ECG interpretation

1.       Patient demographics

2.       Rate

3.       Rhythm

4.       Axis

5.       P wave

6.       PR interval

7.       QRS complex

8.       ST segment

9.       T wave

10.   QT interval

• Rate
  • Normal is 60-100bpm
  •  Workout as 300/(large squares b/w QRS complex)

• Rhythm
  • Regular/irregular?
  •  Use piece of paper to compare distance b/w R-R intervals

• Normal is between -30^o and +90^o
•  < -30^o = left axis deviation
•   > +90^o = right angle deviation
•  Between 180^o and -90^o = far RAD or far LAD (“Northwest”)
•  Identifying the axis:
  • Identify most isoelectric lead (i.e. w/ flattest QRS)
  • Axis is at 90^o to this
  • If deflection is positive
• NB quick method – if I and II are positive= normal
  • If “reaching” towards = RAD
  • If “leaning” away = LA

• P wave
  • P wave = atrial depolarisation
• PR interval
  • PR interval = AV delay
  • Normal = 0.12-0.2s
• QRS
  • QRS complex = ventricular depolarisation (down BoH then up PF)
  • Normal <0.12s
• ST segment
  • Time b/w end of depol and start of repol
  • Should be isoelectric
• T wave
  • Ventricular repolarisation
  • Normal to be inverted in aVR, V1, sometimes V2
• QT interval
  • From beginning of QRS to end of T wave
  • Normal is 0.38-0.42s