Independent risk factors of mortality in streptococcal infective endocarditis
Authors: Chamat-Hedemand S , Dahl A , Oestergaard L , Arpi M , Fosboel E , Boel J , Kaur K P , Oestergaard L B , Lauridsen T K , Gislason G , Torp-Pedersen C , Bruun N E 
Published: October 2021

Abstract

Background
Streptococcal bloodstream infection (BSI) is a common cause of infective endocarditis (IE), yet prognostic factors for mortality are poorly investigated.

Purpose
To investigate risk factors associated with in-hospital and one-year mortality in streptococcal IE.

Methods
All patients with a streptococcal BSI, from 2008 to 2017, were included in a regional population-based setup. Based on microbiological identification of phylogenetic relationship, streptococcal species were classified into eight main subgroups: Anginosus, Bovis, Mitis, Mutans, Salivarius, Pyogenic, nutritionally variant streptococci, and S. pneumoniae. Data were crosslinked with nationwide registries for identification of demographics, concomitant hospitalization with IE, medical history, seasonal variation, and socioeconomic status. Patients were followed up until death or a maximum of 365 days after admittance, whichever came first. Using a multivariable adjusted Cox proportional hazard analysis, independent risk factors associated with in-hospital and one-year mortality were identified.

Results
Among 6,224 patients with a streptococcal BSI, 435 (7.0%) patients with streptococcal IE (mean age 69.0 (SD 14.8), 66% men) were included. The in-hospital mortality in IE patients was 11% (n=48), while the one-year mortality was 23% (n=100). Patients infected with species from the Bovis group had the lowest crude one-year mortality (13%), while patients infected with the Salivarius group had the highest crude mortality (36%). The proportion of deaths among women with IE were significantly higher than among men, both in-hospital (15% versus 9%, p=0.04) and after one year (29% versus 20%, p=0.02). Further, patients dying within one year had a significantly higher prevalence of ischemic heart disease (IHD) (p=0.02), congestive heart failure (CHF) (p&lt;0.0001), cerebral vascular disease (CVD) (p=0.004), cancer (p=0.04), chronic obstructive pulmonary disease (COPD) (p=0.01), and renal disease (p=0.01) than survivors. In the adjusted analysis, age (Hazard Ratio (HR) 1.03, p=0.036) and renal disease (HR 2.46, p=0.045) were associated with higher in-hospital mortality. Furthermore, three independent significant factors associated with one-year mortality were identified; CHF (HR 2.18 [95% confidence interval (CI) 1.30–3.63]), cancer (HR 1.95 [95% CI 1.01–3.77]), and age (HR 1.03 [95% CI 1.01–1.05]) (Figure 1). However, patients infected with species from the Bovis group, had significantly lower risk of death at one-year (HR 0.30 [95% CI 0.10–0.89]) (Figure 1).

Conclusion
Having a renal disease at the time of IE diagnosis was associated with a higher in-hospital mortality in patients with streptococcal infective endocarditis. Further, congestive heart failure and cancer were associated with a higher one-year mortality, while the Bovis group was associated with a lower one-year mortality.

Funding Acknowledgement
Type of funding sources: Other. Main funding source(s): Zealand University Hospital Roskilde and Helsefonden (20-B-0340) Figure 1. Adjusted risk of one-year mortality