Non-invasive assessment of the conjunctival microcirculation in patients with coronary and valvular heart disease

Abstract

Cardiovascular (CV) disease often remains asymptomatic until first presentation with a major adverse cardiovascular event. CV risk assessment is therefore recommended in asymptomatic adults to identify individuals with modifiable vascular risk factors. Changes in the microcirculation occur early in atherosclerotic cardiovascular disease and therefore identification of asymptomatic microvascular dysfunction may allow CV risk recategorisation. The microvasculature of the bulbar
conjunctiva can be assessed non-invasively using a combination of a smartphone and slit-lamp biomicroscope.

This project sought to determine if differences could be observed in parameters of conjunctival microvascular function in patients with coronary artery or valvular heart disease in comparison to age- and sex-matched control cohorts. Chapter 3 describes the comparison of 66 patients with acute myocardial infarction (MI) and 61 controls with angiographically non-obstructive coronary arteries and no history of MI or coronary intervention. In the MI cohort, significant reductions were observed in conjunctival axial- and cross-sectional velocity, blood flow and wall shear rate.

Chapter 4 describes the comparison of 43 patients with invasive evidence of coronary microvascular dysfunction (CMD) and 68 controls with no obstructive coronary artery disease, or invasive evidence of CMD. In the CMD cohort, significant reductions were observed in conjunctival arteriole axial- and cross-sectional velocity, blood flow, wall shear rate and wall shear stress.

Chapter 5 describes the comparison of 90 patients with severe aortic stenosis (SAS) undergoing TAVI and 75 controls with no significant valvular heart disease. There were sex-specific differences in conjunctival microvascular haemodynamics in females in the SAS cohort in comparison to controls. In this sub-group significant increases in arteriole axial- and cross-sectional velocity and wall shear rate were observed following TAVI.

This thesis reports alterations in systemic microvascular function in patients with MI, CMD and SAS. These findings suggest the possible utility of conjunctival microvascular screening in CV risk assessment.

Date of Award	Sept 2022
Original language	English
Sponsors	Northern Ireland Chest Heart and Stroke & Belfast Heart Trust Fund
Supervisor	Andrew Nesbit (Supervisor), Tara Moore (Supervisor) & Mark Spence (Supervisor)