Effect of Obesity on Left Atrial Strain in Persons Aged 35-55 Years (The Asklepios Study)

Obesity increases the risk of heart failure and atrial fibrillation. Left atrial (LA) dysfunction is increasingly recognized as a mediator of cardiovascular disease. Early effects of obesity on LA function have not been examined in large population samples. We quantified LA strain and strain rate (SR) through speckle tracking echocardiography in 1,531 middle-aged community-based participants enrolled in the Asklepios study. We compared LA function between individuals with body mass index (BMI) < 25 kg/m² (n = 779), 25 to 29.9 kg/m² (n = 618) and ≥ 30 kg/m² (n = 134). Significant differences in reservoir longitudinal LA strain (BMI < 25 kg/m² = 35.3%, BMI 25-29.9 kg/m² = 33.1%, and BMI ≥ 30 kg/m² = 30.9%; p < 0.00001) strain rate ([SR] BMI < 25 kg/m² = 151; BMI 25 to 29.9 kg/m² = 141; and BMI ≥ 30 kg/m² = 135 %/s; p <0.00001) and expansion index (BMI < 25 kg/m² = 1.6, BMI 25 to 29.9 kg/m² = 1.4, and BMI ≥ 30 kg/m² = 1.4; p <0.00001) were seen, indicating reduced reservoir function with increasing BMI. Obesity was also associated with impaired LA conduit function, including conduit longitudinal LA strain (BMI < 25 kg/m² = 21.6%, BMI 25 to 29.9 kg/m² = 18.9%, and BMI ≥ 30 kg/m² = 16.7%; p <0.00001), SR (BMI < 25 kg/m² = -189, BMI 25 to 29.9 kg/m² = 166, and BMI ≥ 30 kg/m² = 150 %/s; p <0.0001) and passive LA emptying fraction (BMI < 25 kg/m² = 40.5, BMI 25 to 29.9 kg/m² = 36.5, and BMI ≥ 30 kg/m² = 36%, p <0.00001). These differences persisted after adjustment for age, gender and other potential confounders. In contrast to reservoir and conduit function, obesity was associated with increased booster pump function (active LA emptying fraction: BMI < 25 kg/m² = 19.4%, BMI 25 to 29.9 kg/m² = 20.5%, and BMI ≥ 30 kg/m² = 21.5%; p <0.00001). In middle-aged adults, obesity is associated with impaired reservoir and conduit LA function and higher booster function, which may be compensatory. Loss of booster LA function, either because of more advanced LA dysfunction or atrial fibrillation, may play an important role in precipitating heart failure in obese individuals.