Assessment of the conjunctival microcirculation for patients presenting with acute myocardial infarction compared to healthy controls

Abstract

Microcirculatory dysfunction occurs early in cardiovascular disease (CVD) development. Acute myocardial infarction (MI) is a late consequence of CVD. The conjunctival microcirculation is readily-accessible for quantitative assessment and has not previously been studied in MI patients. We compared the conjunctival microcirculation of acute MI patients and age/sex-matched healthy controls to determine if there were differences in microcirculatory parameters. We acquired images using an iPhone 6s and slit-lamp biomicroscope. Parameters measured included diameter, axial velocity, wall shear rate and blood volume flow. Results are for all vessels as they were not sub-classified into arterioles or venules. The conjunctival microcirculation was assessed in 56 controls and 59 inpatients with a presenting diagnosis of MI. Mean vessel diameter for the controls was 21.41 ± 7.57 μm compared to 22.32 ± 7.66 μm for the MI patients (p < 0.001). Axial velocity for the controls was 0.53 ± 0.15 mm/s compared to 0.49 ± 0.17 mm/s for the MI patients (p < 0.001). Wall shear rate was higher for controls than MI patients (162 ± 93 s−1 vs 145 ± 88 s−1, p < 0.001). Blood volume flow did not differ significantly for the controls and MI patients (153 ± 124 pl/s vs 154 ± 125 pl/s, p = 0.84). This pilot iPhone and slit-lamp assessment of the conjunctival microcirculation found lower axial velocity and wall shear rate in patients with acute MI. Further study is required to correlate these findings further and assess long-term outcomes in this patient group with a severe CVD phenotype.

A novel algorithm for cardiovascular screening using conjunctival microcirculatory parameters and blood biomarkers

“…The aim of this study was to develop a screening tool that could be used to identify patients at risk of CAD. Our previous study detected changes in conjunctival microvascular measurements between control and post-MI patients 31 . As part of the study, blood samples were collected to determine if blood biomarkers could be used in conjunction with microvascular measurements to improve the diagnostic potential of the test.…”

“…Troponin, lipids, NT-proBNP, urate, urea and electrolytes and all other biochemical measurements, were analysed by clinical staff at the Kelvin Building Laboratories, Royal Victoria Hospital, Belfast. Apo-lipoprotein A and B were analysed by the Biochemistry Department, Cardiff and Vale University Hospital, UK as reported previously 31 .…”

“…Blood flow within the conjunctival vasculature can be directly visualised and hence assessment of microcirculatory parameters (e.g. velocity (V), flow (Q), wall shear rate (WSR)) can also be measured non-invasively 29 – 31 . The study by Brennan et al 31 assessed groups of subjects with and without hypertension, diabetes mellitus, dyslipidaemia, reduced left ventricular ejection fraction (< 50%), as well as smokers vs. non-smokers.…”

“…velocity (V), flow (Q), wall shear rate (WSR)) can also be measured non-invasively 29 – 31 . The study by Brennan et al 31 assessed groups of subjects with and without hypertension, diabetes mellitus, dyslipidaemia, reduced left ventricular ejection fraction (< 50%), as well as smokers vs. non-smokers. The results show only the blood flow rate (pl/s) increased significantly in diabetics vs. non-diabetics respectively (181 ± 61 vs. 151 ± 39 pl/s, p = 0.04).…”

COVID-19 hemodynamic and thrombotic effect on the eye microcirculation after hospitalization: A quantitative case-control study

“…Warner et al measured temporal and spatial variations of blood velocity in the healthy human retina using dual beam AOSLO, without reporting capillary diameters [23] which correlate with velocity [24]. CVC hemodynamic metrics have been shown to correlate with hypertension [25], cardiovascular risk [26], diabetic microvasculopathy [27], sickle cell retinopathy [28], acute myocardial infarction [29], oral contraceptives [30] and the administration of medical supplements [31].…”