Endurance athletes have increased prevalence of atrial fibrillation (AF). Data from non-athletes suggest maximal left atrium (LA) volume and total emptying fraction predict future AF. We used cardiovascular magnetic resonance (CMR) to establish if these parameters differ between endurance athletes and sedentary controls and if they relate to aerobic fitness.
65 healthy endurance athletes (11 runners, 27 cyclists, 13 triathletes, 14 rowers) exercising >6 hours/week, aged 18-50, underwent CMR volumetric analysis of left atrial and ventricular size and function and aerobic fitness assessment by cardiopulmonary exercise testing. Sedentary controls (n=25) exercising <3 hours/week underwent identical CMR protocol.
Athletes demonstrated greater LA volume index and lower LA total emptying fraction than sedentary controls. On univariable regression increasing age (p=0.001), male (p=0.005), years training (p=0.009) and VO2max (ml/kg/min) (p=0.006) were associated with greater LA volume. On multivariable regression only increasing age (p=<0.001) and VO2max (ml/kg/min) (p=<0.001) were associated with greater LA volume. Only increasing age was associated with decreased LA total emptying fraction (p=0.011).
Endurance athletes have left atrial dilatation and impaired total emptying fraction compared to sedentary controls, which may be contributing factors to the development of AF. Greater aerobic fitness is associated with increased LA size but not total emptying fraction. Further studies are needed to establish if these parameters predict the risk of AF in endurance athletes.