Extra-media Thickness and Epicardial Fat: Comparison of a Novel Carotid Artery Ultrasound Index and a Well-established Cardiac Magnetic Resonance Fat Quantification Method

Background And Aim: Epicardial and pericardial fat are well-established surrogate markers of cardiovascular diseases and complications. Extra-media thickness (EMT) is a novel ultrasound index corresponding to arterial adventitia and adipose tissue. We aimed to evaluate the association between carotid EMT and epicardial fat (EF) and pericardial fat (PF) and their relation to cardiovascular risk and metabolic syndrome (MS).

Methods And Results: One hundred consecutive patients (age: 51.7 ± 15.4 years; males 70%) scheduled for cardiac magnetic resonance (CMR) were prospectively included in the study. Anthropometric parameters, CMR indices of EF and PF, both common carotid arteries EMT, and ultrasound indices of visceral and subcutaneous fat were measured in patients. In our study group, 53% of patients represented a very high cardiovascular risk, overweight or obesity was found in 68%, high body fat in 45%, and MS in 59% of individuals. Mean EMT (662 ± 129 μm) was significantly associated with EF area (r = 0.46; p < 0.001) and PF area (r = 0.3; p < 0.001). Among all fat indices, only EMT (MS+ 736 ± 140 μm vs. MS-658 ± 97 μm; p = 0.002) and EF area (MS+ 870 ± 451 mm(2) vs. MS 668 ± 333 mm(2); p = 0.02) were significantly increased in patients with MS compared with individuals without MS. Multivariable regression analysis also showed that mean EMT is independently associated with number of cardiovascular risk factors (b = 0.005; p < 0.001). Moreover, very high cardiovascular risk subjects showed significantly increased EMT/BMI (p < 0.001) and EF area/BMI (p = 0.03) ratios. However, there was no significant association between EMT/BMI and EF area/BMI values (p = ns).

Conclusions: Our study showed the first findings on the relations between a novel ultrasound index EMT and EF assessed in a reference method of CMR. Carotid EMT may be a new surrogate marker, including both periarterial fat as a major component and arterial adventitia, which may provide additional data on cardiometabolic risk beyond that derived form a well-established EF alone.