VARIABILITY OF NEAR-FAINTING RESPONSES IN HEALTHY 6-16-YEAR-OLD SUBJECTS

1. Fainting is a common phenomenon in young subjects, but the final ev ents before the actual faint are not well known, The aim of the presen t study was to study the inter-individual variability of haemodynamic events associated with near-fainting in children and teenagers. 2. Six ty-eight healthy subjects (aged 6-16 years) performed a 70 degrees til t-up test with intravascular instrumentation for 5 min, Responses in 2 9 near-fainting subjects were analysed and compared with 39 non-fainti ng subjects, Arterial pressure was measured by Finapres, Left ventricu lar stroke volume was computed from the pressure pulsation waveform, 3 . Inability to maintain vasomotor tone was the mechanism underlying ne ar-fainting in majority of near-fainting subjects, The three classical haemodynamic responses (vasovagal, vasodepressor and vagal) could be recognized, but large individual differences were found, After tilt ba ck, blood pressure in near-fainters showed a mirror response to the st age before tilt-back; blood pressure gradually increased and was norma l at 1 min after tilt-back. 4. The variability in haemodynamic respons es on approach of an orthostatic faint is wide in the young.