CONGRESS ABSTRACT

Introduction: Atrial fibrillation (AF) in hypertrophic obstructive cardiomyopathy (HOCM) is a negative prognostic factor in patients undergoing surgical correction. A precursor sign of AF is an increase in indexed left atrial volume (iLAVol, ml/m 3 ). We aimed to analyze the impact of HOCM surgery on iLAVol and the presence of AF at follow-up. Methods: This retrospective study included patients who underwent surgical correction of HOCM between 2013 and 2024. Only patients who had follow up echocardiography at our center were included. Patients were stratified into two groups based on preoperative rhythm: AF or sinus rhythm (SR). Changes in iLAVol between baseline and follow up were assessed using ANOVA. The association between the presence of AF at follow-up and predictive factors (preoperative AF and iLAVol) was assessed using multivariate logistic regression. Results: A total of 952 patients underwent surgical correction between 2013 and 2024, and 318 (33.4%) patients met the inclusion criteria. Among them, 244 patients (76.7%) were in the SR group and 74 (23.3%) in the AF group. Patients in the SR group were younger than AF patients (52.85±14.39 vs 61.31±10.58, p<0.05) and had a smaller pre-operative iLAVol (46.03±15.83 vs 56.72±24.64, p<0.05). There were no other significsnt differences. Mean follow up was 29.5±19.9 months. At follow-up, 9 patients (3.7%) in the SR group developed AF, while 56 (75.7%) in the AF group were in SR. HOCM surgery caused a significant overall reduction of iLAVol (from 48.52±41.19 to 41.19±15.55, p<0.001). Reduction was statistically significant in the SR group (postop:38.03±12.49 vs preop:46.03±15.83; p<0.001). In the AF group, iLAVol was reduced without reaching statistical significance (post-operative: 51.59±19.71; pre-operative: 56.72±24.64; p=0.15), possibly due to low sample size. In multivariable logistic regression, pre-operative AF (OR=4.47, p=0.002) and iLAVol at follow-up (OR per mL/m² increase=1.05, p<0.001) were independently associated with the presence of AF at follow up. Conclusion: Surgical correction of HOCM promotes favorable left atrial remodeling, which is associated with a higher rate of sinus rhythm maintenance after surgery and, therefore, improved long-term prognosis. Further studies with larger sample size are needed to confirm the result also in patients with pre-operative AF.