Polymicrobial and Multiple Blood Stream Infection Episodes as Risk Factors for On-Pump Mortality in Mechanical Circulatory Support Patients

Abstract

<h3>Purpose</h3> Despite our improving experience with the expanding use of mechanical circulatory support systems for end-stage heart failure, device related infection remains prevalent. This study aims to better characterize the clinical impact of blood stream infections (BSIs) over a 26-year period. <h3>Methods</h3> This was a single center retrospective study of patients with durable mechanical circulatory supports implanted from June 1994 to December 2020 as bridge-to-transplantation. Patients were studied for the incidence of BSIs, number of on-pump support days, transition to transplant and on-pump mortality. Descriptive statistics and relationships between the incidences or types of infections and on-pump mortality were analyzed. <h3>Results</h3> Two-hundred and fifty patients (204 males, 82%) with average age at implant of 52.1±13.7 years and average INTERMACS score of 1.9±0.7 were studied. Implanted devices included 221 (88.4%) left VADs, 17 (6.8%) biVADs and 8 (3.2%) total artificial hearts. Average on-pump duration was 377±381 days. There were 108 (43%) patients with one or more BSIs, and 0.42 events per patient year. Of these cases, 71 (28.4% of total patients, 65.7% of all BSI episodes) were single episodes, whilst 37 had multiple episodes (occurring at least seven days after index infection) and 28 had polymicrobial growths (2 organisms or more during time on-pump). The major responsible organisms for initial BSI were staphylococci (67.6%), streptococci (8.3%) and enterococci (6.5%) species. There were 93 (37.2%) patients with positive microbiology growths from superficial driveline site swabs, of which 46 out of 93 (49.5%) had BSIs. On logistic regression against hypertension, diabetes mellitus and requirement for dialysis, positive driveline microbiology was a significant predictor of mortality (p=0.01). Amongst patients with BSIs, there were significantly increased proportions of on-pump mortality for those who had multiple BSIs (p=0.03) or BSIs with multiple organisms (p<0.01). <h3>Conclusion</h3> Infections, either sequential or with multiple organisms, are significant markers for on-pump mortality. Whilst limiting any infection is important at the outset of device implantation, this study highlights the importance and urgency of timely recognition and early administration of targeted and intensive antimicrobial therapies.