Microvascular dysfunction and pulse wave reflection characterize different vascular pathologies in patients at cardiovascular risk

Abstract

Endothelial function and arterial pulse wave reflections play a crucial role in the pathogenesis of atherosclerosis. While the endothelium-dependent reactive hyperemia index (RHI) of the digital arteries is considered as a marker of microvascular function, an increased augmentation index (AI) may indicate beginning macrovascular damage. In this study we assessed the interrelationships among these noninvasive measures of vascular function. In 178 all-comer patients with documented cardiovascular risk factors (22 % female; 65 % coronary artery disease, CAD), we measured radial AI (rAI) by radial applanation tonometry and digital AI (dAI) as well as RHI by using fingertip peripheral arterial tonometry. A modified SMART risk score was calculated in all participants based on cardiovascular risk factors and preexisting vascular disease. dAI and rAI demonstrated a significant and robust overall correlation (Pearson rank coefficient r = 0.63, p < 0.01), which was not affected by age, sex, diabetes mellitus and CAD. In contrast, both parameters demonstrated at most a weak correlation (dAI: r = 0.26, p < 0.01 and rAI: r = 0.12, p = 0.10) with microvascular function (RHI). While dAI and rAI were significantly correlated to female sex, age, low body height, low heart rate and the presence of CAD, RHI was associated with the presence of diabetes mellitus and nicotine use. Finally, only microvascular function was associated with the modified SMART risk score, but not augmentation indices. RHI and increased pulse wave reflection appear to represent two distinct vascular pathologies in patients with cardiovascular risk. In contrast, RHI might be useful to identify patients at highest cardiovascular risk once atherosclerotic disease has been diagnosed.