Patient 2—left bundle branch area pacing in hereditary transthyretin cardiac amyloidosis: an integrative pacing and imaging approach. (A-1) Magnetic resonance imaging cine image showing significant atrial septal hypertrophy with a septal thickness of 23 mm, indicating severe cardiac structural remodelling. (A-2) Magnetic resonance imaging demonstrating diffuse late gadolinium enhancement throughout the myocardium, consistent with extensive fibrosis typical of amyloid infiltration. (B) Continuous unipolar pacing electrocardiography tracing showing the transition of QRS morphology during left bundle branch area pacing. Note the progressive posterior shift of the notch and eventual development of an rSr’ pattern indicative of right bundle branch block. (C-1) Pre-implantation 12-lead electrocardiography demonstrating a wide QRS complex with a duration of 172 ms, characteristic of a complete left bundle branch block. (C-2) Intraoperative electrocardiography during threshold testing at unipolar 10 V/0.4 ms showing a V6 R-wave peak time of 90 ms and a V1 R-wave peak time of 122 ms, suggestive of non-selective left bundle branch pacing. (C-3) Intraoperative electrocardiography during threshold testing at unipolar 1 V/0.4 ms indicating a V6 R-wave peak time of 91 ms and a V1 R-wave peak time of 133 ms, with a V6-V1 interpeak of 42 ms, denoting selective left bundle branch pacing. (C-4) Post-implantation electrocardiography with bipolar 3 V/0.4 ms pacing demonstrates anodal capture with a narrowed QRS duration of 132 ms, confirming effective lead placement and pacing. (D) Fluoroscopic left anterior oblique view during the procedure showing the pacing lead deeply implanted within the septum due to the considerable septal thickness, a challenge usually encountered in patients with cardiac amyloidosis. An additional lead in the right ventricle is visible, which is a temporary pacing lead used during the procedure. (E) Post-procedure contrast-enhanced computed tomography verifies the precise placement of the pacing lead tip just beneath the left ventricular endocardium at the targeted site, ensuring optimal pacing lead function. V1RWPT, V1 R-wave peak time; V6RWPT, V6 R-wave peak time.