Culture negative infective endocarditis: impact on surgical outcomes.

Introduction: Infective endocarditis (IE) is still associated with a high rate of mortality and morbidity. Whether the absence of positive microbiological specimens, and in turn the subsequent empiric (possibly suboptimal) antibiotic therapy impacts on prognosis is still matter of discussion. The aim of this study is to evaluate in-hospital outcomes in culture negative infective endocarditis (CNIE) patients treated with surgery. Methods: A retrospective study was conducted from January 2000 to December 2018 at our institution and includes 321 patients operated on for infected endocarditis. The primary endpoint was early mortality. Secondary endpoints were ICU stay, mechanical ventilation, sepsis, multi-organ failure, respiratory failure, stroke, acute kidney injury and atrial fibrillation. Results: Among the 321 patients included in the study, 133 (41%) had CNIE and 188 (59%) had culture positive infective endocarditis (CPIE). Main age was 61.30 ± 15.37. Patients were mostly male (75.39%), mean EuroScoreII was 6.55 ± 0.34 and in 17.45% there was a multi-valvular involvement. Causative organisms are reported in Table. Overall in-hospital mortality was 13.08% (42/321 pts). CPIE had a lower early mortality compared to CNIE (9.0%, 17 pts vs 18.80%, 25 pts; p = 0.02). One-to-one propensity matching resulted in 92 pairs with similar preoperative risk profile. Propensity score matched analysis showed that CNIE was associated with a higher risk of in-hospital death (6.50% vs. 17.40%, p = 0.04). No statistically significant differences in ICU stay (p = 0.54), hours of mechanical ventilation (p = 0.80), sepsis during ICU stay (p = 0.14), multi-organ failure (p = 0.24), respiratory failure (p = 0.75), stroke (p = 1), acute kidney injury (p = 1) and atrial fibrillation (p = 0.86) were observed between the two groups. At multivariable logistic regression analysis the absence of microbiological diagnosis was an independent risk factor for early mortality (OR 2.10, 95% CI 1.01-4.47, p = 0.04) along with age (OR 1.03, 95% CI 1.003-1.06, p = 0.03), de novo dialysis (OR 7.92, 95% CI 1.53-39.93, p = 0.01), left ventricular ejection fraction (OR 0.93, 95% CI 0.90-0.97, p < 0.01), associated CABG (OR 4.74 95% CI 1.01-20.55, p = 0.04), multi-valvular disease (OR 2.36, 95% CI 1.00-5.40, p = 0.04), and EuroScoreII (OR 1.03, 95% CI 1.00-1.06, p = 0.04). Conclusions: CNIE are associated with a remarkably high mortality rate after surgery in comparison with CPIE, possibly because of suboptimal empirical antibiotic therapy in some cases of CPIE. Efforts to increase the rates of pre-operative microbiological diagnosis might lead to better post-operative outcomes in this patients population.