Prognosis and follow-up of patients with prosthetic valve endocarditis treated conservatively in relation to WBC-SPECT imaging

Background Our objective was to evaluate in patients with prosthetic valve endocarditis (PVE) treated conservatively, the prognostic value of white blood cell (WBC) signal intensity on SPECT and to describe the evolution of the WBC signal under antibiotics. Methods Patients with PVE treated conservatively and positive WBC-SPECT imaging were identified retrospectively. Signal intensity was classified as intense if equal to or higher, or mild if lower, than the liver signal. Clinical, biological, imaging and follow-up information were collected from medical files. Results Among 47 patients, WBC signal was classified as intense in 10 patients and as mild, in 37. The incidence of the primary composite endpoint (death, late cardiac surgery, or relapse) was significantly higher in patients with intense vs. mild signal (90% vs. 11%). Twenty-five patients underwent a second WBC-SPECT imaging during follow-up. The prevalence of WBC signal decreased progressively from 89% between 3 and 6 weeks to 42% between 6 and 9 weeks and 8% more than 9 weeks after initiation of antibiotics. Conclusions In patients with PVE treated conservatively, intense WBC signal was associated with poor outcome. WBC-SPECT imaging appears as an interesting tool for risk stratification and to monitor locally the efficacy of antibiotic treatment.