Background: The role of Technetium-99 m (Tc-99m) labeled tracers has been discussed
for the detection of viable myocardium. One of the methods that is considered to be used in the diagnosis
of viability is gated Myocardial Perfusion Imaging (gMPI) conducted under the influence
of Beta Blocker Drugs (BBD).
Objective: The aim of this study is twofold: First, to evaluate the role of the Beta Blocker Drugs
(BBD) on fixed perfusion defects on gated Myocardial Perfusion Imaging (gMPI) (myocardial viability)
and second, to assess the role of BBD on the functional parameters of the left ventricle.
Methods: 31 patients (28 men, 3 women) who were on BBD treatment and had fixed perfusion defects
on their gMPI and submitted to fluorodeoxyglucose positron emission tomography/computed
tomography (FDG PET/CT) were prospectively enrolled to the study. One week after the completion
of the stress-rest gMPI, rest gMPI was repeated for each patient while they were on BBD
treatment. All systolic and diastolic functional measurements, perfusion defect extent and size were
obtained during both rest gMPI studies with and without BBD. The parameters derived from FDG
PET/CT were compared to those that were derived from gMPI without BBD.
Results: A statistically significant difference between the scores of both groups was not observed,
except the Time to Peak Filling Rate (TTPFR). End-systolic/diastolic volumes derived from gated
FDG PET/CT were significantly lower than the ones derived from the gMPI presumably due to
higher spatial resolution of the FDG PET/CT while the study did not reveal a statistically significant
difference between the ejection fraction values.
Conclusion: According to our results, metoprolol does not seem to change functional parameters
of the left ventricle that were detected by gMPI except TTPFR. Besides, it seems that metoprolol
does not affect the size of the perfusion defect, and therefore, it does not have a role to demonstrate
the presence of viability that was confirmed via FDG PET/CT.