1. Generation and reading of the 12 lead ECG
AWC Chow

2. The 12 lead ECG Advantages Common clinical tool
Independent marker of cardiac disease
Non-invasive
Rapid information acquisition
Cheap
Gold standard for arrhythmia management

3. The 12 lead ECG Disadvantages Average of potentials Limited resolution
Snapshot of activity
Electrical and not haemodynamic data

5. Non-specialised atrial tissue
Left bundle
Anterior superior fascicle
Right bundle
Posterior inferior fascicle

6. -
+/- +

7. History of the ECG
1842 -Carlo Matteucci shows that an electric current accompanies each heart beat.
Sanderson and Page record the heart's electrical current with a capillary electrometer
British physiologist Augustus D. Waller publishes the first human electrocardiogram.
Einthoven develops the string galvometer
1910 – Eithoven’s triangle

8. Theoretical consideration
Myocytes have a resting potential
Transmembrane flux create voltage difference - activation
Cellular coupling cause rapid deploarisation
Ionic flux seen ECG deflections

9. Theoretical considerations
Resting state - no potential/field change
Depolarisation - boundary potential change
Represented as a dipole/vector
Restitution of polarity: repolarisation

10. Theoretical considerations
Greater muscle mass
Larger potential change
Larger voltage changes of ECG
Direction of activation dependent on
Site of initiation
Specialised conduction system distribution
Anatomical considerations
Barriers (scar, valves)
Muscle mass

11. RA LA I II
III RL LL

12. aVR +210
aVL -30
I 0
II +60
III +120
aVF +90

13. PR T P QT
QRS

14. Diagnostic criteria for LVH
There are many different criteria for LVH.
Sokolow + Lyon (Am Heart J, 1949;37:161)
S V1+ R V5 or V6 > 35 mm
Cornell criteria (Circulation, 1987;3: )
SV3 + R avl > 28 mm in men
SV3 + R avl > 20 mm in women
Framingham criteria (Circulation,1990; 81: )
R avl > 11mm, R V4-6 > 25mm
S V1-3 > 25 mm, S V1 or V2 +
R V5 or V6 > 35 mm, R I + S III > 25 mm
Romhilt + Estes (Am Heart J, 1986:75:752-58)
Point score system

15. Causes of RBBB normal finding in children and tall thin adults
right ventricular hypertrophy
chronic lung disease even without pulmonary hypertension
anterolateral myocardial infarction
left posterior hemiblock
pulmonary embolus
Wolff-Parkinson-White syndrome - left sided accessory pathway
atrial septal defect
ventricular septal defect

16. Causes of LBBB left anterior hemiblock
Q waves of inferior myocardial infarction
artificial cardiac pacing
emphysema
hyperkalaemia
Wolff-Parkinson-White syndrome - right sided accessory pathway
tricuspid atresia
ostium primum ASD

17. ECG Analysis Rate 60-100b/min Rhythm SR PR <200ms QRS <120ms
Axis to +120
QT interval <500ms
ST segment