The document provides information about electrocardiography (EKG/ECG). It describes the conduction system of the heart and how electrical signals are conducted to trigger heart contractions. It explains how an EKG works, including electrode placement and what different parts of the EKG waveform represent. It also covers how to interpret an EKG, such as measuring heart rate and identifying abnormalities. Common abnormalities, their causes, and clinical significance are discussed.

1. Guide
Dr. J. Singh Madam Rakesh Verma

2.  The electrocardiogram (EKG) is a
graphical representation of the
electrical events of the cardiac cycle.
 1895 - William Einthoven, credited for
the invention of EKG
 1924 - William Einthoven got the Noble
prize for the same

5.  SA node is the pacemaker where the electrical
impulse is generated.
 Located along the posterior wall of the right
atrium right beneath the opening of the SVC.
 It is crescent shaped and about 3 mm wide
and 1 cm long.
 The impulse travels from the SA node through
the internodal pathways to the
atrioventricular node (AV node).

6.  The AV node is responsible for conduction of
the impulse from the atria to the ventricles.
 The impulse is delayed slightly at this point to
allow complete emptying of the atria before
the ventricles contract.
 The impulse continues through the AV bundle
and down the left and right bundle branches
of the Purkinje fibers.

7. The Purkinje fibers conduct the
impulse to all parts of the
ventricles

8.  Turn on machine
 Calibrate to 10mm/ mV
 Rate at 25mm/ s
 Record and print
 Label the tracing - Name, DOB, Hospital
number, date and time

9.  10 electrodes in total are placed on the
patient
 The 10 leads are lubricated with jelly
then placed over the respective sites

13.  Chest leads are labelled “V”(vector) and are
numbered from 1 to 6.
 The placement of these electrodes needs to
be exact to give the optimum information.

14.  V1 fourth intercostal space, right sternal edge
 V2 fourth intercostal space, left sternal edge
 V4 at the apex (fifth ICS mid clavicular line)
 V3 midway between V2 and V4
 V5 same level as V4 but on the anterior
axillary line
 V6 same level as V4 and V5 but on the mid
mid-axillary line

15.  Electrical impulse (wave of depolarisation) picked up
by placing electrodes on patient
 The voltage change is sensed by measuring the
current change across 2 electrodes – a positive
electrode and a negative electrode
 If the electrical impulse travels towards the positive
electrode this results in a positive deflection
 If the impulse travels away from the positive
electrode this results in a negative deflection

16.  P wave: Activation (depolarization) of the
right and left atria
 QRS complex: right and left ventricular
depolarization
 T wave: ventricular repolarization

17.  PR interval: time interval from onset of atrial
depolarization (P wave) to onset of ventricular
depolarization (QRS complex)
 QRS duration: duration of ventricular muscle
depolarization
 QT interval: duration of ventricular depolarization and
repolarization
 RR interval: duration of ventricular cardiac cycle (an
indicator of ventricular rate)
 PP interval: duration of atrial cycle (an indicator of
atrial rate)

18.  Symtoms Palpitation, cyanosis, chest pain, syncope, seizure, poisoning
 Signs tachycardia, bradycardia, hypothermia, murmur, Shock
 Evaluation of rheumatic heart disease, congenital heart diseases
 Evaluation of suspected electrolyte imbalance
 Evaluation of cases like drowning, electrocution
 During cardiopulmonary resuscitation (CPR).
 Evaluation of patients with implanted defibrillators and pacemakers
 To detect myocardial injury, ischemia, and the presence of prior
infarction as well.
 Effects and side effects of pharmacotherapy
 Evaluation of metabolic disorders processes among others.
Contraindications
 No absolute contraindications
patient refusal, exist.
patients allergies to adhesive used to affix the leads

20. Limb leads Poles E.g.
Bipolar Positive and
negative poles
I, II, III
Unipolar Positive and zero
poles
aVL, aVR, aVF, chest
leads

24. Calibration
Rate
Rhythm
Axis

25.  Horizontally
◦ One small box - 0.04 s
◦ One large box - 0.20 s
 Vertically
◦ One large box - 0.5 mV
◦ 25mm = 1s

26.  Height 10mm = 1mV
 Half standardisation 5mm=1mV
 One fourth standardisation 2.5mm= 1mV
 (only amplitude is changed not speed)
 Paper speed = 25mm/ s
 25 mm (25 small squares / 5 large squares)
equals one second

27. If the heart rate is regular
 Count the number of large squares
between R waves i. e. the RR interval
in large squares
 Rate = 300/RR(no. of large boxes)
= 1500/RR(no. of small boxes)

28.  If the rhythm is irregular it may be better to estimate
the rate using the rhythm strip at the bottom of the
ECG (usually lead II)
 The rhythm strip is usually 25cm long (250mm i. e.
10 seconds)
 Count the number of R waves on that strip and
multiple by 6 you will get the rate
Heart rate
Regular slow 300/RR (large square)
Regular fast 1500/RR (small square)
Irregular R wave in rhythm strip X 6

29.  New born 110-150/min
 2year 85-125/min
 4year 75-125/min
 6year 65-100/min
 > 6 year 60-100/min
 Tachycardia
 Sinus tachcardia
 Supraventrical
 Ventricular
 Atrial flutter and
fibrillation
 Bradycardia
 Sinus bradycardia
 Heart block

30.  Normal rhythm must have a P wave before each QRS
complex
 The easiest way to tell is to take a sheet of paper and
line up one edge with the tips of the R waves on the
rhythm strip.
 Mark off on the paper the positions of 3 or 4 R wave
tips
 Move the paper along the rhythm strip so that your
first mark lines up with another R wave tip
 See if the subsequent R wave tips line up with the
subsequent marks on your paper
 If they do line up, the rhythm is regular. If not, the
rhythm is irregular

31.  Absent P wave – indicate non sinus rhythm
 SA block
 AV rhythm (may be present)
 Atrial fibrillation
 Idioventricular rhythm
 Multiple P waves
◦ Atrial flutter
◦ Atrial fibrillation
◦ 2nd ar 3rd degree block
 Changing P wave shape
◦ Wandering atrial pacemaker

33. The axis is the overall direction of
the cardiac impulse or wave of
depolarisation of the heart
 An abnormal axis (axis deviation)
can give a clue to possible
pathology

35. Lead I
Lead aVF
Mean axis

36. Lead I Lead aVF Mean axis

38. Equiphasic method

41. Lead (mm)
= R-S amplitude
Lead I = 4-0 = 4mm
Lead aVF = 13-2 = 11mm
Lead I
Lead aVF
Mean
axis

42. Lead I
Lead aVF
Lead I = 5+ (-10)= -5mm
Lead aVF = 17-4 = 13mm

43.  Right Axis Deviation - Right ventricular hypertrophy,
Anterolateral MI, Left Posterior Hemi-block, COPD,
pulmonary arterial hypertension or large pulmonary
embolism
 Left Axis Deviation- Ventricular tachycardia, Left
ventricular hypertrophy, Left Anterior hemi-block
 Wolff-Parkinson-White syndrome can cause both
Left and Right axis deviation

44. Normal values
1. up in all leads
except aVR.
2. Duration.
< 2.5 mm.
3. Amplitude.
< 2.5 mm.
Abnormalities
1. Inverted P-wave
 Junctional rhythm.
2. Wide P-wave (P- mitrale)
 LAE
3. Peaked P-wave (P-
pulmonale)
 RAE
4. Saw-tooth appearance
 Atrial flutter
5. Absent normal P wave
 Atrial fibrillation

53. Definition: the time
interval between
beginning of P-
wave to beginning
of QRS complex.
Normal PR interval
<3yrs – 0.08sec
3-16 yrs – 0.10sec
>16 – 0.12sec
Abnormalities
1. Short PR interval
 WPW syndrome
2. Long PR interval
 First degree heart
block

55. Slide 44

56.  If the PR interval is constant with a missed
QRS complex: 2nd degree heart block,
Mobitz type II, each QRS followed after P
wave
 If there is no relationship between the P
waves and the QRS complexes: 3rd degree
heart block
Block Relation Electrical origin
1st degree Each P has QRS SA node
2nd degree Each QRS has P SA node
3rddegree No Relation Fasciular,Ventricular, or other

59.  Q waves <0.04 second.
 That’s is less than one small square duration.
 Present commonly in I,II,III,aVF, and always
present in V5 and V6 (lateral leads)
 Absent in V1
 Height < 1/4 of R wave height.

62.  The width of the QRS complex should be
less than 0.12 seconds (3 small squares)
 Height of R wave is (V1-V6) >8 mm in at
least one of chest leads.
 Morphology: progression from Short R and
deep S (rS) in V1 to tall R and short S in V6
(qRs).

63.  New born +125
 1 month +90
 3 years +60
 Adult +50
 Preterm 0.04s
 Full term 0.0.5s
 1 -3yrs 0.06s
 >3 years 0.07s
 Adult 0.08s

64.  LAD
◦ LVH
◦ LBBB
◦ Left anterior hemiblock
 RAD
◦ RVH
◦ RBBB
 Superiorly oriented
axis
◦ Left anterior
hemiblock, particularly
with endocardial
cushion defect
◦ RBBB
 Bundle branch block
 Preexication (WPW)
 Intraventricular block
 Idioventricular
rhythm
 Ventricular implanted
pacemaker

65.  Abnormally large
deflections (positive
or negative)
◦ Ventricular
hypertrophy
◦ Ventricular
conduction defects
like - BBB,
preexication,artificial
ventricular
pacemaker
 Low voltage
complex – limb lead
less than 5mm
◦ Myocarditis
◦ Pericardial effusion
◦ Hypothyroidism
◦ Pericarditis

67.  Right axis deviation of +110° or more.
 Dominant R wave in V1
 Dominant S wave in V5 or V6
 Right atrial enlargement (P pulmonale).
 Right ventricular strain pattern = ST
depression / T wave inversion in the right
precordial (V1-4) and inferior (II, III, aVF)
leads.

69.  Left axis deviation
 Increased R wave amplitude in the left-sided ECG leads (I, aVL and
V4-6) and
 Increased S wave depth in the right-sided leads (III, aVR, V1-3).
 The thickened LV wall leads to prolonged depolarisation and delayed
repolarisation (ST and T-wave abnormalities) in the lateral leads.
 Left atrial enlargement (P mitrale).
 Left ventricular strain pattern = ST depression / T wave inversion in
the lateral (I, aVL,V5-V6) leads.

71. In RBBB, activation of the right ventricle is delayed as depolarisation
has to spread across the septum from the left ventricle.
The left ventricle is activated normally, meaning that the early part of
the QRS complex is unchanged.
The delayed right ventricular activation produces a secondary R wave
(R’) in the right precordial leads (V1-3) and a wide, slurred S wave in
the lateral leads (V5-6)
Delayed activation of the right ventricle also gives rise to secondary
repolarization abnormalities, with ST depression and T wave inversion
in the right precordial leads (V1-3)
 QRS duration ≥ 120ms
 rSR’ pattern or notched R wave in V1-3 along with
T wave inversion
 Wide S wave in I and V6

74.  Normally the septum is activated from left to right, producing small Q waves
in the lateral leads.
 In LBBB, the normal direction of septal depolarisation is reversed (becomes
right to left), as the impulse spreads first to the RV to the LV via the septum.
 Eliminates the normal septal Q waves in the lateral leads.
.
 The overall direction of depolarisation (from right to left) produces tall R
waves in the lateral leads (I, V5-6) and deep S waves in the right precordial
leads (V1-3)
 As the ventricles are activated sequentially (right, then left) rather than
simultaneously, this produces a broad or notched (‘M’-shaped) R wave in the
lateral leads.
 QRS duration ≥ 120ms
 Broad R wave in I, aVL, and V5-6
 Prominent QS wave in V1-3
 Absence of q waves (including physiologic q waves) in I and V6

77.  The ST segment should sit on the isoelectric
line (at least in the begining)
 It is abnormal if there is planar (i.e. flat)
elevation or depression of the ST segment

78. 1. ST elevation:
More than one small
square
 Infarcts
 Angina.
 Acute pericarditis.
 Early repolarization
ST depression:
More than one small
square
 Ischemia.
 Ventricular strain.
 BBB.
 Hypokalemia.
 Digoxin effect.

80. ST depression

81.  T wave is best measured in left
precordial leads
 In V5 <1yr 11mm
>1yr 14mm
Abnormalities:
1. Peaked T-wave:
Posterior wall MI.
Hyperkalemia.
.
2. T- inversion:
 Ischemia.
 Myocardial
infarction.
 Myocarditis
 Ventricular strain
 BBB.
 Hypokalemia.
 Digoxin effect.

84.  The normal range for QT is 0.38-0.42 (≤ 11mm )
Definition: Time interval between beginning of
QRS complex to the end of T wave.
QT interval varies with heart rate - As the heart
rate gets faster, the QT interval gets shorter
It is possible to correct the QT interval with
respect to rate by using the following formula:
Bazzet’s formula QTc = QT/ √RR
(QTc = corrected QT)

85.  Long QTc – causes
◦ Drugs – procanamide, quinidine
◦ Hypocalcemia,
◦ hypomagnesemia,
◦ hypokalemia
◦ Hypothermia
◦ AMI
◦ Congenital
 Jerwell and Lange-Neilsen syndrome
 Romano- Ward syndrome
 Short QT interval: hypercalcemia, digitalis
Abnormalities:

87.  U waves occur after the T wave and
are often difficult to see
 They are thought to be due to
repolarisation of the atrial septum
 Prominent U waves can be a sign of
hypokalaemia

88. THANKS