Validation of a Four‐Extrastimulus Ventricular Stimulation Protocol for Arrhythmic Risk Stratification in Tetralogy of Fallot

INTRODUCTION: Risk stratification for sustained ventricular arrhythmias (SVA) in adults with repaired Tetralogy of Fallot (TOF) remains challenging. Although programmed ventricular stimulation (PVS) has shown a high negative predictive value, the prognostic performance of a four-extrastimulus PVS protocol-validated in ischemic heart disease-has not been systematically evaluated in congenital heart disease. METHODS AND RESULTS: We retrospectively included 41 consecutive adults with repaired TOF who underwent EPS using a standardized four-extrastimulus PVS protocol at two right ventricular sites. Inducibility of SVA was assessed. The primary endpoint was the occurrence of clinical SVA during follow-up. Kaplan-Meier analysis and Firth-penalized Cox regression were used to evaluate prognostic performance, and diagnostic accuracy metrics were calculated. Inducibility was observed in 18 patients (44%). During a median follow-up of 1.68 years, SVA occurred exclusively in inducible patients (5/18; 28%), all corresponding to sustained monomorphic ventricular tachycardia. No non-inducible patient developed SVA. Inducibility was associated with significantly lower SVA-free survival (log-rank p = 0.015) and an increased risk of events (HR 13.6; 95% CI 1.5-1804; p = 0.017) in univariate analysis. The four-extrastimulus protocol demonstrated a sensitivity of 100% and specificity of 64%. CONCLUSIONS: In adults with repaired TOF and risk factors for sudden cardiac death, the four-extrastimulus PVS protocol identified a subgroup at high arrhythmic risk while reliably excluding events in non-inducible individuals. These findings support the potential value of PVS as part of multimodal risk stratification, particularly for identifying patients in whom ICD implantation may be deferred.