Aim: The effect of beta blockers (BB) on myocardial imaging has been studied in several SPECT and PET studies with divergent results concerning perfusion and impact on diagnostic accuracy. The present study evaluated the effect of BB withdrawal on virtual SPECT studies modeled from quantitative PET perfusion scans.
Patients, methods: Data from 20 CAD patients scheduled for adenosine 13N-ammonia imaging with and without BB were considered. Modeling the uptake characteristics of 99mTc-MIBI, all parametric stress PET polarmaps were transferred to virtual 20-segment SPECT polarmaps. The SPECT studies were categorized with a 5-point score and read to assess the effect of the BB withdrawal on scan result and interpretation.
Results: The SPECT analysis revealed a mean score of 6.0 ± 4.7 with, and of 5.9 ± 4.5 without BB (p = 0.84). In 260 (74.9%) segments the scores were equal in both conditions. Without BB a downstaging was recorded in 44 segments (12.7%), an upstaging in 43 segments (12.4%). An essentially different interpretation (shift from medical therapy recommendation to angiography) was recorded in one patient. In six cases the interpretation differed mildly.
Conclusion: In the majority of patients studied, scan results and interpretation remain unchanged after discontinuation of the BB. Nevertheless, the segmental scan results are not uniformly affected. The recommendation to stop BBs prior to stress testing in order to ensure the highest MBF remains advisable. If temporary BB withdrawal is unfeasible due to contraindications, a tight clinical schedule, or because a patient forgot to withhold the BB, it is appropriate to perform adenosine stress testing according to the results of this study.
Keywords: Myocardial perfusion imaging; PET; SPECT; adenosine; beta blocker.