Objectives
To compare the cross-sectional associations between cardiorespiratory fitness and echocardiographic measures of cardiac structure and function.
Background
Cardiorespiratory fitness (fitness) is inversely associated with heart failure risk. However, the mechanism through which fitness lowers heart failure risk is not fully understood.
Methods
We included 1,678 men and 1,247 women from the Cooper Center Longitudinal Study who received an echocardiogram from 1999—2011. Fitness was measured by Balke protocol and categorized into age-specific quartiles with quartile 1 representing low fitness. Cross sectional associations between fitness (in METs) and relative wall thickness (RWT), left ventricular end-diastolic diameter indexed to body surface area (LVEDD/BSA), left atrial volume indexed to body surface area (LA Vol/BSA), left ventricular systolic function (LVEF), and E/e′ ratio were determined using multivariable linear regression analysis.
Results
Higher levels of mid life fitness (METs) was associated with larger indexed LA volume (Men: β = 0.769, p <0.0001; Women: β = 0.879, p value = <0.0001) and indexed LVEDD (Men: β = 0.231, p <0.001; Women: β = 0.264, p <0.0001). Similarly, a higher level of fitness was associated with a smaller RWT (Men: β = -0.002; p = 0.04; Women: β = -0.005, p <0.0001) and E/e′ ratio (Men: β = -0.11; p = 0.003; Women: β = -0.13, p value = 0.01). However, there was no association between low fitness and LVEF (P=NS).
Conclusions
Low fitness is associated with a higher prevalence of concentric remodeling and diastolic dysfunction, suggesting that exercise may lower heart failure risk through its effect on favorable cardiac remodeling and improved diastolic function.