Electrocardiogram

Calibration: 1.0 mV vertical box inscription (standard = 10 mm)
Heart rate calculation methods (choose one)
- Regular or irregular rhythm: (Number of QRS complexes in 10-second rhythm strip)*6
- Regular rhythm
  - Rate = 60/RR interval
  - Example when RR interval is one large box (0.2 seconds): 60/0.2 = 300 BPM
- Regular rhythm: Estimation per number of large boxes
  - 1 large box = 300 beats/min (duration = 0.2 sec)
  - 2 large boxes = 150 beats/min (duration = 0.4 sec)
  - 3 large boxes = 100 beats/min (duration = 0.6 sec)
  - 4 large boxes = 75 beats/min (duration = 0.8 sec)
  - 5 large boxes = 60 beats/min (duration = 1.0 sec)
Rhythm
- All QRS complexes preceded by normal P
- No ectopy, i.e. no early beats
Morphology
- PR interval 0.1 to 0.2 seconds (1/2 to 1 large box) and followed by QRS
- QRS
  - Axis: Upright in BOTH lead I and aVF (-30 to +100)
  - Interval < 0.12 ms (3 small boxes)
- QT interval < 440 ms (2 large boxes)
Hypertrophy: No RAD or LAD
- R wave < 35 mm in V5 or V6 + SV1 or V2
- R aVL < 11 mm
Infarction: No Q-waves
Repolarization
- Frontal: T upright where QRS upright
- Precordial: T always upright in V4-V6
- QT < 50% RR interval