Original ArticleCombining body mass index with waist circumference to assess coronary microvascular function in patients with non-obstructive coronary artery disease
Introduction
Obesity is a global epidemic resulting in an increase in cardiovascular disease (CVD). Obesity can be divided into two types—overall obesity measured by body mass index (BMI) and central obesity (CO) measured by waist circumference (WC). CO has been associated with increased cardiometabolic risk and impaired cardiac function and is predictive of subclinical atherosclerosis and cardiovascular disease.1, 2, 3 CO is also strongly correlated with mental stress, inadequate sleep, and an unhealthy lifestyle,4 all of which are related to a higher prevalence of adverse cardiac events.5, 6, 7
Angina pectoris affects approximately 112 million people globally; however, a large proportion of these patients (up to 70%) do not present with obstructive coronary artery disease (CAD).8 Coronary microvascular dysfunction (CMD) occurs early in the progression of atherosclerosis among patients with non-obstructive CAD and may precede obstructive plaque formation and significant angiographic stenosis.9 Pioneering positron emission tomography (PET) studies have demonstrated an association between overall obesity and impairment of coronary circulatory or microvascular function.10, 11, 12 However, at present, there are no reports documenting the impact of different adiposity patterns in CMD.
Conventional non-invasive testing for cardiac risk assessment in CAD includes measuring the angiographic stenosis or obstruction severity and quantification of left ventricular function. However, these approaches do not effectively account for CMD, especially in subclinical high-risk subgroups. Electrocardiography (ECG)-gated myocardial perfusion imaging (MPI) with 13N-ammonia PET has demonstrated excellent diagnostic accuracy of CMD through evaluating myocardial blood flow (MBF) as well as myocardial flow reserve (MFR) and offers the added value of measuring hemodynamic parameters and cardiac function.13,14 In this study, we sought to investigate the associations between CMD and patterns of body adiposity based on BMI and WC among patients with non-obstructive CAD through ECG-gated 13N-ammonia PET-MPI.
Section snippets
Study Population and Design
Patients were prospectively enrolled in our study between March 2017 and January 2021. The study population included consecutive patients who underwent ECG-gated 13N-ammonia PET-MPI for evaluation of suspected CMD based on clinical symptoms, but not obstructive CAD (defined as ≥ 50% luminal stenosis) confirmed by clinically indicated invasive coronary arteriography or coronary computed tomography angiography within 3 months prior to the PET study. The most common indication for testing was the
Patient Characteristics
Table 1 summarizes the demographic and clinical characteristics of the 128 participating patients. Of these, 61 (47.66%) patients were categorized into the normal weight group (BMI < 25 kg/m2); 67 (52.34%) were categorized into the excess weight group (BMI ≥ 25 kg/m2), where 13 patients (10.16%) had a BMI ≥ 30 kg/m2. Of all patients, 61 (47.66%) were categorized into the centrally obese group. Notably, all patients with overall obesity also had CO. Thus, the patients with a BMI ≥ 30 kg/m2 were
Discussion
In this study, we investigated the integrated predictive value of two independent anthropometric indices (BMI and WC) on CMD risk in patients with non-obstructive CAD. We demonstrated, to our knowledge, for the first time that patients with CO showed lower hyperemic MBF and MFR, as well as a higher prevalence of CMD. In particular, patients with NWCO presented the lowest hyperemic MBF and MFR and the highest incidence rates of CMD among patients with non-obstructive CAD. Furthermore, we
Limitations
Our study had certain limitations. First, since this was a single-center study, the findings may not be generalizable to a broad population. Second, statistical power could be limited owning to the relatively small sample size of this study. Furthermore, we inadvertently recruited an unbalanced subgroup based on the representative distribution of participants of normal weight or excess weight. Third, we did not collect information on potentially confounding health behaviors such as disordered
Conclusion
In this study, we report that CO may be associated with decreased coronary microvascular function in patients with non-obstructive CAD, with the highest level of CMD risk observed among patients with NWCO. Hence, hyperemic MBF and MFR could facilitate the clinical management of non-obstructive CAD patients. Future studies are warranted to investigate the potential role of MBF or MFR regarding CVD risk management, while considering a variety of body fat indices.
New Knowledge Gained
In patients with non-obstructive CAD, patients with CO, especially those with normal weight, are more likely to have CMD. On the contrary, being overweight or obese based on BMI criteria does not lead to a higher risk of CMD in the absence of CO. Thus, measurement of WC may complement the use of BMI in CMD risk stratification, especially for patients with a normal BMI.
Funding
Our study was funded by special funds of the Collaborative Innovation Center for Molecular Imaging of Precision Medicine and the National Natural Science Foundation of China (Grant Nos. 81671724, 81901785, 62005150), as well as the 100 Talents Program of Shanxi province.
Disclosures
Our study was funded by special funds of the Collaborative Innovation Center for Molecular Imaging of Precision Medicine and the National Natural Science Foundation of China (Grant Nos. 81671724, 81901785, 62005150), as well as the 100 Talents Program of Shanxi province. None of the authors have anything to disclose.
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Shihao Huangfu and Qi Yao have contributed equally to this study.
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All editorial decisions for this article, including selection of reviewers and the final decision, were made by guest editor Ahmed Tawakol, MD.