex and the start of the T
wave. It reflects the period of zero potential between ventricular
depolarization and repolarization.
T wave
T waves represent ventricular repolarization (atrial repolarization

is obscured by the large QRS complex).
Wave direction and size

Figure 5
(a) A horizontal section through the chest showing (more...)
Figure 5
(a) A horizontal section through the chest showing the orientation

of the chest leads with respect to the chambers of the heart. (b) In
lead V1, depolarization of the interventricular septum occurs
towards the lead, thus creating an upward deflection (R wave) on
the ECG. It is followed by depolarization of the main mass of the

LV, which occurs away from the lead, thus creating a downward
deflection (S wave). This pattern is reversed for lead V6,
explaining the different shapes of the QRS complex. This pattern
should be checked in every ECG. LA: left atrium; LV: left ventricle;
RA: right atrium; RV: right ventricle.
Since the direction of a deflection, upward or downward, is

dependent on whether the electrical activity is going towards or
away from a lead, it differs according to the orientation of the lead
with respect to the heart (see Figure 5
).
The ECG trace reflects the net electrical activity at a given

moment. Consequently, activity in one direction is masked if there
is more activity, eg, by a larger mass, in the other direction. For
example, the left ventricle muscle mass is much greater than the
right, and therefore its depolarization accounts for the direction of
the biggest wave.
Interpreting the ECG
Figure 6
Example of a normal ECG.
Figure 6

.
Example of a normal ECG.
A normal ECG tracing is provided in Figure 6
. The only way to become confident at reading ECGs is to

practice. It is important to be methodical – every ECG reading
should start with an assessment of the rate, rhythm, and axis.
This approach always reveals something about an ECG,
regardless of how unusual it is.
Rate

Table 2
Some common heart rates as determined by analysis of (more...)
Table 2
Some common heart rates as determined by analysis of the QRS

complex
Number of large squares between QRS Heart rate
complexes (bpm)
5 60
4 75
3 100
2 150
Identify the QRS complex (this is generally the biggest wave);
count the number of large squares between one QRS wave and
the next; divide 300 by this number to determine the rate (see
Table 2).
Rhythm
P waves are the key to determining whether a patient is in sinus

rhythm or not. If P waves are not clearly visible in the chest leads,
look for them in the other leads. The presence of P waves
immediately before every QRS complex indicates sinus rhythm. If
there are no P waves, note whether the QRS complexes are wide
or narrow, regular or irregular.
No P waves and irregular narrow QRS complexes

Figure 7
ECG demonstrating atrial fibrillation.
Figure 7
ECG demonstrating atrial fibrillation.
This is the hallmark of atrial fibrillation (see Figure 7
). Sometimes the baseline appears "noisy" and sometimes it

appears entirely flat. However, if there are no P waves and the
QRS complexes appear at randomly irregular intervals, the
diagnosis is atrial fibrillation.
Sawtooth P waves
Figure 8

ECG demonstrating atrial flutter – note the (more...)
Figure 8
ECG demonstrating atrial flutter – note the characteristic sawtooth

waveform.
A sawtooth waveform signifies atrial flutter (see Figure 8
). The number of atrial contractions to one ventricular contraction

should be specified.
Axis
The axis is the net direction of electrical activity during

depolarization. It is altered by left ventricular or right ventricular
hypertrophy or by bundle branch blocks. It is a very
straightforward measurement that, once it has been grasped, can
be calculated instantaneously:

Figure 9
Vector diagram to determine the QRS axis.
Figure 9
Vector diagram to determine the QRS axis.
 find the QRS complex in the I and aVF leads (because these
look at the heart at 0° and +90°, respectively)
 determine the net positivity of the QRS wave from each of
the two leads by subtracting the S wave height (the number
of small squares that it crosses as it dips below the baseline
– if it does) from the R wave height (the number of small
squares that it crosses as it rises) (see Figure 9a and 9b

)
 plot out the net sizes of these QRS waves against each
other on a vector diagram (see Figure 9c
). For the I lead, plot net positives to the right and net
negatives to the left; for the aVF lead, plot positive
downwards and negative upwards
 the direction of the endpoint from the starting point
represents the axis or predominant direction of electrical
depolarization (determined primarily by the muscle mass of
the left ventricle). It is expressed as an angle and can be
estimated quite easily (normal is 0°–120°)
Human Resuscitation

The first electrical resuscitation of a human took place (almost
certainly) in 1872. The resuscitation of a drowned girl with
electricity is described by Guillaume Benjamin Amand Duchenne
de Boulogne, a pioneering neurophysiologist, in the third edition
of his textbook on the medical uses of electricity. Although it is
sometimes described as the first artificial pacing, the stimulation
was of the phrenic nerve and not the myocardium.
ECG abnormalities
This section discusses the most important and most frequently

encountered ECG abnormalities.
Normal variations
 Small Q waves and inverted T waves in lead III often

disappear on deep inspiration. Occasional septal Q waves
can be seen in other leads.
 ST elevation following an S wave ("high take off") is common
in leads V2–V4 and is quite normal. Differentiating this from
pathological ST elevation can be difficult and relies on the
patient's history and the availability of a previous ECG.
These "repolarization abnormalities" are more common in
the young and in athletes.
 T-wave inversion is common in Afro-Caribbean blacks.
 U waves – small extra waves following T waves – are seen
in hypokalemic patients, but can also represent a normal
variant.
 Ventricular extrasystoles – no P waves, broad and abnormal
QRS complexes, and T waves interspersed between normal
sinus rhythm – sometimes occur and do not require further
investigation unless they are associated with symptoms
(such as dizziness, palpitations, exercise intolerance, chest
pain, shortness of breath) or occur several times every
minute.

Pathological variations
Long PR interval
Figure 10
ECG demonstrating first-degree heart block.
Figure 10
ECG demonstrating first-degree heart block.
A distance of more than five small squares from the start of the P
wave to the start of the R wave (or Q wave if there is one)
constitutes first-degree heart block (see Figure 10
). It rarely requires action, but in the presence of other

abnormalities might be a sign of hyperkalemia, digoxin toxicity, or
cardiomyopathy.
EKG or ECG?
There is some debate over exactly who invented the

electrocardiogram. The Dutch "K" (elektrokardiogram) is often
used as a tribute to the Indonesian-born physician Wilhelm
Einthoven who, while working in The Netherlands in 1924,
received the Nobel prize for "the discovery of the mechanism of
the electrocardiogram". In fact, it was Augustus Désiré Waller, a
physician trained in Edinburgh, who presented – to the students
of St Mary's Hospital medical school, London, at the introductory
lecture of the 1888 academic year – his "cardiograph", the first
ever ECG recording in man. It was some years later, in 1901, that
Wilhelm Einthoven reported his string galvanometer – with the
limb leads labeled I, II, and III and the waves labeled P, QRS, and
T as we know them today. In fact, although often credited with
inventing the term electrocardiogram (which is why it is
sometimes spelt the Dutch way), Einthoven credits Waller with
this distinction in his 1895 publication in Pflügers Archives "Über
die Form des menschlichen Elektrokardiogramms".
Q waves
Figure 11
ECG demonstrating abnormal Q waves in V1–V4. (more...)

Figure 11
ECG demonstrating abnormal Q waves in V1–V4. This is

indicative of a previous infarction.
A normal ECG has only very small Q waves. A downward

deflection immediately following a P wave that is wider than two
small squares or greater in height than a third of the subsequent
R wave is significant: such Q waves can represent previous
infarction (see Figure 11

, previous page).
Large QRS complexes
Figure 12
ECG demonstrating left ventricular hypertrophy. Note (more...)

Figure 12
ECG demonstrating left ventricular hypertrophy. Note also the T-

wave inversion in leads V4–V6. This is often labeled "strain".
Left ventricular hypertrophy (LVH) is one of the easiest and most

useful diagnoses to make (see Figure 12
). The Sokolow–Lyon index is the most commonly calculated

index of estimation. Does the sum of the S wave in lead V1 (SV1)
and the R wave in V6 (RV6) add up to more than 3.5 mV, ie, 35
small or seven big squares? If so, the patient has LVH by voltage
criterion. Right ventricular hypertrophy is indicated by a dominant
R wave in V1 (ie, R wave bigger than following S wave; Sokolow–
Lyon index: R in V1 + S in V5 or V6 ≥ 1.05 mV) and right axis
deviation.
Broad QRS complexes and strange-looking ECGs
Figure 13
ECG demonstrating left bundle branch block.

Figure 13
ECG demonstrating left bundle branch block.
Figure 14
The shapes of V1 and V6 QRS complexes in left and (more...)

Figure 14
The shapes of V1 and V6 QRS complexes in left and right bundle

branch block.
A wide QRS complex despite sinus rhythm is the hallmark of

bundle branch block. Left bundle branch block (LBBB) can cause
the ECG to look extremely abnormal (see Figure 13

). When faced with such an ECG – after calculating rate, rhythm,
and axis – check the width of the QRS complex. If it is more than
three small squares wide, it is abnormal. Bundle branch block can
then be diagnosed by pattern recognition of the QRS complexes
in the V1 and V6 leads (see Figure 14
). New LBBB can be diagnostic of myocardial infarction (MI).

ST segment changes
Figure 15
ECG demonstrating anteroseptal myocardial infarction. (more...)
Figure 15
ECG demonstrating anteroseptal myocardial infarction. Note the

ST-segment elevation.

Figure 16
ECG demonstrating ST-segment depression (I, V3–V6). (more...)
Figure 16
ECG demonstrating ST-segment depression (I, V3–V6).
The ST segment extends from the end of the S wave to the start
of the T wave. It should be flat or slightly upsloping and level with
the baseline. Elevation of more than two small squares in the
chest leads or one small square in the limb leads, combined with
a characteristic history, indicates the possibility of MI (see Figure
15

, previous page). ST depression is diagnostic of ischemia (see
Figure 16
). It is worth noting that although ST elevation can localize the

lesion (eg, anterior MI, inferior MI), ST depression cannot.
Concave upwards ST elevation in all 12 leads is diagnostic of
pericarditis.
T waves

Figure 17
ECG demonstrating T-wave inversion.
Figure 17
ECG demonstrating T-wave inversion.
In a normal ECG, T waves are upright in every lead except aVR.

T-wave inversion can represent current ischemia or previous

infarction (see Figure 17
). In combination with LVH and ST depression, it can represent

"strain". This form of LVH carries a poor prognosis.
Long QT interval
Table 3
Causes of a long QT interval
Table 3
Causes of a long QT interval

Congenital Acquired
Jervell and Lange–Nielsen syndrome Amiodarone, sotalol
Romano–Ward syndrome Flecainide
Hypocalcemia
Hypokalemia
Hypomagnesemia
Phenothiazines
Tricyclic antidepressants
Figure 18
ECG demonstrating a long QT interval.

Figure 18
ECG demonstrating a long QT interval.
The QT interval should be less than half of the R–R interval.

Calculation of the corrected QT (QTc) is generally not necessary
and usually will have been done by the ECG machine (but beware
of blindly believing any automated diagnostic system). Conditions
associated with a long QT interval are outlined in Table 3 (see
Figure 18

).
Table 4
Drug-induced increase in the QT interval and torsade (more...)
Table 4
Drug-induced increase in the QT interval and torsade de pointes

QT Torsad QT Torsad
interva e de interva e de
Generic name l pointes Generic name l pointes
Antiarrhythmics Selective serotonin re-uptake
inhibitors
Ajmaline + +
Fluoxetine + +
Amiodarone + +
Paroxetine +
Chinidine + +
Sertraline + +
Disopyramide + +
Dofetilide + + Anticonvulsants
Ibutilide + +
Valproate +
Propafenone + +
Sotalol + + Other
psychopharmaceuticals
Antibiotics (macrolides) Chloralhydrate + +
Azithromycin + Levomethadon + +
e
Clarithromycin + +
Lithium +
Clindamycin +
Naratriptan +
Erythromycin + +
Sumatriptan +
Roxithromycin +
Spiramycin + + Venlafaxine +
Antibiotics (quinolones) Zolmitriptan +

QT Torsad QT Torsad
Gatifloxacin + + Anti-Parkinson's
Grepafloxacina + +
Amantadine +
Levofloxacin +
Budipinec + +
Moxifloxacin + +
Sparfloxacin + + Antimalarials
Other antibiotics
Quinine + +
Amoxicillin +
Chloroquine + +
Halofantrine + +
Trimethoprim- + +
sulfamethoxazol
e
Mefloquine +
Antihistamines
Astemizolea + + Diuretics
Clemastine + Indapamide +
Diphenhydramin +
e
Hydroxyzine + Lipid-lowering agents
Terfenadine + + Probucol + +
Antidepressants
Motility enhancers
Amitriptyline + +
Cisapridea + +

QT Torsad QT Torsad
Clomipramine +
Desipramine + + Nootropic geriatrics
Doxepine + Vincamine + +
Imipramine + +
Chemotherapeutics
Maprotiline + +
Tamoxifen + +
Neuroleptics
Pentamidine + +
Amisulpride +
Clozapine + Immunosuppressants
Chlorpromazine + +
Tacrolimus + +
a
Droperidol + +
Fluphenazine + Peptides
Haloperidol + +
Octreotide +
Melperone + +
Olanzapine + Virostatics
Pimozide + + Foscarnet +
Quetiapine +
Muscle relaxants
Sulpiride + +
Thioridazine + + Tizanidine +
Risperidone +
X-ray contrast agents
Sertindoleb + +

QT Torsad QT Torsad
Tiapride + + Ioxaglate + +
meglumine
Trazodone +
+ A prolonged QT interval can occur or torsade de pointes was

observed
Taken off the market.
Suspended from the market, final decision by the regulatory

authorities still awaited.
Indication limitations have been expressed.
Important tips on the use of the table: information is based on the

latest scientific knowledge as far as it is generally available from
published studies (Medline research), case reports, internet
publications, specialist information, the Red List, and information
from the regulatory authorities. In the case reports available about
torsade de pointes, the causal relationship to the ingestion of the
particular medication is no longer apparent; pure coincidence
cannot be excluded in individual cases.
Long QT syndrome may also be drug-induced (see Table 4, p.

32). Once this occurs, the responsible drug needs to be
discontinued.
Pattern combinations
Digoxin
A reverse tick ST depression is characteristic and does not

indicate toxicity. Digoxin toxicity can result in dysrhythmia.
Pulmonary embolism
Sinus tachycardia is seen in many patients with pulmonary

embolism. New right bundle branch block (RBBB) or right axis
deviation with "strain" can also indicate PE. The classic SIQIIITIII is
less common.
Hyperkalemia
Figure 19
Hyperkalemia. Note the tall, tented T waves.

Figure 19
Hyperkalemia. Note the tall, tented T waves.
Figure 21

ECG demonstrating a sinus-wave QRS pattern.
Figure 21
ECG demonstrating a sinus-wave QRS pattern.
The absolute potassium level is less important than its rate of rise.
ECG changes reflecting a rapid rise demand immediate action
(see Figures 19

–21
). The level of danger increases as the ECG changes progress.

The sequence generally follows the order:

Figure 20
ECG demonstrating a widening of the QRS complex.
Figure 20
ECG demonstrating a widening of the QRS complex.

 tall, tented T waves (see Figure 19
)
 lengthening of the PR interval
 reduction in the P-wave height

 widening of the QRS complex (see Figure 20
)
 "sinus" wave QRS pattern (see Figure 21
A sinus-wave QRS should be treated immediately with calcium

chloride, whilst hyperkalemia associated with lesser ECG
changes can be treated with insulin/glucose infusion.
PQRST?
Nobody knows for sure why these letters became standard.
Certainly, mathematicians used to start lettering systems from the
middle of the alphabet to avoid confusion with the frequently used
letters at the beginning. Einthoven used the letters O to X to mark
the timeline on his ECG diagrams and, of course, P is the letter
that follows O. If the image of the PQRST diagram was striking
enough to be adopted by researchers as a true representation of
the underlying form, it would have been logical to continue the
same naming convention when the more advanced string
galvanometer started creating ECGs a few years later.

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What is an ECG and how does it work?

What is an ECG and how does it work?

What are the different leads used in an ECG and what do they measure?

What are the different leads used in an ECG and what do they measure?

LEARN ECG

Global institute of medical sciences – www.gims-org.com

Conquering the ECG

Besides the stethoscope, the electrocardiogram (ECG) is the

At every beat, the heart is depolarized to trigger its contraction.

ECG terminology has two meanings for the word "lead":

 the cable used to connect an electrode to the ECG recorder

Carrying out an ECG

Dr.G.Bhanu Prakash www.gims-org.com www.facebook.com/doctorbhanuprakash

Standard attachment sites for chest leads.

Standard attachment sites for chest leads.

Dr.G.Bhanu Prakash www.gims-org.com www.facebook.com/doctorbhanuprakash

Dr.G.Bhanu Prakash www.gims-org.com www.facebook.com/doctorbhanuprakash

 lead I: right arm–left arm

The unipolar leads reflect the potential difference between one of

 aVR lead: right arm

Another six electrodes, placed in standard positions on the chest

The limb leads looking at the heart in a vertical (more...)

Dr.G.Bhanu Prakash www.gims-org.com www.facebook.com/doctorbhanuprakash

The limb leads looking at the heart in a vertical plane.

ECG leads and their respective views of the heart

ECG leads and their respective views of the heart

Dr.G.Bhanu Prakash www.gims-org.com www.facebook.com/doctorbhanuprakash

British physiologist Augustus D Waller of St Mary's Medical

The cardiac depolarization route. AVN: atrioventricular (more...)

Dr.G.Bhanu Prakash www.gims-org.com www.facebook.com/doctorbhanuprakash

. The sinoatrial node (SAN) is the heart's pacemaker. From the

The wave of depolarization then proceeds rapidly to the bundle of

Dr.G.Bhanu Prakash www.gims-org.com www.facebook.com/doctorbhanuprakash

 electrical activity towards a lead causes an upward

The basic pattern of electrical activity across the (more...)

Dr.G.Bhanu Prakash www.gims-org.com www.facebook.com/doctorbhanuprakash

The basic pattern of electrical activity across the heart.

The basic pattern of this electrical activity was first discovered

Dr.G.Bhanu Prakash www.gims-org.com www.facebook.com/doctorbhanuprakash

The P wave is a small deflection wave that represents atrial

The PR interval is the time between the first deflection of the P

QRS wave complex

The three waves of the QRS complex represent ventricular

Dr.G.Bhanu Prakash www.gims-org.com www.facebook.com/doctorbhanuprakash

 small Q waves correspond to depolarization of the

The ST segment, which is also known as the ST interval, is the

T waves represent ventricular repolarization (atrial repolarization

Wave direction and size

Dr.G.Bhanu Prakash www.gims-org.com www.facebook.com/doctorbhanuprakash

(a) A horizontal section through the chest showing (more...)

(a) A horizontal section through the chest showing the orientation

Dr.G.Bhanu Prakash www.gims-org.com www.facebook.com/doctorbhanuprakash

Since the direction of a deflection, upward or downward, is

The ECG trace reflects the net electrical activity at a given

Interpreting the ECG

Example of a normal ECG.

Dr.G.Bhanu Prakash www.gims-org.com www.facebook.com/doctorbhanuprakash

Example of a normal ECG.