If the left and right arm electrodes are accidentally swapped over, Lead I will be completely upside down, aVR & aVL will be switched, and II & III will be switched. The easiest of these signs to see is the inverted lead I. The chest leads will not be affected. This error can look similar to dextrocardia, but the difference is that with dextrocardia the chest leads are not normal.See also: Electrode misplacement
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