Association of epicardial adipose tissue volume with heart weight in post-mortem cases

Epicardial adipose tissue (EAT) deposition has been long associated with heart weight. However, recent research has failed to replicate this association. We aimed to determine the association of EAT volume with heart weight in post-mortem cases and identify potential confounding variables. EAT volume derived from post-mortem computed tomography (PMCT) and heart weight were measured in post-mortem cases (N = 87, age: 56 ± 16 years, 28% female). Cases with hypertrophied heart weights (N = 44) were determined from reference tables. Univariable associations were tested using Spearman correlation and simple linear regression. Independence was determined with stepwise regression. In the total cohort, EAT volume (median 66 ± 45 cm3) was positively associated with heart weight (median 435 ± 132 g) at the univariable level (r = 0.6, P < 0.0001) and after adjustment for age, female sex, and various body size metrics (R2 adjusted = 0.41-0.57). Median EAT volume was 1.9-fold greater in cases with hypertrophic hearts (P < 0.0001) but with considerably greater variability, especially in cases with extreme EAT volume or heart weight. As such, EAT volume was not associated with heart weight in hypertrophic cases, while a robust independent association was found in non-hypertrophic cases (R2 adjusted = 0.62-0.86). EAT mass estimated from EAT volume found that EAT comprised approximately 13% of overall heart mass in the total cases. This was significantly greater in cases with hypertrophy (median 15.5%; range, 3.6-36.6%) relative to non-hypertrophied cases (12.5%, 3.3-24.3%) (P = 0.04). EAT volume is independently and positively associated with heart weight in post-mortem cases. Excessive heart weight significantly confounded this association.

Identifying sex differences in predictors of epicardial fat cell morphology

Predictors of overall epicardial adipose tissue deposition have been found to vary between males and females. Whether similar sex differences exist in epicardial fat cell morphology is currently unknown. This study aimed to determine whether epicardial fat cell size is associated with different clinical measurements in males and females. Fat cell sizes were measured from epicardial, paracardial, and appendix adipose tissues of post-mortem cases (N= 118 total, 37 females). Epicardial, extra-pericardial, and visceral fat volumes were measured by computed tomography from a subset of cases (N= 70, 22 females). Correlation analyses and stepwise linear regression were performed to identify predictors of fat cell size in males and females. Median fat cell sizes in all depots did not differ between males and females. Body mass index (BMI) and age were independently predictive of epicardial, paracardial, and appendix fat cell sizes in males, but not in females. Epicardial and appendix fat cell sizes were associated with epicardial and visceral fat volumes, respectively, in males only. In females, paracardial fat cell size was associated with extra-pericardial fat volume, while appendix fat cell size was associated with BMI only. No predictors were associated with epicardial fat cell size in females at the univariable or multivariable levels. To conclude, no clinical measurements were useful surrogates of epicardial fat cell size in females, while BMI, age, and epicardial fat volume were independent, albeit weak, predictors in males only.

Estimating heart mass from heart volume as measured from post-mortem computed tomography

Heart mass can be predicted from heart volume as measured from post-mortem computed tomography (PMCT), but with limited accuracy. Although related to heart mass, age, sex, and body dimensions have not been included in previous studies using heart volume to estimate heart mass. This study aimed to determine whether heart mass estimation can be improved when age, sex, and body dimensions are used as well as heart volume. Eighty-seven (24 female) adult post-mortem cases were investigated. Univariable predictors of heart mass were determined by Spearman correlation and simple linear regression. Stepwise linear regression was used to generate heart mass prediction equations. Heart mass estimate performance was tested using median mass comparison, linear regression, and Bland-Altman plots. Median heart mass (P = 0.0008) and heart volume (P = 0.008) were significantly greater in male relative to female cases. Alongside female sex and body surface area (BSA), heart mass was univariably associated with heart volume in all cases (R² = 0.72) and in male (R² = 0.70) and female cases (R² = 0.64) when segregated. In multivariable regression, heart mass was independently associated with age and BSA (R² adjusted = 0.46-0.54). Addition of heart volume improved multivariable heart mass prediction in the total cohort (R² adjusted = 0.78), and in male (R² adjusted = 0.74) and female (R² adjusted = 0.74) cases. Heart mass estimated from multivariable models incorporating heart volume, age, sex, and BSA was more predictive of actual heart mass (R² = 0.75-0.79) than models incorporating either age, sex, and BSA only (R² = 0.48-0.57) or heart volume only (R² = 0.64-0.73). Heart mass can be more accurately predicted from heart volume measured from PMCT when combined with the classical predictors, age, sex, and BSA.