High density mapping of upper-loop macro-reentry surrounding the superior vena cava: substrate evolved ablation strategy.

Abstract

Background: The circuit of scar-related upper-loop macro-reentry surrounding the superior vena cava (SVC-AFL) has been described by prior case reports. However, the correlation between the circuit and arrhythmogenic substrates, and the corresponding optimized ablation strategy need to be further investigated.

Objective: We aimed to identify the electrophysiological substrate and corresponding ablation strategies of SVC-AFL using high-resolution mapping.

Methods: From June 1, 2017 to May 1, 2023, consecutive patients with macro-reentrant atrial tachycardias (ATs) from 7 institutions were retrospectively evaluated. Patients with SVC-AFL were enrolled and analyzed.

Results: Among 1282 patients with macro-reentrant ATs, 16 patients (1.2%, median age 60.9 years, 8 male) had SVC-AFL (mean cycle length, 281.0±55.1 ms), all identified during high-resolution activation mapping. All patients had prior cardiac surgery (14, 87.5%) or catheter ablation (8, 50.0%). A longitudinal surgical-incision/scar extending from the SVC to the right atrium (RA) was observed in all patients, enabling macro-reentry. SVC-AFLs with shorter circuits (<180 mm) had more slow conduction areas than those with longer circuits (>180 mm) [3.0 (2.0, 4.0) vs. 1.0 (1.0, 1.5), P=0.023]. All ATs were terminated by ablating the channel between the surgical-incision/scar and anatomical barriers. Cavotricuspid isthmus (CTI) block was achieved in all patients. During a 21-month follow-up, all patients were free of atrial arrhythmias except for 4 patients experiencing short-lived paroxysmal ATs that did not require further ablation.

Conclusion: A surgical-incision/scar extending from the SVC to RA promotes the development of SVC-AFL. Substrate-based linear lesions, along with prophylactic CTI ablation, afford favorable clinical outcomes.