Aims: Transcatheter aortic valve implantation (TAVI) is frequently complicated by new left bundle branch block (LBBB). We investigated the development and persistence of LBBB during follow-up and its clinical consequences. Methods and results: ECGs at baseline, within 24 hours, before discharge and at 12 months after TAVI were assessed in 476 patients without pre-existing LBBB and/or pacemaker before or after TAVI. TAVI-induced new LBBB was categorised based on the timing of the occurrence (within 24 hours [acute], after 24 hours but before discharge [subacute], and after discharge [late]), in addition to persistence (transient or persistent). A total of 175 patients (36.8%) developed new LBBB of which 85.7% occurred within 24 hours after TAVI, 12.0% before and 2.3% after hospital discharge, and was persistent in 111 patients (63.4%). Implantation of the Medtronic CoreValve System (MCS) more frequently led to new LBBB than the balloon-expandable Edwards SAPIEN valve (ES) (53.8% versus 21.7%) with less recovery during follow-up (39.0% versus 9.5%). Late new LBBB was only seen in four patients (0.8%). During a median follow-up of 915 (578-1,234) days, persistent LBBB was associated with a significant increase in mortality as compared to no LBBB and temporary LBBB combined (hazard ratio 1.49, 95% confidence interval, 1.10-2.03; p=0.01). Conclusions: TAVI-induced new LBBB occurs in almost 40% of patients, almost all before hospital discharge. It occurs three times more frequently after MCS than after ES valve implantation and has a twofold lower tendency to resolve during follow-up. Persistent LBBB is associated with a higher mortality.