Oral step-down antibiotic treatment of patients with right-sided or device-related endocarditis: a POETry (Clinical implementation of partial oral treatment in infective endocarditis) sub-study

Background The use of oral step-down antibiotic treatment in right-sided and device-related endocarditis (IE) is primarily investigated intravenous drug users, in few smaller randomized studies. The POETry study investigated implementation of oral step-down therapy in Danish patients after findings from the Partial Oral versus Intravenous Antibiotic Treatment of Endocarditis (POET) Trial regarding left-sided IE, were included in Danish guidelines. The purpose of this study was to quantify the use and outcomes of oral step-down antibiotic therapy in patients with right-sided and device-related IE. Methods POETry is a retrospective, multicentre cohort study including all patients diagnosed with IE in Denmark between May 2019 and December 2020. This sub-study included patients with right-sided or device-related IE. Stabilization criteria for oral step-down antibiotic therapy were defined as: Leucocytes <15×10⁹/L, CRP <20 mg/L or <25% of peak value, afebrile for ≥2 days, and no IE progression on transoesophageal echocardiography. The primary outcome was a composite of all-cause mortality, relapse of bacteraemia, embolism, and cardiac surgery within 6 months of completed antibiotic treatment. Results Out of 1155 patients, 163 patients had isolated right-sided or device-related IE, of which 20 patients died during IE hospitalisation and were excluded. The remaining 143 patients (median age 71 years (IQR 54-78) and 76.2% male) were included in the analysis. Of these, 33 (23.1%) received oral step-down antibiotic therapy; these patients were numerically younger (median age 61 years (IQR 44-77), p=0.062) and a significantly larger proportion were IV-drug users (15.2% vs. 2.7%, p=0.022). Tricuspid valve IE constituted a significantly larger proportion of patients switched to oral step-down antibiotic therapy (30.3% vs. 6.4% tricuspid valve IE, p=0.001), and a significantly lower proportion of device-related IE (57.6% vs. 84.5%, p=0.002) (Table 1). POET stabilization criteria were fulfilled in 15 (45.5%) of the patients who received oral step-down antibiotic therapy; median time from diagnosis to switch to oral therapy was 14 days (IQR 11-22). Duration of hospital admission was significantly shorter in patients treated with oral step-down antibiotic therapy (25 vs. 35 days, p=0.005) (Table 1). The primary composite outcome occurred in 15 (13.6%) of patients receiving conventional IV therapy, and in 7 patients (21.2%) receiving partial oral therapy after 6 months follow-up (Figure 1). There was no difference in occurrence of any individual components of the primary composite outcome. Conclusion One in four patients with right-sided or device-related IE were treated with oral step-down antibiotic therapy. While only half of the patients shifted to oral step-down antibiotic therapy fulfilled stabilization criteria, the primary outcome did not differ between patients treated with conventional IV and oral step-down antibiotic therapy.