1. Introduction:
Coronary artery disease (CAD) occurs 5–10 years earlier in Indians(1). Risk stratification using risk calculators like QRISK3 score is a key element in the efforts to prevent premature CAD, and to improve targeted implementation of preventive therapies for CAD. Limitations and lack of validation of these risk scores in local population lead to need for simple and widely accessible novel risk markers to provide a clinically meaningful improvement as a screening tool across the population.
Visceral adipose tissue deposition is a documented risk factor for cardiovascular diseases especially among Indians (2). Epicardial adipose tissue (EAT) mimics visceral fat which is present between epicardium and visceral pericardium, and is associated with metabolic derangements and increased cardiovascular risk. EAT is implicated as an independent risk for CAD because of its proximity to the adventitia of major epicardial coronary arteries and has adverse autocrine and paracrine effect on coronary arteries (3, 4). EAT, including epicardial adipose tissue thickness (EAT-T) by echocardiography and epicardial adipose tissue volume (EAT-V) by computed tomography angiography (CTA) have been associated with CAD(5). Thus, it may have incremental benefits in assessment of CAD risk and needs to be studied in local population.
Epicardial adipose tissue can be measured by three imaging modalities [CTA, magnetic resonance imaging (MRI) and echocardiography](6). Each of these modalities has their attending benefits as well as limitations. CTA has been increasingly used recently because of its high spatial resolution which results in precise measurements of EAT-T as well as three-dimensional EAT volume (EAT-V), along with concurrent assessments of coronary artery calcium (CAC) score, coronary artery stenosis and high-risk plaque features (HRPF). However, CT is limited by the associated ionizing radiation related risks, relatively high cost, and limited availability. MRI avoids radiation exposure. However, limited availability and high costs limit the widespread use of MRI. Echocardiography is the widest available modality and a relatively cheaper method to measure EAT-T. Echocardiography also provides information on cardiac functions, has no radiation exposure, and easy to perform.
Hence, we tried to evaluate the correlation between echocardiographic EAT-T [and indexed EAT-T (EAT-T/ body surface area)] and EAT-V by CTA to know whether EAT-T could be used as surrogate marker for EAT-V, and whether EAT-T and indexed EAT-T are independent predictors of CAD in a multivariate analysis with QRISK3 score.