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Aims: Left bundle branch block (LBBB) is induced in approximately one-third of all transcatheter aortic valve implantation (TAVI) procedures. We investigated electrophysiological remodelling in patients with TAVI-induced LBBB.Methods and Results: This retrospective study comprises 107 patients with initially narrow QRS complex of whom 40 did not and 67 did develop persistent LBBB after TAVI. 12-lead electrocardiograms (ECGs) taken before TAVI, within 24 hours ('acute'), and 1-12 months after TAVI ('chronic') were used to reconstruct vectorcardiograms. From these vectorcardiograms, QRS and T-wave area were calculated as comprehensive indices of depolarization and repolarization abnormalities, respectively. TAVI-induced LBBB resulted in significant acute depolarization and repolarization changes while further repolarization changes were observed with longer lasting LBBB. The amount of long-term repolarization changes (remodelling) was highly variable between patients. The change in T-wave area between acute and chronic LBBB ranged from +57% to - 77%. After dividing the LBBB cohort into tertiles based on the change in T-wave area, only baseline QRS area was larger in the tertile with no significant change in T-wave area. During longer lasting LBBB, the spatial vector gradient (SVG) changed orientation towards the direction of the QRS-vector, indicating that later-activated regions developed shorter action potential duration.Conclusion: This study in patients with TAVI-induced LBBB shows that repolarization changes develop within months after onset of LBBB, and that these changes are highly variable between individual patients. [ABSTRACT FROM AUTHOR]