Prognostic value of quantitative coronary artery calcium and myocardial blood flow assessed by hybrid rubidium-82 PET/CT imaging in patients with suspected coronary artery disease

Background: Aim of this study was to evaluate the long-term prognostic value of coronary artery calcium (CAC) score and myocardial blood flow (MBF) by hybrid 82Rb positron emission tomography (PET)/computed tomography (CT) imaging in a cohort of patients with low-intermediate risk of coronary artery disease (CAD). Methods: A total of 295 (mean age 57 ± 14 years) consecutive patients were studied. CAC score was measured according to the Agatston method and patients were categorized into 3 groups (0, 1-399 and ?400). Baseline and hyperemic MBF were automatically quantified. CFR was calculated as the ratio of hyperemic to baseline MBF and it was considered reduced when <2. Patients were followed up for the presence of composite end point of cardiac death, nonfatal myocardial infarction, or unstable angina requiring coronary revascularization whichever occurred first. Results: The median follow-up was 48±18 months and follow-up data were not available in 26 patients (8%). Patients who experienced event showed a higher ln(CAC + 1) and a lower CFR values as compared to patients without event, while no differences has been observed in baseline and hyperemic MBF between the two groups. Event rate significantly increased with increasing of CAC score categories (P for trend = .000) and it was higher in patients with reduced CFR (P = .001). At multivariable analysis CAC score ?400 (P = .007) and CFR (P = .03) were independent predictors of events. Event-free survival decreased with worsening of CAC score category (P <.001) and in patients with reduced CFR (P <.005). CAC score added prognostic information to a model including in hierarchical order clinical variables, increasing the global chi-square from 21.65 to 28.78 (P = .005). Moreover, the addition of CFR to a model including clinical data and CAC score further significantly increased global chi-square from 28.78 to 34.76 (P = .002). Conclusions: In patients with suspected CAD both the extent of coronary calcification and the presence of coronary vascular dysfunction are associated with increased risk of adverse cardiac events, even after adjustment for cardiovascular risk factors. CAC score?400 and CFR resulted both as independent predictors of events. However, CFR provides incremental prognostic information over established CAD risk factors and CAC score for predicting cardiac adverse events. Combined evaluation of functional and structural abnormalities might allow risk stratification in patients with low-intermediate risk of CAD