Prognostic value of modified coronary flow capacity by rubidium-82 pet/ct in patients with suspected cad and normal myocardial perfusion imaging

Abstract Introduction/Aim Myocardial perfusion imaging (MPI) by positron emission tomography/computed tomography (PET/CT) is able to provide an absolute quantification of myocardial blood flow (MBF) and myocardial flow reserve (MFR). Coronary flow capacity (CFC) has been proposed as a comprehensive measure of the entire coronary vascular status, integrating both hyperemic MBF and MFR results into color-coded scatterplot. Recently, modified CFC (mCFC) concept has been introduced by integrating the regional CFC category within each coronary territory into the entire CFC category for each patient. The purpose of this study is to assess the prognostic value of mCFC in patients with suspected CAD and normal MP at 82Rb cardiac PET/CT imaging. Methods We evaluated 4560 patients without previous history of CAD who underwent stress/rest 82Rb cardiac PET/CT. Patients without previous history of CAD and normal MPI (n=2053) were included. Six CFC categories were obtained according to MBF and MFR results. The mCFC was defined as impaired in patients with "mildly reduced" or worse coronary flow in at least one coronary territory. End- points were defined as cardiovascular death, nonfatal myocardial infarction, unplanned hospitalization for any cardiac reasons, and unplanned coronary revascularization. Results Follow-up was available in 1967 (96%) patients (median age 59±13 years). During a median time of 41 months (range 3-365), 72 events occurred (4% cumulative event rate, AER of 0.7% person-year). Lower hyperemic MBF and MFR values and a higher prevalence of MFR 2, were observed in patients with events as compared to those without (all P .001). Moreover, the prevalence of impaired mCFC was significantly higher in patients with events as compared to those without (P .001). At multivariable Cox's analysis, age, diabetes, MFR 2 and impaired mCFC (p .001) resulted as independent predictors of events. In patients with reduced MFR, as well as in patients with normal MFR, the AER was significantly higher in patients with impaired mCFC as compared to those without (both p .01). At Kaplan-Meier analysis the worse prognosis was observed in patients with impaired mCFC in both MFR groups. Conclusions In patients with suspected CAD and normal MPI, impaired mCFC is associated with a higher risk of cardiac events. The mCFC by 82Rb cardiac PET/CT may be useful to identify patients that may benefit by additional therapies in order to prevent future events.