Surgery for blood culture-negative infective endocarditis: outcomes and the role of molecular biological imaging as diagnostic approach†.

Objectives: The study aimed to analyse outcomes of surgery for blood culture-negative infective endocarditis (BCNIE) and to evaluate the role of molecular biological imaging.

Methods: Patients undergoing surgery for native or prosthetic valve endocarditis from 2013 to 2022 were analysed regarding blood culture-positive infective endocarditis (BCPIE) and BCNIE. For laboratory diagnostics in BCNIE, excised valves or prostheses underwent conventional microbiological culture and fluorescence in situ hybridization combined with 16S rRNA-gene polymerase chain reaction and sequencing (FISHseq).

Results: Of 521 patients overall, we identified 473 patients (342 males, mean age 63 ± 14.4 years) with preoperative blood cultures: 396 with BCPIE (83.7%) and 77 with BCNIE (16.3%). Preoperative characteristics and operative procedures were comparable between groups and the calculated perioperative risk (EuroSCORE II) was identical (BCNIE: 12.2 ± 8.8%, BCPIE: 12.9 ± 11.9%, P = 0.788). At surgery, signs of infective endocarditis were present in 71%, missing in 18% and inconclusive in 10% of patients with BCNIE. While valve cultures alone identified pathogens in 32% of BCNIE patients, the combination with FISHseq confirmed the infective aetiology in 98% and identified causative pathogens in 52%. Overall, early mortality was similar in BCNIE (16.9%) and BCPIE (18.2%, P = 0.620), but increased in 37 BCNIE patients without pathogen identification compared to 40 patients with pathogen identification (27.0% vs 7.5%, P = 0.032).

Conclusions: Integrating FISHseq as molecular biological imaging technique into valve analysis algorithms in patients undergoing surgery for BCNIE increases diagnostic gain and potentially improves outcome.