Wave reflection signatures: identifying early microvascular abnormalities in type 2 diabetes

Microvascular changes occur early in diabetes mellitus. Doppler ultrasound enables non-invasive identification of ocular microvascular haemodynamics through interrogation of blood flow velocity waveforms. Wave decomposition permits the spectrum of sinusoidal components comprising flow velocity waveforms to be quantified. We hypothesised that comprehensive interrogation of waveforms would be more sensitive in identifying microvascular abnormalities than traditional analysis employing the resistive index. Thirty-four subjects with type 2 diabetes and 20 healthy controls between 30 and 70 years old were recruited. Doppler flow velocity waveform signals were captured from the ophthalmic and carotid arteries under standardised conditions. The signals were analysed using a wave decomposition algorithm and the sinusoidal components of average waveforms were compared between groups at both arterial sites. The diabetes group displayed significant differences in the lower frequency sinusoidal components of both the ophthalmic artery (p<0.001) and, to a lesser extent, the carotid artery (p<0.05) waveforms compared with controls, with no difference noted in the resistive index at either site. We conclude that wave decomposition analysis of Doppler flow velocity waveforms, recorded in proximity of the terminal vascular bed of interest, can identify subtle microvascular haemodynamic abnormalities not detected by traditional methods of analysis.