Left Atrial Volume, Cardiorespiratory Fitness, and Diastolic Function in Healthy Individuals: The HUNT Study, Norway

Abstract

Background Left atrial (LA) size and cardiorespiratory fitness (CRF) are predictors of future cardiovascular events in high-risk populations. LA dilatation is a diagnostic criterion for left ventricular diastolic dysfunction. However, LA is dilated in endurance athletes with high CRF, but little is known about the association between CRF and LA size in healthy, free-living individuals. We hypothesized that in a healthy population, LA size was associated with CRF and leisure-time physical activity, but not with echocardiographic indexes of left ventricular diastolic dysfunction. Methods and Results In this cross-sectional study from HUNT (Nord-Trøndelag Health Study), 107 men and 138 women, aged 20 to 82 years, without hypertension, cardiovascular, pulmonary, or malignant disease participated. LA volume was assessed by echocardiography and indexed to body surface area LAVI (left atrial volume index). CRF was measured as peak oxygen uptake (VO_2peak) using ergospirometry, and percent of age- and-sex-predicted VO_2peak was calculated. Indexes of left ventricular diastolic dysfunction were assessed in accordance with latest recommendations. LAVI was >34 mL/m² in 39% of participants, and LAVI was positively associated with VO_2peak and percentage of age- and-sex-predicted VO_2peak (β [95% CI], 0.11 [0.06-0.16] and 0.18 [0.09-0.28], respectively) and weighted minutes of physical activity per week (β [95% CI], 0.01 [0.003-0.015]). LAVI was not associated with other indexes of left ventricular diastolic dysfunction. There was an effect modification between age and VO_2peak/percentage of age- and-sex-predicted VO_2peak showing higher LAVI with advanced age and higher VO_2peak/percentage of age- and-sex-predicted VO_2peak as presented in prediction diagrams. Conclusions Interpretation of LAVI as a marker of diastolic dysfunction should be done in relation to age-relative CRF. Studies on the prognostic value of LAVI in fit subpopulations are needed.

Keywords: echocardiography; endurance training; exercise; heart; physical activity.

Figure 1

Left atrial (LA) assessment. LA volume was measured from B‐mode recordings in apical 4‐chamber view (left) and 2‐chamber view (right). Tracing was done from one side at the mitral annular level following the endocardial border around the atrium and to the opposite site at the mitral annular level. The contour was closed at the mitral annulus with a straight line. The area of the atria in the specific view is annotated LAAs in the figure. Pulmonary veins (green arrow) and LA appendage (blue arrow) were excluded from the tracings. LA length was measured in both views, illustrated by the central line in the 2 tracings (annotated as LALs in the figure). LA volume was measured by the area‐length method (annotated as LAESV A‐L in the figure) and the summation of disks method (annotated as LAESV MOD in the figure).13

Figure 2

Scatterplot of the relationship between left atrial volume index (mL/m²) and percentage of age‐ and sex‐predicted peak oxygen uptake (n=229).

Figure 3

Prediction diagrams of left atrial volume index for ages 40, 50, 60, and 70 years by peak oxygen uptake (VO_2peak) (n=229) (A), percentage of age‐ and sex‐predicted VO _2peak (n=229) (B), and percentage of age‐ and sex‐predicted VO _2peak in men only (n=103) (C).

Figure 4

Take‐home figure. Indexed left atrial volume was positively associated with cardiorespiratory fitness in healthy adults, and the effect was more pronounced with advanced age. Left atrial volume was not associated with other indexes of left ventricular diastolic dysfunction.