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Axis and Hemiblock Determination

by Max Boswell (Special Credit to Bob Page)

Here is a quick refresher for determining axis deveation and hemiblocks...

Axis: Direction of flow of the impulses in the heart. Hemiblock: Block of one of the fascicles of the left bundle branch The axis can be used to:
  1. Diagnose hemiblocks
  2. Diagnose V-tach
  3. Identify high risk patients for complete heart block or a patient becoming unstable (hemodynamically)

How to determine the axis

Easy trick using the 12 lead: All you have to do is look at the "r" axis number on the 12 lead and correlate it to the chart.

It's always the middle number
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Chart method: Looking at leads I, II, and III and determine the mean QRS deflection. Do they go up, down, or stay in the middle? Then simply refer to the above chart of the correlating numbers.

Here is that handy chart
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Now look at these 12 leads, and give your opinion:

  1. Posterior Hemiblock because the 'r' axis is 132
  2. Anterior Hemiblock because the "r" axis is -49
  3. The rhythm is ventricular in origin
  4. Pathological Left Axis because the QTc is 497