Preserved Left Atrial Mechanics Following a 5-h Laboratory Triathlon in Euhydrated Athletes

The purpose of this study was to investigate echocardiographic changes in left ventricular (LV) diastolic filling and left atrial (LA) strain mechanics following prolonged exercise. Ten male triathletes completed a 60-min swim, 180-min bike exercise, and a 60-min all-out run in a laboratory environment. Special attention was paid to prevent dehydration and energy deficit during the exercise protocol. All participants underwent comprehensive echocardiographic analyses of Doppler- and volumetric-derived LV diastolic filling indices and novel speckle-tracking echocardiography (STE)-derived LA strain indices. LV stroke volume (pre: 108.0±15.9 vs. post: 88.8±19.0 mL; p=0.03) and LA passive emptying volume (pre: 31.2±7.5 vs. post: 22.4±9.8 mL; p=0.05) were significantly reduced following the exercise protocol. Of the STE-derived indices of LA function, reservoir and conduit strain did not change significantly, while there was a trend towards enhanced contraction strain (pre: 15.1±3.8 vs. post: 19.4±4.8%; p=0.07). Resting heart rate was significantly higher post-exercise (53.1±5.0 vs. 81.9±16.9 bpm; p<0.001) and its change correlated strongly with depression of Doppler-derived ratio of early to late ventricular filling velocities (r=0.74, p=0.01) and reduction of LA passive emptying volume (r=0.86, p=0.01). Following prolonged exercise, LV stroke volume was reduced due to heart rate related reduction in LA passive emptying volume whereas global LA strain mechanics were not compromised in this study.