Postoperative heart valve infection, when and which bacteria: a nationwide cohort study

Abstract Background In patients undergoing heart valve surgery, subsequent bacteremia and infective endocarditis are feared events due to the associated high mortality. Knowledge on the incidence and specification of bacteremia following left-sided valve surgery are sparse and may have implications for prophylactic strategies and follow-up. Purpose To examine the six months incidence of bacteremia and infective endocarditis following left-sided heart valve surgery. Methods In the period from January 2010 to December 2021 all patients undergoing left-sided valve surgery were identified using Danish nationwide registries. Patients were followed until a maximum of six months, end of study, emigration, death, or outcome of interest (i.e., bacteremia or infective endocarditis). Cumulative incidence curves were computed with death as a competing risk stratified on bacterial species and for subgroups of interest: type of valve surgery, age, and sex. Results A total of 14,305 patients were included in the study. The majority of the study population were male (68.6%), and the median age was 70.2 years (25th-75th percentile 62.0-76.0 years). In total, 10,469 (73.2%) of the study population underwent aortic valve surgery, 3,497 (24.5%) underwent mitral valve surgery, while 339 (2.4%) underwent surgery on both valves. The cumulative incidence of bacteremia at six months of follow-up was 2.4% (95% CI 2.2-2.7%), Figure 1. For the overall study population, the most frequently occurring bacteremia was with Coagulase-negative Staphylococci (28%) and Staphylococcus aureus (14%). Within 30 days 0.35% of the patients had bacteremia with coagulase-negative staphylococci while this was 0.68% at six months of follow-up. For Staphylococcus aureus this was 0.19% and 0.34%, respectively. The cumulative incidence of infective endocarditis at six months of follow up was 1.0% (95% CI 0.8-1.2%). The majority of the infective endocarditis incidents were blood culture negative (27%) or caused by Enterococci (19%), Streptococci (17%) or Coagulase-negative Staphylococci (17%) while Staphylococcus aureus accounted for 14%. In crude analysis, simultaneous surgery on the mitral and aortic valve was associated with a statistically significant higher rate of bacteremia (P=0.004). Similarly, higher age was associated with a statistically significant higher rate of bacteremia (P<0.001). On the contrary, in crude analysis, no difference in the risk of bacteremia was found between sexes (P=0.9). Conclusions Bacteremia following left-sided heart valve surgery occurred in little over 2%. The majority was with Staphylococci, and half of these occurred within 30 days of the surgery. There is a continued need to optimize prophylactic strategies.