Overcoming left bundle branch block by permanent His bundle pacing: Evidence of longitudinal dissociation in the His via recordings from a permanent pacing lead

Key Teaching Points•Left bundle branch block or delay can occur within fibers that are predestined to become the left bundle branch in the bundle of His. This is the concept of longitudinal dissociation within the His bundle.•In such cases, permanent His bundle pacing can overcome this delay and normalize the QRS duration.•It is possible in rare and well-mapped cases to demonstrate this intra-Hisian delay during His bundle pacing lead implantation. •Left bundle branch block or delay can occur within fibers that are predestined to become the left bundle branch in the bundle of His. This is the concept of longitudinal dissociation within the His bundle.•In such cases, permanent His bundle pacing can overcome this delay and normalize the QRS duration.•It is possible in rare and well-mapped cases to demonstrate this intra-Hisian delay during His bundle pacing lead implantation.