Transverse conduction across the crista terminalis with pseudo-focal activation pattern in patients with upper loop reentry atrial tachycardia

Abstract Background Upper loop reentry (ULR) is a rare form of macroreentrant atrial tachycardia (AT) and an area of slow conduction exists in the crista terminalis (CT) where ablation is successful in eliminating the circuit. Transverse conduction across the CT during ULR AT has not yet been fully investigated. Purpose To investigate the transverse CT conduction during ULR AT Methods One hundred and five consecutive patients with macroreentrant AT were enrolled. The diagnosis of ULR was made based on endocardial activation mapping and entrainment pacing from multiple sites around the superior vena cava (SVC). Pseudo-focal pattern was defined as follows; (1) unsuccessful termination of ULR AT after extensive ablation along the CT and (2) distance from the earliest activation site (breakthrough) to the linear scar along the CT >5 mm and a later activation site exists between the breakthrough and the CT. Results Nine (8.6%) of the 105 patients were diagnosed with ULR AT and studied. Seven (77.8%) of the ULR patients had a history of cardiac surgery or cavotricuspid isthmus ablation. Pseudo-focal pattern was observed in 4 (44.4%) patients who exhibited a linear scar along the CT connecting the SVC with the inferior vena cava. The median missing tachycardia cycle length (TCL) was 49.5 ms on the endocardial activation map. The median distance between the early-meets-late line (linear scar along the CT) and the breakthrough was 12 mm. RF application at the breakthrough successfully eliminated the ULR AT in all patients. Conclusions Nearly half of the patients with ULR AT exhibited pseudo-focal pattern suggesting a transverse conduction across the CT utilizing an epicardial connection such as the intercaval bundle. Ablating the breakthrough site is a better therapeutic option than ablating within the linear scar along the CT.Patient characteristicsRepresentative case