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The Role of Cardiac Resynchronization Therapy in the Young

Cardiac resynchronization therapy (CRT) has proven to be effective for adult patients with moderate to severe heart failure and evidence of ventricular dyssynchrony. Large randomized controlled clinical trials have demonstrated that CRT improves symptoms of heart failure, New York Heart Association (NYHA) functional class, exercise tolerance, hemodynamics, quality of life, and all-cause mortality.1 Current heart failure treatment guidelines recommend CRT for patients with NYHA functional class III-IV heart failure not responding to optimal medical therapy and who have sinus rhythm, QRS duration ≥120 ms, and a left ventricular ejection fraction of 35% or less. Presently, trials are underway to evaluate the potential of CRT in adult patients with NYHA functional class I and II heart failure. In addition, there is increasing evidence that ventricular dyssynchrony induced by conventional right ventricular (RV) apical pacing has adverse effects on left ventricular (LV) function.2-4 The use of CRT as therapy for heart failure in children and adolescents with congenital heart disease (CHD) and dilated cardiomyopathy has only just started. Heart failure is an important cause of late morbidity in CHD patients and is often associated with ventricular dyssynchrony induced by conventional pacemaker therapy or due to intrinsic conduction delay after surgery. CRT appears to be a promising therapy for heart failure in this group of patients; however, the data to support it remain very scarce. The large randomized CRT trials evaluated the effectiveness of CRT in patients with a mean age over 60 years with mostly ischemic heart disease. These data cannot simply be translated to a young population with a wide variety of congenital heart defects, including patients with systemic RV and different types of single ventricles. Several pediatric studies after congenital heart surgery have convincingly demonstrated that CRT improved hemodynamics in the acute postoperative phase.5-8 Multiple temporary epicardial pacing wires were used for atrioventricular and intraventricular resynchronization in young children with either systemic or pulmonary ventricular failure, including children with single ventricle physiology. These studies, including approximately 90 children, have shown that acute postoperative CRT significantly decreased QRS duration and increased blood pressure and/or cardiac index. Thus far, permanent CRT studies in children and adolescents were limited to case reports, small case series, and