Abstract 18282: Reducing Radiation in Patients with Prior SPECT Myocardial Perfusion Imaging: Is a Second Rest Study Really Necessary?
Background: We performed a single center, academic, retrospective analysis of MPI stress tests in patients with repeat studies, to determine if the repeat resting scan had an impact on interpretation of the stress test and establish if omitting the resting scan would have an impact on interpretation of the stress test.
Methods: Two independent, blinded readers reviewed 98 consecutive SPECT MPI studies in patients who have a prior resting study, with no pre-test evidence that the resting perfusion pattern may have been altered between test dates. Patients were excluded if since their past resting scan they had developed ACS, revascularization, new LBBB or pacemaker, excess weight change, or different position in each study.
Results: 50 of these patients (51%) qualified for stress only imaging. There was high correlation between results from stress only protocol compared to rest-stress protocol (r=0.88). Mean score on stress only protocol was 2.6, and on standard protocol 3.1. When interpretations with old and new resting scans were performed, 41 of 50 patients had a difference in summed difference score (SDS) between 0 and 2. Of the remaining 9 patients, 7 had greater SDS on the stress imaging when compared with the old resting scan than with the new resting scan. Two patients had lower scores with the new-stress/old-rest technique, but each of these patients had large enough scores with each technique (both severe), that no change in clinical risk categorization occurred.
Conclusions: Very similar data is obtained with stress-only imaging in patients who have a prior resting study, with no pre-test evidence that the resting perfusion pattern may have been altered between test dates. When perfusion abnormalities are noted, particularly when a substantial change in the stress study has occurred between tests, repeating the resting study would be prudent. In this population, 86% of the studies could have been performed by repeating the study with stress-only and comparison with a prior resting study. Assuming usual doses of 10 and 30 mCi for a rest/stress protocol and for stress only, repeating the resting study (with another 10 mCi on a second day) only if there is an apparent increase in reversible ischemia, would have reduced the radiation in this population by 71.5%.
- © 2010 by American Heart Association, Inc.