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Close-coupled pacing to identify the "functional" substrate of ventricular tachycardia: Long-term outcomes of the
Derek Crinion1, Victor Neira1, Nasser Al Hamad1
1Heart Rhythm Service, Queen's University, Kingston Health Sciences, Ontario, Canada.
Insights
This study shows that functional substrate ablation is a feasible and effective strategy for ventricular tachycardia (VT), achieving high rates of noninducibility and freedom from VT recurrence.
Area of Science:
- Electrophysiology
- Cardiovascular Medicine
- Interventional Cardiology
Background:
- Macroreentrant ventricular tachycardia (VT) involves critical isthmuses with functional conduction delay and block.
- Close-coupled pacing can reveal functional substrates by stressing myocardial conduction capacity.
- Targeting these functional substrates is an emerging strategy for VT ablation.
Purpose of the Study:
- To evaluate the feasibility and efficacy of a functional substrate ablation strategy for ventricular tachycardia (VT).
Main Methods:
- Recruited patients with scar-related VT undergoing their first ablation.
- Utilized high-density mapping with a closely coupled extrastimulus at the right ventricular apex.
- Identified functional impaired conduction sites by increased electrogram duration, late potentials, and fractionation.
Main Results:
- Achieved noninducibility in 85% of patients (34/40).
- Demonstrated high freedom from VT recurrence (89.7%) during a median follow-up of 711 days.
- Median functional substrate area was 41.9 cm² and was similarly distributed across bipolar voltage zones.
Conclusions:
- Functional substrate ablation is effective in achieving VT noninducibility and freedom from recurrence.
- Mapping times were significantly increased, suggesting a need for optimized techniques.
- Further randomized multicenter trials are recommended to validate this approach for VT ablation.
Background:
The conduction delay and block that compose the critical isthmus of macroreentrant ventricular tachycardia (VT) is partly "functional" in that they only occur at faster cycle lengths. Close-coupled pacing stresses the myocardium's conduction capacity and may reveal late potentials (LPs) and fractionation. Interest has emerged in targeting this functional substrate.
Objective:
The purpose of this study was to assess the feasibility and efficacy of a functional substrate VT ablation strategy.
Methods:
Patients with scar-related VT undergoing their first ablation were recruited. A closely coupled extrastimulus (ventricular effective refractory period + 30 ms) was delivered at the right ventricular apex while mapping with a high-density catheter. Sites of functional impaired conduction exhibited increased electrogram duration due to LPs/fractionation. The time to last deflection was annotated on an electroanatomic map, readily identifying ablation targets.
Results:
A total of 40 patients were recruited (34 [85%] ischemic). Median procedure duration was 330 minutes (interquartile range [IQR] 300-369), and ablation time was 49.4 minutes (IQR 33.8-48.3). Median functional substrate area was 41.9 cm2 (IQR 22.1-73.9). It was similarly distributed across bipolar voltage zones. Noninducibility was achieved in 34 of 40 patients (85%). Median follow-up was 711 days (IQR 255.5-972.8), during which 35 of 39 patients (89.7%) did not have VT recurrence, and 3 of 39 (7.5%) died. Antiarrhythmic drugs were continued in 53.8% (21/39).
Conclusion:
Functional substrate ablation resulted in high rates of noninducibility and freedom from VT. Mapping times were increased considerably. Our findings add to the encouraging trend reported by related techniques. Randomized multicenter trials are warranted to assess this next phase of VT ablation.
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