CHANGES IN OSCILLATORY PATTERNS OF CARDIORHYTHM AS AN INDICATOR OF COMPENSATORY MECHANISMS TO ORTHOSTATIC LOAD IN PATIENTS WITH NEUROGENIC SYNCOPE

Abstract

Purpose . To study the characteristics of the oscillatory patterns of cardiorhythm during an active orthostatic test in patients with neurogenic syncope using spectral analysis of heart rate variability. Materials and methods . There was carried out the spectral analysis of short five-minute plots of cardiorhythm including the determination of the oscillatory power in the range of high, low and very low frequencies. There were compared the changes in the indicators within the selected ranges during an active orthostatic test in 82 patients with neurogenic syncope. Results . There was disclosed autonomic failure in 70 % of the patients. It declared itself in the reduction of the power of low frequency oscillations by 50 % in average and a more marked decrease of high-frequency oscillations by more than 80 % from baseline in the supine position, which provides the urgent compensatory response to maintain sympathetic vasomotor influence during orthostatic stress. The reduced power of oscillations in the range of very low frequency indicates a failure of the system of a long-term compensation to orthostatic hypotension in patients with neurogenic syncope.