Last week, a colleague told me he didn’t use the term “incomplete” or “partial” right bundle branch block (RBBB).He is probably correct, but nevertheless, it is established in the literature as an rSr’ pattern in V1/V2 with a QRS of 100 -120 ms. I wrote a memo on this some time back and it is time for a revisit.Here is such an ECG:

It really is not much different from this one with a QRS of <0.10 sec which is clearly normal.

The report for this latter ECG said incomplete right bundle branch block and the GP asked for guidance on what investigations should be done.I decided to look at a bunch of ECGs with RSR’ patterns.

Although there is a tendency toward more prominent R waves, the changes are subtle across the “incomplete RBBB spectrum”.The question is whether any of these patterns are really abnormal and should we forget the terminology and just call them all normal?Even the ECG interpretive algorithms get confused:

Occasionally we still see the term “complete RBBB”. This should never be used, as the next day the QRS may be wider still and is therefore “more complete RBBB”.The association between RBBB and right ventricular hypertrophy has always troubled me. I was taught by the doyens of ECG interpretation, that the diagnosis depends on deep T wave inversion from V1 to V3 as well as an rsR’ pattern.

But is this correct?Don’t forget myocardial ischaemia or even left ventricular hypertrophy.In the days before echocardiography, we used to stress the importance of a RBBB with atrial septal defects.These days the resting 12-lead ECG is not much use, as we have better tools.However, there is a subtle sign seen on the ECG, called the Crochetage sign and named because of its similarity to a crochet hook.

There is a tiny notch in the inferior leads and often in more than one lead. In this case, the notch is quite prominent.The larger the shunt the more likely the notch will be present. It is usually high on the R wave and may disappear if the shunt is closed. It has also been reported with patent foramen ovale and therefore is worth looking for in patients with cryptogenic stroke.So, what about incomplete right bundle branch block?If you want to use the term, make sure the QRS is 100 to 120 ms and there is an rSr’ pattern. I prefer to also say the ECG is normal!If it is normal, report it as normal!Harry Mond