The Histopathological Correlate of Peri-Vascular Adipose Tissue Attenuation on Computed Tomography in Surgical Ascending Aorta Aneurysms: Is This a Measure of Tissue Inflammation?

Abstract

On computed tomography (CT) imaging, a peri-vascular adipose tissue attenuation (pVAT) measure has been proposed as a non-invasive correlate of inflammation in the coronary artery vessels, and a single research group provided histopathological demonstration of this radiological/pathological correspondence. Our group has shown that patients with surgical-grade ascending aorta (AA) aneurysm display higher pVAT compared with patients with smaller aneurysms or normal AA. Based on histopathological studies on coronary arteries, we speculated that this correlation may be related to a non-otherwise specified aortic inflammatory process. However, since adipose tissue around the AA is often scant, and there are no histopathological studies confirming such hypothesized association between higher pVAT and inflammation around the AA, we cannot exclude that this pVAT change is secondary to different mechanisms, unrelated to the actual presence of peri-vascular inflammation. We performed a retrospective clinical/radiological/pathological study in 78 patients who underwent AA surgery with the aim to correlate pre-operatory pVAT on CT with histopathological findings from the surgical specimens. Histopathological review and immunohistochemistry were performed on the surgical aortic samples. The AA adventitial/periadventitial adipose tissue had higher pVAT by an increasing collagen fiber deposition, which progressively makes the fat hypotrophic and, in the late stages of this process, it replaces the normal soft tissue composition in this location. In the ascending aorta, pVAT on CT imaging is probably not a proxy for the presence of current vascular inflammation, although it may track changes involving the progressive substitution of perivascular adipose cells by higher-pVAT tissues, mainly fibrotic replacement.

Added Value of CCTA-Derived Features to Predict MACEs in Stable Patients Undergoing Coronary Computed Tomography

“…It has been widely demonstrated that pFAI correlates with plaque attenuation components in patients with non-ST-elevation acute coronary syndrome. Antonopoulos et al [ 21 ] firstly reported that the detection and quantification of coronary inflammation is a useful noninvasive imaging biomarker of perivascular inflammation and immune activation which are known to be important determinants of plaque vulnerability Our results are in agreement with those of Gaibazzi et al [ 14 ], who found higher pFAI values in patients with non-obstructive coronary arteries. Interestingly, in accordance with Gaibazzi et al [ 14 ], we also found in our small population of 15 patients with CAD-RADS ≤ 1 and pFAI ≥ −70 HU higher rates of hypertension and smoke habit.…”

“…Antonopoulos et al [ 21 ] firstly reported that the detection and quantification of coronary inflammation is a useful noninvasive imaging biomarker of perivascular inflammation and immune activation which are known to be important determinants of plaque vulnerability Our results are in agreement with those of Gaibazzi et al [ 14 ], who found higher pFAI values in patients with non-obstructive coronary arteries. Interestingly, in accordance with Gaibazzi et al [ 14 ], we also found in our small population of 15 patients with CAD-RADS ≤ 1 and pFAI ≥ −70 HU higher rates of hypertension and smoke habit. With the exception of age and diabetes, the rates of cardiovascular risk factors in our small subgroup were similar to the LAP group, suggesting that cardiovascular risk factors may alter pericoronary fat, leading with time to unfavorable plaques.…”

“…Due to the relatively high occurrence and severity of events in patients with non-obstructive CAD [ 13 , 14 , 15 , 16 ], the incorporation of CCTA into clinical decision-making can be of great importance for improved identification of adverse events. The main finding of our study is that there is a positive correlation between CTCA-derived features and MACEs in our very selected population of patients with mild to moderate CAD.…”

“…There is also increasing evidence that pericoronary fat inflammation (pFAI) measured in the right coronary artery (RCA) is an independent predictor of cardiovascular events and mortality [ 12 , 13 , 14 , 15 , 16 , 17 ]. In addition, other evidence exists about the role of elevated pFAI in patients with myocarditis, myocardial infarction with nonobstructive coronary arteries (MINOCA) and Takotsubo syndrome [ 13 , 14 ]. Indeed, pericoronary adipose tissue releases proinflammatory cytokines that can alter the structure of the coronary wall, leading to CAD [ 15 ].…”

Atrial Fibrillation and Peri-Atrial Inflammation Measured through Adipose Tissue Attenuation on Cardiac Computed Tomography

“…Several studies have indirectly suggested that inflammation is involved in atrial fibrillation, however, direct evidence of local inflammatory activity in the atria of patients with AF is scarce [8][9][10][11][12][13][14]. We hypothesized that the density of adipose tissue, also defined as "attenuation" when measured with CCTA, in close anatomic continuum with the LA, may be considered as a marker of the local inflammatory status, similarly to what has been previously demonstrated for peri-vascular adipose tissue attenuation and vascular inflammation [15][16][17][18][19][20]. The assessment of the mean density of adipose tissue in continuum with the LA will confirm (or contradict) such atrial inflammatory involvement in AF, using in-vivo imaging.…”