Delayed Pericardial Effusion Following Ethanol Infusion of the Vein of Marshall

BACKGROUND Ethanol infusion of the vein of Marshall (EIVOM) improves outcomes in atrial fibrillation (AF) ablation. However, its association with delayed pericardial effusion (PE)-specifically its incidence, clinical features, and mechanism-remains poorly defined. OBJECTIVES This study sought to investigate the risk of delayed PE associated with EIVOM and characterize its clinical profile, management, and outcomes. METHODS This study analyzed 15,101 patients with persistent AF from the China-AF Registry, stratified into an EIVOM group (n = 8,151) and a non-EIVOM group (n = 6,950). The primary endpoint was delayed PE, defined as newly detected PE >10 mm occurring ≥7 days after ablation and resulting in rehospitalization. Propensity score overlap weighting was applied to balance baseline covariates between groups. RESULTS Delayed PE occurred in 0.17% of the total cohort, with a higher incidence in the EIVOM group compared with the non-EIVOM group (0.25% vs 0.07%). EIVOM was an independent risk factor for delayed PE (overlap-weighted HR: 3.18; 95% CI: 1.15-8.74; P = 0.025). Delayed PE in the EIVOM group tended to manifest late (median 38 days vs 14 days), with large effusion size and severe systemic inflammation. Management in the EIVOM group frequently required invasive intervention (17 of 20 [85%]). Notably, 20% (4 of 20) of patients with EIVOM-related delayed PE experienced recurrence post-discharge, requiring prolonged management. CONCLUSIONS EIVOM is associated with an increased risk of delayed PE, characterized by late onset, systemic inflammation, frequent need for invasive management, and high recurrence risk. These findings support the need for extended echocardiographic monitoring beyond the standard postprocedural period.