Ventricular septal defect characteristics influence presence and properties of septal anatomical isthmuses in patients with repaired tetralogy of Fallot

Abstract

Abstract Background In repaired tetralogy of Fallot (rTOF), the septal anatomical isthmuses (AI), 3, between the ventricular septal defect (VSD) and pulmonary annulus, and 4, between the VSD and tricuspid annulus, are important ventricular tachycardia (VT) substrates when slow conducting. Patients with rTOF can have different VSD characteristics which may influence presence and properties of septal AIs. Methods This study included all consecutive patients with rTOF who underwent electroanatomical mapping (EAM) between 2005 and March 2023 for ventricular arrhythmias, risk stratification, or before pulmonary valve replacement and had a surgical report of initial repair available. Results In 130 of 154 (84%) patients a surgical report was available (35% female, median age at EAM 38 years [IQR 20-49]), with provided VSD details in 90 (69%). The majority of patients had an outlet perimembranous VSD (n=77, 86%), 7 (8%) a doubly-committed juxta-arterial (DC-JA) VSD, and 4 (4%) a muscular outlet VSD. All patients with a DC-JA VSD had a blocked/absent AI 3. Among patients with a DC-JA VSD with a muscular posteroinferior rim, 50% had AI 4, which was not observed in patients with a fibrous posteroinferior rim. In patients with a muscular VSD, AI 4 was present in 25%. In contrast, in patients with an outlet perimembranous VSD, an AI 4 or a blocked/absent AI 3 were rare findings (1% and 4%, respectively). Conclusions VSD characteristics influence presence and properties of septal AIs. In patients with DC-JA VSD septal VT substrates seem to be rare. Detailed surgical information is desirable for patient management.