Elsevier

Heart Rhythm

Volume 6, Issue 8, August 2009, Pages 1178-1185
Heart Rhythm

Original-clinical
Imaging/mapping
Cardiac resynchronization therapy in pediatric congenital heart disease: Insights from noninvasive electrocardiographic imaging

https://doi.org/10.1016/j.hrthm.2009.04.017Get rights and content

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.

Introduction

Cardiac resynchronization therapy (CRT) has been extensively studied in adult heart failure patients with two ventricles and a systemic left ventricle (LV). There has been less investigation of CRT in patients with congenital heart disease (CHD) who make up a substantially different population that is characterized by unusual anatomy including univentricular hearts, systemic right ventricles (RV), and other anomalies. CRT has been demonstrated to benefit certain CHD patients but significantly varies by substrate.1

Electrocardiographic imaging (ECGI) is a novel noninvasive functional imaging modality for cardiac electrophysiology (EP). It images epicardial potentials (voltage maps), electrograms, activation (isochrones), and repolarization patterns.2, 3, 4, 5, 6, 7 ECGI is based on 250-channel body surface electrocardiograms (ECGs) and an accurate heart-torso anatomy derived from ECG-gated thoracic computed tomography (CT). It has been applied to image cardiac EP in adult heart failure patients undergoing CRT.5 ECGI has been also applied successfully to guide intracardiac mapping and ablation of accessory pathways in pediatric patients with complex CHD and structurally abnormal hearts.6, 7 We hypothesize that ECGI can (1) be used to identify patients with CHD who have substantial ventricular electrical dyssynchrony (ED) in the baseline rhythm and thus may benefit from CRT; (2) help guide resynchronization lead placement by identifying both the EP substrate and the area of latest electrical activation; and (3) evaluate intraventricular ED post-CRT.

Section snippets

Methods

The study population included pediatric patients who met the following criteria: (1) age ≤21 years, (2) presence of CHD, (3) heart failure symptoms, and (4) undergoing evaluation for CRT or having a CRT device in place. Patients were chosen irrespective of their QRS duration. All patients were maximized on oral therapy before CRT.

For patients undergoing evaluation for CRT, an ECGI was performed in baseline rhythm. If the patient had a pacemaker in place and was not pacemaker dependent, ECGI was

Results

Eight pediatric patients (age 12 ± 6 years) were enrolled in the study with a total of four pre-CRT, two pre- and post-CRT, and two post-CRT studies. There was a wide variety of congenital heart lesions (Table 1) including (1) systemic LV, (2) systemic RV, or (3) univentricular heart.

Discussion

Pre-CRT echocardiographic testing used to determine dyssynchrony is fraught with limitations, mostly interobserver variability. The unusual anatomy of patients with CHD further imposes technical limitations on the utility of standard echocardiographic methods for objective evaluation. ECGI provides an objective rather than a subjective method in the assessment of dyssynchrony. The use of ECGI in selecting patients likely to benefit from CRT presupposes that mechanical dyssynchrony is preceded

Conclusions

This study reports the first experience with application of a novel noninvasive cardiac EP imaging modality for evaluation of CRT in a small group of pediatric CHD patients. It shows that ECGI can be used objectively to measure ED, which does not correlate with QRS duration. ECGI may help to correctly identify patients (with substantially large ED compared with controls) who would likely benefit from CRT. ECGI activation maps can help guide resynchronization lead placement by defining the EP

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The first two authors contributed equally to preparation of this manuscript.

The study was supported by Merit Award no. R37-HL-033343 and grant no. R01-HL-49054 from the National Heart, Lung, and Blood Institute to Y. Rudy. Dr. Rudy is the Fred Saigh Distinguished Professor at Washington University in St. Louis.

Y. Rudy chairs the scientific advisory board and holds equity in CardioInsight Technologies (CIT). CIT does not support any research conducted by Y. Rudy, including that presented here.

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