How to read ECG systematically with practice strips

Dr. Khaled H Alkhodari
Clinical Teaching Assistant at IUG
2020-2021
ECG revision & Practice

• https://litfl.com/ecg-library/

Anatomic Groups
(Anterior Wall)

Anatomic Groups
(Lateral Wall)

Anatomic Groups
(Inferior Wall)

https://ecgwaves.com/topic/localization-localize-myocardial-
infarction-ischemia-coronary-artery-occlusion-culprit-stemi/

Interpretation Steps
• Hx and Examination
• Name and Date
• Calibration
• Detect errors
• Cardiac Axis
• Rhythm
• Rate
• P wave
• PR interval
• QRS complex
• T wave
• ST segment
• QT interval

• speed of 25mm/sec
Small square = 1 mm = 0.04 s = 40 ms
Large square = 5 mm = 0.2 s = 200 ms

Determining the Axis
• The Quadrant Approach
• The Equiphasic Approach

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)

Determining the Axis
Predominantly
Positive
Predominantly
Negative
Equiphasic

The Quadrant Approach
1. Examine the QRS complex in leads I and aVF to determine if they
are predominantly positive or predominantly negative. The
combination should place the axis into one of the 4 quadrants
below.
Or normal

The Quadrant Approach
2. In the event that LAD is present, examine lead II to determine if
this deviation is pathologic. If the QRS in II is predominantly
positive, the LAD is non-pathologic (in other words, the axis is
normal). If it is predominantly negative, it is pathologic.

Quadrant Approach: Example 1
Negative in I, positive in aVF  RAD
The Alan E. Lindsay
ECG Learning Center
http://medstat.med.utah.
edu/kw/ecg/

Quadrant Approach: Example 2
Positive in I, negative in aVF  Predominantly positive in II 
Normal Axis
The Alan E. Lindsay
ECG Learning Center
http://medstat.med.utah.
edu/kw/ecg/

• Normal Axis: (-30 – 90) degree
• Left Axis deviation (LAD): < - 30 degree
• Normal variant / mechanical shift (high diaphragm)
• Left anterior hemiblock / LBBB / WPW / Inferior MI
• LVH / Ostium primum ASD
• Right Axis Deviation (RAD): > 90 degree
• Normal variant (tall & thin persons) / Chronic Lung Disease
• Left posterior hemiblock / RVH / PHTN (PE)
• Ostium secondum ASD / VSD / Anterolateral MI / WPW

Rate
Regular
300/no of large squares
300/4.5 = 67b/m

Short P-R
WPW
Long P-R
1st degree HB

Benign with
tachycardia
Ischemic in
99%
Ischemic in
50%

T inversion
T inversion : normal variant in
black patents, hypertrophy
(HOCM) ischemia, digoxin

(CULPRIT LESION): LM:
• Widespread horizontal ST depression, most prominent in leads I, II and V4-6 or ≥ 8 LEADS
• ST elevation in aVR ≥ 1mm
• ST elevation in aVR ≥ V1
• Except Tachycardia-Related ST Depression Widespread ST depression (with reciprocal STE in aVR)
is a common finding in patients with supraventricular tachycardias such as AVNRT or atrial
flutter. and may be due to:
1. Rate-related ischaemia (O2 demand > supply)
2. Unmasking of underlying coronary artery disease (i.e. tachycardia as a “stress test”)
3. A pure electrical phenomenon (e.g. the young patient with SVT who is relatively asymptomatic and has normal
coronary arteries)

However, ST elevation in aVR is not entirely specific to LMCA
occlusion. It may also be seen with:
• Proximal left anterior descending artery (LAD) occlusion
• Severe triple-vessel disease (3VD)
• Diffuse subendocardial ischaemia – e.g. due to O2 supply/demand
mismatch

Anterior MI ST elevation v1-4
Several ECG criteria have been reported to indicate a LAD
artery occlusion proximal to the first septal perforator
branch:
• (1) ST elevation in lead aVR
• (2) right bundle branch block
• (3) ST depression in lead V5 or Q wave in aVL
• (4) ST elevation in lead V1 of greater than 2.5 mm
• (5) ST depression in lead II,III and aVF

Inferior MI RCA
• 1.ST↑ V3R, V4R
• 2. Ratio of ST↓ V3 to ST↑ III, <0.5 = proximal RCA , 0.5–1.2 = distal
RCA
• 3. S:R wave ratio aVL >3
• 4. ST↑ III > II
• 5. ST↓ aVL > I

Inferior LCX
• 1. No ST↓ aVL
• 2. Ratio of ST↓ V3 to ST↑ III > 1.2
• 3. S:R wave ratio aVL < 3
• 4. V4R: ST depression and inverted T wavs
• 5. ST elevation in posterior leads

SUMMARYRate Rhythm Axis Intervals Hypertrophy Infarct
To summarize:
1. Calculate RATE
2. Determine RHYTHM
3. Determine QRS AXIS
– Normal
– Left axis deviation
– Right axis deviation
– Right superior axis deviation

To summarize:
1. Calculate RATE
2. Determine RHYTHM
4. Calculate INTERVALS
– PR
– QRS
– QT

To summarize:
1. Calculate RATE
2. Determine RHYTHM
5. Assess for HYPERTROPHY
– Right and left atrial enlargement
– Right and left ventricular hypertrophy

To summarize:
1. Calculate RATE
2. Determine RHYTHM
6. Look for evidence of INFARCTION
– Abnormal Q waves
– ST elevation or depression
– Peaked, flat or inverted T waves

To summarize:
1. Calculate RATE
2. Determine RHYTHM
6. Look for evidence of INFARCTION
Now to finish this module lets analyze a 12-lead ECG!

Detect errors
Lead I +ve normally
• If Lead I –ve + -ve aVR with normal R progression  Missed lead
• If Lead I –ve + +ve aVR with poor R progression  dextrocardia
• If Lead I +ve with poor R progression think about  AMI, DCM, HTN
• If V1 R tall  (dextrocardia, postMI, WPW A, RBBB, RVH)

25- Missed lead
If Lead I –ve with normal R progression

20-PVCs
• Etiology: One or more ventricular cells are
depolarizing and the impulses are abnormally
conducting through the ventricles.

Rhythm #18
60 bpm
• Rate?
• Regularity? regular
normal
0.08 s
• P waves?
• PR interval? 0.36 s
• QRS duration?
Interpretation? 1st Degree AV Block

Rhythm #17
50 bpm
• Rate?
• Regularity? regularly irregular
nl, but 4th no QRS
0.08 s
• P waves?
• PR interval? lengthens
• QRS duration?
Interpretation? 2nd Degree AV Block,
Type I

18-2nd Degree AV Block, Type I
•Deviation from NSR
• PR interval progressively lengthens, then
the impulse is completely blocked (P wave
not followed by QRS).

Rhythm #17
40 bpm
• Rate?
• Regularity? regular
nl, 2 of 3 no QRS
0.08 s
• P waves?
• PR interval? 0.14 s
• QRS duration?
Interpretation? 2nd Degree AV Block,
Type II

17-2nd Degree AV Block, Type II
•Deviation from NSR
• Occasional P waves are completely blocked
(P wave not followed by QRS).

15-Interpretation
Yes, this person is having an acute anterior wall
myocardial infarction.

14-Inferior Wall MI
This is an inferior MI. Note the ST elevation in leads II,
III and aVF.

13-Anterolateral MI
This person’s MI involves both the anterior wall (V2-
V4) and the lateral wall (V5-V6, I, and aVL)!

12-Left Ventricular Hypertrophy

ECG Diagnostic Criteria for LVH
Sensitivity Specificity
Sokolow-Lyon Index
SV1 + (RV5 or RV6)>35mm
22 100
Cornell Voltage Criteria
SV3+RaVL>28 mm (men), 20mm(women)
42 96
R1 + SIII>25 mm 11 100
R in aVL> 11mm 11 100
Other Criteria include Romhilt and Estes Point Score System
Chan TC, Brady WJ, Harrigan RA et al. ECG in Emergency Medicine and
Acute Care. 1st ed. Pennsylvania: Elsevier Mosby; 2005.

11 Pulmonary Embolism
Clues:
Sinus tachycardia
S1Q3T3 pattern
Incomplete RBBB with R precordial T wave inversions

10-Ant Inf MI
• Anterior-inferior STEMI
• ST elevation is present throughout the precordial and inferior
leads.
• There are hyperacute T waves, most prominent in V1-3.
• Q waves are forming in V1-3, as well as leads III and aVF.
• This pattern is suggestive of occlusion occurring in “type III” or
“wraparound” LAD (i.e. one that wraps around the cardiac apex
to supply the inferior wall)

8
• extensive Anterior STEMI (acute)
• ST elevation in V1-6 plus I and aVL (most marked in V2-4).
• Minimal reciprocal ST depression in III and aVF.
• Q waves in V1-2, reduced R wave height (a Q-wave equivalent) in
V3-4.
• There is a premature ventricular complex (PVC) with “R on T’
phenomenon at the end of the ECG; this puts the patient at risk for
malignant ventricular arrhythmias.

7
• Extensive anterior MI (“tombstoning” pattern)
• Massive ST elevation with “tombstone” morphology is present
throughout the precordial (V1-6) and high lateral leads (I, aVL).
• This pattern is seen in proximal LAD occlusion and indicates a
large territory infarction with a poor LV ejection fraction and high
likelihood of cardiogenic shock and death.

6-A
• Inferolateral STEMI. Posterior extension is suggested by:
• Horizontal ST depression in V1-3
• Tall, broad R waves (> 30ms) in V2-3
• Dominant R wave (R/S ratio > 1) in V2
• Upright T waves in V2-3

6
• Marked ST elevation in V7-9 with Q-
wave formation confirms involvement
of the posterior wall, making this an
inferior-lateral-posterior STEMI (= big
territory infarct!).

3-LBBB with acute MI
V3: 4/-12= - 0.33

A 60- year- old woman presents with acute- onset chest pain for 45 minutes with the
electrocardiography findings as shown in This ECG. Examination shows heart rate at 105 beats
per minute; blood pressure, 95/ 60 mm Hg; increased jugular venous pressure (JVP); clear
lungs; and no murmurs or gallops. Which of the following treatments is a class III (evidence or
general agreement that the treatment is not useful or effective) indication?
A. Intravenous fluids
B. Dobutamine
C. Nitroglycerin
D. Dopamine

• A-66-year old man known to have heart failure on Bisoprolol, furosemide, and digoxin presented to you for
follow up. His ECG is shown, what is the most likely cause of his ECG finding?
A. Ischemic changes
B. Bisoprolol effect
C. Digoxin effect
D. Left ventricular hypertrophy
E. No answer is true.

Focal atrial tachycardia
• Focal atrial tachycardia (focal AT) is characterized as a rapid regular rhythm
arising from a discrete area within the atria. It occurs in a wide range of
clinical conditions, including catecholamine excess, digoxin toxicity,
pediatric congenital heart disease, and cardiomyopathy. Focal AT is a
regular tachycardia and is often confused with other regular
supraventricular tachycardias, specifically re-entry tachycardias, sinus
tachycardia, and atrial flutter. It may be difficult to diagnose by ECG alone.
The diagnosis of focal AT is usually based on ECG, clinical history, and
response to interventions such as vagal maneuvers and adenosine.
• ECG shows a regular atrial tachycardia with P-wave morphology different
from that in sinus tachycardia.

Orthodromic atrioventricular re-entry
tachycardia (AVRT)

Ventricular Tachycardia – Monomorphic VT

V Fib
• ECG Findings
• Chaotic irregular deflections of varying amplitude
• No identifiable P waves, QRS complexes, or T waves
• Rate 150 to 500 per minute
• Amplitude decreases with duration (coarse VF -> fine VF)

Pericarditis
Diffuse ST elevations
Typically, no reciprocal changes
PR displacement

Cardiac Tamponade
Tamponade Triad (specific, not sensitive):
1. Sinus tachycardia except in?
2. Low voltage QRS
3. Electrical alternans

Wolff-Parkinson-White
WPW Triad:
1. Short PR interval
2. Wide QRS
3. Delta wave

How to read ECG systematically with practice strips

How to read ECG systematically with practice strips

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