I recently had a patient sent from the GP surgery with a letter stating ‘widespread t-wave changes ? MI’. I looked at the ECG for a few seconds then realised what was wrong – limb lead reversal. Here is an example (not my patient) of left/right lead swappage There are other ECGs to see at ECG Pedia which show other combinations of lead reversal. Remember to look at the precordial leads too – if the QRS complexes get smaller as you go towards v6, positive QRS in aVR and negative QRS in aVL you could have bagged yourself an ECG in a dextrocardic person 🙂