Adult definitions for dyssynchrony are inappropriate for pediatric patients.

Background: Cardiac resynchronization therapy (CRT) is a promising approach to improve cardiac function in children in heart failure with cardiomyopathy. Cardiac timing measures in pediatrics are typically based on age and heart rate. However, pediatric CRT studies to date have used adult based timing cutoff values. We investigated the applicability of using these adult standards in pediatric patients with normal hearts.

Methods: We studied 88 outpatients referred for cardiac evaluation who had a normal cardiac evaluation. Subjects had 12 lead EKG and normal echocardiogram. Patients with known heart disease or abnormal rhythms were excluded. 2D echo and Doppler including color tissue Doppler imaging (TDI, Vivid 7 GE Ultrasound, Norway) were obtained. TDI was performed on three standard apical views (four chamber, two chamber, and long axis). Longitudinal dyssynchrony was determined from (1) Yu index--standard deviation of differences in timing of peak TDI velocity of all 12 basal and mid LV wall segments, adult cutoff >32 ms and (2) opposing wall difference (OWD) in timing of peak TDI velocity of 12 LV wall segments, adult cutoff >65 ms. Radial dyssynchrony was determined from differences in timing of peak radial strain between anterior-septal and posterior LV segments from speckle tracking of 2D LV views, adult cutoff >130 ms.

Results: Median age was 11.5 years; median heart rate was 74.5. Longitudinal dyssynchrony was present in 40% of normals based on Yu index, and in 43% based on OWD. No child had Radial dyssynchrony.

Conclusions: This pilot study of children with normal hearts suggests that current adult CRT dyssynchrony cutoff values are inappropriate in the pediatric population.