Epicardial adipose tissue of atrioventricular grooves is a reliable and early MRI biomarker of the effect of metabolic diseases on atrial myocardium

Abstract

Abstract Introduction Epicardial adipose tissue (EAT), the visceral adipose tissue surrounding the heart, is implicated in a host of cardiovascular diseases playing a transducer role between systemic metabolic conditions and the myocardium, as illustrated by higher risk of atrial fibrillation in patients with diabetes or obesity. MRI affords comprehensive and non-invasive insights into myocardial structure, function and tissue properties. However, the clinical usefulness of whole atrial EAT is limited by its challenging measurability in clinical routine in several imaging modalities, including MRI. Purpose We hypothesized that atrioventricular groove epicardial adipose tissue (GEAT) which can be measured routinely based on established anatomic landmarks may be: 1) a relevant surrogate of atrial EAT and 2) a relevant imaging biomarker to characterize atrial alterations in patients with varied degrees of metabolic disorders. Methods Ninety-nine patients from the METACARDIS cohort (EU FP7) who had MRI, all in sinus rhythm and without overt clinical heart disease, were divided into 4 groups based on distinct metabolic profiles: metabolic syndrome (MS, n=24), severe obesity (SO, BMI ≥35 kg/m2, n=17), type-2 diabetes (T2D, n=41) and healthy controls (n=17). Atrioventricular groove EAT volume was measured from cine SSFP MRI images in four-, three-, two-chamber and short-axis views; atrial EAT volume was measured from four- and two-chamber views. Native T1-mapping values of EAT at the anterior atrioventricular groove excluding the coronary vessels were measured from the MOLLI sequence (basal short-axis slice). Results We found a high correlation between GEAT and atrial EAT volumes (r=0.96; p<0.0001) indicating that GEAT may reflect global atrial EAT volume. Next, we compared GEAT volume across study groups and found an increased GEAT volume in the 3 groups of patients with metabolic diseases compared to controls, with a significantly higher volume in MS (4.7±1.5 ml), SO (4.1±1.2 ml), and T2D (3.7±1.1 ml) than in Controls (2.6±0.6 ml; p≤0.001, p≤0.01, p≤0.05, respectively). In addition, T2D patients had lower native T1 values within GEAT compared to healthy controls (250±26 ms versus 280±31 ms; p≤0.01). Conclusion Atrioventricular groove EAT can be easily measured from conventional cine SSFP MRI images and could be used as a surrogate of global atrial EAT. Both volume and properties of GEAT are related to the metabolic status of patients. Furthermore, given its pure epicardial origin and pericoronary distribution, GEAT appears as a relevant biomarker of metabolic impacts on atrial myocardium. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Annee-recherche, Agence Regionale de Sante Ile-de-France