Normal ECG

The normal ECG has the following characteristics

• Regular rhythm (<10% variation at RR intervals)

• Heart rate of 60-100 bpm

• P waves originating in the sinus node

  • Upright in I, II, aVF, and V2-V6 (best seen in II)

  • Inverted in aVR

  • Variable in III, and aVL

• PR interval between 120-200 msec

• QRS duration of 60-110 msec

• QRS Axis of -30° to 90°

• No pathologic Q waves

• Isoelectric ST segments

• Normal T Waves

  • Height <2/3 the size of the preceding R Wave

  • In the same direction of the predominant QRS deflection

• Corrected QT interval:

  • 390-450 msec (men)

  • 390-460 msec (women)