Evaluation of Mechanical Dyssynchrony in Children With Idiopathic Dilated Cardiomyopathy and Associated Clinical Outcomes Mark Kevin Friedberg, MD*, Susan Lucy Roche, MD, Mervin Balasingam, Elizabeth Stephenson, MD, Cameron Slorach, RDCS, Cheryl Fackoury, RDCS, and Paul Fraser Kantor, MBBCh, DCH 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 transplan- tation 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. © 2008 Elsevier Inc. All rights reserved. (Am J Cardiol 2008;101:1191–1195) We hypothesized that the presence of mechanical dyssyn- chrony, as defined by the adult criterion of a dyssynchrony index (DI) of 32.6 ms, 1,2 is applicable in children to diag- nose mechanical dyssynchrony and that children with idio- pathic dilated cardiomyopathy (IDC) and a DI above this value may have a worse functional status and clinical out- come. Therefore, we investigated the presence of mechan- ical dyssynchrony in children with IDC using criteria pre- viously defined in the adult population and the association among mechanical dyssynchrony, functional status, and clinical outcome in this group of patients. Methods We retrospectively recruited children 0 to 18 years of age who had undergone echocardiography from January 2006 to February 2007 if they had IDC, defined as a dilated left ventricle (end-diastolic dimension by M mode 2 SDs) for body surface area with decreased left ventricular (LV) sys- tolic function (LV ejection fraction 55%). Patients with major structural congenital heart disease or with an im- planted pacemaker were excluded. No patient underwent cardiac resynchronization therapy (CRT). Clinical data were obtained from medical records. Death or listing for heart transplantation served as the clinical end point. Healthy children with structurally and functionally normal echocardiograms investigated for an innocent mur- mur or screening purposes were used as controls for eval- uation of mechanical dyssynchrony. The study was ap- proved by the institutional research ethics board. Echocardiography was performed on a Vivid 7 echocar- diographic system (GE Corp., Wauwatosa, Wisconsin) with probe frequencies appropriate for patient size. LV ejection fraction was calculated by the biplane Simpson method. Color tissue Doppler imaging was acquired from apical 4-, 3-, and 2-chamber views. Image position, depth, and sector width were optimized for frame rate and insonation angle. Frame rates were kept 100 fps (mean 153), except in 1 patient in whom rates were 84 fps. Echocardiographic data were transferred to an Echopac workstation (GE Corp.) for offline analysis. Due to obvious differences in echocardio- graphic appearance between IDC and normal, it was not practical to blind the data analysis operator to patient diag- nosis. Tissue Doppler sample volumes of 5 mm were placed Division of Pediatric Cardiology, Hospital for Sick Children, Toronto, Ontario, Canada. Manuscript received November 13, 2007; revised manu- script received and accepted December 9, 2007. *Corresponding author: Tel: 416-813-7239; fax: 416-813-7547. (M.K. Friedberg). E-mail address: mark.friedberg@sickkids.ca 0002-9149/08/$ – see front matter © 2008 Elsevier Inc. All rights reserved. www.AJConline.org doi:10.1016/j.amjcard.2007.12.017