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

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, <400 or ≥400. MPR was considered reduced when <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 < 0.01), had higher PCFT (13 ± 2 vs 11 ± 2 mm, p < 0.001), higher prevalence of CAC score ≥400 (48% vs. 21%, p < 0.01), and lower MPR (2.1 ± 0.7 vs. 2.7 ± 0.7, p < 0.001) compared to those without. A higher prevalence of MPR <2 was observed in patients with events (48% vs. 18, p < 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 < 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 < 0.001). At Cox univariate analysis, age (p < 0.05), PCFT >11.2 mm (p < 0.001), CAC score ≥400 (p < 0.01), and MPR <2 (p < 0.001) were predictors of events. At multivariate analysis, only PCFT >11.2 mm and MPR <2 were independent predictors of events (both p < 0.01). At incremental analysis, adding PCFT >11.2 to a model including clinical data and MPR <2 increased the global chi-square from 26 to 35 (p < 0.01). Classification tree analysis produced 3 terminal groups. For patients with MPR <2, no further split was needed (event rate 12% vs. 3%, p < 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 < 0.001) PCFT >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.

Prognostic Value Of Normal Myocardial Perfusion Imaging In Asymptomatic Diabetic Patients With Moderate And High Calcium Scores

The purpose of this study was to evaluate the intermediate prognostic value of normal myocardial perfusion imaging (MPI) in asymptomatic diabetic patients with intermediate and high coronary artery calcium (CAC) scores. Methods: A total of 115 asymptomatic diabetic patients with no known coronary artery disease (CAD) underwent MPI after multi-slice computed tomography CAC assessment for the detection of suspected CAD. The study included 75 patients with normal MPI results. A 17-segment model for myocardial perfusion and function analysis was used. Patients were divided into three groups: I gr-20 patients with a diabetes duration between 1-5 years; II gr-24 patients with a diabetes duration 5-10 years; and III gr-31 patients with a diabetes duration >10 years. End points (cardiac death, non-fatal myocardial infarction, heart failure, new angina, revascularization) were assessed at 6, 12 and 24 months. All patients had normal resting left ventricular function and normal myocardial perfusion scans. Forty patients had moderate coronary artery calcification with an average CAC of 290+/−95. Thirty-five patients had severe coronary calcification with an average CAC of 568+/−67. A correlation was found between diabetes duration and CAC severity (r-0,62 for diabetes duration over 10 years). Three cardiac events were identified at 24--month follow-up (new angina with percutaneous coronary intervention-PCI). Hard events (cardiac death, nonfatal myocardial infarction) were observed at a rate of 0% in group I, 4.2% in group II and 6.4% in group III. The overall event rate at 24--month follow-up was 4.0%. MPI and CAC are valuable techniques for the preclinical assessment of CAD in asymptomatic diabetic patients. This could guide decision-making to result in optimal treatment and prognosis. Even diabetic patients with normal MPI are at increased intermediate risk for CV events.