Abstract
The aim of this study was to evaluate whether endurance athletes who exhibit deep
bradycardia are more prone to arrhythmias and reflex syncope than their non-bradycardic
peers. 46 healthy men (ages 19–35) were divided into 3 groups based on whether they
were sedentary (SED,<2 h/week) or endurance trained (ET,>6 h/week), and non-bradycardic
(NB, resting heart rate (HR)≥60 bpm) or bradycardic (B, resting HR<50 bpm). Resting
HR was lower in ETB vs. ETNB and SED (43.8±3.1, 61.3±3.3, 66.1±5.9 bpm, respectively; p<0.001). Thus, 16
SED, 13 ETNB and 17 ETB underwent resting echocardiography, maximal exercise test,
tilt test (TT) and 24 h-Holter ECG. Subjects were followed-up during 4.7±1.1 years
for training, syncope and cardiac events. Our results showed that incidence of arrhythmias
and hypotensive susceptibility did not differ between groups. During follow-up, no
episode of syncope or near-syncope was reported. However, cardio-inhibitory syncope
occurrence tended to be higher in ETB. Left ventricular end-diastolic diameter index
was increased in ETB vs. ETNB and was correlated with resting HR (r=− 0.64; p<0.001).
As a result, athletes with deep bradycardia do not present more arrhythmias and more
hypotensive susceptibility than their non-bradycardic peers. Cardiac enlargement and
autonomic alteration both seem to be involved in an athlete’s bradycardia.
Key words
athlete’s heart - bradycardia - arrhythmias - syncope