Introduction: Endothelial dysfunction is associated with short term and long term cardiovascular events. African Americans (AA) have worse cardiovascular outcomes than Non-African Americans (NAA). AAs have higher chronic stress exposure due to socioeconomic deprivation which may affect vascular responses to stress and contribute to health disparities. Our hypothesis was that AA would have abnormal microvascular function after a standardized mental stress as compared to NAA.
Methods: We evaluated 692 patients (208 AA) with confirmed coronary artery disease (CAD), who underwent a standardized mental stress challenge. Endothelial function measurements were obtained before and 30 minutes after mental stress testing using a speaking task. Reactive hyperemia index (RHI) was measured using peripheral arterial tonometry (PAT) (Itamar Inc) as the ratio of hyperemic to baseline finger-tip microvascular blood flow signal. Flow-mediated dilation (FMD) was measured using ultrasound as the ratio of hyperemic to baseline brachial artery diameter.
Results: As compared to NAA, AA patients were younger, had lower levels of education, and income, and a higher prevalence of co-morbidities. AA patients prior to stress had similar mean RHI (2.07 vs 2.13, p=0.3) but lower mean FMD (3.54 vs 4.76, p=0.0005) as compared to NAA. However, after mental stress, mean RHI was significantly lower in AA, (1.98 vs 2.2, p=0.0002) and mean FMD continued to be lower in AA (2.87 vs 3.81, p=0.005). After adjusting for baseline RHI in addition to age, sex, BMI, cardiovascular risk factors, and depression in a multivariable model, race remained significantly associated with post-stress RHI (p= 0.004). However, race was no longer associated with post-stress FMD after adjusting for pre-stress FMD. (p=0.37).
Conclusion: AA patients with CAD, compared with NAA, have worse baseline endothelial-dependent function, which persists after mental stress. Furthermore, AA have a more pronounced decrease in endothelial function with mental stress compared with NAA. Whether this more adverse vascular reactivity with stress is implicated in race-based disparities in cardiovascular disease requires further study.