Evolution of Right Ventricular Electromechanical Dyssynchrony during Childhood after Tetralogy of Fallot Repair.

Abstract

Background: 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.

Methods: 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 between 2010-2020. Mechanical dyssynchrony parameters were evaluated at age 8-12 and 14-18 years.

Results: 95 patients (61% male) were followed for a median of 15.7 years (range 8-18). 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- -1.9) for every 10ms increase in QRSd (p<0.001). Patients with QRSd z-score>2 had a declining RVEF, despite a stable pulmonary insufficiency (PI) 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 (OR 0.94 [0.9-1], p=0.05) and RV longitudinal strain (OR 1.02 [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 (124ms [107-136] vs. 100ms [93-118], p=0.019).

Conclusions: Electrical dyssynchrony is associated with progressive RV dysfunction and exercise intolerance over the course of childhood in rTOF, independent of PI. This raises the question of considering RV resynchronization therapy in selected patients with symptomatic RV dysfunction and EMD .