Results
A total of 155 patients underwent a Micra TPS implant procedure from July 2015 to July 2019 of which 15 patients (9.7%) developed a bacteraemia during follow-up. Bacteraemia occurred at a median of 226 days (range: 3-1129) after the implant procedure. Median duration of follow-up after the bacteraemia was 263 days (range: 15-1134). The baseline characteristics of the population is summarized in Table 1. Patients with bacteraemia had a median age of 81-years (77-82) and were largely similar to the other patients with two exceptions. First, they had a more frequent history of valve intervention (66.7% vs.27.9%, p=0.002) and secondly, there was a higher incidence of severe renal dysfunction requiring haemodialysis (20% vs. 3.6%, p= 0.006).
Gram positive species accounted for 73.3 % (n=11) of the bacteraemia including Staphylococcus (n=5), Enterococcus (n=3) andStreptococcus (n=3) (Table 2). The source of infection was identified in 9 patients (60%) including endocarditis in 4 patients, the urinary tract in 3 patients, and the skin in 2 patients. All patients underwent at least one transoesophageal echocardiography that did not reveal the presence of vegetation on the Micra. Thirteen patients were successfully treated with intravenous antibiotics. Two patients with endocarditis underwent valvular replacement with preventive removal of the Micra in the absence of definite signs of device infection including negative transoesophageal echocardiography. In both, the culture of the explanted device remained negative. All treatments led to negative conversion of the blood cultures and no patient experienced any recurrent bacteraemia during follow-up. Four patients died during follow-up of which 3 patients with endocarditis. Both patients who had removal of the Micra with valve replacement for endocarditis died of multi-organ failure respectively 14 and 43 days after surgery. A third patient also died of multi-organ failure 20 days after valve surgery for endocarditis. The fourth patient died at home from causes unrelated to the bacteraemia.
18FDG PET/CT imaging was performed in 6 patients to identify the site of infection. No patient had abnormal18F-FDG uptake detected around the Micra on the PET/CT fusion images (Figure 1). Two patients with endocarditis had increased18F-FDG uptake on infected valves confirmed by positive post-operative valve culture. Two other patients had increased focal 18-FDG uptake compatible with infectious arthritis (Table 2).