September 21, 2010 (Boston, Massachusetts) — Despite advances in the design of ventricular assist devices (VAD) for patients with advanced heart failure, infections continue to be a major problem and are common both before and after VAD implantation, according to a late-breaker poster presentation here at the 50th Interscience Conference on Antimicrobial Agents and Chemotherapy.
"VAD infections are common despite newer-generation devices. Particularly important pathogens are Staphylococcus aureus, coagulase-negative Staphylococcus, and Pseudomonas," said lead investigator Rachel Gordon, MD, assistant professor of clinical medicine and epidemiology at Columbia University in New York City.
The researchers conducted a large multicenter trial involving 150 patients at 11 different cardiac centers who were implanted with a VAD. In the 30 days before VAD implantation, 40 patients (27%) had nosocomial infections — mainly urinary tract, bloodstream, pneumonia, and surgical wound infections. After VAD implantation, infections were documented in 32 patients (21%). The driveline of the pump was the most common site of infection, found in 20 (72%) cases.
"We think the driveline is where the infection starts," she said. "Often there are local signs or omens warning that infection is present, such as serosanguinous drainage in the drive line."
Microbiologic data were available for the 32 post-VAD infections. "These infections were due to a variety of pathogens, but the main sources were Staphylococcus and Pseudomonas," she said.
Median time to a documented infection was 80 days post-VAD implantation. "This seems late, and it is not clear whether these infections are occurring later or whether there was a time lag until diagnosis. We need to analyze our data further to determine this," Dr. Gordon said.
"We are still analyzing the microbiologic data. Four clusters of Staphylococcus epidermidis occurring pre-, during, and post-VAD [implantation] accounted for more than half of all isolates we cultured, suggesting that this infection is clonal across the United States," she said.
In Dr. Gordon's study, 60% of patients received continuous flow VAD and 40% received pulsatile flow devices. In a similar study conducted at Henry Ford Hospital in Detroit, Michigan, more than 75% of patients on continuous flow VAD had infections, and 77% of infections were Gram-negative, said the author, Alan Gross, PharmD, an infectious disease pharmacy resident at Midwestern University in Downer's Grove, Illinois.
"Usually Gram-positive organisms cause these infections, but Gram-negative infections may become more prevalent as patients are living longer with VAD devices. Proper care of the implantation site is needed to reduce the frequency of infection. Patients need continued reinforcement about aseptic techniques and to wear a binder to stabilize the device," he said.
Dr. Gordon and Dr. Gross have disclosed no relevant financial relationships.
50th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC): Abstract K-1005a. Presented September 13, 2010.
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