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Propagation of cardiac impulse
The Normal Conduction System
ECG machine
Generation of normal ECG complex
What is the heart rate?
www.uptodate.com
(300 / 6) = 50 bpm
What is the axis?
Normal- QRS up in I and aVF
What is the diagnosis?
Acute inferior MI with ST elevation
in
leads II, III, aVF
What is this rhythm?
First degree AV block
What is this rhythm?
Type 1 second degree block (Wenckebach)
What is this rhythm?
Type 2 second degree AV block
Dropped QRS
What is this rhythm?
3rd degree heart block (complete)
ECTOPIC BEATS
14
ECTOPIC BEATS
15
16
ECG Leads
Limb leads: I, II, III, aVR, aVL, aVF,
Chest leads: V1-V6
Anterior surface: V1-4.
 Inferior surface: II, III and aVF.
 Lateral surface: I, aVL and V5-6.

ECG Paper
Normal ECG
P-wave
Normal values
1. Polarity.
up in I&II and down
in 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 P wave
 Atrial fibrillation
P- mitrale
(LAE)
P- pulmonale
(RAE)
PR interval
Definition: the time
interval between
beginning of P-wave
to beginning of QRS
complex.
Normal PR interval
3-5mm (0.12-0.2 sec)
Abnormalities
1. Short PR interval
 WPW syndrome
2. Long PR interval
 First degree heart
block
QRS complex
Normal values
 Duration: < 3 mm.

Morphology: progression
from Short R and deep S
(rS) in V1 to tall R and
short S in V6 with small Q
in V5-6 (qRs).
Abnormalities:
1. Wide QRS complex
 Bundle branch block.

Ventricular rhythm.
2. Tall R in V1
 RVH.
 RBBB.
 Posterior MI.
 WPW syndrome.
3. abnormal Q wave
[ > 25% of R wave]
 MI.
 Hypertrophic
cardiomyopathy.
 Normal variant.
Normal Q wave
Q wave in MI
Q wave in septal hypertrophy
ST- segment
Normally it's isoelectric.
[i.e. at same level of
TP segment]
Abnormalities:
1. ST elevation:

Acute MI.
Prinzmetal angina.
Acute pericarditis.

Early repolarization.


2. ST depression:
Ischemia.
 Ventricular strain.
 BBB.
 Hypokalemia.
 Digoxin effect.

Abnormalities of ST- segment
T-wave
Normal values.
1. Polarity:
 Always up in I,II,V4-6
 Always down in aVR.
 Variable in III, aVL, aVF,
V1-3.
2. amplitude: < 10mm in the
chest leads.
Abnormalities:
1. Peaked T-wave:
 Hyper-acute MI.
 Hyperkalemia.
 Normal variant.
2. T- inversion:
 Ischemia.
 Myocardial infarction.
 Myocarditis
 Ventricular strain
 BBB.
 Hypokalemia.
 Digoxin effect.
QT- interval
Definition: Time interval between beginning of
QRS complex to the end of T wave.
Normally: At normal HR: QT ≤ 11mm (0.44 sec)
(or) QTc = QT/ √RR
Abnormalities:
1.
2.
Prolonged QT interval: hypocalcemia and
congenital long QT syndrome.
Short QT interval: hypercalcemia.
INTERPRETATION OF ECG
STANDARD? NAME? DATE?
 P(SR-nonSR ? rate? regular or irregular?)
 ORS(wide or narrow? LBBB OR RBBB?
rate? regular or irregular?)
 T(tall? invert?
biphasic?)
 P-R(long? short? fixed or no? relation?)
 ST(elevate? Depressed? )
 QT(long? short?)
 AXIS?

Rate
Rule of 300- Divide 300 by the number of 
boxes between each QRS = rate
Number of
big boxes
Rate
1
300
2
150
3
100
4
75
5
60
6
50
Rate
HR of 60-100 per minute is normal
HR > 100 = tachycardia
HR < 60 = bradycardia
Interpretation of ECG
cont.
4. Axis (mean QRS axis): normally -30 to +100
LAD:
 LVH
 LAFB
 Inf. MI
RAD:
 Normal
 RVH
 Lat. MI
 LPFB
5. Analysis of complete ECG complex in each lead.
Calculation of electrical axis depending
on QRS polarity in leads I and aVF
WPW
Long QT syndrome
Bundle branch block
Left Bundle branch block (LBBB)
Right Bundle branch block
(RBBB)
VT
(with RBBB pattern)
VT
(with LBBB pattern)
ECG changes in IHD


1.
2.
1.
2.
Signs of ischemia:
Reversible ST depression, ST elevation
or T inversion.
Signs of MI:
Hyperacute T wave.
ST elevation (STEMI)
ST depression(NSTEMI)
Q wave (Q or transmural infarction)
T inversion.
Evolution of ECG changes in MI
Q wave infarction
Localization of MI
1. anterior MI
Localization of MI
2. lateral MI
Localization of MI
3. inferior MI
Hyperacute MI
Acute anteroseptal MI (STEMI)
Acute anterolateral MI
(with hyperacute T)
Acute anterolateral MI
Old inferior MI
Acute inferior MI
Right ventricular infarction
Old ant. MI
Old inf. MI
Old inf. MI
Criteria of ventricular enlargement
LVH:
RVH:
1. SV1 + (RV5 or RV6)
≥ 35 mm
(or)
RV5 or RV6 ≥ 25 mm
2. LV strain
3. LAE
1. Relatively tall R in V1
2. RV strain
3. RAD
LVH
LVH
RVH with RAE
RAE
LAE
Acute pericarditis
SAH
Hyperkalemia
Sever hyperkalemia
PAC
PAC bigeminy
PVC
PVC
PVC. bigeminy
PVC. trigeminy
VT
Multifocal PVC
PVC. Couplet
Sinus tachycardia
Paroxysmal supraventricular tachycardia
[PSVT]
PSVT
Atrial fibrillation [fine]
Non-sustained VT
VT
Ventricular fibrillation
Sinus bradycardia
Junctional rhythm
Sinus arrest
Sinus arrest
First degree heart block
Second degree heart block
Mobitz type I (Wenckebach block)
Complete heart block
Complete heart block
Sinus rhythm (SR), rate 60,
normal ECG.
SR rate 66, benign early repolarization
(BER).
SR, rate 91, with first degree
AV block.
Ectopic atrial rhythm, rate 82,
otherwise normal ECG.
AV junctional rhythm,
rate 50
Accelerated idioventricular rhythm
(AIVR), rate 65
SR, rate 100, right bundle
branch block (RBBB)
SR, rate 80, first degree AV block, left
bundle branch block (LBBB),old inf MI
SR, rate 85, RBBB, left posterior
fascicular block (LPFB)
rate 50, acute anterolateral myocardial
infarction
SR with second degree AV block type 1 (Mobitz I,
Wenckebach), rate 50, left ventricular hypertrophy
(LVH), RBBB.
Ventricular tachycardia (VT),
rate 140
SR, rate 87, Wolff-ParkinsonWhite syndrome (WPW)
ST, rate 155
This ECG was recorded from a 25-year-old pregnant woman who complained of an
irregular heart beat.
Auscultation revealed a soft systolic murmur but her heart was otherwise normal. ^
ANSWER 1
The ECG shows:
• Sinus rhythm
• Ventricular extrasystoles
• Normal axis
• Normal QRS complexes and T waves
Clinical interpretation
The extrasystoles are fairly frequent but the ECG
is otherwise normal. Ventricular extrasystoles are
very common in pregnancy, and systolic murmurs
are almost universal. Her heart is almost certainly
normal.
What to do
Remember anaemia
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