According to this study, insulin resistance, as defined by the TyG-BMI, is associated with left ventricular dyssynchrony in patients with type 2 diabetes, which worsens with increasing TyG-BMI, and this association remains stable even after taking into account relevant confounders. In particular, the TyG-BMI had a more significant effect on left ventricular dyssynchrony in type 2 diabetic patients younger than 55 years of age, men, and nonhypertensive individuals. As a result, it seems that the TyG-BMI can alert people at high risk to take more proactive preventative and follow-up measures.
With the concept of diabetes-related cardiomyopathy, an increasing number of experimental and clinical studies have confirmed the risk of heart failure in patients with diabetic cardiomyopathy. In diabetic cardiomyopathy patients with a normal LVEF, Arezoo et al. reported that left ventricular dyssynchrony occurred[27]. This resulted in an uncoordinated contraction of the left ventricle, a rise in left ventricular end-diastolic pressure, a shorter diastolic filling time, impaired heart efficiency[28], and an acceleration of heart failure[29]. Kapenatakis et al. demonstrated that the systolic dyssynchrony index (SDI) is a reliable measure of left ventricular dyssynchrony; higher SDI values are associated with greater systolic dysfunction[30-32]. Although the exact mechanism affecting left ventricular synchrony in diabetic patients remains unclear, insulin resistance, which is one of many factors contributing to diabetic cardiomyopathy, has a complex interaction with heart failure and can form a vicious cycle as a key link in diabetic cardiomyopathy[33]. In recent years, several studies have explored various methods that can easily predict IR calculated from lipid parameters and related parameters, and among these existing methods for assessing insulin resistance, several have demonstrated the outstanding ability of the TyG-BMI to measure insulin resistance and to predict early cardiovascular disease risk[34-37]. Dou et al. showed a strong association between the TyG-BMI and all-cause mortality and its predictive value for clinical outcomes in patients with heart failure[14]. Xu et al. also suggested that the TyG-BMI may assist in identifying those at risk of heart failure[38]. Nevertheless, there is insufficient evidence to support the conclusion that the TyG-BMI is associated with impaired left ventricular synchrony in patients with type 2 diabetes. In light of the ability of the TyG-BMI to predict cardiovascular disease, we investigated whether left ventricular dyssynchrony could be associated with cardiovascular disease.
In this study, we found that a substantial number of cardiovascular risk factors were associated with increasing quartiles of the TyG-BMI, including a higher incidence of hypertension, higher heart rate, lower density of lipoproteins, greater body mass index, etc., and prolonged SDI. This is in accordance with previous findings[39]. Additionally, multiple linear regression analysis indicated that the TyG-BMI was independently associated with the SDI, a measure of left ventricular dyssynchrony severity. These results suggest that the TyG-BMI may be a reliable indicator of left ventricular dyssynchrony in patients with T2DM.
As reported by Li et al., obesity, diabetes, and age are among the most important factors contributing to impaired left ventricular synchrony in metabolic syndrome patients, while hypertension does not play a major role[40]. A number of studies have demonstrated that age plays an important role in left ventricular hypertrophy and interstitial fibrosis and is an independent predictor of impaired left ventricular synchrony[41]. Furthermore, Boaz et al also demonstrated that increasing age was associated with greater left ventricular dyssynchrony[42]. However, there is a difference between the sexes in terms of myocardial responses to aging and specific cardiovascular risk exposures. The results of a multiethnic study of atherosclerosis (MESA) revealed that women and men differed not only in cardiac structure, function, and myocardial remodeling, but also in the induction and progression of left ventricular dyssynchrony[43].
To examine the relationship between the TyG-BMI and SDI in different populations, subgroup analyses were conducted on the basis of age and sex. The results demonstrated that the TyG-BMI was significantly associated with the SDI in younger patients (≤ 55 years) but not in older patients. This may be because elderly patients suffer from a greater number of cardiovascular risk factors than younger and middle-aged individuals. In addition to the loss of functional cardiac cells associated with aging, compensatory myocardial hypertrophy also increases, directly impairing cardiac function. Changes in metabolism, hypertension, and lipid metabolism are also associated with aging [44-46]. It is therefore necessary to conduct further research to clarify the relationship between the TyG-BMI and left ventricular dyssynchrony among elderly individuals. Additionally, the TyG-BMI was significantly associated with the SDI in male patients in the sex subgroup, which was more significant than that in the general population. These two subgroup results were similar to those of another Chinese study, which also revealed that the TyG-BMI was significantly positively associated with cardiovascular disease and cardiovascular mortality in young adults, whereas the TyG-BMI was more strongly associated with cardiovascular disease in men than in women[47]. This phenomenon may be attributed to the effects of sex hormones[48]. According to the studies of Qing et al., the TyG-BMI was superior in predicting visceral adiposity in men, with men accumulating more abdominal and visceral fat rather than fat under the skin, to the sex-specific regional adipose tissue distribution, which leads to greater risk of insulin resistance and cardiovascular disease due to androgen activity factors[49, 50]. However, studies on differences in the association between age and sex in terms of the TyG-BMI and cardiovascular disease risk are not uniform[51-54], possibly because of differences in study design, population characteristics, sex ratio, and age distribution. These findings may require additional large studies and meta-analyses in the future to validate them.
Strengths and limitations of the study
This study provides new insight into the association between the TyG-BMI and left ventricular dyssynchrony in a type 2 diabetic population, and subgroup analyses were conducted to determine whether this association is stable across different populations. However, the study has several limitations. First, since this was a single-center cross-sectional study, the scope and number of participants were somewhat limited. Second, this study excluded obese and elderly individuals who were suffering from chronic lung disease, which may have affected RT-3DE image quality, and the effect of the TyG-BMI on left ventricular dyssynchrony in diabetic patients, particularly elderly diabetic patients, may be underestimated. In addition, we did not follow up diabetic patients after admission to obtain data on the dynamic changes in triglycerides, blood glucose, and left ventricular dyssynchrony, which limited the ability to determine causality. Finally, because our study subjects were only Chinese individuals, the results may not be applicable to populations of other ethnicities.