Cardiac resynchronization therapy in pediatric congenital heart disease: Insights from noninvasive electrocardiographic imaging

Background: Electrocardiographic imaging (ECGI) is a novel electrophysiologic imaging modality that may help guide patient selection and lead placement for cardiac resynchronization therapy (CRT). Objective: The purpose of this study was to apply noninvasive ECGI to pediatric heart failure patients with congenital heart disease (CHD) undergoing evaluation for CRT. Methods: ECGI was applied in eight patients with CHD who were either being evaluated for CRT or undergoing CRT. An electrical dyssynchrony (ED) index was computed from the ECGI epicardial activation maps as the standard deviation of activation times at 500 epicardial sites of the systemic ventricle. A normal ED of 20 ± 4 ms was calculated from a control group of normal pediatric patients. Results: Four patients had an ECGI assessment for ED but did not undergo CRT implant. Two other patients had ECGI assessment pre-CRT that demonstrated abnormal ED and went on to CRT implant. In both cases, the resynchronization lead was placed at the site of latest electrical activation (as determined by ECGI) in pre-CRT baseline rhythm. A total of four patients (two responders, two nonresponders) were studied with post-CRT in multiple rhythms. Responders had an average ED of 22 ms in optimal CRT conditions. The nonresponder had very elevated ED (37 ms) in all rhythms including optimal CRT settings. ED and ECG QRS duration showed weak correlation (r = 0.58). Conclusions: ECGI can be used in pediatric heart failure patients to evaluate ventricular ED and identify suitable candidates for CRT. In addition, ECGI can guide resynchronization lead placement to the area of latest electrical activation. It could also be used in noninvasive follow-ups for assessing synchrony and the electrophysiological substrate over time.