Left ventricular assist device is the major treatment choice for patients with heart failure in advanced disease, both as a destination therapy or as a bridge to transplantation. The principal complication of this lifesaving device is infection. The accuracy of FDG PET/CT in the diagnosis of prosthetic graft and pacemaker related infections is high and well described in the literature, but the information regarding the application of metabolic imaging in left ventricular assist device infection (LVADI) is poorer. We evaluated the role of FDG PET/CT for LVSDI: confirming or excluding the presence of infection, defining the extent of the device involvement and helping in the decision whether to change treatment therapy or to remove the device.
Between 2013 and 2014 eight consecutive patients, all males (age 51-69, mean 60.8), with Heartmate II and infections of the exit of the driveline, underwent 14 FDG PET/CT. A complete whole body scan was performed after 1 hour from FDG injection in fasting condition. At FDG imaging, LVADI was classified into four sites: driveline (DL), prosthetic device (PD), inflow valve housing (IV) and outflow valve housing (OV); for each site of infection it was distinguished focal from extended tracer uptake and the grade of involvement according to SUV max values and SUV ratio between infection site and liver (mild, moderate and severe). FDG uptake was also checked in non-attenuation corrected images (NAC).
Microbioloy cultures from percutaneus DL and blood mainly isolated Staphylococcus Aureus, coagulase-negative staphylococci and Burkholderia Cepacia only in one case.
Twelve PET were positive and infectious sites were attributed to the DL in 11, IV in 7, PD in 4, OV in 7. The grade of infection was mild in 7 PET, moderate in 2 and severe in 3 scans. All patients were treated with the most suitable antibiotics according to the pathogens and the extension of the LVADI. Among the two patients with severe involvement at PET and uptake in the PD, one patient underwent transplantation after 3 months of antibiotic therapy while the other one in still on a high dose antibiotic treatment and a continuous worsening of his healthy condition. All patients with mild grade and focal uptake of LVADI had their personalized antibiotic treatments and at follow-up they are in good life conditions. One patient with moderate involvement of the PD was transplanted with confirmation of the infection also in the PD. One patient died for non-infectious reasons. In our study we did not see any changes in the OV tracer uptake during different antibiotic treatments, the SUV values and the extension of the uptake were always mild and focal respectively, suggesting a chronic inflammatory response to the prosthetic graft material rather than a site of infection.
None of these patients revealed the presence of septic embolism at PET imaging.
In this small sample of patients, FDG PET/CT was helpful to the clinicians in recognizing the sites, the extension and grade of LVADI, which had important implications on patient management.