Kiehl EL, et al. - Researchers conducted this post-hoc analysis to compare clinical results of narrow vs prolonged intra-ventricular conduction on electrocardiogram (ECG) stratified by QRS morphology and cardiovascular disease (CVD) status. Participants in the study were patients with centrally-adjudicated, non-paced baseline ECGs. Duration of QRS was classified as narrow (≤100 ms) vs prolonged (>100 ms) with additional left (LBBB) or right (RBBB) bundle branch block categorization or non-specific intra-ventricular conduction delay (IVCD). Of 24,081 subjects randomized, 22,067 were involved with follow-up 34±13 months. In patients with and at-risk for CVD, left ventricular conduction delay, whether LBBB or L-IVCD, was strongly linked to increased mortality.