Right Bundle Branch Block - ECG
Right bundle branch block (RBBB) is a relatively common finding. In ECG we find the most important changes in lead V1. Its QRS complex is deformed and its largest amplitude points in the upper direction and the QRS often has a split shape resembling the letter “M”. In addition, the lead V1 usually contains a negative T wave. Negative T wave accompanied by a deep S wave in the QRS may also be found in V6 lead. The QRS in lead V6 may have (but not always) the form of a letter “W”. The QRS complexes are typically dilated to more than 100ms.
Note: We distinguish the complete and incomplete RBBB. The complete block has a QRS width above 120 ms and the second positive R wave is greater than the first in V1 lead.
This ECG shows signs of a complete RBBB. In V1, we see the positive second R wave and negative T wave (red). In lead V6, there is a relatively deep and broad S wave (blue). QRS complex is wider than 120ms. This is my own ECG record showing the signs of incomplete RBBB (iRBBB). The QRS complex in V1 has two R waves (red), but the second is not higher than the first. In addition, we see a negative T in V1. In V6 we can talk about a little bit larger S wave in the QRS complex (blue) but we need a little imagination for that in this case. The total width of QRS is certainly less than 120ms.
Conclusion: Right bundle branch block (especially incomplete) may have no clinical significance and it may be randomly found even in completely healthy individuals. However, it is also present in various pathologies. When there is a newly developed RBBB together with chest pain and sudden shortness of breath, it is especially suspicious of an acute pulmonary embolism.