[Arrhythmia and vago-sympathetic equilibrium in athletic divers]

Two series of electrocardiographic recordings by the Holter method were performed in 16 athletic divers : the first series in a man-made tank 15 m deep and containing water at 28 degrees C, with only exercises in apnoea ; the second series in a natural environment, with exercises in both apnoea and aqualung. Bradycardia was recorded in the second part of the apnoea. It was more marked and long-lasting in the artificial environment than in the natural one, and its degree correlated with the degree of experience of the driver (r = 0.90 ; p less than 0.001) . In 70 p. 100 of the cases, bradycardia was associated with atrial and/or ventricular extrasystoles in the artificial environment. In the natural environment, tachycardia was globally predominant and could reach maximum heart rate during exercises in the aqualung. The authors discuss the shift observe in vasosympathetic balance and its electrophysiological consequences when diving.