The electrocardiogram (ECG) is widely available and may contribute to a better risk stratification for sudden cardiac death in tetralogy of Fallot.

To identify ECG predictors of appropriate therapies in patients with tetralogy of Fallot and implantable cardioverter defibrillator (ICD).

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.

A total of 134 patients (median age 41.7 years, 70.7% males) were enrolled. During a median (IQR) follow-up of 6.1 (2.7–10.2) years, 59 (44.0%) patients received at least one appropriate ICD therapy, giving annual incidence of 5.5% and 7.1% in primary and secondary prevention, respectively (P=0.058). Overall, QRSd ≥180ms (P=0.073), QRS fragmentation (P=0.052), and QRS vector magnitude (vm, P=0.327) were not significantly associated with appropriate ICD therapies, whereas the association of QRSd ≥180ms and QRS fragmentation (HR=1.9, 95% CI: 1.1–3.4, P=0.036) were associated with an increased risk of appropriates ICD therapies. In patients with ICD for primary prevention (47 patients, 35.1%), while non-sustained ventricular tachycardia (NSVT) considered isolated was not associated with events during follow-up (P=0.069), combinations with QRSd ≥180ms (HR=7.2, 95% CI: 1.6–32.7, P=0.011), QRS fragmentation (HR=3.8, 95% CI: 1.2–12.4, P=0.025), or decreased QRS vm (HR=3.6, 95% CI: 1.1–12.1, P=0.042) were all associated with a higher incidence of appropriate ICD therapies.

Our findings highlight that cumulative risk score derived from ECG may contribute to improve risk stratification in patients with tetralogy of Fallot, in particular QRS fragmentation and QRS vm in association with QRS duration and other traditional risk factors.