Clinical Resources

Ischemic VT Reentry Circuit Algorithm

Entrainment-based pacing algorithm to identify catheter position relative to the VT circuit

Key Concepts

  • Concealed fusion: Paced QRS = VT QRS (catheter inside the protected isthmus)
  • Manifest fusion: Paced QRS ≠ VT QRS (catheter outside the circuit)
  • PPI − TCL: Post-pacing interval minus tachycardia cycle length — indicates distance from circuit
  • PPI − TCL <30 ms = within or at entrance/exit of isthmus
  • PPI − TCL >30 ms = bystander or outer loop
  • SA − EGM: Stimulus to electrogram — indicates catheter position in circuit

Reference

Stevenson et al. 1997 (JACC) — Identification of reentry circuit sites during catheter mapping and radiofrequency ablation of ventricular tachycardia late after myocardial infarction