We investigated the electrocardiographic mechanisms of asymmetric two-dimensional Poincare plots (PPs) obtained by 24-hour Holter monitoring (HoM). Twenty-seven (11 females) young athletes (A) aged 25 plusmn 4 years and ten healthy age-matched controls (B) underwent HoM using a Spiderviewtrade recorder. Two- dimensional PPs were constructed and systematically explored regarding the underlying ECG waveforms Asymmetry (DeltaW) was due to: (1) wandering atrial pacemaker activity) (100%), (2) sudden decreases in cycle lengths (SDC); (60%), (3) sudden increases in cycle length (SIC) (70%), and (4) frequent blocked premature atrial depolarizations (10%). Asymmetry was strongly correlated to instantaneous HRV and, thus, may be a measure of efferent vagal activity.
