The Kaplan–Meier survival curves for the combined endpoint of all-cause mortality/hospital admission for heart failure in patients with and without QRS narrowing. LBBB QRS denotes patients with left bundle branch block; ALL QRS denotes whole studied cohort; non-LBBB denotes patients with remaining native QRS morphologies; RV-paced denotes patients with permanent right ventricular pacing; Yes/No denotes groups with and without acute QRS narrowing. LBBB, left bundle branch block; RV, right ventricle.