Lesson plan
Right axis deviation
The electrical axis of the heart is the net direction in which the wave of depolarization travels. It is measured using an electrocardiogram (ECG). Normally, this begins at the sinoatrial node (SA node); from here the wave of depolarisation travels down to the apex of the heart. The hexaxial reference system can be used to visualise the directions in which the depolarisation wave may travel. On a hexaxial diagram (see figure 1): * If the electrical axis falls between the values of -30° and +90° this is considered normal. * If the electrical axis is between -30° and -90° this is considered left axis deviation. * If the electrical axis is between +90° and +180° this is considered right axis deviation (RAD). RAD is an ECG finding that arises either as an anatomically normal variant or an indicator of underlying pathology.
Article summary
The electrical axis of the heart is the net direction in which the wave of depolarization travels. It is measured using an electrocardiogram (ECG). Normally, this begins at the sinoatrial node (SA node); from here the wave of depolarisation travels down to the apex of the heart. The hexaxial reference system can be used to visualise the directions in which the depolarisation wave may travel. On a hexaxial diagram (see figure 1): * If the electrical axis falls between the values of -30° and +90° this is considered normal. * If the electrical axis is between -30° and -90° this is considered left axis deviation. * If the electrical axis is between +90° and +180° this is considered right axis deviation (RAD). RAD is an ECG finding that arises either as an anatomically normal variant or an indicator of underlying pathology.
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Discussion questions
- Summarise the article in your own words. Which single claim would you verify first, and why?
- Which claim in this article is most likely to be revised as the sources update? How would you check its current status?
- If two sources disagreed about one of these facts, what would you need in order to trust one over the other?
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