Population-based characterization of left atrial and appendage variations: Prevalence, risk factor associations, and sex-specific morphology

Introduction: With the increasing use of cardiac computed tomography (CT), left atrial (LA) and left atrial appendage (LAA) anatomical variants are frequently encountered, yet population-based data on their prevalence, clinical correlates, and sex-specific patterns remain limited. Methods: Contrast-enhanced cardiac CT from the Copenhagen General Population Study was analyzed to identify LA and LAA anatomical variants. Associations with demographic characteristics and cardiovascular risk factors were assessed using multivariable regression models. Results: Among 4630 individuals (median age 61 years; 56% women), the most common findings were LA diverticula (41.1%) and atrial septal pouch (37.0%), followed by accessory appendages (5.8%), patent foramen ovale (4.9%), atrial septal aneurysm (3.7%), lipomatous atrial septal hypertrophy (3.0%), atrial septal defect (0.8%), and cor triatriatum (0.2%). Women more frequently had atrial septal aneurysm and atrial septal defect. Lipomatous atrial septal hypertrophy was associated with older age, higher body mass index, diabetes, and smoking. Women had smaller indexed LA volumes, but similar indexed LAA volume compared with men, along with larger indexed LAA orifice area and fewer LAA lobes. Conclusions: In this population-based cardiac CT cohort, LA and LAA anatomical variants were common and showed distinct sex-specific patterns. Most variants were not associated with cardiovascular risk factors, supporting a presumed congenital origin, whereas lipomatous atrial septal hypertrophy was associated with cardiovascular risk factors. These findings provide reference data on atrial anatomical variation and support interpretation of incidental CT findings.