Bradycardia induced by negative acceleration.
Four volunteers were subjected to negative acceleration in a human centrifuge for the purpose of testing a standard lap belt. Three subjects developed a sinus bradycardia. The fourth developed a sinus arrest with a junctional rhythm at -2 G. With return to +1 G, the sinus mechanism recovered with a prolonged P-R interval. Within 2 h, the P-R interval returned to normal. Negative acceleration maneuvers, well within the capabilities of high-performance aircraft, can effect marked changes in the cardiac rhythm. This phenomenon appears to be vagally induced and is remarkably well tolerated.
D000054:Acceleration / Q000009:adverse effects*; D000337:Aerospace Medicine; D001919:Bradycardia / Q000209:etiology*; D006801:Humans