Abstract
Purpose:
Endothelial dysfunction is strongly associated with type 2 diabetes and cardiovascular disease. Digital reactive hyperemia (Endopat®) following brachial ischaemia-induced hyperemia has traditionally been used to examine endothelial function, however, it only measures large artery endothelial function. Flicker light-induced retinal vasodilation has been shown to reflect endothelial function in the retinal circulation while previous studies have shown that reduction in retinal vasodilation after flicker light stimulation is independently associated with diabetes. We aimed to determine if a novel method of assessing endothelial function, ECG-gated retinal artery flicker provocation, is associated in subjects with and without type-2 diabetes mellitus (T2DM), and we confirmed the presence of endothelial dysfunction with digital reactive hyperemia.
Methods:
Thirty non-diabetic age-sex matched control subjects and 30 patients from the outpatient diabetes clinic in Westmead Hospital, Sydney, Australia were randomly selected to participate in this study. ECG-gated retinal fundus photographs were taken at 10-second intervals for a period of 1 minute pre-flicker, 2 minutes with flicker light-stimulation, and 1 minute post-flicker. A semi-automated software analysis program, developed in-house, was used to measure retinal vessel caliber in ECG-gated photographs. Reactive hyperemic index (RHI) was also examined (EndoPAT 2000). Subjects with proliferative diabetic retinopathy and cardiovascular complications were excluded. The independent t-test was used to assess statistical significance.
Results:
The mean age of participants and the duration of diabetes in subjects with T2DM was 36.9±14.2 and 12.1± 8.8 years respectively. The majority of subjects were female (62%) and all subjects with diabetes had minimal to no diabetic retinopathy. Mean arterial vasodilation in response to flicker was significantly impaired in subjects with T2DM compared with controls (1.76 ± 0.70 vs. 3.16 ± 1.31%, p<0.001). RHI was also significantly reduced in patients with diabetes compared with controls (1.68± 0.64 vs. 1.98 ± 0.53, p=0.002).
Conclusions:
This ECG-gated retinal imaging system demonstrated an impairment of retinal artery vasodilation during flicker provocation in T2DM. This system may represent a useful, non-invasive method for the assessment of endothelial function in patients with diabetes.