Predictive value of system immune-inflammation index for the severity of coronary stenosis in patients with coronary heart disease and diabetes mellitus

Coronary heart disease (CHD) has been recognized as a chronic progressive inflammatory disorder, and Diabetes mellitus (DM) is an independent risk factor for the pathogenesis of CHD. Recent research has underscored the systemic immune-inflammation index (SII) as a potent prognostic indicator for individuals suffering from acute coronary syndrome (ACS). This study aimed to delve into the relationship between SII and the degree of coronary atherosclerotic stenosis in non-acute myocardial infarction patients with or without DM. We enrolled a total of 2760 patients with cardiovascular disease between November 2023 and May 2024. All eligible participants were divided into the CHD group and the DM & CHD group according to the existence of comorbid DM. Our study revealed that the SII values were significantly higher in diabetic patients with CHD compared to those with CHD alone (P < 0.05). Furthermore, among patients with both CHD and DM, higher SII values were associated with a greater likelihood of developing complex, triple-branch coronary artery lesions, while the opposite trend was observed in CHD populations (P < 0.05). In the regression model completely adjusted for potential confounders, the correlation between high SII levels and co-existing DM status in CHD patients persisted as statistically significant even after attaining guideline-recommended LDL-C and TG goals (P < 0.05). Moreover, our findings demonstrated a significant link between SII levels and the severity of coronary artery stenosis as assessed by coronary angiography, particularly in the DM and CHD patient cohorts (P < 0.05). Further stratified analysis revealed a novel finding that SII levels in DM and CHD patients maintained a positive linear relationship with coronary plaque burden even under stringent glycemic control (P < 0.01, r = 0.37), whereas this correlation was absent in CHD patients who had FBG of 7 mmol/L or lower upon admission (P < 0.01, r < 0.30). These important findings underscore the SII as an independent predictor of the severity of coronary plaque burden in diabetic patients with CHD, offering valuable insights that can aid clinicians in refining risk stratification and implementing personalized management strategies for those at elevated risk.