In terms of intrahospital mortality, hospital and intensive care unit (ICU) stay, and 3-year mortality, no statistically significant differences were found between patients with blood culture positive endocarditis (BCPE) and those with blood culture negative endocarditis (BCNE) undergoing cardiac surgery, according to authors of a study published in the Journal of Cardiothoracic Surgery.

Although patients in the BCPE group had higher levels of procalcitonin, in a multivariate analysis this was not independently associated with mortality. Staphylococcus aureus, the most common microorganism in the BCPE group, was associated with independently higher intrahospital mortality than other causative microorganisms.

According to the authors, in patients with infective endocarditis (IE), prompt diagnosis combined with identification of the causative microorganism for targeted antibiotic treatment can have a significant impact on prognosis and future health status. Yet in 30% or more cases of IE, they explained, the causative agent is unidentified and the case is considered blood culture-negative. This can be associated with delayed diagnosis, worse outcomes, and a higher number of intraoperative and postoperative complications.

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The investigators analyzed short-term and long-term mortality as well as differences between clinical, laboratory, and echocardiography parameters in patients with BCPE vs BCNE, seeking to determine the possible impact on health outcomes. They performed a retrospective analysis of medical records of all IE patients who underwent cardiac surgery at Pauls Stradins Clinical University Hospital, Latvia, from 2016 to 2019.

As this is the only center for cardiac surgery in the country, these 207 patients represent the entire surgically treated IE patient population in Latvia for that time period. Because the hospital had no IE specialists, IE diagnoses were made by cardiologists, cardiac surgeons, and other specialists using modified Duke criteria.

Among the 207 patients with IE, 114 (55.1%) were BCPE and 93 (44.9%) were BCNE. The most common pathogens in the BCPE group were S aureus in 36 cases (31.6%), Streptococcus spp. in 27 cases (23.7%), Enterococcus faecalis in 24 cases (21.1%), and other microorganisms in 27 cases (23.7%). No statistically significant differences were seen between the groups in locally uncontrolled infection, embolic events, vegetation size, and hemodynamic instability.

Although patients with embolic events (n=60 of 207, 28.9%) did have larger vegetations, no significant association was seen (mean size for those with embolic events compared with without: 16.0 [11.3] mm vs 15.5 [7.9] mm; P =.795). After conducting laboratory analyses, researchers found significantly higher procalcitonin levels, lower hemoglobin levels, and lower hematocrit levels in the BCPE group. Although intrahospital mortality was 14.04% in the BCPE group compared with 5.38% in the BCNE group, this difference did not reach statistical significance (P =.062).

Despite the study limitations of a relatively small sample size of patients treated at a single center, the investigators concluded, “There are no statistically significant differences between groups [with] BCPE [vs] BCNE in terms of intrahospital mortality, hospital and ICU stay or 3-year mortality. Although BCPE patients have higher intrahospital and long-term mortality than BCNE patients, BCPE is not independently associated with mortality in multivariate analysis.

There were higher levels of procalcitonin in [the] BCPE group; however, procalcitonin failed to show independent association with mortality in multivariate analysis. The most common microorganism in the BCPE group was S aureus. It was associated with independently higher intrahospital mortality (OR rate of 3.332 and 4.408 in uni- and multivariate analyses) when compared [with] other causative microorganisms.”


Meidrops K, Zuravlova A, Osipovs JD, et al. Comparison of outcome between blood culture positive and negative infective endocarditis patients undergoing cardiac surgery Published online May 27, 2021. J Cardiothorac Surg. doi:10.1186/s13019-021-01532-9