Safety and hemodynamic stability during s3 functional substrate mapping in ventricular tachycardia ablation
N Pierucci, R Pittorru, J Reventos-Presmates, T Rosseel, P Bhagirath, M Regany-Closa, J P Guichard, J M Tolosana, E Guash, L Mont, J Brugada, E Arbelo, A Porta-Sanchez, I Roca-LuqueAbstract
Background
Periprocedural acute hemodynamic decompensation during ventricular tachycardia (VT) ablation is associated with a markedly increased risk of mortality. Functional substrate mapping through the S3 protocol, involving double ventricular extrastimuli, has emerged as a valuable technique to enhance the delineation of arrhythmogenic substrate during VT ablation. However, repeated use of this stimulation protocol may also increase the likelihood of recurrent induction of VT and the consequent risk of hemodynamic instability.
Purpose
To evaluate whether systematic use of a whole-ventricle S3 stimulation protocol increases the risk of periprocedural acute hemodynamic decompensation during VT ablation.
Methods
We retrospectively analyzed all VT ablation procedures in which the S3 protocol was attempted between November 2021 and July 2025 in our centre. All procedures were performed under general anesthesia. Hemodynamic decompensation was defined as persistent hypotension despite vasopressors requiring mechanical support or procedure discontinuation. Mapping was performed using the S3 protocol (drive train S1 followed by S2 = ERP + 30 ms and S3 = ERP + 50 ms, stimulating from the right ventricle) using the HD Grid catheter and EnSite X mapping system.
Results
Eighty-seven patients were included in the analysis (mean age 67 ± 10 years, 96.6% male). Ischemic heart disease was present in 64%. The mean left ventricular ejection fraction was 31 ± 10%. VT storm was the indication for ablation in 13% of patients. The average PAINESD score was 12.7 ± 5.7. In 15 patients (17%), the S3 protocol could not be completed because of repeated VT induction, leading to continuation of substrate mapping using conventional S1 pacing. Among the remaining 72 patients (83%) in whom S3 stimulation was feasible, 11 underwent a partial protocol limited to S2 mapping due to repetitive arrhythmia induction, while the others 61 patients successfully completed the full S3 protocol. No episodes of acute periprocedural hemodynamic decompensation occurred during or immediately after the procedure in the 61 patients mapped with the full S3 protocol. The different PAINESD score for each population was: S1 only patients 16.3±3.1; S1+S2 patients 13.8±4.9; S1+S2+S3 patients13±4.5; the PAINESD score was significantly higher in S1 only patients compared to S1+S2 and S1+S2+S3 groups (p < 0.05), while no significant difference was observed between the latter two groups.
Conclusion
Systematic whole-ventricle S3 stimulation during VT ablation appears to be safe in a high risk population, as its potential benefits in unmasking arrhythmogenic substrate are not associated with an increased risk of periprocedural hemodynamic decompensation.Hemodynamic stability during S3 mappingLeft ventricle S3 mapping