Tachyarrhythmias after extracardiac conduit Fontan procedure in the long-term follow-up: may native anatomy of single ventricle predict their occurrence?

Abstract Funding Acknowledgements Type of funding sources: None. Background Arrhythmic complications, especially tachycardias, represent a common and important comorbidity during long-term follow up (FU) in patients with Fontan palliation for complexes congenital heart diseases (CHDs) with univentricular hearts. Surgical Fontan technique has evolved from direct atrio-pulmonary connection via the intracardiac lateral tunnel to the latest extracardiac conduit (ECC) procedure. Despite its shorter FU compared to previous techniques, the ECC variation is nowadays the main approach for many improvements, including lower incidence of arrhythmic complications (especially atrial arrhythmias). Purpose The aim of this study was to evaluate, during a long-term FU, the incidence of tachyarrhythmias and their correlation with the morphology of CHDs’ single ventricle native anatomy in a large cohort of patients with previous ECC Fontan procedure. Methods In this single centre observational cohort study, we retrospectively evaluated 351 patients treated with ECC Fontan palliation in our Institution between January 1987 and October 2017. Exclusion criteria were ECC Fontan take-down and a FU less than 5 years. CHD diagnosis, single ventricle native anatomy and surgical history were reviewed. Patients had cardiac examination once a year. We divided the overall study population in 2 groups based on unique ventricle's morphology: left-type (LV group) or right-type (RV group). Results A total of 303 patients [56% males; mean age at last FU 20 (IQR 15-28) years; 64.7% LV group] with ECC Fontan were enrolled. The mean FU was 16 (IQR 11-20, the longest 33) years. No sudden arrhythmic cardiac death occurred. Ten patients (6 of the LV group) underwent cardiac transplantation for Fontan failure. During FU, 34 patients of the LV (17.3%) and 22 of the RV group (20.2%) showed at least one tachyarrhythmia after a mean time of 12.1 and 12.9 years from ECC procedure, respectively. One patient (LV group) had one tachyarrhythmia in the early time period, <30 days from procedure. LV group showed a higher incidence of supraventricular tachyarrhythmias (SVTs) than RV group (68% vs 41% of total arrhythmias, p=0.08); in contrast, in RV group we found a higher number of ventricular tachyarrhythmias (VTs) compared to the other group (73% vs 41%, p=0.04). We observed both types of tachyarrhythmias (SVT and VT) in 3 patients of LV and 2 of RV group. Conclusions This study, with one of the largest cohort and longest FU after ECC Fontan, shows that ECC is associated with higher arrhythmic complications than previously reported, even though with longer latency period than other Fontan procedures. Moreover, our results suggest that patients with right-type single ventricle native anatomy are significantly more prone to develop VTs compared to those with left-type ventricle. This may reflect the drawbacks of the right ventricle physiology within Fontan circulation where the right ventricle acts for long time as the main pump of the circulatory system.