Prognostic value of pericoronary adipose tissue and coronary vascular function by cardiac 82Rb PET/CT imaging in patients with suspected coronary artery disease and normal myocardial perfusion imaging
Authors: Gaudieri V , Zampella E , Nappi C , Assante R , Mannarino T , D"antonio A , Giordano A , Buongiorno P , Petretta M , Acampa W , Arumugam P , Cuocolo A 
Published: February 2021

Abstract

Funding Acknowledgements
Type of funding sources: None.

Introduction
Pericoronary adipose tissue, due to its proximity to coronary arteries, has been proposed contribute to the progression of coronary atherosclerosis.

Purpose
The aim of this study was to evaluate the prognostic value of pericoronary fat thickness (PCFT), coronary artery calcium (CAC) score and myocardial perfusion reserve (MPR) by hybrid 82Rubidium (82Rb) PET/CT imaging in patients with suspected coronary artery disease (CAD) and normal myocardial perfusion imaging (MPI).

Methods
A total of 640 patients without overt CAD and with normal rest-stress 82Rb PET/CT MPI were studied. PCFT was calculated on CT images as the maximum fat thickness (mm) between heart surface and visceral epicardium surrounding the main coronary arteries. CAC score was categorized as 0, &lt;400 or ≥400. MPR was considered reduced when &lt;2. Endpoints events were cardiac death, nonfatal myocardial infarction and coronary revascularization.

Results
During a follow-up of 42 ± 13 months, 29 events occurred (cumulative event rate 5%). Patients with events were older (66 ± 13 vs. 60 ± 13 years, p &lt; 0.01), had higher PCFT (13 ± 2 vs 11 ± 2 mm, p &lt; 0.001), higher prevalence of CAC score ≥400 (48% vs. 21%, p &lt; 0.01), and lower MPR (2.1 ± 0.7 vs. 2.7 ± 0.7, p &lt; 0.001) compared to those without. A higher prevalence of MPR &lt;2 was observed in patients with events (48% vs. 18, p &lt; 0.001) compared to those without. Patients with reduced MPR had higher PCFT compared to those with normal MPR (12 ± 2 vs. 11 ± 1 mm, p &lt; 0.01). A PCFT value of 11.2 mm was the best trade-off between sensitivity and specificity to detect a reduced MPR. Event rate was higher in patients above this threshold compared to those below (8% vs. 1.5%, p &lt; 0.001). At Cox univariate analysis, age (p &lt; 0.05), PCFT &gt;11.2 mm (p &lt; 0.001), CAC score ≥400 (p &lt; 0.01), and MPR &lt;2 (p &lt; 0.001) were predictors of events. At multivariate analysis, only PCFT &gt;11.2 mm and MPR &lt;2 were independent predictors of events (both p &lt; 0.01). At incremental analysis, adding PCFT &gt;11.2 to a model including clinical data and MPR &lt;2 increased the global chi-square from 26 to 35 (p &lt; 0.01). Classification tree analysis produced 3 terminal groups. For patients with MPR &lt;2, no further split was needed (event rate 12% vs. 3%, p &lt; 0.001). On the contrary, patients with MPR ≥2 were further stratified by PCFT (event rate 7% in patients with and 0.3% in those without (p &lt; 0.001) PCFT &gt;11.2.

Conclusions
In patients with suspected CAD and normal stress MPI, coronary vascular dysfunction and high PCFT are associated with increased cardiac risk. PCFT could help in identifying patients at higher risk of events. Combined evaluation of anatomical and functional vascular abnormalities by 82Rb PET/CT might allow a better risk stratification.