Aims

• The ECG complex• Step by step

interpretation• Rhythm

disturbances• Axis• QRS abnormalities• Acute and chronic

ischaemia• Miscellaneous ECG

abnormalities

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The ECG Complex

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The ECG Complex• (diagram of ECG complex)

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Nomenclature

• P Wave• QRS complex• T wave• U wave• PR interval• QT interval• RR interval (ventricular) heart rate

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Intra-cardiac electrical conduction

• (diagram of intra cardiac electrical conduction)

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Standard 12 Lead ECG

(Example of normal ECG)

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Standard Times

Interval (ms)

PR 120 – 200

QTc (Corrected for heart rate)

Men: 390-450Women: 390-460

QRS <110

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Step by step interpretation

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Step by step interpretation

• Rate• Rhythm• Axis• QRS complex• ST segments

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RATE

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Rate• Normal heart rate 60-100bpm• Bradycardia < 60bpm• Tachycardia > 100bpm

• Divide tachycardia into ‘broad’ and ‘narrow complex’

• Broad = QRS > 110ms• Narrow = QRS <110ms

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Rhythm

12

Regular or irregular?

• Measure R-R interval between different complexes

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Sinus rhythm

Rhythm14

(example showing sinus rhythm)

Where else may heart rhythm originate from?

• Atria – Atrial fibrillation– Atrial flutter– Atrial tachycardia

• In/around AV node– nodal ‘junctional’ rhythm– AVNRT/AVRT

• Ventricle– VT/VF

* Will be demonstrated

Rhythm15

Atrial Fibrillation

• Erratic atrial depolarisation• No discernible p waves• Rate varies• Irregular

(example showing atrial fibrillation)

Rhythm16

Atrial Flutter

• Cyclical electrical activity around right atrium

• Atrial complexes occur at approx 300/min• ‘Sawtooth’ appearance on ECG• Almost always associated with degree of

AV block(example showing atrial flutter)

Rhythm17

Junctional (Nodal) Rhythm

• Uncommon• Rhythm arises from around AV node• Narrow complex

(example showing junctional rhythm)

Rhythm18

Accelerated ‘Idioventricular’ rhythm

• Unusual• Heart rhythm controlled by ventricular

focus• Usually 60-120bpm

(example showing idioventricular rhythm)

Rhythm19

Ventricular tachycardia

• Wide QRS• Heart rate >120bpm• Life-threatening

• (example of VT)

Rhythm20

Ventricular Fibrillation

Rhythm21

• (example showing ventricular fibrillation)

Bradycardia

• Types– Sinus bradycardia (very rarely less than

40bpm)– Sick sinus syndrome– Slow AF/atrial flutter (usually drug related)– Atrioventricular (AV) block

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Sinus Bradycardia

• (example showing sinus bradycardia)

Rhythm23

Sick Sinus Syndrome

• Sinus arrest

• (example of sinus arrest)

Rhythm24

AV block

• 1st degree (prolonged PR interval)

• (example of 1st degree AV block)

Rhythm25

2nd Degree AV block

• Mobitz type 1 (Wenckebach)

• (Example showing 2nd degree mobitz type 1 block)

Rhythm26

2nd Degree AV block

• Mobitz type 2• (Example showing Mobitz type 2 2:1 AV

block)

Rhythm27

AV Block

• 3rd degree (complete heart block)

• (Example of complete heart block)

Rhythm28

Axis

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Axis

• ‘Mean frontal plane axis’• Determined by vector of dominant

(maximal QRS deflection)• Normal: -30 to 90 degrees• Left deviation -90 to -30 degrees• Right deviation 90 to 180 degrees

Axis30

Axis

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• (diagram explaining axis alongside normal ECG)

Axis

• Check leads I and II• If the complexes are both positive: normal• If the complexes ‘Leave’ each other: Left• If the complexes ’Reach’ each other: Right

Axis32

QRS abnormalities

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QRS complexes

• Wide? (> 110ms) – Suggests either rhythm arising below AV node or– Conduction delay down bundle of his

QRS abnormalities34

Left bundle branch block

QRS abnormalities35

• (diagrams of LBBB and diagram of leads V1 and V6)

Right bundle branch block

QRS abnormalities36

• (diagrams of LBBB and diagram of leads V1 and V6)

Left/right bundle

WiliaM

MarroW

QRS abnormalities37

• (diagrams of leads V1 and V6)

LVH/RVH

• LVH Criteria:– S wave in V1 + tallest R wave in V5 >35mm– Many other criteria – Caution when LBBB present

• RVH criteria:– Dominant R wave (>6mm) V1– Deep S wave >10mm V5 or >3mm V6

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Ischaemia

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Ischaemic territories

Ischaemia40

(Illustrated example showing ischaemic territories)

Chronic ischaemia/ Q waves

• Normal in aVR/V1• > ½ small square wide and 1 small square

tall

(example of q wave)

Ischaemia41

Acute ischaemia

• T wave inversion

(example of t wave inversion)

Ischaemia42

ST depression/elevation

• Describe how far J point is depressed/elevated from isoelectric line

• (diagram of j point)

Ischaemia43

Acute ischaemia

• ST depression(example of ST depression)

Ischaemia44

Acute ST elevation

Ischaemia45

• (example of acute ST elevation)

Miscellaneous Abnormalities

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Digoxin effect

Miscellaneous abnormalities47

• (example of digoxin effect)

QT prolongation

• May be acquired or inherited• (ECG of QT prolongation)

Miscellaneous abnormalities48

Hypokalaemia

Miscellaneous abnormalities49

• (example of hypokalaemia)

Hyperkalaemia

Miscellaneous abnormalities50

• (example of hyperkalaemia)

End of session

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