Cardiac Resynchronization Therapy in Congenital Heart Diseases With Systemic Right Ventricle

Heart failure is henceforth the main cause of death in adult patients with congenital heart disease (CHD). The number of affected patients is expected to continue to grow exponentially due to the important increase and aging of this population.

In symptomatic patients despite optimal pharmacological therapy, Cardiac Resynchronization Therapy (CRT) offers a well-recognized therapeutic option in dilated and ischemic cardiomyopathies with severely impaired left ventricle ejection fraction and complete left bundle branch block. In patients with CHD, the level of evidence is much more limited. Underlying phenotypes are heterogeneous, including systemic right ventricles (SRVs), isolated sub-pulmonary right ventricle dysfunctions, single ventricles, and most of patients have a right bundle branch block. All these specificities question the extrapolation of data reported in patients with acquired cardiomyopathies. Despite the lack of evidence, CRT systems have been progressively used in CHD patients, also because alternative options are poor, mainly represented by cardiac transplantation, but grafts are rare and congenital patients frequently have contraindications.

A positive impact of CRT in CHD has first been suggested in small series where hemodynamic invasive parameters (e.g. dP/dt max) were improved and QRS narrowed by multisite pacing. A few subsequent studies then reported an improvement of ventricular functions and patient-reported functional subjective parameters (mainly NYHA classification). However, the number of patients included in most studies was limited and heterogeneous forms of CHD were often pooled when interpreting results. The studies evaluating CRT specifically in patients with SRV are very rare and demonstrated conflicting results. The largest study to date assessing specifically CRT in patients with SRV included 20 patients with congenitally corrected transposition of the great arteries (cc-TGA) and demonstrated an acute improvement in two-thirds of patients.

Although patients with SRV represent one of the main groups of CHD patients currently implanted with CRT, the paucity of specific data in this population has been highlighted as a major evidence gap and as a high-impact research question by the American Heart Association/American College of Cardiology guidelines committee.