Coronary artery disease (CAD), a cardiovascular disorder precipitated by the atherosclerotic narrowing or occlusion of the coronary arteries, culminates in myocardial ischemia, hypoxia, or necrosis. As one of the foremost causes of morbidity and mortality worldwide, CAD represents an escalating public health concern. Chronic coronary syndrome (CCS) refers to the stable, long-term clinical manifestations of coronary artery disease (CAD), representing a progressive and sustained phase of the condition. Coronary microvascular dysfunction (CMD) is characterized by alterations in the structure and function of the coronary microcirculation, a condition frequently encountered in clinical practice. The presence of CMD, particularly when associated with atherosclerosis, may exacerbate myocardial ischemia in patients with chronic coronary syndrome (CCS). CMD is prevalent across a broad range of cardiovascular conditions, including heart failure with preserved ejection fraction (HFpEF), Takotsubo syndrome (TTS), acute coronary syndrome (ACS), myocardial infarction with non-obstructive coronary arteries (MINOCA), and CCS. It plays a pivotal role in the pathophysiology and prognosis of these diseases. Substantial evidence indicates that coronary microvascular dysfunction (CMD) is prevalent in patients with chronic coronary syndrome (CCS) and is closely linked to the pathogenesis and unfavorable prognosis of the condition. Therefore, the diagnosis of CMD carries significant implications for the management of CCS patients and the prevention of adverse outcomes.

The molecular mechanisms of CMD are not yet fully understood, but impaired pathologic dilation or increased constriction of coronary microvessels due to oxidative stress and inflammatory responses are thought to be the vital causative mechanisms of CMD.Studies have demonstrated that hyperglycemic states play a crucial role in CMD by altering the oxygen demand of cardiomyocytes, which leads to abnormal vascular regulation.Stress-induced hyperglycemia may aggravate coronary microvascular dysfunction (CMD) through mechanisms such as the induction of endothelial dysfunction and the promotion of oxidative stress, thereby contributing to adverse outcomes. Acute hyperglycemia, often undetected due to the lack of precise and effective monitoring methods, may arise from either pre-existing chronic hyperglycemia or acute physiological stress, leading to a transient increase in blood glucose levels upon hospital admission. In these instances, the stress hyperglycemia ratio (SHR) has been proposed as a novel marker to more accurately reflect the acute hyperglycemic state. The SHR is defined as the ratio of the blood glucose level at admission to the estimated average chronic glycemic value. SHR exerts a significant influence in numerous cardiovascular diseases, including MINOCA (myocardial infarction with non - obstructive coronary arteries), HFpEF (heart failure with preserved ejection fraction), and CAD (coronary artery disease). It thereby demonstrates its predictive capacity regarding survival risk and its value in risk-stratification procedures. To date, no studies have specifically investigated the prognostic implications of the stress hyperglycemia ratio (SHR) in CMD patients with CCS, highlighting the need for further research. Therefore, this study seeks to evaluate the predictive value of the stress hyperglycemia ratio (SHR) in CMD patients with CCS, and to elucidate its clinical relevance and significance, which remain poorly understood in this patient cohort.