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ECG diagnosis

Aims

• • • •

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

QRS waveform nomenclature

R

r

qR

qRs

Qrs

QS

Qr

Rs

rS

qs

rSr’

rSR’

The 10 rules for a normal ECG

I II III

aVR aVL aVF

V1 V2 V3

V4 V5 V6

.2

Rule 1

1.0

Millivolts

0.5

R PR interval

PR interval should be 120 to 200 milliseconds or 3 to 5 little squares

T P Q

0

S

-0.5

0

200

400

Milliseconds

600

Rule 2

1.0

R

The width of the QRS complex should not exceed 110 ms, less than 3 little squares

Millivolts

0.5

T P Q

0

S

-0.5

QRS 0

200

400

Milliseconds

600

Rule 3

I II III

aVR aVL aVF

The QRS complex should be dominantly upright in leads I and II

Rule 4

I II III

aVR aVL aVF

QRS and T waves tend to have the same general direction in the limb leads

Rule 5

All waves are negative in lead aVR

P

T Q

S

Rule 6

V1

V2

V3

V4

V5

V6

The R wave in the precordial leads must grow from V1 to at least V4

Rule 7

I II III

aVR aVL aVF

V1 V2 V3

V4 V5 V6

The ST segment should start isoelectric except in V1 and V2 where it may be elevated

Rule 8

I II III

aVR aVL aVF

V1 V2 V3

V4 V5 V6

The P waves should be upright in I, II, and V2 to V6

Rule 9

I II III

aVR aVL aVF

V1 V2 V3

V4 V5 V6

There should be no Q wave or only a small q less than 0.04 seconds in width in I, II, V2 to V6

Rule 10

I II III

aVR aVL aVF

V1 V2 V3

V4 V5 V6

The T wave must be upright in I, II, V2 to V6

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

ST elevation

• Occurs in the early stages

R ST P

Q

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

Deep Q wave

• Only diagnostic change of myocardial infarction

R ST

• At least 0.04 seconds in duration

P T Q

• Depth of more than 25% of ensuing R wave

T wave changes

• Late change R

• Occurs as ST elevation is returning to normal

ST

P

• Apparent in many leads T Q

Bundle branch block Anterior wall MI I II III

aVR aVL aVF

Left bundle branch block V1 V2 V3

V4 V5 V6

I II III

aVR aVL aVF

V1 V2 V3

V4 V5 V6

Sequence of changes in evolving AMI R

R T

R

ST

ST

P

P Q S

P T

Q

1 minute after onset

Q

1 hour or so after onset

A few hours after onset

R ST

P

ST

P T

Q

A day or so after onset

T

P T

Q

Later changes

Q

A few months after AMI

Anterior infarction Anterior infarction

I II III

Left coronary artery

aVR aVL aVF

V1 V2 V3

V4 V5 V6

Inferior infarction Inferior infarction

I II III

Right coronary artery

aVR aVL aVF

V1 V2 V3

V4 V5 V6

Lateral infarction Lateral infarction

I II III

Left circumflex coronary artery

aVR aVL aVF

V1 V2 V3

V4 V5 V6

Location of infarct combinations

I

aVR

LATERAL aVL

II

V1 ANT POST V2

V4

ANT SEPTAL

V5 ANT

V3 III

INFERIOR

aVF

V6

LAT

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