Classic-Pattern Dyssynchrony and Electrical Activation Delays in Pediatric Dilated Cardiomyopathy

Background: Progressive heart failure leading to transplantation or death is common in pediatric dilated cardiomyopathy (DCM), and treatment options are limited. Select children with DCM have improved after cardiac resynchronization therapy (CRT), but predicting response is challenging. Nonetheless, considering the frequency of death or transplantation in this population, identifying any candidate would be valuable. Classic-pattern dyssynchrony (CPD) identifies mechanical dyssynchrony patterns consistent with underlying electrical activation delays and strongly predicts CRT response in adult DCM but has not been evaluated in pediatric DCM. The aim of this study was to test the hypothesis that CPD is present in a subgroup of patients with pediatric DCM and is associated with activation delays. Methods: Fifty-nine subjects with pediatric DCM (left ventricular end-diastolic diameter Z score > 2 and left ventricular ejection fraction < 40%) who underwent echocardiography with a functional protocol with apical images optimized for two-dimensional speckle-tracking strain analysis (EchoPAC) were retrospectively analyzed for CPD. Electrocardiograms were evaluated for activation delays (prolonged QRS duration and strict criteria for left bundle branch block [LBBB]). Forty control subjects with no cardiac disease and good imaging widows were also analyzed. Results: The mean age was 5.4 years (range, 1 day to 20 years); idiopathic DCM was most common (57%). Severe cardiomyopathy was present in 75% (end-diastolic diameter Z score > 4.6 and left ventricular ejection fraction < 32%). CPD was identified in seven subjects (12%), and prolonged QRS durations were present in 13 (22%), but only two subjects met strict criteria for LBBB. Six of seven subjects in the CPD group had prolonged QRS durations, and two of seven had LBBB. No control subjects had CPD. The CPD analysis was highly feasible and reproducible. Conclusions: In this severely affected cohort, the small CPD subgroup is potentially important because their progressive disease may respond to CRT. CPD is associated with activation delays, although not necessarily strict LBBB. This has important potential implications for prospective evaluation of CRT in this disease.