Cardiac Resynchronization Therapy (CRT)

• Related:

  • Pacemakers
  • Left Bundle Branch Block
  • Conduction System Pacing

• Cardiac resynchronization therapy (CRT) response is dependent on >90% biventricular pacing.

  • The mortality benefit associated with CRT has been shown to be steeply dependent on a ventricular pacing percentage that is near 100%.

![[Cardiac Resynchronization Therapy CRT-1747237188375.webp]]

CRT Non-response

• Preimplantation causes of CRT nonresponse include non–LBBB native conduction or a relatively narrow native QRS.
  • recall this was part of the impetus for development of the Strauss criteria for complete LBBB
• Loss of LV lead capture
  • When the LV threshold has changed from implantation, LV noncapture may be correctible by ↑ the LV stimulation output or selecting an alternate stimulation vector.
• Poor LV lead position
• Diminished pacing
  • AFib with rapid conduction,
  • inappropriate device programming, and
  • frequent ventricular ectopy, e.g. PVCs
    • In a prospective database of CRT implantation, 10% of the patients with a lack of CRT response had frequent PVCs. PVC ablation in this group restored CRT response in two-thirds of the patients who underwent a successful PVC ablation.
  • excessive LV scar burden