Evaluating the Impact of Ursodeoxycholic Acid on Hepatic Clearance of [99mTc]Tc-Sestamibi: A Randomized Controlled Trial to Improve Myocardial Perfusion Imaging.

Background: Intense hepatobiliary uptake of [^99mTc]Tc-sestamibi in myocardial perfusion scintigraphy (MPS) often degrades image quality by obscuring the inferior myocardial wall, leading to equivocal studies. While nonpharmacological interventions are inconsistent, the choleretic agent ursodeoxycholic acid (UDCA) could potentially accelerate hepatic clearance. The effectiveness of a convenient, single-dose UDCA intervention has not been rigorously evaluated. This study determines if a single oral dose of UDCA administered shortly before imaging could significantly improve hepatic clearance and enhance image quality in MPS. Methods: In this prospective, randomized, double-blind, placebo-controlled trial, 174 patients undergoing 1 d MPS were randomized. The intervention group (n = 87) received a single 300 mg oral dose of UDCA, whereas the control group (n = 87) received an identical placebo (300 mg vitamin C) 1 h before the stress radiotracer injection. All participants and interpreting physicians were blinded. Primary end points were the semiquantitative liver-to-background (L/B) and myocardium-to-liver (M/L) ratios from SPECT images. Results: Baseline characteristics were well-matched. The primary analysis revealed no statistically significant benefit from UDCA. The mean L/B ratio was 1.82 ± 0.45 in the UDCA group versus 1.89 ± 0.52 in the placebo group (p = 0.48). The mean M/L ratio was 1.15 ± 0.31 versus 1.11 ± 0.29, respectively (p = 0.41). A post hoc power analysis revealed the study was underpowered to detect a small effect size. Conclusions: A single 300 mg oral dose of UDCA administered 1 h before stress imaging does not significantly improve hepatic clearance of [^99mTc]Tc-sestamibi or enhance M/L ratios. This is likely due to a pharmacokinetically insufficient regimen, as a single dose is unlikely to achieve the necessary biliary concentration for a significant choleretic effect. Future research should focus on alternative interventions or optimized UDCA dosing schedules, such as multiday protocols, combined with advanced imaging techniques like SPECT/CT, to conclusively determine effective strategies for improving MPS image quality.