Assessment of indices of conjunctival microvascular function in patients with and without obstructive coronary artery disease

Background: Atherosclerotic heart disease often remains asymptomatic until presentation with a major adverse cardiovascular event. Primary preventive therapies improve outcomes, but conventional screening often misattributes risk. Vascular imaging can be utilised to detect atherosclerosis, but often involves ionising radiation. The conjunctiva is a readily accessible vascular network allowing non-invasive hemodynamic evaluation. Aim: To compare conjunctival microcirculatory function in patients with and without obstructive coronary artery disease. Methods: We compared the conjunctival microcirculation of myocardial infarction patients (MI-cohort) to controls with no obstructive coronary artery disease (NO-CAD cohort). Conjunctival imaging was performed using a smartphone and slit-lamp biomicroscope combination. Microvascular indices of axial (V _a) and cross-sectional (V _cs) velocity; blood flow rate (Q); and wall shear rate (WSR) were compared in all conjunctival vessels between 5 and 45 μm in diameter. Results: A total of 127 patients were recruited (66 MI vs 61 NO-CAD) and 3602 conjunctival vessels analysed (2414 MI vs 1188 NO-CAD). Mean V _a, V _cs and Q were significantly lower in the MI vs NO-CAD cohort (V _a 0.50 ± 0.17 mm/s vs 0.55 ± 0.15 mm/s, p < 0.001; V _cs 0.35 ± 0.12 mm/s vs 0.38 ± 0.10 mm/s, p < 0.001; Q 154 ± 116 pl/s vs 198 ± 130 pl/s, p < 0.001). To correct for differences in mean vessel diameter, WSR was compared in 10–36 μm vessels (3268/3602 vessels) and was lower in the MI-cohort (134 ± 64 s ⁻¹ vs 140 ± 63 s ⁻¹, p = 0.002). Conclusions: Conjunctival microcirculatory alterations can be observed in patients with obstructive coronary artery disease. The conjunctival microvasculature merits further evaluation in cardiovascular risk screening.