Evaluation of ^99mTechnetium-Vancomycin Imaging Potential in Experimental Rat Model for the Diagnosis of Infective Endocarditis

Background: Infective endocarditis (IE) is an infection of the heart’s endocardial surface. In recent years, nuclear imaging methods have gained importance in the diagnosis of IE. The present study aims to investigate the imaging potential of ^99mTc-labeled vancomycin (^99mTc-Vancomycin) as a new agent that would enable the diagnosis of IE in its early stages when it is difficult to diagnose or has small vegetation in the experimental rat model. Methods:^99mTc-Vancomycin scintigraphy was evaluated for its accumulation in IE with Staphylococcus aureus performed in an experimental rat model. Serial planar scintigraphic and biodistribution analysis of infected vegetations are compared to rats with sterile vegetations. The heart was identified as an infected organ, the liver was identified as a non-infected organ and the heart/liver uptake ratio (T / NT ratio) was compared between infective endocarditis and sterile endocarditis groups. Results: Planar scintigrams (in vivo measurements) showed more uptake in the heart of rats in the infective endocarditis group compared to the uptake in the heart of rats in the sterile endocarditis group, but this difference was not statistically significant (p>0.05). From the ex vivo measurements, the ^99mTc-Vancomycin heart uptake increased significantly (p = 0.016), liver uptake was significantly decreased (p = 0.045) and the T/NT ratio was significantly higher (p = 0.014) in the infective endocarditis group compared to the sterile endocarditis group. Conclusion: In this experimental study, ^99mTc-Vancomycin scintigraphy ensured the detection of ex vivo infected tissue in a rat model of IE. In addition, the absence of significant ^99mTc-Vancomycin uptake in the sterile endocarditis group indicates that this agent targeted the infected tissue instead of the sterile inflammatory tissue. Finally, this agent should also be evaluated with animal- specific imaging devices.