Abstract
Intrathoracic fat volume, more specifically, epicardial fat volume, is an emerging imaging biomarker of adverse cardiovascular events. The purpose of this work is to show the feasibility and reproducibility of intrathoracic fat volume measurement applied to contrast-enhanced multidetector computed tomography images. A retrospective cohort study of 62 subjects free of cardiovascular disease (55% females, age = 49 ± 11 years) conducted from 2008 to 2011 formed the study group. Intrathoracic fat volume was defined as all fat voxels measuring −50 to −250 Hounsfield Unit within the intrathoracic cavity from the level of the pulmonary artery bifurcation to the heart apex. The intrathoracic fat was separated into epicardial and extrapericardial fat by tracing the pericardium. The measurements were obtained by 2 readers and compared for interrater reproducibility. The fat volume measurements for the study group were 141 ± 72 cm3 for intrathoracic fat, 58 ± 27 cm3 for epicardial fat, and 84 ± 50 cm3 for extrapericardial fat. There was no statistically significant difference in intrathoracic fat volume measurements between the 2 readers, with correlation coefficients of 0.88 (P = .55) for intrathoracic fat volume and −0.12 (P = .33) for epicardial fat volume. Voxel-based measurement of intrathoracic fat, including the separation into epicardial and extrapericardial fat, is feasible and highly reproducible from multidetector computed tomography scans.
Highlights
Cardiovascular disease (CVD) remains the number one cause of mortality among adult men and women in the USA despite recent decrease in the mortality rate [1]
We used the pericardium as a landmark to divide the intrathoracic fat into intra- and extrapericardial fat compartments, as they have different embryological origins, blood supply, and functional properties such as the secretion of adipokines
The epicardial fat, known as intrapericardial fat, is defined as the fat tissue enclosed by the visceral pericardium that is composed of mesothelial cells and is supplied by the coronary arteries that supply the myocardium [17, 20]
Summary
Cardiovascular disease (CVD) remains the number one cause of mortality among adult men and women in the USA despite recent decrease in the mortality rate [1]. Waist circumference and body mass index (BMI) are commonly used anthropometric measures for quantifying general and regional adiposity [3,4,5,6,7,8] Both measures have been criticized for providing general measurements that do not directly correlate well with the underlying visceral fat component [6,7,8], such as abdominal and intrathoracic fat that are more highly correlated with cardiovascular risk compared with waist circumference and BMI alone [9, 10]. An independent association between increased intrathoracic fat volume (ie, intrapericardial fat) and abdominal fat volume with atrial fibrillation and coronary artery disease (CAD) was shown [11,12,13] Most of these studies do not explicitly describe the methodology used to quantify thoracic fat or define intrathoracic fat compartments. We discuss the definitions of intrathoracic fat, its clinical significance, and the methodology of quantifying intrathoracic fat volume
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