Feasibility and Safety of Strategic Multielectrode Positioning Guided by S3 Protocol for Hemodynamically Unstable Ventricular Tachycardia

BACKGROUND: Catheter ablation of scar-related ventricular tachycardia (VT) is often limited by hemodynamic instability. Strategic Multielectrode Positioning (STaMP) mapping has been proposed to enable rapid identification of the diastolic components of VT circuits in these patients. OBJECTIVES: This study sought to evaluate the feasibility and safety of STaMP mapping during nontolerated VT and the role of functional mapping with the S3 protocol. METHODS: We analyzed 30 consecutive patients (mean age 63 ± 12 years; left ventricular ejection fraction 35% ± 10%) undergoing scar-related VT ablation with unstable VT. All patients underwent cardiac magnetic resonance imaging with semiautomated channel analysis. Functional mapping with the S3 protocol identified slow-conduction regions where high-density catheters were positioned for STaMP mapping. Patients with diastolic electrograms during VT were defined as STaMP-positive. RESULTS: STaMP mapping was successful in 22 of 30 patients (73%), delineating the full diastolic pathway in 60%. Mean mapping time was 20 ± 12 seconds (STaMP-positive: 14 seconds vs 34.5 seconds; P = 0.003). Features associated with STaMP positivity included shorter mapping time (OR: 0.88; P = 0.009), slower conduction in the deceleration zone identified on the S3 map (OR: 1.04; P = 0.048), and presence of magnetic resonance imaging conducting channels (OR: 16.7; P = 0.007). The S3 protocol revealed additional STaMP-positive zones in 27% of patients. Although 16 patients were at high PAINESD risk, no acute hemodynamic decompensation occurred. During a median follow-up of 19 months, VT recurrence was 23%, with no difference between groups (log-rank P = 0.20). CONCLUSIONS: STaMP mapping is feasible, rapid, and safe for identifying critical diastolic pathways in nontolerated VT. Integration of S3 functional mapping enhances diagnostic yield, supporting STaMP as a pragmatic tool to refine substrate-guided VT ablation.