Abstract
BackgroundPericardial adipose tissue (PAT) has been shown to be an independent predictor of coronary artery disease. To date its assessment has been restricted to the use of surrogate echocardiographic indices such as measurement of epicardial fat thickness over the right ventricular free wall, which have limitations. Cardiovascular magnetic resonance (CMR) offers the potential to non-invasively assess total PAT, however like other imaging modalities, CMR has not yet been validated for this purpose. Thus, we sought to describe a novel technique for assessing total PAT with validation in an ovine model.Methods11 merino sheep were studied. A standard clinical series of ventricular short axis CMR images (1.5T Siemens Sonata) were obtained during mechanical ventilation breath-holds. Beginning at the mitral annulus, consecutive end-diastolic ventricular images were used to determine the area and volume of epicardial, paracardial and pericardial adipose tissue. In addition adipose thickness was measured at the right ventricular free wall. Following euthanasia, the paracardial adipose tissue was removed from the ventricle and weighed to allow comparison with corresponding CMR measurements.ResultsThere was a strong correlation between CMR-derived paracardial adipose tissue volume and ex vivo paracardial mass (R2 = 0.89, p < 0.001). In contrast, CMR measurements of corresponding RV free wall paracardial adipose thickness did not correlate with ex vivo paracardial mass (R2 = 0.003, p = 0.878).ConclusionIn this ovine model, CMR-derived paracardial adipose tissue volume, but not the corresponding and conventional measure of paracardial adipose thickness over the RV free wall, accurately reflected paracardial adipose tissue mass. This study validates for the first time, the use of clinically utilised CMR sequences for the accurate and reproducible assessment of pericardial adiposity. Furthermore this non-invasive modality does not use ionising radiation and therefore is ideally suited for future studies of PAT and its role in cardiovascular risk prediction and disease in clinical practice.
Highlights
Pericardial adipose tissue (PAT) has been shown to be an independent predictor of coronary artery disease
In this paper we describe a novel method of assessing complete PAT by volume, and validate ovine paracardial adipose mass collected at necropsy with its corresponding Cardiovascular magnetic resonance (CMR) derived volume
A secondary analysis was performed to determine whether single thickness measurement of adipose tissue over the right ventricular (RV) free wall reflects an accurate surrogate assessment compared to the corresponding adipose tissue mass measured at necropsy
Summary
Pericardial adipose tissue (PAT) has been shown to be an independent predictor of coronary artery disease. Pericardial adipose tissue (PAT) is the layer of fat that surrounds the heart It covers 80% of the heart and constitutes between 20 and 50% of its mass[1]. The visceral, epicardial fat layer is mainly located within the interventricular and atrioventricular grooves, with lesser amounts located around the atria and right ventricle This visceral pericardial layer (or epicardial layer) originates embryologically from mesothelial cells that migrate from the septum transversum and obtains its vascular supply from the coronary arteries[4,5]. The paracardial fat (or mediastinal fat) is situated external to the parietal layer of the pericardium This layer originates from the primitive thoracic mesenchymal cells and derives its blood supply from non-coronary sources such as the pericardiacophrenic branch of the internal mammary artery[5]
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