How To determine the Mean Electrical Axis in ECG?????? Simple isn't it!!!

Electrical axis...

  • Mean direction of the QRS complex in the frontal plane towards which the QRS complex is predominately
  • Since by definition it is calculated in frontal plane only, therefore MEAN ELECTRICAL AXIS is calculated
 only from the frontal or Limb leads.
Mean QRS Axis Calculation
  • the mean QRS axis is oriented at right angles (90°) to any lead showing a bi-phasic complex
  • the mean QRS axis points midway between any two leads that show tall R waves of equal height
This program demonstrates changes in the frontal surface leads with shifts in the cardiac axis .

Calculation of frontal plane axis : If the QRS complex is positive in leads I and II, it falls between -30 and 90°
 and is normal, as indicated by the yellow area. If the QRS complex is negative in I and positive in aVF, 
there is right axis deviation. If the QRS complex is positive in I and negative in II, there is left axis deviation.
 If the QRS complex is negative in I and aVF, there is extreme axis deviation.

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