ECG basics- the normal ECG

Question 1

Normal sinus rhythm and what we’d expect to see

Answer 1

• 60-100
  -regular
  -contain P wave (atria depolarisation, contraction)
  -QRS complex (ventricle depolarisation, contraction)
  -PR interval- start of P wave to start QRS complex
  -PR segment- end of P wave to start QRS
  -J point- end of S wave, helps identify ST elevation
  -ST segment- between S and T wave
  -T wave- ventricular repolarisation

Question 2

Normal intervals

Answer 2

PR interval
-0.12- 0.2 secs, 3-5 small squares
QRS complex
-less than 0.12 seconds, 3 small squares
QT interval (start of QRS to end of T)
-males= 440ms
-females= 460ms

Question 3

What is the isoelectric line

Answer 3

-flat line, where you measure the positive or negative deflections from

Question 4

Wave definitions

Answer 4

P Wave – Low amplitude wave, usually positive, precedes QRS
complex
QRS Complex:
-Q Wave – Negative deflection, not after a positive deflection (apart from P wave)
-R Wave – Positive deflection
-S Wave – Negative deflection, following a positive deflection
T Wave – Broad wave, following QRS complex, may be positive or
negative (depending on lead