This document contains a summary of an ECG intensive course for medical students presented on July 13, 2021. It discusses various arrhythmias and abnormalities seen on ECGs such as atrial flutter, atrial fibrillation, premature atrial contractions, paroxysmal supraventricular tachycardia, Wolff-Parkinson-White syndrome, junctional tachycardia, premature junctional contractions and provides clinical tips for identifying each on an ECG. It also reviews what should be looked for when interpreting an ECG including the rhythm, P waves, cardiac axis, QRS complex, ST segment, T waves and troubleshooting common ECG problems.

1. Dr. Abdulkadir Insi, MD

2. July 13, 2021 ECG intensive course for Medical students 2
Supraventricular tachycardias

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Atrial flutter
• When the atrial rate is greater than 250bpm and
there is no flat baseline between the P waves.

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• P Waves: Flutter waves have a saw-toothed appearance
Atrial flutter
• AV node conducts impulses to the ventricles at a
2:1, 3:1, 4:1, or greater ratio (rarely 1:1).
• Degree of AV block may be consistent or variable.

5. ♥ Clinical Tip
oThe presence of A-flutter may be the first indication of
cardiac disease.
oSigns and symptoms depend on ventricular response
rate.
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Atrial Fibrillation (A-fib)
o Rapid, erratic electrical discharge comes from
multiple atrial ectopic foci.
o No organized atrial contractions are detectable.
o When the atrial muscle fibers contract independently
there are no P waves on the ECG, only an irregular
line

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8. ♥ Clinical Tip
oA-fib is usually a chronic arrhythmia associated with
underlying heart disease.
oSigns and symptoms depend on ventricular response
rate.
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9. PrematureAtrial Contraction (PAC)
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oA single complex occurs earlier than the next
expected sinus complex.
oAfter the PAC, sinus rhythm usually resumes.

10. ♥ Clinical Tip
In patients with heart disease, frequent PACs may
precede paroxysmal SV tachycardia (PSVT), A-fib,
or A-flutter.
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11. Paroxysmal SupraventricularTachycardia
(PSVT)
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• PSVT is a rapid rhythm that starts and stops suddenly.
• For accurate interpretation, the beginning or end of the
PSVT must be seen.
• PSVT is sometimes called paroxysmal atrial tachycardia
(PAT).

12. ♥ Clinical Tip
The patient may feel palpitations, dizziness, light-
headedness, or anxiety.
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13. Wolff-Parkinson-White (WPW) Syndrome
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• The only normal electrical connection between
the atria and ventricles is the His bindle.
• In WPW an accessory conduction pathway is
present between the atria and the ventricles.

14. • Electrical impulses are rapidly conducted to the
ventricles.
• These rapid impulses create a slurring of the
initial portion of the QRS called the delta wave.
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• Rate: Depends on rate of underlying rhythm
• Rhythm: Regular unless associated with A-fib
• P Waves: Normal (upright and uniform) unless A-fib is present
• PR Interval: Short (0.12 sec) if P wave is present
• QRS: Wide (0.10 sec); delta wave present

16. ♥ Clinical Tip
WPW is associated with narrow-complex tachycardias,
including A-flutter and A-fib.
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17. Junctional Tachycardia
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♥ Clinical Tip
• Signs and symptoms of decreased CO may be seen in
response to the rapid rate.

18. Junctional Escape Beat
An escape complex comes later than the next expected
sinus complex.
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19. Premature Junctional Contraction (PJC)
Enhanced automaticity in the AV junction produces
PJCs.
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20. ♥ Clinical Tip
Before deciding that isolated PJCs may be insignificant,
consider the cause.
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• Finally remember:
oThe ECG is easy to understand.

22. Reminders
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23. The normal ECG
Limits of normal duration:
oPR interval=200ms
oQRS complex duration=120ms
oQT interval=450ms
Rhythm:
oSinus arrhythmia
oSupraventricular extrasystoles are always normal
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24. The cardiac axis:
oNormal axis=QRS complex predominantly upward
in leads I,II and III; still normal if QRS complex is
downward in lead III.
oMinor degrees of right and left axis deviation are
within the normal range.
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25. QRS complex:
oSmall Q waves normal in leads I, VL and V6
(septal Q waves)
oRSR1 pattern in lead V1 normal if the duration
<120 ms (partial RBBB)
oR wave smaller than S wave in lead V1
oR wave in lead V6<25mm
oR wave in lead V6 plus S wave in lead V1<35mm
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26. ST segment:
oShould be isoelectric
T wave:
• May be inverted in:
oLead III
oLead VR
oLead V1
oLead V2
oLead V3, in black people
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27. What to look for:
1. The rhythm
2. P wave abnormalities:
- Peaked, tall: RAH
- Notched, broad: LAH
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28. 3. The cardiac axis:
• Rt axis deviation: Lead I downward
• Lt axis deviation: leads II and III or lead VF
downward
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29. What to look for:
4. The QRS complex:
• If wide, ventricular origin or BBB
• Tall R waves in V1= RVH
• Tall R waves in V6= LVH
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30. • Transposition point:
- R and S waves are equal in the chest leads
over the inter-ventricular septum (normally V3 or
V4)
- Clockwise rotation indicates chronic lung
disease
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31. • Q waves:
Small (septal) Q waves are normal in leads I, VL
and V6
Q wave in lead III but not VF is a normal variant
If present in more than one lead, longer than
40ms in duration and deeper than 2mm
indicates infarction
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What to look for:

32. Q waves in lead III but not in VF, plus Rt axis
deviation may indicate pulmonary embolism
Leads showing Q waves indicate site of
infarction
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33. What to look for:
5. The ST segment:
oRaised= acute MI and pericarditis
oDepressed= ischemia and with digoxin
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34. 6. T waves:
• Peaked= hyperkalemia
• Flat and prolonged= hypokalemia
• Inverted: -normal in some leads -ischemia -
infarction -Lt or Rt VH -may be inverted in V1-3
in PE -BBB
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35. What to look for:
7. U waves:
oCan be normal
oHypokalemia
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36. Troubleshooting ECG Problems
■ Place leads in the correct position.
■ Incorrect placement can give false readings.
■ Avoid placing leads over bony areas.
■ In patients with large breasts, place the electrodes under
the breast.
■ Accurate tracings are obtained through the least amount
of fat tissue.
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37. ■ Apply tincture of benzoin to the electrode sites if the
patient is diaphoretic.
■ The electrodes will adhere to the skin better.
■ Shave hair at the electrode site if it interferes with
contact between the electrode and skin.
■ Discard old electrodes and use new ones if the gel
on the back of the electrode dries.
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38. Cable Connections
• It is important to know if you are using an
American or European cable for ECG monitoring.
• The colors of the wires differ as shown below.
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40. REFERENCES:
1. The ECG made easy; John R. Hampton
2. The ECG in practice; John R. Hampton
3. 150 ECG problems; John R. Hampton
4. Others
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