Dr Han Naung @ Henry Han : Electrophysiology and Heart Rhythm : Cardiac implantable electronic devices (CIEDs) and Infections

Cardiac Device and Infection : What we know and how to Prevent ?

Cardiac implantable electronic devices (CIEDs) are being used more and more often nowadays. Indications have grown, and access to implantation facilities has increased as well. These devices are often lifesaving, and they can be associated with many other benefits. However, as with any medical procedure, complications can occur. In fact, CIED infection is a prevalent complication that can cause high morbidity and can even lead to death. It is important that most clinicians be familiar with signs and symptoms associated with CIED infection as early diagnosis and treatment lead to better outcomes. Nonetheless, the prevention of such infections remains the cornerstone in the management of CIED-related infections. In this paper, we will review in detail the most significant risk factors that can lead to CIED infection. We will also explore the different available tools that can help decrease the incidence of this complication. In addition, we will summarize the different treatment modalities and the major prevention methods.

Bacterial inoculation often occurs as a result of bacterial colonisation of the operative site at time of CIED implantation. Staphylococcus species from the skin, especially, may contaminate the wound, likely during pocket formation, and later cause pocket infection and/or erosion. Most investigators concur that the majority of infections seen within the first year are attributed to this early colonisation and the formation of biofilm on device surfaces. Later, pocket erosion may also be caused by operative contamination and biofilm formation. Bacteria in biofilm are protected from killing by host defences and antimicrobial agents. Secondary seeding of the CIED may also occur, especially in Staphylococcus aureus bacteraemia. Thus, removal of the entire device is necessary when treating CIED infections.

KEY CLINICAL POINTS ( ADAPTED BY NEJM)

Infections Related to Cardiovascular Implantable Electronic Devices

The rate at which cardiovascular implantable electronic devices (CIEDs) are being implanted has been increasing, with an associated increase in the number of CIED infections.

Common risk factors for CIED infections include complications involving the generator pocket site (hematoma and poor wound healing), revision or replacement of the device, and renal failure.

Staphylococcus species account for the majority of CIED infections.

Complete removal of the device is required for cure, even when signs of infection are limited to the generator pocket site, and should be performed at a medical center with expertise in lead extraction.

Antibiotic therapy is also given for up to 2 weeks (longer if there is evidence of endocarditis).

Perioperative antibiotic prophylaxis is effective in reducing the risk of CIED infection.

What are the most common microbial causes of ICED infection?

Staphylococci (and Gram-positive bacteria in general) cause the majority (68%–93%) of infections.

Gram-negative bacteria cause fewer than 18% of infections.

Approximately 15% of ICED infections are culture negative.

The microbiology of ICED infections is relevant to the pathogenesis of infection and the selection of both antimicrobial prophylaxis and empirical treatment regimens. Eighteen studies that included at least 100 patients were reviewed. Despite considerable heterogeneity in the design of studies, the microbial epidemiology of ICED infections was found to be remarkably consistent. Gram-positive bacteria were by far the most commonly isolated microorganisms (from 67.5% of patients to 92.5% of isolates across ten studies reporting the proportion of Gram-positives),with CoNS the most consistently isolated bacteria followed closely by Staphylococcus aureus. Gram-negative bacilli were isolated in 1%–17% of patient episodes (6%–10.6% of isolates in studies using the total number of isolates as the denominator). Fungal infection is uncommon, occurring in no more than 2% of patients. The proportion of patients with polymicrobial infection was reported in seven studies and ranged from 2% to 24.5%. Twelve studies reported the proportion of patients with clinical infection but negative cultures, which ranged from 12% to 49% of patients.

PREVENTION

The increasing rate of CIED infection has prompted a reevaluation of the usual insertion practices and an examination of novel interventions (discussed below). A meta-analysis of seven randomized trials suggested that antibiotic prophylaxis given at the time of permanent pacemaker insertion significantly reduced the infection rate (pooled odds ratio, 0.26; 95% confidence interval, 0.10 to 0.66); however, the individual trials were underpowered, included a variety of penicillin and cephalosporin regimens, and yielded inconsistent results.2 Still, the overall finding that systemic perioperative antibiotic prophylaxis was beneficial is consistent with the results of two case–control studies,a large, prospective registry, and a retrospective population-based study. Cefazolin prophylaxis was used predominantly in one of the case–control studies; unidentified beta-lactam antibiotics were used in the other case–control study and for most of the patients included in the large, prospective registry.

A large, randomized, double-blind, placebo-controlled trial of cefazolin for prophylaxis was stopped early (after enrollment of 649 patients, with a planned total enrollment of 1000 patients) because an interim data analysis showed substantial benefit. The incidence of device-related infection was significantly lower in the cefazolin group than in the placebo group (0.63% vs. 3.28%). On multivariable analysis, hematoma formation at the pocket site and the lack of perioperative cefazolin use were independent predictors of device-related infection.

The presence of a CIED is not considered an indication for systemic antibiotic prophylaxis for invasive procedures. Evidence to suggest that transient bacteremia associated with dental, gastrointestinal, or genitourinary procedures can result in CIED infections is lacking. Moreover, staphylococci, which are the most common microbiologic causes of CIED infections, are infrequently associated with the transient bacteremia related to these procedures.

Patients receiving more complex devices for an expanding list of indications are usually ill with multiple coexisting conditions that affect various organ systems.Therefore, extensive training in surgical techniques, including pocket formation and wound management to diminish the risk of complications, is an important component of electrophysiology fellowship programs. In addition, the implementation of a comprehensive infection prevention and control program would be expected to reduce the rate of CIED infection.