Late Saphenous Vein Graft Disease: Cut to the Chase

Dear editor

We read the interesting article entitled “The Role of Systemic Immune Inflammation Index for Predicting Saphenous Vein Graft Disease in Patients with Coronary Artery Bypass Grafting.” ¹ We would like to discuss some additional points.

The authors ¹ included 716 consecutive patients who underwent elective coronary angiography >1 year after coronary artery bypass grafting (CABG). They investigated the role of the systemic immune inflammation index (SII) in predicting the development of saphenous vein graft disease (SVGD) in these patients.

Mechanisms similar to atherosclerosis play a role in the development of late SVGD. ² When the saphenous vein encounters arterial pressure, it adapts to this situation. ² Endothelial cells are sensitive to shear stress changes, and vascular smooth muscle cells (VSMC) sense pressure changes. ³ Thus, arterialization occurs in the vein wall. If this situation cannot be controlled, it results in intimal hyperplasia and SVGD.^2,3 Various transcription factors (Kruppel-like factor 4, signaling pathways, like p38 mitogen-activated protein kinase, and nuclear factor kappa-light-chain enhancer of activated B cells) are involved in this process. ⁴ These factors affect the expression of contractile proteins in VSMC.^4,5

The SII value also indicates the severity of atherosclerosis. ⁶ A significant correlation was shown with the SYNTAX score in patients with coronary artery disease. ⁶ Could the high SII values in the study ¹ be related to the high SYNTAX score? Moreover, atherosclerosis is a systemic disease. Could the severity of atherosclerosis in the entire arterial system of these patients have affected the SII values?

In their multivariate analysis, the authors identified SII and neutrophil-lymphocyte ratio (NLR) as independent predictors of SVGD. ¹ The SII value is obtained by multiplying the NLR value with the platelet count. The inclusion of two variables with common content in the same multivariate analysis may be misleading.

In conclusion, the development of SVGD is a complex process. Many factors may affect the development of SVGD, such as the preparation technique of the graft, the diameter of the target coronary vessel, whether percutaneous intervention has been performed on the target coronary vessel before, the extent of atherosclerosis in the target coronary vessel, and the adherence of the patients with their medical treatment.^7,8