INTRODUCTION
Congestive heart failure (HF) and atrial fibrillation (AF), two major cardiovascular conditions, often coexist. Patients with HF usually have chronically elevated filling pressures, that favour left atrial enlargement and atrial arrhythmias, either AF or atrial tachycardia (AT) occurrence. Besides, AF worsens their functional capacity and increases mortality, regardless of whether they have preserved or reduced left ventricular ejection fraction (LVEF).1,2 Catheter ablation (CA) of AF in a setting of HF with reduced LVEF is safe, and has proven effectiveness in improving functional status, quality of life, LVEF,3–5 and mortality.6 Data regarding CA for AF in case of HF with preserved LVEF (HFpEF) are limited but encouraging. 7,8 AF and AT often coexist as they shared risk factors and underlying substrate, especially in HF. Nevertheless, these procedures can be challenging in HF patients, who are likely to experience more recurrences, and repeated ablations than patients with normal cardiac function, despite the use of three-dimensional electroanatomic (3D) mapping systems.7,9 The novel ultra-high-density (UHD) mapping system (Rhythmia™, Boston Scientific, Inc., Marlborough, MA, USA) using a dedicated 64-pole mini-basket catheter (IntellaMap Orion™, Boston Scientific) has been now widely used, enabling rapid and accurate mapping with low signal/noise ratio and limited need for additional manual editing. Several studies have reported the ability of this system to elucidate complex arrhythmias. 10,11 However, data about clinical use of this UHD mapping system in HF patients are scarce, and whether this UHD system could improve CA results, with no clear data on safety in this particular population is unknown. The aim of our study was to assess clinical outcomes after Rhythmia™-guided ablation procedures of complex atrial arrhythmias in patients with clinical HF with and without reduced LVEF, compared to patients normal LVEF and no HF.