Evaluation of mechanical dyssynchrony in children with idiopathic dilated cardiomyopathy and associated clinical outcomes.

We studied mechanical dyssynchrony and its association with clinical status in children with idiopathic dilated cardiomyopathy (IDC). The SD of QRS to peak systolic velocity interval by tissue Doppler was measured in 12 left ventricular segments, as a dyssynchrony index (DI), in each child with IDC during a 12-month period. Results were compared with a control cohort. We used the adult-defined DI cutpoint of 32.6 ms to define patients with IDC as "dyssynchronous" or "synchronous" and compared clinical status and outcomes (transplantation listing/death) between these groups. Patients with IDC (n = 23) and controls (n = 14) had similar age, gender, and QRS duration. Patients with IDC had a higher DI than controls (44.8 +/- 23.7 vs 19.9 +/- 8 ms, p <0.0001). A DI >32.6 ms defined mechanical dyssynchrony in 65% of patients with IDC. Dyssynchronous and synchronous patients had similar QRS durations. Age at diagnosis, at dyssynchrony evaluation, and duration of clinical illness were similar in the 2 groups. New York Heart Association score was better in dyssynchronous than in synchronous patients (2 vs 3.1, p <0.05). Number of synchronous and dyssynchronous patients reaching the end point of death or transplantation was similar, although synchronous patients had poorer actuarial survival from the time of diagnosis (hazard ratio 3.25, p = .04). In conclusion, left ventricular mechanical dyssynchrony is prevalent in pediatric IDC. QRS duration alone is inadequate to define dyssynchrony in pediatric IDC, whereas the adult-derived DI of >32.6 ms seems applicable to the pediatric population. In this cohort, the presence of mechanical dyssynchrony was not associated with more severe clinical status or adverse outcomes.