FIG 22.33 Dual-chamber implantable cardioverter/defibrillator The top channel is the atrial electrogram The second channel is the ventricular electrogram The sixth ventricular beat occurs on top of the sinus ventricular complex, resulting in polymorphic ventricular tachycardia 20 J of energy delivered at the bottom tracing shows conversion to sinus rhythm Cardiac Resynchronization Therapy More than 70% of cardiac resynchronization therapy (CRT) cases in pediatrics is undertaken in congenital heart disease patients who have not responded to maximal medical therapy (Fig 22.34) CRT can result in the improvement in heart failure symptoms, reduced morbidity, mortality, and an improved quality of life in patients with New York Heart Association functional class III/IV It can result in improved ejection fraction, reduced left ventricle remodeling and reduced mitral regurgitation.181 The goal of CRT is to restore myocardial function by reestablishing cardiac synchrony at the AV, interventricular, and intraventricular levels; this is effective in about two-thirds of patients Diminished cardiac output may occur in patients with a left-bundle-branch-block pattern on ECG, which results in delayed depolarization of the lateral LV wall.191 Long-term RV pacing has been an identified risk factor for symptomatic dyssynchrony and is greatest among younger patients who are exposed to ventricular pacing for many decades Studies have suggested that chronic RV apical pacing in young patients, primarily those with congenital complete heart block, can lead to adverse histologic changes, ventricular dilation, and dysfunction FIG 22.34 An anteroposterior chest radiograph of an infant with congenital complete heart block and a dilated cardiomyopathy The pacing leads are epicardial and connected to a cardiac resynchronization therapy device in the abdomen Most adult resynchronization procedures are performed by transvenously placing the LV lead via the coronary sinus into a lateral cardiac vein and on the epicardial LV surface This is technically more challenging in pediatric and congenital heart disease patients, and there are increased risks Biventricular pacing systems in pediatric patients commonly involve a median sternotomy or thoracotomy for proper placement of the LV lead Prior to consideration of a CRT device, a detailed assessment of the patient's prior device therapy, pathology, cardiac conduction abnormalities, and degree of heart failure must be performed To identify candidates in whom therapy would be most successful, it is best to identify the LV lead position, myocardial scar distribution, etiology of systolic dysfunction, percentage of biventricular pacing, lack of mechanical dyssynchrony, and QRS morphology and duration To date, outcomes of CRT in pediatric and congenital heart disease patients are limited to two multicenter studies and one single-center study Findings ranged from 10.7% to 18.5% nonresponders with complications in 9.2% to 29% of patients.192–194 CRT promotes an increase in stroke volume, stabilizes the diastolic filling time, and diminishes mitral regurgitation with favorable outcomes in pediatric and congenital heart disease patients that are not dissimilar ... This is technically more challenging in pediatric and congenital heart disease patients, and there are increased risks Biventricular pacing systems in pediatric patients commonly involve a median sternotomy or...Cardiac Resynchronization Therapy More than 70% of cardiac resynchronization therapy (CRT) cases in pediatrics is undertaken in congenital heart disease patients who have not responded to maximal medical therapy (Fig... distribution, etiology of systolic dysfunction, percentage of biventricular pacing, lack of mechanical dyssynchrony, and QRS morphology and duration To date, outcomes of CRT in pediatric and congenital heart disease patients are limited to two multicenter studies and one single-center study