Ventricular arrhythmias and sudden death are feared late complications in patients with tetralogy of Fallot. Selection of candidates for primary prevention implantable cardioverter defibrillator (ICD) remains challenging.

To identify patients with tetralogy of Fallot at high-risk of sudden cardiac death in primary prevention.

The DAI-T4F study is an ongoing national French registry including all patients with tetralogy of Fallot and ICD (NCT03837574). Information have been collected prospectively since 2010. Cox proportional hazard models were used to identify factors associated with appropriate ICD therapies.

Among 134 patients enrolled, 47 (35.1%) underwent ICD implantation for primary prevention (median age 49.1 years, 76.6% males). At baseline, 20 (42.6%) patients had NSVT, 17 (36.2%) had altered LVEF ≤35%, 16 (34.0%) had positive programmed ventricular stimulation, and 16 (34.0%) had QRS duration ≥180ms. During a median (IQR) follow-up duration of 5.3 (2.1–8.0) years, 14 (29.8%) patients had at least one appropriate ICD therapy. The annual incidence of appropriate ICD therapies were 2.8%, 4.6%, 6.3%, and 8.6% in patients with none, one, two, or ≥three of these factors (P for trend=0.145). None of predictors, considered isolated, was significantly associated with ICD appropriate therapies. Patients with non-sustained ventricular tachycardia (NSVT) and positive programmed ventricular stimulation had a significant increased risk of ICD appropriate therapies (HR=3.8, 95% CI: 1.1–14.3, P=0.035), as well as patients with NSVT and QRSd ≥180ms (HR=7.2, 95% CI: 1.6–32.7, P=0.003). No patient with severe altered LVEF without other risk factor had appropriate ICD therapy.

Our data illustrate that specific risk stratification and primary prevention for sudden cardiac death in patients with tetralogy of Fallot may be improved. The value of a severely altered LVEF appears low in the absence of other risk factors.