1. Introduction to the E.C.G.
E.C.G is Electrocardiograph or electrocardiogram
It can provide evidence to support a diagnosis, but remember…..LOOK AT THE PATIENT NOT JUST THE PAPER
Is essential in the diagnosis of chest pain and abnormal heart rhythms
Is helpful in diagnosing breathlessness

2. The Electricity of the Heart
Any muscle contraction causes an electrical change – depolarisation
These changes can be detected by electrodes on the surface of the body
To ensure recording of only cardiac electrical activity, the patient must be relaxed
Although a four chamber organ, for E.C.G purposes, the heart can be thought of as two, as the atria and ventricles contract together

4. The Electrical Pathway of the Heart
Each electrical discharge starts in the sino-atrial node, located in the right atrium
Then spreads through the atrial muscle fibres
There is a delay while depolarisation spreads through the atrio-ventricular node
Then along single carriageway Bundle of His along to parallel carriageways of the Right and Left Bundle Branches
Left Bundle Branch carriageway divides into two and conduction spreads through specialised Purkinje fibres
Normal heart rate is called sinus rhythm and implies that the electrical activity has commenced in the SA node

5. The Shape of the ECG
Atrial muscle mass is smaller compared with the ventricles – so the is the electrical charge
Atrial contraction is the P wave
Ventricular muscle mass is larger and creates a bigger deflection on the ECG
This is represented by the QRS complex
T wave represents repolarisation – the ventricular muscle mass returning to a resting state
P,Q,R & S are waves, Q,R & S make up a complex, interval between S and T is called the ST segment

7. ECG Recording
ECG machines record electrical activity on moving paper – the speed and the squared paper is standardised
Each large (5mm) square represents 0.2 sec, so 5 large squares per second
1 QRS per 5 squares means a pulse of 60 beats per minute
PR interval should be 3 – 5 small squares
QRS is usually 3 small squares – any abnormally long conduction shows as a widened QRS complex

9. Recording an ECG
12 lead means 12 different “electrical pictures”; does not refer to wires that connect patient to machine
Good skin contact is essential (chest shaving may be required)
One electrode on each limb, and one that is positioned in 6 different places on the chest (or has 6 “terminals”)
Electrodes labelled Left Arm, Right Arm, Left Leg and Right Leg, plus chest 1 to 6

10. Electrode Placement
Lead V1 is placed over the 4th intercostal space, to the right of the sternum
Lead V2 is placed over the 4th intercostal space, to the left of the sternum
Lead V4 is placed over the 5th intercostal space in the mid-clavicular line
Lead V3 is placed midway between V2 and V4
Lead V5 is placed on the same horizontal level as V4 but at the anterior axilliary line
Lead V6 is placed on the same horizontal level as V4 and V5 but on the mid axilliary line

12. The Shape of the QRS Complex
Normal hearts have more muscle in left ventricle compared to right
QRS complex represents ventricular activity and is normally the largest deflection
Information can be gathered from looking at rhythm strips

13. Layout of the ECG
12 views are represented and the segments are labelled I,II, III, aVR, aVL, and aVF.
Most machines display each view horizontally, and vertically across the page
A rhythm strip is included at the end to enable the reader to determine rate and regularity of heart rhythm

14. Normal ECG A normal ECG will contain regular complexes
Each complex will be made up of a P wave, swiftly followed by a QRS
The QRS should be pointed
The complexes should be of uniform appearance

15. Normal ECG

16. Abnormal ECG

17. Abnormal ECG

18. Left Bundle Branch Block

19. Acute ST Depression

20. Acute ST Elevation Inferior MI

21. Acute ST Elevation Posterior MI

22. Atrial Flutter

23. Atrial Fibrillation

25. Ventricular Fibrillation

26. You Have Now Finished the Learning
Please click the ‘Test’ icon in the left column. You may need to maximise the column by clicking the top left icon.
Remember to click the ‘Home’ icon when you finish the Test to save your results