QTQS2 ratio as an index of autonomic tone changes

摘要: Abstract The effects of changes in sympathetic tone on QT QS 2 ratio were studied 10 healthy subjects aged 21 to 24 years. underwent a bicycle ergometer exercise, tilt test, decrease carotid transmural pressure induced by means pneumatic neck chamber, an i.v. injection phenylephrine. A phonocardiogram and ECG simultaneously recorded at paper speed 100 mm/s evaluate QS2 intervals each test. In basal conditions, the was less than 1, whereas it increased progressively during physical exercise became greater 1 peak exercise. Both upright position increase neck-tissue significant as compared with values, administration phenylephrine reduced significantly ratio. These results demonstrate that those stimuli which induce rise adrenergic activity may contrast, reflex inhibition is accompanied reduction Therefore, might represent reliable index cardiac tone.