Atrial structure and function in middle-aged, physically-active males and females: A cardiac magnetic resonance study

Abstract

Recent studies have reported on an association between endurance sport, atrial enlargement and the development of lone atrial fibrillation in younger, male cohorts. The atrial morphology and function of middle-aged, physically-active males and females have not been well studied. We hypothesized that middle-aged males would demonstrate larger left atrium (LA) and right atrium (RA) volumes compared to females, but atrial function would not differ. LA and RA volume and function were evaluated at rest in healthy adults, using a standardized 3.0Tesla cardiac magnetic resonance protocol. Physical activity, medical history, and maximal oxygen consumption ( $\dot{V}{O}_{2\text{peak}}$ ) were also assessed. Physically-active, middle-aged men (n = 60; 54 ± 5 years old) and women (n = 30; 54 ± 5 years old) completed this study. Males had a higher body mass index, systolic blood pressure, and $\dot{V}{O}_{2\text{peak}}$ than females (p < .05 for all), despite similar reported physical activity levels. Absolute and BSA and height-indexed LA and RA maximum volumes were higher in males relative to females, despite no differences in ejection fractions (p < .05 for all). In multivariable regression, male sex p < .001) and $\dot{V}{O}_{2\text{peak}}$ (p = .004) were predictors of LA volume (model R² = 0.252), whereas $\dot{V}{O}_{2\text{peak}}$ (p < .001), male sex (p = .03), and RV EF (p < .05) were predictors of RA volume (model R² = 0.377). While middle-aged males exhibited larger atrial volumes relative to females, larger, prospective studies are needed to explore the magnitude of physiologic atrial remodeling and functional adaptations in relation to phenotypic factors.

Keywords: cardiac imaging; endurance exercise; middle-age.

FIGURE 1

Example of the manual delineation of the left (orange) and right (light blue) atrium with cardiac magnetic resonance imaging (cMRI). The LA includes the left atrial appendage, but excludes the pulmonary vein, while the RA includes the right atrial appendage, while excludes the superior and inferior vena cava. Ao, aorta; LA, left atrium; RA, right atrium