If the limb lead that was supposed to be attached to the right arm is put on the left arm and vise-versa, a characteristic appearance will be seen on ECG that includes:
Predominantly negative P wave, QRS complex, and T wave in lead I
Predominantly upward P wave, QRS complex, and T wave in aVR
This is the opposite that is seen in a normal ECG. The above findings are similar to that seen in a person with dextrocardia, however if the heart is located in the right side of the chest instead of the left, the voltage in leads V3-V6 will be very low. This would not be seen in simple limb lead reversal.
1. Surawicz B et al. ACC/AHA recommendations for the standardization and interpretation of the electrocardiogram. Circulation. 2009;119:e235-240.
2. Chou's Electrocardiography in Clinical Practice: Adult and Pediatric, 6e
By Steven Lome