1. ECGs By Samantha Conroy and Sophie Harris
MedSoc Teaching
presents
ECGs
By Samantha Conroy and Sophie Harris

2. Normal Waveform

3. Normal Waveform Timings

4. Interpreting an ECG
Check patient is correct Check date and time Check relevant clinical info Check speed and calibration

5. Interpreting an ECG 1) Rate -------------->
2) Rhythm >
3) Axis >
4) P wave >
5) PR interval >
6) QRS complexes-->
7) ST segment >
8) T wave >
Rutting
Round
Anuses
Pays
PRices
when Qualifying for
Sexually Transmitted
Trachomatis

6. Rate Normal = 60-100 bpm Calculation:
Rhythm
Axis
P wave PR
QRS
ST seg
T wave
Rate
Normal = bpm
Calculation:
300 / number of large squares in R-R interval OR
Number of QRS x 6
(because average strip is a measure of 10s)

7. Work out the rate

8. Rhythm Irregular / Regular? P wave for every QRS complex?
Rate
Rhythm
Axis
P wave PR
QRS
ST seg
T wave
Rhythm
Irregular / Regular?
P wave for every QRS complex?
Sinus rhythm or not?

9. Atrial Fibrillation–different lengths between QRS
Rate
Rhythm
Axis
P wave PR
QRS
ST seg
T wave
Atrial Fibrillation–different lengths between QRS

10. Atrial Flutter – saw-toothed baseline, usually regular QRS
Rate
Rhythm
Axis
P wave PR
QRS
ST seg
T wave
Atrial Flutter – saw-toothed baseline, usually regular QRS
Due to re-entry of depolarisation into the atria
Atrial rate of bpm
Ventricular rate of

11. Axis Average direction of electrical depolarisation
Rate
Rhythm
Axis
P wave PR
QRS
ST seg
T wave
Axis
Average direction of electrical depolarisation
Look at leads I + II (also aVF to check)

12. P wave and PR interval P wave - Irregular / Regular?
Rate
Rhythm
Axis
P wave PR
QRS
ST seg
T wave
P wave and PR interval
P wave - Irregular / Regular?
P wave for every QRS complex?
(sinus rhythm?)
PR interval normal?

13. Short PR Wolff Parkinson White Syndrome Short PR Delta Wave
Rate
Rhythm
Axis
P wave PR
QRS
ST seg
T wave
Short PR
Wolff Parkinson White Syndrome
Short PR
Delta Wave
T inversion

14. Long PR = Heart Block 1st Degree – PR consistently longer than normal
Rate
Rhythm
Axis
P wave PR
QRS
ST seg
T wave
Long PR = Heart Block
1st Degree – PR consistently longer than normal
2nd Degree:
Mobitz Type 1 (Wenckebach) – progressive increase in PR length until there is a missed QRS complex. It then resets this cycle
Mobitz Type 2 – there is a ratio of P waves to QRS complexes (usually 1:1), that is 2:1 or 3:1
Symptomatic type 2 will need a pacemaker.

15. Rate
Rhythm
Axis
P wave PR
QRS
ST seg
T wave
Long PR = Heart Block

16. Random PR 3rd Degree – dissociation between P waves and QRS complexes
Rate
Rhythm
Axis
P wave PR
QRS
ST seg
T wave
Random PR
3rd Degree – dissociation between P waves and QRS complexes
Atria and ventricles have their own rhythms that do not correspond with each other
Is an indication for a pacemaker.

17. Rate
Rhythm
Axis
P wave PR
QRS
ST seg
T wave
Tall QRS complex
Larger bulk of myocardium is depolarising, hence LVH/RVH
Add R height in V1 and V6, if greater than 7 big sq (35 small sq) = hypertrophy.
S wave depth in V1/2 + tallest R wave in V5/6
= LVH (Some Receive Love)
Tallest R wave in V1/2 + deepest S in V5/6
= RVH (Rooney Shags Rio)

18. Rate
Rhythm
Axis
P wave PR
QRS
ST seg
T wave

19. Rate
Rhythm
Axis
P wave PR
QRS
ST seg
T wave
Broad QRS complex
Blockage of depolarisation, that makes the QRS broader (ie takes longer to travel through myocardium)
Left = WiLLiaM
Deep S in V1 (W) and tall R in V6 (M)
Right = MaRRoW
Tall R in V1 (M) and deep S in V6 (W)

20. Rate
Rhythm
Axis
P wave PR
QRS
ST seg
T wave
Left Right

21. ST Elevation Is a full thickness MI (STEMI) Rate Rhythm Axis P wave PR
QRS
ST seg
T wave
ST Elevation
Is a full thickness MI (STEMI)

22. ST Depression
Rate
Rhythm
Axis
P wave PR
QRS
ST seg
T wave
Caused by Ischemia of the myocardium, that can be demonstrated on an exercises tolerance test.
Usually used to determine the severity of angina.
Needs to be >2mm to be significant

23. Topics Not Covered T wave abnormalities Ventricular Tachycardia NSTEMI
Electrolyte Disturbances / Digoxin Toxicity
Pericarditis
Changes during the progression of a STEMI