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Background Hypertrophic Cardiomyopathy (HCM) is associated with a >25% prevalence of atrial fibrillation (AF). AF in HCM is associated with >2-fold risk in 10-year cardiovascular death rate. ESC guidelines recommend rhythm-control for these patients, though pharmacological options are limited. AF-Ablation with conventional thermal-ablation is safe, though with double the AF-recurrence compared with non-HCM patients. Recent international data supports AF-Ablation utilising Pulsed Field Ablation (PFA) as potentially offering greater safety and efficacy profiles for HCM patients with AF compared with thermal AF-Ablation.Methods This was a retrospective observational analysis of efficacy and safety outcomes for HCM patients who underwent PFA for AF in participating centres within the preceding 24-months. Cases were identified through procedural lists of participating electrophysiologists. All cases where a patient had a listed diagnosis of HCM, and who had undergone PFA for AF were included. Demographics and clinical data were gathered from clinic letters, imaging results, non-invasive monitoring and device interrogations. Procedural data was collected from procedural letters and physiologist logs. Safety data and follow-up data, including arrhythmia re-occurrence, were obtained from follow-up clinic letters and device interrogations.Results A total of 19 patients were included. Acute isolation was achieved in 100% of cases. Posterior wall ablation was included in 9 cases; ablation of the mitral isthmus was included in 6 cases; and 1 case underwent CTI during their procedure. At the time of data collection, 6 patients experienced AF-recurrence during 12-month follow-up, of which 2 underwent repeat PFA - neither have experienced further sustained AF/AT to date. 2 patients experienced atrial flutter/atrial tachycardia following post-procedural blanking-period, 1 of whom required AV-nodal ablation; 1 patient required DCCV during the blanking-period. There were no peri-procedural or post-procedural complications.Conclusion Our results suggest a viable role for PFA for treating AF in HCM patients, demonstrating a low complication rate, though greater patient numbers and follow-up data are required.Abstract 69 Table 1Baseline clinical data for HCM patients who had undergone PFA AF-ablation in participating electrophysiology centres Parameter Value Patients with Available Data (n=) Parameter Value Patients with Available Data (n=) Sex, male (n=) 14 19 Obesity (n=) 6 19 Mean age at PFA-PVI (years) 53.89 (SD=14.2) 19 Obstructive Sleep Apnoea (n=) 1 19 Mean BMI (kg/m2) 29.32 (SD=4.73) 10 Hypertension (n=) 4 19 Mean LA diameter (mm) 44.61 (SD=8.86) 14 Diabetes (n=) 3 19 Mean LVEF (%) 58.33 (SD=8.47) 15 Previous MI/PCI/CABG (n=) 2 19 Mean Max Wall Thickness (mm) 18.92 (SD=4.23) 15 Peripheral Vascular Disease (n=) 1 19 Systolic Anterior Motion of Mitral Valve (n=) 2 15 Previous CVA/TIA (n=) 1 19 Mean Peak LVOT Gradient (mmHg) 10.92 (Median=20.88) 13 Chronic Kidney Disease (n=) 0 19 Moderate or Severe Mitral Regurgitation (n=) 3 Moderate0 Severe 15 COPD (n=) 0 19 Significant LGE on CMR (i.e. ≥15%) (n=) 5 8 AF Subcategory (n=) 10 Paroxysmal9 Persistent 19 Apical Aneurysm (n=) 0 8 Mean Time Since AF Diagnosis (years) 3.57 (Median=1) 14 Previous Cardiac Surgery (n=) 0 19 Anti-Arrhythmic Drug Use at Baseline (n=) 4 Amiodarone3 Sotalol1 Mexilitene1 Flecainide 16 ICD/CRT-D (n=) 8 ICD1 PPM 19 Previous DCCV (n=) 8 19 Thyroid Dysfunction (n=) 1 Subclinical Hyperthyroidism 19 Previous Thermal PVI (n=) 5 19