Macroreentrant scar-mediated atrial tachycardia terminated by a nonpropagated stimulus within a narrow diastolic isthmus: Electroanatomic correlation

  • Reginald T. Ho
    Address reprint requests and correspondence: Dr Reginald T. Ho, Department of Medicine, Division of Cardiology, Thomas Jefferson University Hospital, 925 Chestnut St, Mezzanine Level, Philadelphia, PA 19107.
    Department of Medicine, Division of Cardiology, Thomas Jefferson University Hospital, Philadelphia, Pennsylvania
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Published:October 27, 2022DOI:
      A 76-year-old woman with coronary artery disease status post coronary artery bypass grafting and paroxysmal atrial fibrillation and flutter status post cavotricuspid isthmus ablation underwent radiofrequency (RF) ablation of recurrent, symptomatic atrial tachycardia (AT) (cycle length [CL] 378 ms). High-density activation mapping using a Biosense Webster (Diamond Bar, CA) PentaRay® catheter revealed a macroreentrant circuit rotating clockwise (right anterior oblique, caudal view) along the right atrial free wall and conducting slowly through a narrow isthmus (zigzag line) (Figure 1A). With the PentaRay splines straddling the isthmus, a low-amplitude, highly fractionated, 93-ms mid-diastolic electrogram (EGM) was recorded in the isthmus (Penta 3,4) bounded by nonconducting (electrically silent; Penta 1, 2, 5, 7–9) and poorly conducting (2:1 activation; Penta 6) scar (gray) (Figure 1B). Burst pacing (350 ms) was delivered from the isthmus (blue tag, Penta 3) in an attempt to entrain tachycardia, the first stimulus of which terminated AT without global capture. Subsequent pacing stimuli captured the atrium with long stimulus (St)-P interval (172 ms, arrows) identical to the EGM-P interval and identical paced and AT activation sequence and P-wave morphology. A corresponding voltage map is shown in Supplemental Figure 1. After termination, AT could not be induced. Therefore, RF energy was delivered to this site but also linearly connecting the tricuspid valve to the scar (anteriorly) and the scar to the inferior vena cava (inferiorly) to disrupt other potential AT circuits in the region.
      Figure thumbnail gr1
      Figure 1A: High-density activation mapping. B: Electrogram. CS = coronary sinus; IVC = inferior vena cava; SVC = superior vena cava; TV = tricuspid valve.


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