Abstract 159: Evaluation of Downstream Utilization Following Stress-only versus Rest-Stress Myocardial Perfusion Imaging

Abstract

Background: Current evidence and guidelines in nuclear cardiology support the use of stress-only myocardial perfusion imaging (SO-MPI), without rest imaging, to decrease radiation dose to the patient. We sought to determine the downstream utilization of cardiac procedures in patients undergoing SO-MPI in comparison to those undergoing rest-stress myocardial perfusion imaging (RS-MPI). Demonstration of the decreased need for cardiac procedures following SO-MPI would increase the confidence of interpreting nuclear cardiologists and referring physicians. Methods: We retrospectively analyzed the nuclear cardiology database at Allegheny General Hospital for patients undergoing stress testing with MPI from Jan 2010 to June 2011. Selection criteria for SO-MPI in our laboratory, includes no prior history of revascularization and low pre-test probability of coronary artery disease (CAD) based on symptoms and risk factors. We analyzed the rate of follow-up cardiac catherizations and repeat stress testing upto12 months after the index stress MPI. We compared the rate of procedure utilization following SO-MPI and RS-MPI. Results: A total of 5269 stress tests were performed during the enrollment period, of which 829 (16%) underwent SO-MPI, and the remainder (n=4440, 84%) had RS-MPI. Abnormal MPI was more likely in patients undergoing RS-MPI vs SO-MPI (525 vs 5; p<0.05). Patients undergoing RS-MPI were more likely to have a follow-up procedure compared to those undergoing SO-MPI (odds ratio 2.5; p<0.0001). Specifically the rate of cardiac catherization (565/4440; 13% in RS-MPI vs 27/829; 3%in SO-MPI p<0.05) and the rate of repeat stress testing (177/4440; 4% in RS-MPI vs 15/829; 1.8% in SO-MPI, p<0.05) were significantly higher in the RS-MPI group. Among patients undergoing SO-MPI, rate of cardiac catherization was significantly higher in patients having follow-up rest images compared to those that did not (odds ratio: 12.5, p<0.001). There were 6 revascularizations in the SO-MPI group in the follow-up period of which 5 occurred in those with abnormal MPI and 1 occurred in a patient with normal SO-MPI but in the setting of an acute infarct. Conclusions: Downstream procedure utilization following a SO-MPI strategy is low. This complements the low mortality rate noted in this population by prior studies. It further confirms that the current selection criteria for SO-MPI is appropriate as most patients require only one image and do not need additional testing. In patients with low-intermediate pretest probability for CAD that are referred for MPI, SO-MPI with limited use of rest imaging can facilitate throughput, reduce patient radiation dose and is associated with appropriately low downstream utilization.