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

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.

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%.

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.