An Optical Illusion

Report:

Sinus tachycardia 116/min

First degree AV block

PR 0.40”

Normal axis

Left bundle branch block

QRS 0.125”

Comment:

This is one of the traces I originally misreported (as NPJT). One way for any ECG to find its way into this Library is to have been originally misreported, preferably by a Cardiologist! Those misreported by myself provide even greater interest, but less pleasure.

We all tend to underestimate the possibility of really long PR intervals; Marriott devoted an article to this8.

The optical illusion is the apparent negativity immediately after the QRS complex, especially in leads 2 and 3, as well as the pointy upward bits just before the T wave in 1 and aVL. I mistook them all, somehow, for retrograde P waves. As, again, Marriott points out, one needs to be an “expert” to mistake the P wave polarity in this manner9.

Closer scrutiny leads to recognition of normal upright P waves, properly negative in aVR and terminally negative in V1. I only recognised the error by reporting a subsequent ECG, which still had a respectable 1o AV block of 0.30” (Fig 13a) and looking at the appended previous trace.

Fig 13a. Sinus P waves can now be recognised as “bumps” hugging the tail of QRS complexes in the previous trace.

Fig 14. 68 year old woman with ischaemic cardiomyopathy.