Symptomatic but not asymptomatic non-sustained ventricular tachycardia is associated with appropriate implantable cardioverter therapy in tetralogy of Fallot

Background: A recently developed risk score model aims to predict appropriate implantable cardioverter defibrillator (ICD) therapy for primary prevention of sudden cardiac death in tetralogy of Fallot (TOF). We assessed the validity of the proposed risk score model.

Methods: Patients included in a retrospective international cohort were stratified according to the risk score system. Risk factors were prior shunt, inducible sustained ventricular tachycardia, QRS ≥ 180 ms, ventriculotomy incision, nonsustained ventricular tachycardia (NSVT) and left ventricular end-diastolic pressure ≥ 12 mmHg (LVEDP). Left ventricular ejection fraction ≤ 35% measured by means of echocardiography was used because LVEDP values were incomplete in our cohort.

Results: Thirty-six adults had TOF and ICD for primary prevention (72% male, mean age 37 ± 12). Seven patients (19%) received appropriate shocks during a median follow-up of 5.5 years. Of the proposed risk factors only NSVT was associated with appropriate shocks (HR 2.6, CI 1.1-6.0, P=0.02). Patients with asymptomatic NSVT did not receive any appropriate shocks. The 8-year Kaplan-Meier estimate from the first appropriate shock was 86%, 78% and 75% for low, intermediate and high risk patients, respectively. In this study, the annual rate of appropriate shocks was 4.1% in the high risk group which was considerably lower than that reported by Khairy and colleagues (17.5%).

Conclusions: The risk score model of Khairy and colleagues was capable of identifying low versus intermediate/high risk patients. However, event rates of lethal arrhythmias were lower in our cohort than previously reported. Symptomatic but not asymptomatic NSVT was the sole clinical variable associated with appropriate ICD therapy in TOF.