Prophylactic Versus Reactive Ventricular Tachycardia Ablation in Repaired Tetralogy of Fallot: A Narrative Review.

Ventricular tachycardia and sudden cardiac death remain the principal late causes of mortality in repaired tetralogy of Fallot. Clinical practice is evolving from a "reactive" paradigm centered on defibrillator therapy and post-event ablation toward a "proactive" paradigm targeting slowly conducting anatomical isthmuses before clinical arrhythmias become manifest. Monomorphic ventricular tachycardia in this population typically occurs due to a discrete, anatomically defined set of slowly conducting isthmuses bounded by surgical patches or incisions and valve annuli. Substrate-targeted catheter and surgical ablation are technically feasible, safe, and associated with high arrhythmia-free survival when complete bidirectional block is achieved. The current indication for "proactive" ablation is for substrate evaluation before transcatheter pulmonary valve replacement, after which endocardial access to the dominant isthmus may be permanently obscured. Pulmonary valve replacement alone does not abolish the arrhythmogenic substrate, thus providing the rationale for combining valve intervention with proactive ablation. This narrative review discusses substrate biology, risk stratification, comparative outcomes of reactive and proactive ablation strategies, and the role of pulmonary valve replacement. It also proposes an operational pathway integrating both approaches within shared decision-making. The ongoing CATAPULT-TOF study and subsequent multicenter work will determine the populations in which proactive substrate evaluation should become routine.