* '''Left-right arm reversals''' lead to a negative complex in lead I with a negative P wave in lead I. They are one of the most common causes of right axis deviation on the ECG!
* '''Arm-foot switches''' lead to a very small or 'far field' signal in leads II or III.
* '''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.
Image:cableReversal1.png|Right and left arm lead reversal can be distinguished from the (much rarer) dextrocardia by
looking at 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)