Right bundle branch block with right upper quadrant axis


ECG shows rsR’ pattern in V1, rS pattern in I, aVL and V6 – all features of right bundle branch block (RBBB). The amplitude of r waves in lateral leads are quite low. QRS width is a little more than 120 ms. The QRS axis in the North West region (right upper quadrant), which can mean either extreme right axis or extreme left axis deviation. rS pattern is seen both in inferior leads and in lateral leads. Hence it is rather difficult to say whether it is left anterior hemiblock (LAHB) or left posterior hemiblock (LPHB) which is associated with the RBBB. PR interval is normal. Hence it can be considered as bifascicular block. QRS pattern in chest leads show a clockwise rotation with S waves persisting up to V6. The slurred R’ in V1 and slurred S waves in lateral leads suggest delayed activation of the right ventricular myocardium which proceeds by conduction through the myocardium rather than through the specialized conduction system of the heart.