LEFT ATRIAL STRAIN RESPONDS TO EXERCISE AND PREDICTS EXERCISE CAPACITY IN HEALTHY SUBJECTS: THE HEALTH EHEART STUDY

Background

Left atrial (LA) structure and function are altered in heart disease and predict exercise capacity; however, LA strain (ε), a descriptor atrial filling during LV systole, and its relation to exercise, is not well defined. In a healthy population, we sought to establish normal global peak positive longitudinal LA ε values at rest and with exercise and to associate these values with exercise capacity.

Methods

Volunteers from the Health eHeart Study, internet-based study, underwent graded supine bicycle exercise in 30 watt stages. Resting and stress transthoracic echocardiography was performed and analyzed using the GE Vivid E9 system and EchoPAC software. LA global peak positive ε by speckle tracking echocardiography was calculated as the mean of regional ε of 18 segments in triplane apical views. Exercise capacity was expressed as METs achieved. The association of LA global ε with peak exercise capacity was made with regression models adjusting for age, sex, left ventricle (LV) ejection fraction, LV mass index, and LV diastolic function category.

Results

Overall, the cohort (N=72; 43±14 years; 49% female) had normal exercise capacity (8.9±2.4 METs). In fully adjusted models, LA global ε increased significantly between rest and peak stress (37.3±7.5 to 49.5±9.6, p<0.01); LA ε for all segments increased significantly though with regional variation. Rest LA global ε decreased with age (β=-0.184, 95% C.I. -0.3 - -7.2 x 10-2, p<.01) as did stress LA global ε, whereas ability to augment strain with exercise in absolute and relative terms did not. In fully adjusted models, rest LA global ε was associated with exercise capacity (β=7.7 x 10-2, 95% C.I. 3.9 x 10-3 - 0.15, p=0.04).

Conclusions

In a cohort of healthy participants, resting global LA ε augments with exercise. Rest and stress LA global ε decrease with age, whereas ability to augment does not. Notably, resting global LA ε independently predicts exercise capacity. Atrial filling occurs through a combination of atrial relaxation and descent of the cardiac base. Since LA ε quantitates the product of these mechanisms, atrial function and its role in exercise can be seen to derive from a superimposed combination of atrial and ventricular forces. 

 


Autor / Fonte:Randell C. Thomas; Qizhi Fang; Dwight Bibby; et al. J Am Coll Cardiol. 2016;67(13_S):1805-1805. doi:10.1016/S0735-1097(16)31806-X.
Link: http://content.onlinejacc.org/data/Journals/JAC/935148/1806X.pdf