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South Med J. 2013 Aug;106(8):485-9. doi: 10.1097/SMJ.0b013e3182a1456c.

Electrical alternans: a sign, not a diagnosis.

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Cardiology Service, Carl R. Darnall Army Medical Center, Fort Hood, TX 76544, USA.


Electrical alternans is an electrocardiographic phenomenon defined as an alternating amplitude or axis of the QRS complexes in any or all leads. It is most commonly associated with a large pericardial effusion and impending threat of cardiac tamponade; however, a literature review showed that this electrocardiographic finding can be seen in a variety of other clinical scenarios with varying etiologies and prognoses. Several electrocardiogram examples are presented with a brief review of the potential mechanisms and clinical significance and demonstrate that electrical alternans is more correctly considered an electrocardiographic sign, rather than a diagnosis, with a broad differential for potential etiologies. For some causes, the clinical significance is well known, but for others, further research is needed.

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