Left Atrial Structure in Relationship to Age, Sex, Ethnicity, and Cardiovascular Risk Factors

Background - Left atrial (LA) size is a marker of diastolic function and is associated with atrial fibrillation and cardiovascular outcomes. However, there are no large population studies measuring LA structure. The relationship of demographics and cardiovascular risk factors to LA size is largely unknown. This study aimed to determine associations of LA size with demographic factors, cardiac structure and function, and cardiovascular risk factors. Methods and Results - LA volume indexed to body surface area was measured by cardiovascular magnetic resonance steady-state free precession and fast gradient echo cine long- and short-axis images in 2576 asymptomatic participants of MESA ([Multi-Ethnic Study of Atherosclerosis] 68.7 years, 53.0% women, white 42.2%, Chinese American 12.0%, black 24.5%, and Hispanic 21.2%) using biplane and short-axis images. The mean LA volume index was 36.5±11.4 mL/m 2 in the entire cohort and 35.5±10.1 mL/m 2 in subjects free of cardiovascular risk factors (n=283). Multivariable analysis included adjustment for demographics, ethnicity, cardiovascular risk factors, serological studies, socioeconomic status, left ventricular structure, and medications. In the adjusted analysis, age (β=0.2 mL/m 2 per year, P<0.0001), male sex (β=-4.2 mL/m 2, P<0.0001), obesity (β=1.3 mL/m 2, P<0.01), end-diastolic volume index (β=0.4 mL/m 2, P<0.0001), Chinese American (β=-2.6 mL/m 2, P<0.0001), and Hispanic (β=1.1 mL/m 2, P<0.05) ethnicities were associated with LA volume index. Diabetes mellitus and smoking were not associated with LA volume index. LA volumes measured by steady-state free precession were 3% larger than by fast gradient echo cine cardiovascular magnetic resonance (P<0.001). Conclusions - Age, sex, ethnicity and left ventricular structural parameters were associated with LA size. Importantly, the study provides reference values of normal LA volume index.