ECG diagnosis

1
ECG diagnosis
2
Aims

• 10 ECG rules
• ECG signs of M.I.
• Evolution of changes in M.I.
• Classical Appearences

3
QRS waveform nomenclature
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The 10 rules for a normal ECG
.2
5
Rule 1
1.0
R
PR interval should be 120 to 200 milliseconds or
3 to 5 little squares
0.5
T
P
Millivolts
Q
0
S
-0.5
0
200
400
600
Milliseconds
6
Rule 2
1.0
The width of the QRS complex should not exceed
110 ms, less than 3 little squares
0.5
Millivolts
0
-0.5
QRS
0
200
400
600
Milliseconds
7
Rule 3
The QRS complex should be dominantly upright in
leads I and II
8
Rule 4
QRS and T waves tend to have the same general
direction in the limb leads
9
Rule 5
All waves are negative in lead aVR
10
Rule 6
V6
V5
V4
V3
V2
V1
The R wave in the precordial leads must grow from
V1 to at least V4
11
Rule 7
The ST segment should start isoelectric except in
V1 and V2 where it may be elevated
12
Rule 8
The P waves should be upright in I, II, and V2 to
V6
13
Rule 9
There should be no Q wave or only a small q less
than 0.04 seconds in width in I, II, V2 to V6
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Rule 10
The T wave must be upright in I, II, V2 to V6
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Characteristic changes in AMI

• ST segment elevation over area of damage
• ST depression in leads opposite infarction
• Pathological Q waves
• Reduced R waves
• Inverted T waves

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ST elevation

• Occurs in the early stages
• Occurs in the leads facing the infarction
• Slight ST elevation may be normal in V1 or V2

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Deep Q wave

• Only diagnostic change of myocardial infarction
• At least 0.04 seconds in duration
• Depth of more than 25 of ensuing R wave

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T wave changes

• Late change
• Occurs as ST elevation is returning to normal
• Apparent in many leads

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Bundle branch block
Anterior wall MI
Left bundle branch block
I II III
aVR aVL aVF
V1 V2 V3
V4 V5 V6
I II III
aVR aVL aVF
V1 V2 V3
V4 V5 V6
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Sequence of changes in evolving AMI
R
R
R
ST
ST
T
P
P
P
T
Q
Q
S
Q
1 minute after onset
1 hour or so after onset
A few hours after onset
R
ST
T
ST
P
P
P
T
T
Q
Q
Q
A day or so after onset
Later changes
A few months after AMI
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Anterior infarction
Anterior infarction
Left coronary artery
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Inferior infarction
Inferior infarction
Right coronary artery
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Lateral infarction
Lateral infarction
Left circumflex coronary artery
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Location of infarct combinations
aVR
I
V1
V4
ANT POST
LATERAL
ANT SEPTAL
aVL
II
V2
V5
ANT LAT
V3
V6
aVF
III
INFERIOR
25
Diagnostic criteria for AMI

• Q wave duration of more than 0.04 seconds
• Q wave depth of more than 25 of ensuing r wave
• ST elevation in leads facing infarct (or
  depression in opposite leads)
• Deep T wave inversion overlying and adjacent to
  infarct
• Cardiac arrhythmias