First catheter-based high-density endocardial 3D electroanatomical mapping of the right atrium in standing horses

Background: Three-dimensional electroanatomical mapping is of potential interest in equine cardiology to identify arrhythmia mechanisms, characterise electroanatomical substrates and guide ablation strategies. Objectives: To describe three-dimensional electroanatomical mapping in standing horses. Study design: Research methodology, proof of concept study. Methods: Four Standardbred horses (2 geldings, 2 mares, median age 4.5 [4-9] years, mean bodyweight 485 [440-550] kg) were sedated and placed in stocks. Via the jugular vein, a high-density multipolar grid catheter (Advisor^™ HD Grid Mapping Catheter with EnSite VelocityTM, Abbott Medical) was used for endocardial mapping of the right atrium. The P-wave on the surface ECG was used as a timing reference for simultaneous local activation time- and bipolar voltage-mapping. For a positional reference a 10-pole catheter (Abbott Medical) was placed in the caudal vena cava. Results: Endocardial right atrial mapping guided by the three-dimensional mapping system and local electrograms was successfully performed in all four horses. A median of 32719 [25499-65078] points, covering the entire right atrium, were collected. Three-dimensional electroanatomical mapping provided detailed information about activation patterns and electrogram-characteristics of the sinoatrial node, intervenous tubercle and cavotricuspid isthmus. Additionally, transvenous biopsy forceps connected to the mapping system were visualised on screen to guide biopsy collection. Main limitations: The feasibility of electroanatomical mapping for the left atrium and in larger breeds requires further study. Conclusions: High-density three-dimensional electroanatomical mapping of the right atrium is feasible in the standing horse.