Ecg workshop

What is a 12 lead
ECG?
Records the electrical activity of the heart (depolarisation and
repolarisation of the myocardium)
Views the surfaces of the left ventricle from 12 different angles

Why do a 12 lead
ECG?
Monitor patients heart rate and rhythm
Evaluate the effects of diseases or injury on heart function
Detect presence of electrolyte and other disturbances

Anatomical Position
of the Heart

Impulse Conduction & the ECG
Sinoatrial node
AV node
Bundle of His
Bundle Branches
Purkinje fibers

The “PQRST”
 P wave - Atrial
depolarization
• T wave - Ventricular
repolarization
• QRS - Ventricular
depolarization

Limb Leads
3 Unipolar leads
 avR - right arm (+)
 avL - left arm (+)
 avF - left foot (+)
 note that right foot is a ground lead

Limb Leads
3 Bipolar Leads
form (Einthovens Triangle)
Lead I - measures electrical potential
between right arm (-) and left arm (+)
Lead II - measures electrical potential
between right arm (-) and left leg (+)
Lead III - measures electrical potential
between left arm (-) and left leg (+)

Chest Leads
6 Unipolar leads
Also known as precordial leads
V1, V2, V3, V4, V5 and V6 - all positive

Think of the positive electrode as an
‘eye’…
the position of the positive electrode on
the body determines the area of the
heart ‘seen’ by that lead.

ECG Waveforms
When an electrical impulse
travels towards a positive
electrode, there will be a
positive deflection on the ECG
If the impulse travels away
from the positive electrode, a
negative deflection will be
seen

The Normal EKG
P
Q
R
S
T
Right Arm
Left Leg
QTPR
0.12-0.2 s approx. 0.44 s
Atrial muscle
depolarization
Ventricular muscle
depolarization
Ventricular
muscle
repolarization
“Lead II”

Positive electrodes of limb leads
0o
30o
-30o
60o
-60o
-90o
-120o
90o120o
150o
180o
-150o
I
II
avF
avLavR
Limb leads
I = +0o
II = +60o
III = +120o
Augmented leads
avL = -30o
avF = +90o
avR = -150o
I
IIIII

AXIS
Axis refers to the mean QRS axis
(or vector) during ventricular
depolarization.

The QRS Axis
By near-consensus, the
normal QRS axis is defined
as ranging from -30° to +90°.
-30° to -90° is referred to as a
left axis deviation (LAD)
+90° to +180° is referred to as
a right axis deviation (RAD)

0o
30o
-30o
60o
-60o
-90o
-120o
90o120o
150o
180o
-150o
AXIS
… if the QRS is negative in lead I and negative in lead II what is the QRS
axis? (normal, left, right or right superior axis deviation)
QRS Complexes
I
AxisI II
+ +
+ -
- +
- -
normal
left axis deviation
right axis deviation
right superior
axis deviation
0o
30o
-30o
60o
-60o
-90o
-120o
90o120o
150o
180o
-150o
II

AXIS
Is the QRS axis normal in this ECG? No, there is left axis
deviation.
The QRS is
positive in I and
negative in II.

The ECG Paper
 Horizontally
 One small box - 0.04 s
 One large box - 0.20 s
 Vertically
 One large box - 0.5 mV

The standard 12 Lead ECG
6 Limb Leads 6 Chest Leads (Precordial leads)
avR, avL, avF, I, II, III V1, V2, V3, V4, V5 and V6
Rhythm Strip

69 year old man without symptoms. What is the rhythm?
Sinus rhythm with markedly prolonged PR interval.
(Also, LBBB.)

Normal Impulse Conduction
Sinoatrial node
AV node
Bundle of His
Bundle Branches
Purkinje fibers

Rhythm Analysis
 Step 1: Calculate rate.
 Step 2: Determine regularity.
 Step 3: Assess the P waves.
 Step 4: Determine PR interval.
 Step 5: Determine QRS duration.

Step 1: Calculate Rate
 Option 1
 Count the # of R waves in a 6 second rhythm strip, then multiply by 10.
 Reminder: all rhythm strips in the Modules are 6 seconds in length.
Interpretation?
9 x 10 = 90 bpm
3 sec 3 sec

 Option 2
 Find a R wave that lands on a bold line.
 Count the # of large boxes to the next R wave. If the second R wave is 1
large box away the rate is 300, 2 boxes - 150, 3 boxes - 100, 4 boxes - 75,
etc. (cont)
R wave

 Option 2 (cont)
 Memorize the sequence:
300 - 150 - 100 - 75 - 60 - 50
Interpretation?
3
0
0
1
5
0
1
0
0
7
5
6
0
5
0
Approx. 1 box less than
100 = 95 bpm

Step 2: Determine regularity
 Look at the R-R distances (using a caliper or
markings on a pen or paper).
 Regular (are they equidistant apart)?
Occasionally irregular? Regularly irregular?
Irregularly irregular?
Interpretation?
Regular
R R

Step 3: Assess the P waves
 Are there P waves?
 Do the P waves all look alike?
 Do the P waves occur at a regular rate?
 Is there one P wave before each QRS?
Interpretation?
Normal P waves with 1 P
wave for every QRS

Step 4: Determine PR interval
 Normal: 0.12 - 0.20 seconds.
(3 - 5 boxes)
Interpretation?
0.12 seconds

Step 5: QRS duration
 Normal: 0.04 - 0.12 seconds.
(1 - 3 boxes)
Interpretation?
0.08 seconds

Rhythm Summary
 Rate 90-95 bpm
 Regularity regular
 P waves normal
 PR interval 0.12 s
 QRS duration 0.08 s
Interpretation?
Normal Sinus Rhythm

 Etiology: SA node is depolarizing faster than normal, impulse is
conducted normally.
 Remember: sinus tachycardia is a response to physical or
psychological stress, not a primary arrhythmia.

Ventricular Conduction
Normal
Signal moves rapidly
through the ventricles
Abnormal
Signal moves slowly
through the ventricles

EMO ASK ABOUT GIVING LIDOCAINE

FOLLOWING STRESS TEST RHYTHM SUDDENLY CHANGES PATIENT
ALERT AND DENIES CHEST PAIN

Man suddenly collapses while in the aerobic class

You are responding to middle aged female who suddenly
lost consciousness in delivery room during birth of the child

Motor vehicle accident victim pulse less not breathing

2nd
Degree AV Block
Type 1
(Wenckebach)
EKG Characteristics: Progressive prolongation of the PR interval until a P
wave is not conducted.
As the PR interval prolongs, the RR interval actually
shortens
EKG Characteristics: Constant PR interval with intermittent failure to conduct
Type 2

Remember
 When an impulse originates in a ventricle, conduction through the
ventricles will be inefficient and the QRS will be wide and bizarre.

Bundle Branch Blocks
So, depolarization of
the Bundle Branches
and Purkinje fibers are
seen as the QRS
complex on the ECG.
Therefore, a conduction
block of the Bundle
Branches would be
reflected as a change in
the QRS complex.
Right
BBB

Left Bundle Branch Block
Criteria
 QRS duration ≥ 120ms
 Broad R wave in I and V6
 Prominent QS wave in V1
 Absence of q waves (including physiologic q waves) in I and V6

Right Bundle Branch Block
Criteria
 QRS duration ≥ 110ms
 rSR’ pattern or notched R wave in V1
 Wide S wave in I and V6

ISCHEMIC CHANGES
 S-T segment elevationS-T segment elevation
 S-T segment depressionS-T segment depression
 Hyper-acute T-wavesHyper-acute T-waves
 T-wave inversionT-wave inversion
 Pathological Q-wavesPathological Q-waves
 Left bundle branch blockLeft bundle branch block

ST ELEVATION
One way to diagnose anOne way to diagnose an
acute MI is to look foracute MI is to look for
elevation of the STelevation of the ST
segment.segment.

Inferior
II, III, AVF
Septal-Anterior
V1,V2, V3,V4
Lateral
I, AVL, V5,
V6
Posterior
V1,
V2, V3
RIGHT LEFT

ST-DEPRESSION
Can be characterised as:-Can be characterised as:-
DownslopingDownsloping
UpslopingUpsloping
HorizontalHorizontal

Q Waves
Non Pathological Q wavesNon Pathological Q waves
Q waves of less than 2mm are normalQ waves of less than 2mm are normal
Pathological Q wavesPathological Q waves
Q waves of more than 2mmQ waves of more than 2mm
indicate full thickness myocardialindicate full thickness myocardial
damage from an infarctdamage from an infarct
Late sign of MI (evolved)Late sign of MI (evolved)

Left Atrial Enlargement
Criteria
P wave duration in II ≥120ms
or
Negative component of
biphasic P wave in V1 ≥ 1 “small
box” in area

Right Atrial Enlargement
Criteria
P wave height in II ≥ 2.4mm
or
Positive component of
biphasic P wave in V1 ≥ 1
“small box” in area

Left Ventricular Hypertrophy
Many sets of criteria for diagnosing LVH have been
proposed:
Sensitivity Specificity
The sum of the S wave in V1 and
the R wave in either V5 or V6 > 35
mm
43% 95%
Sum of the largest precordial R
wave and the largest precordial S
wave > 45 mm
45% 93%
Romhilt-Estes Point System 50-54% 95-97%

RVH
V1 Lead:
- R/S ratio > 1 and negative T wave
V5 or V6
- R/S ratio in V5 or V6 < 1

Conclusion
Reading ECG is not difficult
but mastering needs
persistent reading with
sequence.
For diagnoses and
management one has to
combine ECG findings with
patients clinical status.

Rhythm assessment
In ACLS recognizing and
treating arrhythmias saves
life.
In chronic rhythm disorder
timely diagnosis guide
major treatment decisions

Case-1
60 years man with 2
hours of crushing
chest pain suddenly
collapse

Case-2
50 yrs well controlled
HTNsive female on
amlodipine 5mg having
palpitation for last 1 week.

ECG – 2
50 yrs well controled hypertensive female on amlodipine 5mg having
palpitation for last 1 week

Case-3
70 years old man
with weakness,
lethargy and
exercise intolerance.

Case-4
55 yrs male H/O of
Inf. MI 10 yrs back lost
to follow up came to
ER with 2 hours of
palpitations.

ECG-4
55 yrs male H/O of Inf. MI 10 yrs back lost to follow up came to
ER with 2 hours of palpitations.

Case-5
72 yrs male having
H/O two episodes of
syncope in last two
weeks.

ECG – 5
72 yrs male having H/O two episodes of syncope in last two weeks.

Clues of cardiac
and non-cardiac
diseases

Effects of disease or Injury
Timely diagnosis of acute
diseases guide to specific
life saving treatment.
Chronic disease indicators
provides clues towards
number of cardiac and
non-cardiac diseases.

Case-6
40 years female
with 2 hours of
pleuritic chest pain
breathlessness.

Case-7
76 years male SOB
for few months
severe for last two
days with
palpitation.

Case-8
63 yrs diabetic male
with no other co-
morbids going for
cataract surgery.

ECG-863 yrs diabetic male with no other co-morbids going for
cataract surgery.

Case-9
A 56 years male
with breathlessness
and raised JVP.

ECG- 11
58 yrs diabetic female sudden severe central chest discomfort
for last 15 minutes.

ECG- 12
66 yrs male with SOB on minimal exertion since last 1 month.66 yrs male with SOB on minimal exertion since last 1 month.

ECG – 13
22 yrs male visited ER for the first time with headache found to have BP of 190/110

ECG -14
55 years male, smoker with prolong history of SOB and cough ,
increased in last three month.

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