ECG axis

ECG Axis

Limb and augmented leads

Precordial leads

Normal Axis

• -30°→90°
• Dominant QRS direction (positive or negative) can be used to approximate axis
  • Normal axis if positive QRS in leads I and aVF

Right Axis Deviation

• Causes:
  • Right ventricular hypertrophy
  • Pulmonary hypertension & chronic lung disease
  • COPD
  • Pulmonary embolism
  • Left posterior fascicular block
  • Lateral MI (from Q-waves in lead I)
  • Ventricular ectopy (VT)
  • TCA toxicity, sodium channel blocker toxicity
  • Hyperkalemia
  • Lead misplacement
  • Dextrocardia
  • Normal thin adults with horizontally positioned hearts

Left Axis Deviation

• Causes:
  • Left anterior fascicular block
  • Left Bundle Branch Block
  • Inferior MI (from Qs)
  • Left Ventricular Hypertrophy
  • Pacer
  • WPW
  • Hyperkalemia
  • Normal variant

See Also

• ECG (Main)

Video

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External Links

• DDxOf: ECG Guide