The Upside Down ECG

Figures 1 and 2 are from a normal control. The tracing is normal in 1 and the leads reversed in 2 so that the arm leads are now on the feet and the leg leads are attached to the arms. Lead I looks at the legs and not the arms and its isoelectric appearance not surprising.I see about two examples of this per month.If you don’t, then you are not looking hard enough!

Figure 3 is a comparison of the lead positions with the classical features listed below.

The ECG should be repeated as important pathology may be missed. For example, the rhythm in figure 4 puzzled us and we eventually went with a supraventricular tachycardia, despite a consistent irregularity and possible p waves in V6. The isoelectric lead I made us ask for a repeat (figure 5). The P waves now emerge and the diagnosis is sinus tachycardia and atrial ectopics

Assoc Prof Harry Mond