Abstract 323: The Incremental Prognostic Value of Myocardial Perfusion Parameters as Measured by Rubidium-82 Positron Emission Tomography
Myocardial perfusion imaging with positron emission tomography (PET MPI) is more accurate in characterizing perfusion abnormalities than single-photon emission computed tomography (SPECT) among individuals with suspected or known CAD. However, the prognostic capacity of PET MPI with respect to clinical outcomes is not as fully established as SPECT. Accordingly, this retrospective cohort study examined 4320 sequential patients referred for rubidium-82 (Rb-82) PET MPI for evaluation of suspected or known CAD at the Heart Center of Niagara between April 2000 and June 2006. Medical charts were abstracted to collect information on demographics, physical examination findings, medical history, and medication use on the day of PET. PET images were assessed by a single experienced reader blinded to outcome, and perfusion defects defined as percentage of left ventricular mass (in 5% increments) hypoperfused with pharmacological stress. Mortality information was obtained through the National Death Index with follow-up through December 31, 2006. Cox proportional hazards models were developed to identify pre-PET predictors of mortality endpoints. Percentage of LV mass hypoperfused as determined by PET was subsequently added to models to determine incremental prognostic value. A history of MI and/or revascularization was reported by 29% of the study cohort. Mean pre-PET likelihood of CAD was 31% among individuals without previous MI or revascularization. Stress perfusion defects were identified via PET in 33% of the study cohort. Annual cardiac mortality rates among individuals with 0% (no perfusion defect), 5%, 10–15%, and ≥ 20% of LV mass hypoperfused with stress were 0.5%, 0.9%, 1.5%, and 2.8% per year, respectively. Adjusted hazard ratios (95% CI) across stress perfusion defect groups (compared to no perfusion defect group) were 1.5 (0.8, 3.1), 2.0 (1.2, 3.4), and 3.0 (1.9, 4.8), respectively (p<0.0001). Adjusted hazard ratios for all-cause mortality were 1.0 (0.7, 1.6), 1.7 (1.2, 2.2), and 2.0 (1.5, 2.6) respectively (p<0.0001). Rb-82 PET MPI provides strong prognostic information for mortality endpoints. Future studies will evaluate the value of PET MPI for guiding therapeutic management for risk minimization.
This research has received full or partial funding support from the American Heart Association, Founders Affiliate (Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Rhode Island, Vermont).