* '''Chest lead reversals''' lead to inappropriate R wave progression (increase-decrease-increase) and are often easily recognized.
Therefore '''any right axis or small signal in an extremity lead''' should be reason enough to check lead positioning. A previous ECG can be very helpful.
<div style="float:right"> <gallery> Image:cableReversal1.png|Right and left arm lead reversal can be distinguished from the (much rarer) dextrocardia by examination of the precordial R wave progression. Image:cableReversal2.png|Right arm and left leg lead reversal. Lead II now measures the signal between the left and right leg, which is remote from the heart. Image:dextrocardia.jpg|A patient with dextrocardia (and previous inferior myocardial infarction) </gallery> </div>
More specific patterns with every lead reversal:
*right and left arm electrodes:
It is possible to distinguish lead reversal and [[w:Dextrocardia|dextrocardia]] by watching the precordial leads. Dextrocardia will not show any R wave progression in leads V1-V6, whereas lead reversal will.