Evolution of Right Ventricular Electromechanical Dyssynchrony During Childhood After Tetralogy of Fallot Repair

Patients with repaired tetralogy of Fallot (rTOF) develop electromechanical dyssynchrony (EMD), which detrimentally affects right ventricular (RV) function and exercise capacity. However, EMD evolution over childhood is unknown.

We retrospectively studied serial ECG, Holter, echocardiography, cardiac magnetic resonance, and exercise data of rTOF patients, over the first 18-years of life, who underwent repair from 2010 to 2020. Mechanical dyssynchrony parameters were evaluated at ages 8-12 and 14-18 years.

A total of 95 patients (61% male) were followed for a median 15.7 years (range 8-18 years). QRS duration (QRSd) increased steeply in the first 6 years and gradually through adolescence. Prolonged QRSd was associated with decreased VO₂ (P = 0.001), peak workload (P = 0.008), and RV ejection fraction (RVEF). RVEF decreased by 1.3% (-0.7 to -1.9) for every 10 ms increase in QRSd (P < 0.001). Patients with QRSd z score > 2 had a declining RVEF, despite a stable pulmonary insufficiency fraction and indexed RV end-diastolic volume throughout childhood. QRS fractionation (fQRS) increased during the first 6 years and then again in adolescence, which temporally coincided with the onset of arrhythmias. fQRS was associated with decreased RVEF (odds ratio [OR] 0.94; 95% confidence interval [CI] 0.9-1; P = 0.05) and RV longitudinal strain (OR 1.02; 95% CI 1.01-1.04; P = 0.008). 70.5% of patients had a septal flash at the first mechanical dyssynchrony assessment, which was associated with longer QRSd (median 124 ms [interquartile range (IQR) 107-136 ms] vs 100 ms [IQR 93-118 ms]; P = 0.019).

Electrical dyssynchrony is associated with progressive RV dysfunction and exercise intolerance over the course of childhood in rTOF, independently from pulmonary insufficiency. This raises the question of considering RV resynchronisation therapy in selected patients with symptomatic RV dysfunction and EMD.