Beat-to-beat QRS amplitude variability in elite endurance athletes.

Results from variance electrocardiography, displaying the wide-band, phase-locked electrical micro-variability during the depolarization phase, was analysed versus clinical data, echocardiographic structural and functional variables and myocardial scintigraphic findings in 174 elite orienteers compared with 37 age-matched elite endurance athletes and 50 age-matched, healthy medical students. PCA analysis identified a subgroup of five orienteers deviating from the rest of the study group and both control groups with regard to their QRS amplitude variability. No correlations were found between pathology by medical history or any of the echocardiographic and scintigraphic variables or by the variance electrocardiographic aberrations in any of the groups studied.