Characterization of atrial substrate to predict AF ablation success

FUNDING ACKNOWLEDGEMENTS: Type of funding sources: Private company. Main funding source(s): The study has been financially supported by an investigator-initiated research grant by Biosense Webster (Study ID – IIS-532) (MRM) BACKGROUND: Left atrial (LA) substrate may have mechanistic relevance for ablation of atrial fibrillation (AF). We sought to analyze the relationship between low-voltage zones (LVZ), transition-zones (TrZ) and AF recurrence in patients undergoing pulmonary vein isolation (PVI). METHODS: We conducted a prospective multicenter study on consecutive patients undergoing PVI-only approach. LVZ and TrZ (0.5-1mV) were analyzed offline on high-density electroanatomical maps collected prior to PVI. RESULTS: 262 patients (61±11 years, 31% female) with paroxysmal (130 pts) or persistent (132 pts) AF were included. After 28 months of follow-up, 73 (28%) patients experienced recurrence. An extension of more than 5% LVZ in paroxysmal AF and more than 15% in persistent AF were associated with recurrence (HR=4.4 [2.0-9.8], p<0.001 and HR=1.9 [1.1-3.7], p=0.045, respectively). Significant linear association was found between LVZ and TrZ and between LVZ and left atrial volume index (LAVI) (both p<0.001). One-third of patients had significantly increased LAVI without LVZ. Eight percent of the patients had LVZ despite normal LAVI. Older age, female sex, oncological history and increased AF recurrence characterized this latter subgroup. CONCLUSIONS: In patients undergoing first PVI, the impact of LVZ on outcomes occurs with lower burden in paroxysmal than persistent AF suggesting that not all LVZs have equal prognostic implications. A proportional area of moderately decreased voltages accompanies LVZ, suggesting a continuous fibrotic substrate instead of the dichotomous division of healthy or diseased tissue. LAVI generally correlates with LVZ but a small subgroup of patients may present with disproportionate atrial remodeling, despite normal LAVI. [Figure: see text]