Application of wavelet analysis to detect dysfunction in cerebral blood flow autoregulation during experimental hyperhomocysteinaemia.

Abstract

The purpose of the present study was to investigate the use of laser Doppler flowmetry (LDF) signals coupled with spectral wavelet analysis to detect endothelial link dysfunction in the autoregulation of cerebral blood flow in the setting of hyperhomocysteinaemia (HHcy). Fifty-one rats were assigned to three groups (intact, control, and HHcy) according to the results of biochemical assays of homocysteine level in blood plasma. LDF signals on the rat brain were recorded by LAKK-02 device to measure the microcirculatory blood flow. The laser operating wavelength and output power density were1064nm and 0.051W/mm2, respectively. A Morlet mother wavelet transform was applied to the measured 8-min LDF signals, and periodic oscillations with five frequency intervals were identified (0.01-0.04Hz, 0.04-0.15Hz, 0.15-0.4Hz, 0.4-2Hz, and 2-5Hz) corresponding to endothelial, neurogenic, myogenic, respiratory, and cardiac origins, respectively. In initial state, the amplitude of the oscillations decreased by 38% (P < 0.05) in the endothelial range in HHcy rats than in control rats. Cerebral autoregulation was challenged by hemorrhagic hypotension. The lower limit of autoregulation raised in a rat model of chronic HHcy (71.5 ± 0.7mmHg in HHcy vs. 62.3 ± 0.5mmHg in control). The data obtained indicate that the laser Doppler method and wavelet analysis may be successfully applied to detect the dysfunction of the endothelial link in cerebral vessel tone and to reveal the pathological shift of lower limit of autoregulation.