Key result
RF ablation lines connecting pacing-defined electrically unexcitable scar regions abolished inducible VT in 71% of patients and reduced spontaneous VT from 142 to 0.9 episodes/month (P=0.002).
Why the study?
Delineating electrically unexcitable scar within low-voltage infarct regions was hypothesized to locate reentry circuit isthmuses by defining their borders, but the pacing threshold and electrogram amplitude that best determine electrically unexcitable scar were unknown.
Does electrically unexcitable scar mapping based on pacing threshold identify reentry circuit isthmuses and reduce VT episodes in patients undergoing VT ablation?
Observational (n=14)
Does electrically unexcitable scar mapping based on pacing threshold identify reentry circuit isthmuses and reduce VT episodes in patients undergoing VT ablation?
Mapping electrically unexcitable scar using pacing thresholds >10 mA accurately identifies VT reentry circuit isthmuses and facilitates effective ablation during sinus rhythm.
Answers are grounded in this paper and cite their sources.
Should not change VT ablation practice; leaves open prospective validation of EUS mapping.
BACKGROUND: We hypothesized that delineating electrically unexcitable scar (EUS) within low-voltage infarct regions will locate reentry circuit isthmuses by defining their borders. The pacing threshold and electrogram amplitude that best determines EUS is unknown. METHODS AND RESULTS: The change in dimension of the virtual electrode was estimated in 11 patients and observed to increase by 4.4+/-2.5 mm as stimulus strength increases from threshold (2.9+/-1.8 mA) to 10 mA. EUS was defined as a threshold >10 mA. In 14 consecutive patients, mapping and ablation of ventricular tachycardia (VT) were performed using an electroanatomic mapping system. During sinus rhythm, unipolar pacing was performed at sites with bipolar electrogram amplitude <1.5 mV. EUS regions were marked on the maps. Reentry circuit isthmuses were identified by entrainment mapping or pace mapping, and ablation was performed. EUS was identified in the infarct in all 14 patients (11.8+/-13.9 cm2). All 20 VT circuit isthmuses identified were adjacent to EUS. Although electrogram amplitude correlated with pacing threshold (r=0.64, P<0.0001), many isthmuses had very low-amplitude electrograms, and EUS could not be identified from electrogram amplitude alone. RF ablation lines connecting selected EUS regions abolished all inducible VTs in 10 patients (71%); spontaneous VT was markedly reduced during follow-up (from 142+/-360 to 0.9+/-2.0 episodes per month, P=0.002). CONCLUSIONS: This new method of identifying EUS provides complimentary information to the electrogram amplitude in delineating potential reentry circuit paths, potentially facilitating ablation during sinus rhythm.
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Soejima et al. (2002) conducted an observational in Ventricular tachycardia (VT) and low-voltage infarct (n=14). Electrically unexcitable scar (EUS) mapping using unipolar pacing threshold (>10 mA) and guiding RF ablation vs. Electrogram amplitude mapping alone / baseline pre-ablation status was evaluated on Abolition of inducible ventricular tachycardia and reduction in spontaneous VT episodes (p=0.002). RF ablation lines connecting pacing-defined electrically unexcitable scar regions abolished inducible VT in 71% of patients and reduced spontaneous VT from 142 to 0.9 episodes/month (P=0.002).
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