Ultra-low voltage zones as a marker of atrial cardiomyopathy: insights from high-density mapping

Background Low-voltage areas (LVAs) are a recognized marker of atrial fibrosis and structural remodeling in atrial fibrillation (AF). However, the diagnostic and prognostic significance of ultra-low voltage zones (ULVZs, <0.1 mV) has not been fully characterized. These extremely low-voltage regions may correspond to areas of dense fibrosis or electrically silent myocardium, representing the most advanced form of atrial disease. Identifying such areas could refine the electroanatomical definition of atrial cardiomyopathy and guide ablation strategies beyond pulmonary vein isolation (PVI). Methods We prospectively analyzed 120 consecutive patients undergoing first-time catheter ablation for AF (paroxysmal n=72, persistent n=48). High-density bipolar voltage maps (>10,000 points) of the left atrium were obtained during stable sinus rhythm using a multipolar mapping catheter. LVAs were defined as bipolar voltage <0.5 mV and ULVZs as <0.1 mV. The percentage of atrial surface occupied by each was quantified and correlated with left atrial volume, AF duration, and procedural outcomes. Recurrence of atrial arrhythmias was assessed by periodic ECG, Holter monitoring, and device interrogation during a 12-month follow-up. Results ULVZs were detected in 41% of patients, occupying a median of 6% (IQR 3–10%) of the atrial surface. Their distribution was heterogeneous, predominantly in the posterior and inferior walls. Patients with ULVZs exhibited larger left atria, longer AF history, and more frequent comorbidities such as hypertension and sleep apnea (all p<0.05). Freedom from atrial arrhythmia at 12 months was significantly lower in patients with ULVZs compared with those without (69% vs 86%, p=0.02). Multivariate analysis identified ULVZ extent ≥5% as an independent predictor of recurrence (HR 2.7, 95% CI 1.4–5.1), outperforming traditional LVA burden. Conclusion Ultra-low voltage zones represent an advanced stage of atrial remodeling that independently predicts poorer post-ablation outcomes. Their systematic detection may enhance the understanding of atrial cardiomyopathy, improve risk stratification, and promote individualized ablation strategies targeting both triggers and diseased substrate.