Senesael E, et al. - Researchers examined 321 patients (33% female, age 74 ± 11 years) diagnosed with incomplete left bundle branch block (iLBBB) between July 2013 and April 2018 for their profile and outcome. Further, they sought for the risk of progression to complete left bundle branch block (cLBBB) in these patients. During the follow-up of 21 (8;34) months, the evolution of iLBBB patients to non-strict cLBBB was noted in 33% and to strict cLBBB in 27%. Among iLBBB patients, those who were older, had more frequently reduced left ventricular ejection fraction, and had more often QRS notching/slurring in the lateral leads and inferior leads, showed higher likelihood to evolve to non-strict or strict cLBBB. The strongest predictor for progression toward cLBBB was the presence of QRS notching/slurring in the lateral leads during iLBBB.