Avoid It or Reach It? The Cardiac Conduction Axis as a Common yet Divergent Determinant of Patient Outcomes in Transcatheter Aortic Valve Replacement and Conduction-System Pacing.

Transcatheter aortic valve replacement (TAVR)-related conduction injury and the benefit of conduction-system pacing (CSP) are usually considered in isolation, despite depending on one structure: the His-Purkinje axis crossing the basal interventricular septum. We argue that implant position relative to that axis is the dominant modifiable determinant of outcome in both. In TAVR, pacemaker rates remain near 16% in contemporary multicenter practice, while single-center strategies interpreting depth against membranous septum length have reached 3-5%; the odds of pacing rise 25% per millimeter of implantation below the estimated His bundle. In CSP, capture is categorical; beyond that threshold, each millimeter closer to the left bundle branch origin adds a 0.25% absolute gain in ejection fraction, and each millimeter closer to the left ventricular endocardium 0.63%, chiefly in patients with depressed baseline function. Reconstruction of the axis from routine cardiac computed tomography has entered clinical evaluation.