Root-MUSIC analysis of nitric oxide-mediated changes in ophthalmic artery blood flow velocity waveforms

Clinical and experimental studies indicate that structural and functional changes in the microvasculature can predate or accompany risk factors for cardiovascular disease at the earliest stages in the disease process. In the current work, both simulated and actual Doppler ultrasound maximum blood velocity waveform envelopes recorded from the ophthalmic artery were analysed using a root-MUSIC and least squares fitting approach to determine amplitude frequency spectra. Both amplitude and frequency components of noise contaminated simulated waveforms were reliably determined indicating the robustness of the technique. The technique was then used to compare the spectral content of the ophthalmic artery blood velocity waveforms of normal controls in three test states: at baseline, following administration of GTN, a nitric oxide donor, and following administration of L-Name, a nitric oxide inhibitor. Principal components derived from root-MUSIC analysis discriminated between waveforms in baseline and non-baseline test states (p<0.00001) and between GTN and non-GTN test states (p=0.0002).