Considering the lack of appropriate non-invasive serological indices for the clinical assessment of the extent of CAD in patients with ACS, we designed the present study to investigate the relationship between the TyG-BMI index and the extent of CAD in patients with ACS. The main findings can be summarised as follows: (1) the TyG-BMI index is associated with an increased risk of complex CAD (moderate/high SYNTAX scores) among female patients, and (2) the inclusion of TyG-BMI index has limited ability to improve the predictive power of the baseline risk model in female patients with ACS.
IR is an important pathogenetic mechanism in type 2 diabetes [30]. IR usually refers to the reduced sensitivity or responsiveness of the body to insulin metabolism and contributes to the development of CVD through a variety of mechanisms, including alterations in classical CVD risk factors and down-regulation of insulin signalling pathways, with the reduced production of nitric oxide, caused by IR, playing an important role in the development of CVD [5, 31]. The HOMA score is a reliable measure of IR, whereas the TyG index, a simple and easily accessible metric, has recently been recognised as being superior to HOMA in identifying IR [6, 8]. In addition, obesity, defined by BMI, plays an important role in the progression of IR [18]. A study based on a Korean population showed that the TyG-BMI index, calculated using the TyG index and BMI, predicted IR and outperformed the TyG index alone [20], providing new insights into the relationship between the TyG-BMI index and poor cardiovascular prognosis by correcting the TyG index for BMI. Currently, TyG-BMI index is considered a simple, powerful, and clinically useful alternative marker for early detection of IR [27]. However, to date, the relationship between the TyG-BMI index and the extent of CAD in patients with ACS is unclear. In the present study, we focused on the relationship between the TyG-BMI index and the extent of CAD in patients with ACS and found that the TyG-BMI index was associated with an increased risk of complex CAD among female patients and had some predictive value. It is worth noting that the TyG-BMI index contains three typical CVD risk indicators, i.e., lipid-, glycaemic-, and obesity-related components, and therefore, we performed this analysis to obtain accurate associations. To the best of our knowledge, the current study may be the first to examine the relationship between the TyG-BMI index and the extent of CAD in patients with ACS. In our study, the SYNTAX score was used to quantify coronary disease severity. Further, we adjusted for possible risk factors. Intriguingly, we did not find a significant association between the TyG-BMI index and complex CAD in the entire study population. Therefore, we performed exploratory analyses of sex, age, and DM subgroups. The results showed that in female patients, a higher TyG-BMI index was associated with a greater risk of complex CAD. Previous studies have also shown a correlation between TyG-BMI index and major adverse cardiac and cerebrovascular events (MACCEs) in female patients [32, 33]. Cheng et al. [32] included 2,533 subjects treated with PCI and drug-eluting stent implantation in a retrospective cohort study with the endpoint defined as the composite of acute MI, repeat haemodialysis, stroke, and all-cause mortality at the 34-month follow-up and found that in older and female patients, higher TyG-BMI index was associated with a higher incidence of MACCEs. Similarly, Zhang et al. [33], included 2,533 patients who underwent PCI in a retrospective cohort study with a median follow-up period of 29.8 months, with the endpoint defined as the occurrence of MACCEs and found that the TyG-BMI index was significantly associated with MACCEs in women and in elderly patients. This indirectly validates that TyG-BMI index may be associated with an increased risk of complex CAD in female patients with ACS, which is consistent with the findings of our study. In contrast, there was no significant correlation between TyG-BMI index and complex CAD in male patients. The reasons for this sex difference are unclear but may be partially explained as follows. First, women have a higher burden of cardiovascular risk factors compared to men, and lipid levels and hypertension have a greater adverse effect on women [34]. Second, testosterone is the main male sex hormone, and low testosterone levels are associated with increased cardiovascular risk; hormonal differences between sexes may therefore partly explain the sex differences in patients with ACS and complex CAD [35, 36]. Finally, most women in this study were in the menopausal transition period or in menopause, and oestrogen has a protective effect on the cardiovascular system [37]. Women are at increased risk of vascular endothelial dysfunction during the menopausal transition or after menopause when the protective effect of oestrogen on the circulatory system is diminished or lost [38, 39]. However, more research is needed to validate this association and investigate its exact mechanism. Therefore, there is an urgent need to conduct further studies to provide more evidence on whether the TyG-BMI index can predict cardiovascular prognosis in patients with ACS. Furthermore, in female patients, the addition of TyG-BMI index to the baseline risk model had no significant incremental effect on predicting the risk of complex CAD. However, unlike a previously cited study, we did not observe an association between TyG-BMI index and an increased risk of complex CAD in elderly patients with ACS, and we hypothesise that this may have been due to the inclusion of younger patients in groups T3 and T2 when compared with that in group T1 as well as an insufficient sample size. Alternatively, this may have been due to the heterogeneity of the included population and the study design.
Strength and limitations
This is the first time that a higher TyG-BMI index has been proposed to be linearly associated with the risk of developing complex coronary lesions in female patients with ACS. However, this study has some shortcomings. First, this was a single-centre study that included only Asian patients, and thus, our results should be interpreted with caution. Secondly, the current study is limited by its retrospective design, which does not allow inferences regarding causality to be drawn, and further prospective multi-centre studies are needed to validate these results. In addition, we cannot completely exclude the possibility of unmeasured or unknown confounders that may explain the associations observed in this study.