Abstract 325: Impaired Myocardial Flow Reserve Measured Using Rubidium-82 PET Predicts Outcomes in Patients With Suspected Myocardial Ischemia
Objectives: The added utility of myocardial flow reserve (MFR) using Rb-82 PET is unknown. We sought to assess the prognostic value of Rb-82 PET MFR in patients (pts) with suspected ischemia. We hypothesized that in pts with a normal or abnormal summed stress score (SSS), a reduction in MFR would be related to a higher adverse event rate versus preserved MFR.
Methods: We prospectively enrolled 280 consecutive pts referred for Rb-82 PET (01/2008–05/2008). A total of 247 (88%) pts with successful follow up to 1 year were classified as: I-a) normal SSS (<4) and normal global MFR (≥2); I-b) SSS <4 and abnormal MFR (<2); II-a) abnormal SSS (≥4) and MFR ≥2 and II-b) SSS ≥4 and MFR<2. Primary outcome was the composite of major adverse cardiac events (MACE; cardiac death, non-fatal MI, late revascularization or cardiac hospitalization).
Results: During follow up, 23 (9.3%) pts had at least 1 cardiac event with 2 suffering cardiac death. There was an interaction between MFR and SSS, such that a lower level of MFR when combined with a higher SSS predicts additional MACE (p=0.031; fig⇓). The difference in events for pts in group I-a vs I-b (2.6 vs 6%) and for II-a vs II-b (6% vs 24%) can be shown with examples. If SSS=3 and MFR increases from 0.5 to 1, the risk is reduced by 19%; HR 0.81 (0.67, 0.98); if SSS=8 and MFR increases from 1 to 2, the risk is reduced by 73%; HR 0.27 (0.08, 0.87). The only other predictors of primary outcomes besides MFR and SSS were prior PCI or CABG (p<0.01).
Conclusions: These data support that in pts with suspected ischemia, global impairment in MFR measured with Rb-82 PET is a predictor of adverse events. Quantitative PET would be a useful clinical tool to advance risk stratification of such pts.