Abstract
BackgroundThere is growing evidence about the importance of epicardial adiposity on cardiometabolic risk. However, the relation of location-specific epicardial adipose tissue (EAT) thickness to coronary atherosclerotic burden is still unclear.MethodsThis meta-analysis was used to study the relations between location-specific EAT thickness and obstructive coronary artery disease (CAD). A systemic literature search to identify eligible studies that met the inclusion criteria from the beginning until January 2014 was made. We conducted the meta-analysis of all included 10 published studies. Pre-specified subgroup analyses were performed according to ethnicity, body mass index, diagnostic tools for CAD, and measurement tool if presence of high heterogeneity between studies. Potential publication bias was also assessed.ResultsWe identified ten observed studies with a total of 1625 subjects for planned comparison. With regard to the association between obstructive CAD and location-specific EAT thickness at the right ventricular free wall, caution is warranted. The pooled estimate showed that location-specific EAT thickness at the right ventricular free wall was significantly higher in the CAD group than non-CAD group (standardized mean difference (SMD): 0.70 mm, 95% CI: 0.26-1.13, P = 0.002), although heterogeneity was high (I2 = 93%). It should be clear that only the result of echocardiography-based studies showed a significant association (SMD: 0.98 mm, 95% CI: 0.43-1.53, P = 0.0005), and the result of all included CT-based studies showed a non-significant association (SMD: 0.06 mm, 95% CI: -0.12-0.25, P = 0.50). In the subgroup analysis, the “diagnostic tools for CAD” or “measurement tool of EAT thickness” are potential major sources of heterogeneity between studies. With regard to location-specific EAT thickness at the left atrioventricular (AV) groove, it was significantly higher in the CAD group than non-CAD group (SMD: 0.74 mm, 95% CI: 0.55-0.92, P <0.00001; I2 = 0%).ConclusionOur meta-analysis suggests that significantly elevated location-specific EAT thickness at the left AV groove is associated with obstructive CAD. Based on the current evidence, the location-specific EAT thickness at the left AV groove appears to be a good predictor in obstructive CAD, especially in Asian populations. Furthermore well-designed studies are warranted because of the current limited number of studies.
Highlights
There is growing evidence about the importance of epicardial adiposity on cardiometabolic risk
The pre-specified inclusion criteria were as follows: (a) observational studies to investigate the relationship between location-specific epicardial adipose tissue (EAT) thickness and coronary artery disease (CAD) measured by echocardiography, Computed tomography (CT) or Magnetic resonance imaging (MRI)-based quantitative measurements; (b) subjects with suspicion of CAD or at high risk of CAD clinically, and subsequently divided into CAD and non-CAD groups assessed by coronary angiography, coronary CT angiography and coronary MR angiography
Of these 11 studies, five studies were excluded because they did not report the detailed data for the meta-analysis [27-31]; two studies were excluded because of an investigation of the relationship between the EAT volume or area with CAD [32,33]; two studies were excluded because the study subjects were not well-defined or did not meet the criteria [15,34]; and the remaining two were letters and experimental studies [5,35]
Summary
There is growing evidence about the importance of epicardial adiposity on cardiometabolic risk. The relation of location-specific epicardial adipose tissue (EAT) thickness to coronary atherosclerotic burden is still unclear. Excessive epicardial adipose tissue (EAT) accumulation within the pericardial sac has been suggested to play an important role in the development of coronary artery atherosclerosis through potential paracrine or endocrine mechanism by exerting inflammatory mediators such as TNF-alpha, IL-6, adipocytokines, and leptin [1-5]. Current evidence about the association between location-specific EAT thickness at the right ventricular free wall and coronary artery disease (CAD) is still controversial. Several studies using echocardiography have demonstrated a significant relationship between CAD and location-specific EAT thickness measured at right ventricular free wall [13,14,16,17], while some studies using echocardiography or CT failed to observe a significant association [11,12,19,20]. Recent evidence has suggested that there is increasing attention on location-specific EAT thickness at the left AV groove as a potentially new biomarker associated with cardiometabolic risks by using 2D CT or MR measurement [11,19,21,22]. We conducted a meta-analysis to study the relationship between location-specific EAT thickness and obstructive CAD, which may serve as a reliable predictor and improve CAD risk stratification in the future
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