Impact of Microbiological Organism Type on Surgically Managed Endocarditis

This study describes the impact of organism and valve type on surgically managed infective endocarditis (IE) from The Society of Thoracic Surgeons (STS) database. We developed a risk model for surgically managed endocarditis that includes the microbiological organism.

The STS database was queried for adult patients with surgically managed endocarditis from July 1, 2011, to June 30, 2016. Outcomes were compared based on (1) causative microbiological organism, (2) valve type (native vs prosthetic), and (3) endocarditis on the right (tricuspid) vs left (mitral, aortic) sides. Univariate and risk adjusted models were developed with odds ratios for mortality for each organism type referenced against Streptococcus.

The study population included 21,388 operations (93%) for left-sided IE and 1698 (7%) for right-sided IE. Streptococcus (28%) and Staphylococcus (27%) were the most common infecting organisms, followed by Enterococcus (11%). After multivariate adjustment, microbiological organism type was significantly associated with operative mortality for patients with left-sided endocarditis, with an adjusted odds ratio of 2.9 for fungal, 1.4 for Staphylococcus, and 1.3 for culture-negative vs Streptococcus. For right-sided endocarditis, there were no differences in outcomes by organism type. Left-sided prosthetic valve endocarditis had a higher operative mortality than left-sided native valve endocarditis (12% vs 8%, P < .001). In contrast, surgery for right-sided endocarditis carried lower operative mortality, with no mortality difference between prosthetic valve endocarditis and native valve endocarditis (5% vs 4%, P = .6).

Organism type influences the operative mortality for left-sided endocarditis. Surgery for left-sided and prosthetic valve endocarditis is associated with higher operative mortality. Risk adjustment for operative outcomes in endocarditis may need to account for microbiological organism type.