Colour Doppler ultrasound of the ocular circulation in patients with systemic lupus erythematosus identifies altered microcirculatory haemodynamics

Abstract

We assessed whether quantitative analysis of Doppler flow velocity waveforms is able to identify subclinical microvascular abnormalities in SLE and whether eigenvector analysis can detect changes not detectable using the resistive index (RI). Fifty-four SLE patients with no conventional cardiovascular risk factors, major organ involvement or retinopathy were compared to 32 controls. Flow velocity waveforms were obtained from the ophthalmic artery (OA), central retinal artery (CRA) and common carotid artery (CA). The waveforms were analysed using eigenvector decomposition and compared between groups at each arterial site. The RI was also determined. The RI was comparable between groups. In the OA and CRA, there were significant differences in the lower frequency sinusoidal components (P < 0.05 for each component). No differences were apparent in the CA between groups. Eigenvector analysis of Doppler flow waveforms, recorded in proximity of the terminal vascular bed, identified altered ocular microvascular haemodynamics in SLE. Altered waveform structure could not be identified by changes in RI, the traditional measure of downstream vascular resistance. This analytical approach to waveform analysis is more sensitive in detecting preclinical microvascular abnormalities in SLE. It may hold potential as a useful tool for assessing disease activity, response to treatment, and predicting future vascular complications.

Ocular Blood Flow Analysis Detects Microvascular Abnormalities in Impaired Glucose Tolerance

“…In this study, changes were identified in waveforms from a large artery (carotid) in addition to those recorded from the microvasculature (ophthalmic and central retinal arteries); however, the differences were not independent of blood pressure and other confounding factors. This highlights the importance of recording the flow velocity signal in close proximity to the microvascular bed, and supports previous observations [38].…”

“…The results from this study support previous findings demonstrating changes in the OA waveform that may be quantified using spectral analysis techniques, but not by the RI, the conventional measure of downstream vascular resistance [23]. More recently, our group has shown that frequency domain analysis, but not RI identifies ocular microcirculatory changes in SLE [38].…”

Comparison of Wavelet Transform and Time-Domain Analysis of Second Trimester Uterine Artery Doppler Waveforms in Screening for Pre-Eclampsia

“…Time-frequency domain analysis such as the WT reported in this paper describes the component frequencies that make up any particular waveform. There is no direct correlation between certain frequencies and obvious features such as notches on the waveform [14,15,16,19,20]. …”

“…Frequency-domain analysis incorporates the entire waveform data and extracts information from blood flow velocity waveforms not achieved through the use of established time-domain parameters such as the RI and PI [14,16]. Frequency-domain analysis has also been shown to be superior to conventional time-domain analysis in detecting microvascular abnormalities in patients with diabetes and autoimmune diseases [14,15,16]. …”

“…Traditional time-domain analysis using the resistance index (RI) and pulsatility index (PI) utilizes systolic, diastolic and mean velocities derived from Doppler waveforms to assess the downstream vascular resistance. As these indices are derived from isolated points along the entire waveform, they largely ignore its dynamic nature [14,15,16]. Frequency-domain analysis incorporates the entire waveform data and extracts information from blood flow velocity waveforms not achieved through the use of established time-domain parameters such as the RI and PI [14,16].…”