• Normal and Abnormal Heart Axis
• ECG and Extreme Axis Deviation
• Causes of Extreme Axis Deviation

Normal and Abnormal Heart Axis

• Normal (intermediate) heart axis vector points between -30° and +90° (yellow)
• Right Axis Deviation vector points between +90° and +180° (green)
• Left Axis Deviation vector points between -30° and -90° (red)
• Extreme Axis Deviation vector points between -90° and +180° (blue)

Normal (intermediate) Heart Axis

• If positive leads (I, aVF)
• Then the vector points to the lower left quadrant (0° to 90°) and the axis is normal
• If Lead I is positive and aVF is negative
• Then the vector points to the upper left quadrant (0° to -90°)
• Lead aVL (-30°) is the boundary
• between normal axis and left axis deviation
• Lead II is perpendicular to lead aVL
• According to biphasic QRS in lead II, it is determined whether it is a normal axis or left axis deviation

Causes of Extreme Axis Deviation

• Ventricular Tachycardia
• Hyperkalemia
• Severe Right Ventricular Hypertrophy

Extreme Axis Deviation

• Extreme Axis Deviation
• Lower leads (II, III, aVF) are negative
• Hyperkalemia (7.2 mmol/l)
• Tall, peaked T waves
• Resemble the Eiffel Tower
• Consider hyperkalemia whenever T waves are higher than R waves (leads V1-4, II, III, aVR, aVF)
• Wide QRS complexes (0.28s)
• AV Block I Degree
• After correcting hyperkalemia, the ECG normalized to sinus rhythm