Microvascular reactivity in rehabilitating cardiac patients based on measurements of retinal blood vessel diameters

Abstract Background Exercise-based rehabilitation improves general cardiovascular fitness. The impact on the microvascular system has been studied in less detail. We measured changes in retinal blood vessel diameters, as a proxy for microvascular reactivity, in cardiac patients and we assessed the impact of a rehabilitation program on retinal vessel diameters. Design Cardiac patients (n = 78) and age-matched healthy controls (n = 32) performed an initial maximal endurance cycling test. Patients then participated in a 12-week rehabilitation program with additional endurance tests being performed six and twelve weeks after the initial test. Methods Fundus images were collected immediately before and 0, 5, 10, 15 and 30 min after the endurance test. Widths of retinal blood vessels, represented as Central Retinal Arteriolar/Venular Equivalent (CRAE/CRVE) were calculated from the images. Results At the start of the rehabilitation program, CRAE and CRVE values of the patients changed immediately after the endurance test with respectively −1.90 μm (95% CI: −3.58; −0.22) and −5.32 μm (95% CI: −7.33; −3.30) compared to baseline values. In contrast, CRAE and CRVE values of healthy controls were respectively increased [3.52 μm (95% CI: 2.34; 4.69)] and decreased [−3.17 μm (95% CI: −5.27; −1.07)]. After six and twelve weeks, CRAE responses of patients immediately after endurance test increased respectively with 5.98 μm (95% CI: 4.25; 7.71) and 4.44 μm (95% CI: 3.18; 5.71). These responses were similar to the microvascular reactions observed in the control group. Conclusions Arteriolar and venular retinal microvascular responses in cardiac patients were different from the ones of healthy controls. Retinal microvascular response of cardiac patients improved during rehabilitation.