Sinus node arrest and asystole from vaso-vagal phenomena during lower body negative pressure in a healthy pilot

We present a case study of sinus node arrest and asystole in a healthy 34-year-old fighter pilot during the third minute of exposure to lower body negative pressure (LBNP). These disturbances lasted more than 17 s, and were accompanied by complete loss of consciousness and tonicclonic body movements of short duration. Routine blood examination, EEG, standard and dynamic ECG (on a treadmill, in a human centrifuge, and upon Holter monitoring), 2 D D echocardiogram, exercise heart scintiscan, tilt table test, carotid sinus massage and electrophysiological heart examination with esophagal electrode stimulation before and after intravenous atropine injection, revealed no pathology. The pilot's tolerance to +Gz acceleration of 6.3-8.0 G was very good. We discuss the clinical, certification, legal, and ethical aspects of this case, asserting that neither normal results of widely applied clinical diagnostic tests of the autonomic and circulatory systems, nor very good tolerance to +Gz acceleration eliminate the possibility of the occurrence of strong vasovagal reflex with sinus node arrest, asystole, and loss of consciousness. Such a reflex may be provoked by the LBNP in the absence of disease.