Mechanisms of Right Ventricular Electromechanical Dyssynchrony and Mechanical Inefficiency in Children After Repair of Tetralogy of Fallot
Background—Right bundle branch block (RBBB) and right ventricular (RV) dysfunction are common after Tetralogy of Fallot repair (rTOF). We hypothesized that RBBB is associated with specific RV mechanical dyssynchrony and inefficient contraction.
Methods and Results—We studied rTOF children and age-matched controls. QRS duration and morphology were assessed. RV mechanical dyssynchrony, indicated by early septal activation (right-sided septal flash), RV lateral wall pre-stretch/ late contraction, post-systolic shortening (PSS) and intra-ventricular delay were analyzed using 2D strain echocardiography. Peak oxygen consumption (VO2) reflected exercise capacity. Pulmonary regurgitation and RV volumes were assessed by magnetic resonance imaging (MRI). 46 rTOF patients and 46 controls were studied. 93% of rTOF patients demonstrated a 'right-sided septal flash' with simultaneous RV basal-lateral wall pre-stretch/late-activation. The RV basal segment was the most delayed in onset (115 (0-194) ms vs. 35(0-96) ms) and termination (462 (369-706) ms vs. 412 (325-529) ms) of longitudinal shortening, with PSS. QRS duration correlated with RV basal time to onset and peak shortening (p<0.05). Intra-RV delay was higher in rTOF (p<0.05) in association with RV dilatation (r=0.33, p=0.04). In rTOF, RV mechanics were inefficient with pre-stretch and PSS comprising 15±11% and 16±9% of total shortening, respectively. A composite parameter of electrical and mechanical dyssynchrony correlated with RV end-diastolic volume (r=0.39, p=0.03).
Conclusions—Typical electromechanical dyssynchrony associated with mechanical inefficiency, regional dysfunction and RV dilation is common in rTOF children possibly contributing to progressive RV dysfunction. The potential of cardiac resynchronization in appropriate patients requires further study.
- Received August 14, 2013.
- Accepted April 28, 2014.