ECG Underwriting Puzzler Presented by: William Rooney, M.D.

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What is the major abnormality on this ECG? QUESTION???? What is the major abnormality on this ECG? ECG #1

Would it help if you discovered the ECG below had been done on the same person 1 week later?

The two ECG’s obtained one week apart are completely different in appearance. Let’s look at ECG #1 again. Notice that the ECG was obtained at ½ standard (5 mm/mV) ECG’s are frequently recorded at ½ standard when there is excessive amplitude in the QRS complexes (frequently seen in LVH for instance) However, I don’t see this concern on ECG #1. The voltages all appear relatively normal. Changing the voltage to ½ standard is frowned upon when the change is not required so I would consider this a mistake by the technician. As a general rule of thumb when I see one “mistake” like this I frequently keep my eye out for others. It can save you from making mistakes in interpretation by remembering this strategy.

Let’s enlarge part of this lead to make the point Another clue to a another technical mistake on this ECG is found when reviewing lead II Let’s enlarge part of this lead to make the point Notice that both the p waves and the t waves are inverted. This is a clue that the RA and the LL electrode cables have been switched Notice that lead II in ECG #2 appears normal—Here is a small segment from ECG #2

The question you might ask at this point is whether the ECG is still interpretable and if so, how would you interpret it With RA and LL electrode cable reversal the following applies: Lead I Actually is lead III when inverted upside down Lead II Actually is lead II inverted upside down Lead III Actually is lead I inverted upside down Lead aVR Actually is lead aVF Lead aVL Unchanged…is aVL Lead aVF Actually is lead aVR

ECG Puzzler Solved—It is a technical problem In summary there are two technical problems with ECG #1 The ECG is recorded at ½ standard (5 mm/mV)!! The RA and LL electrode cables were switched!! You can make the modifications to the ECG in your mind per the table on the previous slide and say when accounting for these technical problems the ECG is WNL or you could have the ECG repeated like in this case. Either way you will end up with the same conclusion--the ECG is WNL. This concludes this issue’s ECG Puzzler. Contact me if you have questions!