October 13, 2016

CIED Infections: Know Your Enemy

High rates of methicillin-resistant staph demand vigilance, analysis shows

methicillin-resistant staph organisms

Methicillin-resistant staphylococci were implicated in 33.8 percent of all cardiac implantable electronic device (CIED) infections requiring transvenous lead extraction over a recent 12-year period at a high-volume U.S. tertiary care center.

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So reports a new analysis of the microbiology of CIED infections at Cleveland Clinic from 2000 to 2011. The study also revealed an increase in methicillin-resistant staphylococci as the culprit organism over this period, raising concern about overuse of empiric antibiotic therapy.

Khaldoun Tarakji, MD, MPH

Khaldoun Tarakji, MD, MPH

“The fact that one in three patients with device infection referred to us for extraction had methicillin-resistant staphylococci is concerning,” says Cleveland Clinic electrophysiologist Khaldoun Tarakji, MD, MPH, principal author of the study, published in the August 2016 issue of JACC: Clinical Electrophysiology.

As the largest analysis of its kind to date, the paper has earned kudos for illuminating the contemporary microbiology of CIED infections in a way that can shape clinical practice. An accompanying editorial notes that the authors “should be commended in reporting their large experience and reiterating the importance of rising antibiotic resistance in CIED infection.”

Know your enemy

About 500,000 CIEDs are implanted in the U.S every year, and the patients who receive them are increasingly older and increasingly likely to have multiple coexisting illnesses. CIED recipients are living longer and requiring more device revisions or upgrades.

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These factors conspire to increase the rate of infection, the most feared CIED complication. One-year mortality from CIED infection is as high as 20 percent, even with treatment. “We take CIED infection seriously, because the stakes are high,” says Dr. Tarakji.

But although the CIED infection rate has climbed, outdated information on the responsible organisms has caused treatment to remain largely unchanged since the 1990s. The Cleveland Clinic team undertook its study to determine (1) whether the organisms have changed over time and (2) whether different organisms are responsible for infections that occur soon after device placement versus more than one year later (early versus late infections).

“You must know the enemy you’re fighting,” says Dr. Tarakji. “The main question is whether it’s the same enemy as before.”

A growing concern

The researchers used a prospectively maintained database to identify 816 consecutive patients with confirmed CIED infection who were referred to Cleveland Clinic and underwent transvenous lead extraction at Cleveland Clinic from 2000 to 2011. It thus provided a real-life snapshot of pathogens in the community.

Infections were categorized as pocket or endovascular, and early or late (less or more than one year after last device intervention).

Blood cultures were obtained from all patients. Leads, lead material, pocket tissue and pocket swabs were cultured as well. Among the key findings:

  • More than two-thirds of CIED infections were caused by staphylococcal species, consistent with prior reports. Half of these (33.8 percent overall) were methicillin-resistant — a higher percentage than in reports over the previous decade.
  • 15 percent of all CIED infections were due to methicillin-resistant Staphylococcus aureus — an eightfold increase over earlier reports.
  • No pathogen could be cultured in 13 percent of patients. “We postulate that the reason behind this high percentage of negative cultures is that by the time many of these patients were referred to us, they had failed multiple courses of antibiotic therapy,” says Dr. Tarakji. “This suppresses growth of the microorganism but doesn’t heal the patient until the hardware is removed.”
  • Despite the above observations, there did not seem to be a temporal trend in the epidemiology of responsible organisms over the 12-year period.
  • Half of pocket infections occurred at least a full year after pocket manipulation, and a majority were caused by coagulase-negative staphylococci, likely acquired during the initial intervention.
  • 22 percent of patients with endovascular infection had concomitant infections. “Sometimes it’s the culprit, sometimes it’s the consequence,” says Dr. Tarakji. “In either case the organism needs to be identified and treated.”

Longer follow-up needed

The study reinforces the notion that patients should be followed for more than 12 months after CIED implantation in order to accurately define the rate of infection. “Half of the patients with pocket infection and two-thirds with endovascular infection presented with infection beyond one year,” says Dr. Tarakji. “Studies generally report follow-up at three, six and 12 months, but this is insufficient to provide a clear understanding of lifetime infection risk.”

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Any symptom should prompt vigilance

Pocket infections are hard to miss, but the subtle presentation of endovascular infection provides ample opportunity for misdiagnosis. Front-line physicians should be alert to these patients and avoid treating them empirically, which can delay diagnosis.

“Any symptom of infection, no matter how vague, should raise a red flag in a patient with a device,” says Dr. Tarakji. “Sending out blood cultures can help tailor the therapy toward a specific organism after initial empiric therapy targeting methicillin-resistant species first.”

“Sending out blood cultures before initiating antibiotics will help tailor the therapy toward a specific organism, although empiric therapy, if required, should target methicillin-resistant species first.”

CIED management involves a multidisciplinary team comprising electrophysiologists and other cardiologists, infectious disease specialists, anesthesiologists and cardiac surgeons. “We work closely with our infectious disease colleagues and rely on their recommendations to guide the choice of antibiotic, duration of therapy, and timing of extraction and reimplantation if indicated,” Dr. Tarakji notes.

Top image credit: Centers for Disease Control and Prevention, Janice Haney Carr

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