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Left axis deviation – Quick Plot

Use ECG paper

• Lead I plots along horizontal axis: 0 degrees
• Lead aVF plots along vertical axis: +90 degrees
• Draw 45 degree guide(s)
• Plot perpendiculars to algebraic vector sums (red)
• Draw mean electrical axis (black arrow)

Result

• Mean QRS axis measures about -70 degrees
• Computerized readout was -67 degrees