Introduction
Epicardial fat (Efat) is an active ectopic fat depot, directly surrounding coronary arteries, and secreting high level of inflammatory adipokines; its development has been associated with coronary atherosclerosis. We investigated the relationship between Efat and endothelium dependent vasoreactivity of the coronary microcirculation.
Methods
Myocardial blood flow (MBF) was determined by measuring coronary sinus flow with velocity-encoded cine magnetic resonance imaging at 3 teslas. We measured MBF at baseline and in response to sympathetic stimulation by cold pressor testing (CPT) in 17 healthy volunteers with normal left ventricular function (age 24±6 years, BMI=21.1±2.6kg/m2). Efat volume was volumetrically assessed by manual delineation on short-axis views. CPT was applied by immersing one foot in ice water for 4 minutes.
Results
A significant increase in MBF was observed: 1.18±0.58 vs 0.84±0.47mL.min-1.g-1, CPT vs rest, p=0.002. Mean relative MBF increase (ΔMBF) was 50±47%. Mean Efat volume was 82±31mL and varied from 43 to 131 mL; mean LV mass and Left ventricular ejection fraction were 104±31g and 64±5%, respectively. CPT significantly increased heart rate (HR) by 28±13%, systolic blood pressure (BP) by 17±13%, diastolic BP by 23±19% and rate-pressure product by 52±25%, p<0.01, indicating an increase in myocardial work load. The increase in HR, reflecting sympathetic stimulation, was not influenced by sex, age or Efat volume. CPT induced a decrease in coronary vascular resistance (150±93 vs 114±44 mmHg.mL-1.min.g) by trend (p=0.08). Interestingly, we found a significant negative correlation between Efat volume and ΔMBF (r=-0.51, p=0.03), which remained significant after adjusting for age and sex. ΔMBF was not associated with waist circumference, BMI, CRP, lipid or glycemic parameters.
Conclusion
The increase in Efat is associated with a decrease in endothelium dependent vasoreactivity response, suggesting that Efat could early influence endothelial function.