Slowly conducting anatomic isthmuses of tetralogy of Fallot: An opportunity for "prophylactic" ventricular tachycardia ablation

Bryce V Johnson; Mark Sonderman; Matthew J Magoon; Andrew Pistner; Bishoy Hanna; Graham H Bevan; Rosemary McDonagh; Patrick M Boyle; Melissa R Robinson; Nazem Akoum; Neal A Chatterjee; Eric V Krieger; Babak Nazer

doi:10.1016/j.hrthm.2024.10.073

Slowly conducting anatomic isthmuses of tetralogy of Fallot: An opportunity for "prophylactic" ventricular tachycardia ablation

Heart Rhythm. 2024 Nov 17:S1547-5271(24)03539-2. doi: 10.1016/j.hrthm.2024.10.073. Online ahead of print.

Affiliations

¹ Division of Cardiology, University of Washington Medical Center, Seattle, Washington.
² Department of Bioengineering, University of Washington Medical Center, Seattle, Washington.
³ Biosense Webster International, Irvine, California.
⁴ Providence Heart Institute at St Patrick's Hospital, Missoula, Montana.
⁵ Division of Cardiology, University of Washington Medical Center, Seattle, Washington. Electronic address: bnazer@uw.edu.

PMID: 39561932
DOI: 10.1016/j.hrthm.2024.10.073

Abstract

Background: Patients with repaired tetralogy of Fallot are at risk of ventricular tachycardia (VT) and sudden cardiac death. Most VTs arise from 5 slowly conducting anatomic isthmuses (SCAIs; conduction velocity ≤0.5 m/s) bound by the right ventriculotomy, ventricular septal defect patch, and tricuspid and pulmonic valves. Historically, risk stratification electrophysiologic studies involved programmed ventricular stimulation with VT induction guiding implantable cardioverter-defibrillator (ICD) implantation or VT ablation.

Objective: This study aimed to evaluate a "prophylactic" strategy of ablating SCAIs even in the absence of inducible VT to reduce ICD implantation and arrhythmic events and to compare this with the "historical" strategy.

Methods: This was a single-center, retrospective cohort study. The historical cohort underwent programmed ventricular stimulation to guide ICD implantation or VT ablation. The prophylactic cohort underwent right ventricular electroanatomic mapping and ablation of SCAIs. A composite end point of arrhythmic death, cardiac arrest, sustained VT, and ICD complication was compared between the cohorts.

Results: Ninety-two patients with repaired tetralogy of Fallot had risk stratification electrophysiologic studies. Of 57 prophylactic patients, SCAIs were identified or ablated in 33 (58%), 16 (28%) had inducible VT before ablation, and 1 received ICD. Of 35 historical patients, 15 (43%) had inducible VT; 3 had cryoablation during pulmonic valve replacement and 11 received ICDs. No prophylactic patients met the composite end point during a median 21 months (interquartile range, 8-35 months) vs 10 (29%) historical patients during a median 125 months (interquartile range, 90-142 months; P = .017). There were no ablation-related complications.

Conclusion: Prophylactic SCAI ablation is associated with fewer ICD implantations and a reduction in incident arrhythmic events without ablation-related complications.

Keywords: Ablation; Arrhythmia prevention; Sudden death; Tetralogy of Fallot; Ventricular tachycardia.