Clinical phenotypes of severe atrial cardiomyopathy and their outcome: A cluster analysis.

Background: Atrial cardiomyopathy (AtCM) encompasses patients with diverse demographics and comorbidities. This study aimed to identify phenotype groups with similar clinical characteristics, compare their mortality and atrial fibrillation (AF) event rates, and assess predictors of mortality. Methods and Results: We performed a hierarchical cluster analysis using Ward's Method, based on 11 clinical variables. Among 724 consecutive patients with a dilated left atrium (LA), only 196 met the criterion for severe AtCM- defined as a dilated LA with a volume index ≥ 50 ml/m2. We identified 4 clusters: Cluster 1 -younger overweight patients with paroxysmal AF; Cluster 2 -older patients with heart failure (HF) and low BMI; Cluster 3 - diabetic patients with HF; and Cluster 4 - older patients with tachycardia-bradycardia syndrome and implanted pacemakers. Over a median follow-up of 20.6 months, Cluster 2 had the highest mortality rate (29.1 %), followed by Cluster 3 (20.6 %), compared to Clusters 1 and 4 (11.4 % and 10.8 %, respectively, p = 0.045). For AF events, Cluster 1 had the highest incidence (37 %), followed by Cluster 3 (35 %), Cluster 2 (24 %), and Cluster 4 (19 %, p = 0.309). Heart failure (HR 4.4, CI 1.5-12.7, p = 0.006), cancer (HR 3.3, CI 1.6-6.9, p = 0.002), and severe tricuspid regurgitation (HR 5.4, CI 2.6-11.3, p < 0.001) were predictors of poor outcomes. Conclusion: In severe AtCM patients, four clusters were identified, each with unique comorbidities and mortality rates but similar AF event rates. Clinical and echocardiographic factors were linked to higher mortality risk.