Validation of cardiovascular magnetic resonance assessment of pericardial adipose tissue volume

11 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.There 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).In 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.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]. Historically, this adipose layer has largely been regarded as an inert layer that, at most, may provide some mechanical protection to the coronary arteries[2]. More recently however, the benign nature of this fatty tissue is being re-evaluated.Pericardial adipose tissue is largely brown adipose tissue[3] and is divided into two layers. The visceral, epicardial