This document provides an overview of abnormalities seen on electrocardiograms (ECGs). It discusses abnormalities of P waves, QRS complexes, ST segments, and T waves. Key things to evaluate when analyzing an ECG are listed as the heart rate, rhythm, QRS axis, intervals (PR, QRS, QT), evidence of hypertrophy (atrial or ventricular), and signs of infarction such as abnormal Q waves, ST elevation or depression, and peaked, flat, or inverted T waves. The overall goal of ECG analysis is outlined as calculating the rate, determining the rhythm and axis, evaluating intervals, assessing for hypertrophy, and looking for signs of infarction.

1. Dr. Abdulkadir Insi, MD

2. Abnormalities of P waves, QRS
complexes and T waves
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3. Abnormalities of the P waves
• Apart from alterations of the shape of the P
wave associated with rhythm changes, there are
only two important abnormalities:
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4. 1. Anything that causes the RA to become
hypertorphied causes the P wave to become
peaked (P pulmonale).
2. Left atrial hypertrophy causes a broad and bifid
P wave (P mitrale).
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5. Right atrial enlargement
• To diagnose RAE you can use the following
criteria:
1. II P > 2.5 mm, or
2. V1 or V2 P > 1.5 mm
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Remember 1 small
box in height = 1 mm
> 2 ½ boxes (in height)
> 1 ½ boxes (in height)

6. Left atrial enlargement
• To diagnose LAE you can use the following
criteria:
•II > 0.04 s (1 box) b/w notched peaks, or
•V1 Neg. deflection > 1 box wide x 1 box deep
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8. Abnormalities of the QRS complex
• The normal QRS complex has 4 characteristics:
1. Its duration is no greater than 120ms
2. In a RT ventricular lead (V1), the S wave is
greater than the R wave.
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9. 3. In a LT ventricular lead (V5 or V6), the height
of the R wave is less than 25mm
4. Left ventricular leads may show Q waves due
to septal depolarization, but these are less than
1mm across and less than 2mm deep.
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10. Abnormalities of the width
• Wide QRS complexes:
1. BBB
2. Ventricular escape
3. Extrasystoles
4. Tachycardia
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11. Increased height of the QRS
• Right ventricular hypertrophy: best seen in V1
• Usually associated with RT axis deviation, a
peaked P wave and in severe cases inversion
of T waves in V1,2 and some times V3 or even
V4.
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12. Right ventricular hypertrophy
• To diagnose RVH you can use the following criteria:
• Right axis deviation, and
• V1 R wave > 7mm tall
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13. Pulmonary embolism
• The ECG may show features of RVH, but many
cases there is no thing abnormal other than sinus
tachycardia.
• When you suspect PE look for the following:
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14. 1. Peaked P waves
2. Rt axis deviation
3. RBBB
4. Dominant R waves in lead V1
5. Inverted T waves in V1-3
6. Deep S waves in lead V6
• The classic pattern for pulmonary embolism: S1Q3T3
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15. Left ventricular hypertrophy
• To diagnose LVH you can use the following criteria:
• R in V5 (or V6) + S in V1 (or V2) > 35 mm, or
• aVL R > 13 mm
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S = 13 mm
R = 25 mm

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18. • Left ventricular hypertrophy: tall R wave >25mm
in V5 or V6 and deep S wave in V1 or V2.
• With significant hypertrophy there are also inverted
T waves in I, VL, V5 and V6.
• There may be left axis deviation.
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20. Infarction
•When analyzing a 12-lead ECG for evidence of an
infarction you want to look for the following:
oAbnormal Q waves
oST elevation or depression
oPeaked, flat or inverted T waves
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21. Q waves
• Q waves > one small square in width and 2mm in
depth have a quite different and indicate a
myocardial infarction.
• The leads in which the Q wave appears give some
indication of the part of the heart that has been
damaged.
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22. • Infarction of the anterior wall of LV: V2-4 or V5
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23. • Infarction of both ant. And lateral surfaces: V3-4, I, aVL, V5-6
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24. • Infarction of inferior wall: III and a VF
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25. • The presence of a Q wave does not give any
indication of the age of the infarction, because once
a Q wave has developed it is usually permanent.
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26. Abnormalities of the ST segment
• ST segment abnormalities may be elevated or depressed
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27. • Elevation of the ST segment is an indication of
acute myocardial injury, usually due either to a
recent infarction or to pericarditis.
• The leads in which the elevation occurs indicate the
part of the heart that is damaged.
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28. • Anterior damage shows in the V leads, and the
inferior damage in leads III and a VF.
• Pericarditis causes ST elevation in most leads.
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29. • Elevation of the ST segment (greater than 1 small box) in
2 leads is consistent with a myocardial infarction.
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32. • Horizontal depression of the ST segment,
associated with an upright T wave, is usually a
sign of the ischemia.
• Downward sloping ST segments are usually due to
treatment with digoxin treatment.
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33. Sequence of ECG changes in MI
1. Normal ECG
2. Raised ST segments
3. Appearance of Q waves
4. Normalization of ST segments
5. Inversion of T waves
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34. Things to remember
1. Tall P wave: RAH
2. Broad P waves: LAH
3. Broadening of QRS: BBB, ventricular rhythm
4. Increased height of QRS in V1: RVH
5. Increased height of QRS in V5-6: LVH
6. Q waves > 1mm across and 2 mm deep: MI
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35. Things to remember
7. ST segment elevation: acute MI or pericardiatis
8. ST segment depression and T wave inversion:
ischemia, VH, abnormal intraventricular conduction
or digoxin.
9. T wave inversion is normal: III, aVR and V1
10. T wave flattening or peaking with an unusually long
or short QT interval may be due to electrolyte
abnormalities.
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36. SUMMARY
To summarize:
1. Calculate RATE
2. Determine RHYTHM
3. Determine QRS AXIS
– Normal
– Left axis deviation
– Right axis deviation
– Right superior axis deviation
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37. SUMMARY
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To summarize:
1. Calculate RATE
2. Determine RHYTHM
3. Determine QRS AXIS
4. Calculate INTERVALS
– PR
– QRS
– QT

38. Summary
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To summarize:
1. Calculate RATE
2. Determine RHYTHM
3. Determine QRS AXIS
4. Calculate INTERVALS
5. Assess for HYPERTROPHY
– Right and left atrial enlargement
– Right and left ventricular hypertrophy

39. Summary
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To summarize:
1. Calculate RATE
2. Determine RHYTHM
3. Determine QRS AXIS
4. Calculate INTERVALS
5. Assess for HYPERTROPHY
6. Look for evidence of INFARCTION
– Abnormal Q waves
– ST elevation or depression
– Peaked, flat or inverted T waves

40. Summary
To summarize:
1. Calculate RATE
2. Determine RHYTHM
3. Determine QRS AXIS
4. Calculate INTERVALS
5. Assess for HYPERTROPHY
6. Look for evidence of INFARCTION
Now to finish this module lets analyze a 12-lead ECG!
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