Association of obstructive sleep apnea with endothelial function and heart remodeling in hypertension: A cross-sectional study

Introduction

Hypertension (HTN) is one of the most common chronic diseases and the most imperative cardiovascular risk factor.

In China, about 23.2% of adults have HTN. Endothelial dysfunction is a fundamental aspect of the vascular damage observed in HTN. Moreover, HTN can increase the prevalence of adverse heart remodeling. Recent research confirms a close association between HTN and obstructive sleep apnea (OSA). In patients with hypertension, the prevalence of OSA is up to 50% ^, , and about 30-70% of OSA patients have HTN. OSA is defined as episodes of obstruction of the upper airway during sleep. AHI is defined by the average number of apnea and hypopnea events per hour. According to AHI, OSA is graded into 3 severity groups: mild OSA (5 ≤ AHI < 15 events/h), moderate OSA (15 ≤ AHI < 30 events/h), and severe OSA (AHI ≥ 30 events/h). OSA has become a health problem of global concern, estimated to affect approximately 13-33% of males and 6-19% of females. ^, Hypoxia and hypercapnia caused by OSA are closely associated with endothelial dysfunction and heart remodeling and would eventually boost the risk of cardiovascular events. HTN and OSA can induce a systemic pro-inflammatory state, which is the main cause of endothelial dysfunction and heart remodeling. C-reactive protein (CRP), an inflammatory factor, has a predictive value for cardiovascular events.

Furthermore, CRP seems to be the most promising inflammatory biomarker for clinical research.

Portable sleep monitoring (PSM) is a technology that can simultaneously record and analyze multiple sleep physiological parameters (including AHI, minimal oxygen saturation, and duration of oxygen saturation <90%) and can conduct sleep medical research and sleep disease diagnosis outside the sleeping room. Measurement of endothelial function in patients has recently emerged as a helpful tool for atherosclerosis research. The endothelial function can be accurately reflected by measuring the flow-mediated vasodilation (FMD) of the brachial artery with high-resolution ultrasound. Meanwhile, the operation is simple, non-invasive, and has good repeatability.

^, A considerable number of clinical studies have revealed that FMD can be used as a predictor of cardiovascular events in general populations. Transthoracic echocardiography is a non-invasive, low-cost, and accurate technology for assessing alterations in heart structure and function. LVMI obtained by echocardiography is one of the prognostic factors of cardiovascular morbidity and mortality and has been demonstrated to be a sensitive tool for detecting LVH. ^, Regarding patients with HTN and OSA, it is more likely to have an additive deleterious effect on endothelial function and heart structure. However, there is little research on whether there is a correlation between endothelial dysfunction and heart remodeling indices and OSA in patients with HTN. This cross-sectional study is conducted to investigate the association of OSA with endothelial function and heart structure in patients with HTN, so as to provide a reference for clinical treatment.