Introduction: Catheter ablation of atrial fibrillation (AF) and/or atrial tachycardia (AT) in heart failure (HF) patients provides improvement in symptoms cardiac function and survival. However, these procedures remain challenging with higher recurrence and complication rates compared to patients with normal cardiac function. We aimed to compare outcomes of AF/AT ablations guided by an ultra-high density mapping system between HF patients and controls. Methods and results: Primary endpoint was the one-year recurrence rate of AF/AT. We retrospectively examined all Rhythmia™-guided procedures performed in Caen and Toulouse University Hospitals between 2015 and 2018 for AF/AT. Patients with reduced left ventricular ejection fraction (LVEF) (i.e. <50%), or with preserved LVEF and signs/symptoms of HF were constituted the HF group and were subsequently classified in two subgroups of HF patients with preserved (HFpEF) or reduced/mildly reduced (HFrEF) LVEF. 246 patients were included, 135 in the HF group. At one-year, 71 patients had experienced AF/AT recurrences, with no difference between HF group versus non-HF group (31.9 vs 25.2% respectively, p=0.262). AF/AT recurrence rates were not different between HFpEF and HFrEF subgroups (37.1 vs 26.4% respectively, p=0.196). In multivariate analysis, patients with mitral regurgitation (p=0.011), hypertrophic cardiomyopathy (p=0.011) and persistent AF (p=0.02) were at higher risk of recurrence. AF/AT recurrence was not significantly associated with HF hospitalization (p=0.078) but HF status was the only independent predictive factor of HF hospitalization (p=0.002). Patients in the HF group showed significant improvement in both their NYHA class and LVEF than non-HF patients. After ablation procedures, while patients with HFrEF and HFpEF showed similar NYHA class improvement, LVEF only improved in HFrEF patients. The rate of complications were comparable in both groups. Conclusion: Clinical outcomes of AF/AT ablations guided by UHD mapping system appear similar in HF and non-HF patients. During the follow-up period, patients with HF exhibit improvement of NYHA status and LVEF.