Assessment of hemodynamic indices of conjunctival microvascular function in patients with coronary microvascular dysfunction

Objective: Coronary microvascular dysfunction (CMD) is a cause of ischaemia with non-obstructive coronary arteries (INOCA). It is notoriously underdiagnosed due to the need for invasive microvascular function testing. We hypothesized that systemic microvascular dysfunction could be demonstrated non-invasively in the micro -circulation of the bulbar conjunctiva in patients with CMD. Methods: Patients undergoing coronary angiography for the investigation of chest pain or dyspnoea, with physiologically insignificant epicardial disease (fractional flow reserve >= 0.80) were recruited. All patients un-derwent invasive coronary microvascular function testing. We compared a cohort of patients with evidence of CMD (IMR >= 25 or CFR <2.0); to a group of controls (IMR <25 and CFR >= 2.0). Conjunctival imaging was performed using a previously validated combination of a smartphone and slit-lamp biomicroscope. This tech-nique allows measurement of vessel diameter and other indices of microvascular function by tracking erythrocyte motion. Results: A total of 111 patients were included (43 CMD and 68 controls). There were no differences in baseline demographics, co-morbidities or epicardial coronary disease severity. The mean number of vessel segments analysed per patient was 21.0 +/- 12.8 (3.2 +/- 3.5 arterioles and 14.8 +/- 10.8 venules). In the CMD cohort, sig-nificant reductions were observed in axial/cross-sectional velocity, blood flow, wall shear rate and stress. Conclusion: The changes in microvascular function linked to CMD can be observed non-invasively in the bulbar conjunctiva. Conjunctival vascular imaging may have utility as a non-invasive tool to both diagnose CMD and augment conventional cardiovascular risk assessment.

Automated summary

Coronary microvascular dysfunction (CMD) can be observed non-invasively in the bulbar conjunctiva, which suggests that conjunctival vascular imaging may serve as a non-invasive tool for diagnosing CMD and enhancing conventional cardiovascular risk assessment.