4.3.2 ECG

Question 1

How is ECG recorded?

Answer 1

Electrodes attached to patient with wires to machine (3 real, 1 earth)

Comparison between points

Question 2

What gives rise to electrical signals recorded?

Answer 2

Pattern of depolaristaion and repolarisation of heart > regular detectable differences between points on skin surface

Question 3

What info is derived from ECG?

Answer 3

Rate, rhythm, nature of cardiac depolarisation and repolarisation

Question 4

How is ECG interpreted?

Answer 4

Depolarisation of atria = P wave
Depolarisation of septae = flat, start of Q
Ventricular depolarisation = R
End of ventricular depolarisation = S
contraction = T wave

Question 5

Not a P for every QRS

Answer 5

Ventricular depolarisation not proceeded by normal atrial depolarisation
- premature complexes
- sinus arrest with escape complexes
- no organised atrial depolarisation

Question 6

Atrial fibrilation

Answer 6

Enlarged atria with multiple waves of depolarisation spreading disorganisedly

Question 7

No QRS after P wave

Answer 7

Failure of Av conduction
- second degree AV block
- third degree AV block

Question 8

Differentiate origin sites of complexes

Answer 8

Ventricular origin:
- wide and bizarre
- AV dissociation, no P waves

Supraventricular origin:
- narrow upright QRS