**2.3 Risk factors**

Several studies have identified the following risk factors for the development of infection on CIED [2, 7, 8, 11–13]:

Factors associated with the patient: Several of them coexist in up to 50% of patients [7].


Factors associated with the procedure

• Non-first implant: Infection is more frequent in replacement or update procedures (1–4%) than in first implantation (0.5–0.8%) The risk of CIED infection is much greater after generator change or device revision. It has been suggested that this is related to bacterial contamination of the avascular pocket that is formed around the generator, which may impede penetration of systemic antimicrobials and inflammatory cells during generator replacement. For this reason, some operators advocate the removal of the capsule in battery replacement.


Factors related to other procedures and health care


#### **2.4 Physiopathology and etiology**

According to estimates from the U.S Food and Drug Administration (FDA) and the European trade association representing the medical technology industries, (MedTech Europe), more than 500000 types of medical devices have currently entered the global market. Invasive medical devices, including indwelling and implantable devices, represent just a fraction of these [14, 15]. More than a million cardiovascular electronic devices are implanted worldwide each year [16]. Devices used in cardiovascular surgery and interventionism are inserted into the body tissues by breaching the skin or mucous membranes. No matter where the surgically invasive device is placed, it is a foreign body. Even a mild tissue response alters the local immune defenses, creating a "locus minoris resistentiae", which is vulnerable to bacterial attack. Especially the devices in contact with the bloodstream, can potentially cause sepsis.

CIED infection, can have a local or a distant origin.

#### *2.4.1 Local origin*

Human skin is very resistant to infection. This resistance is due to physical (thickness, exfoliation), chemical (pH, secretions) and immunological (cellular and humoral) factors.

The resident flora is also an important factor. This flora is made up of bacteria that live attached to the skin and under normal circumstances, they do not cause infection and prevent the proliferation of other strains as well. When the skin barrier is broken, the entry of microorganisms from the adjacent skin is facilitated. Most infections from these devices are caused by coagulase negative staphylococci

**123**

**Figure 1.**

*BIOFILM formation.*

*Endocarditis and Cardiac Device Infections DOI: http://dx.doi.org/10.5772/intechopen.96909*

**Phases of infection**

diabetics, some skin diseases, and hospital workers.

(CoNS), which are the most common microorganisms in the normal flora of the upper part of the skin of the thorax (especially *Staphylococcus epidermidis*). *Staphylococcus aureus* is not part of this resident flora, but it can become a persistent colonizer of the nasal mucosa, pharynx, and skin, especially in kidney patients,

• **Colonization** of the CIED pocket by microorganisms from the surgical

equipment (air or personnel) or more frequently from the patient's own skin. Disinfection reduces the number of bacterial colonies, but in the presence of a foreign body, the inoculum to produce an infection is lower. The susceptibility of surgically invasive devices to bacterial colonization is due to reduced effectiveness of human immune defenses at the implant–tissue interface [12]. The longer the procedure, the higher the rate of colonization of the surgical sites.

However, colonization is not synonymous with infection, since it must occur:

• *Initial reversible anchoring* of bacteria in "planktonic" or "free" form to surfaces

• *Irreversible anchorage*: Once anchored, a bacterial monolayer will begin to form and an extracellular protective matrix composed of extracellular polysaccharides, extracellular proteins, cellular debris and nucleic acids will begin to be produced. Both, along with the collagen and fibrinogen deposited in damaged tissues and on biomaterials, favors the anchorage of bacteria with specific

• *Maturation:* the development of a biofilm favors the growth of the colonies, with a complex three-dimensional framework and a great resistance to antibiotics. Sometimes different bacterial species can coexist in the same biofilm. There are complex genetic interactions between the bacteria in these biolayers

receptors. The formation of hematomas facilitates this process.

Adhesion and BIOFILM formation (**Figure 1**) [13, 14].

Biofilm formation occurs in five steps:

by unspecific forces.

known as "quorum sensing".

## *Endocarditis and Cardiac Device Infections DOI: http://dx.doi.org/10.5772/intechopen.96909*

(CoNS), which are the most common microorganisms in the normal flora of the upper part of the skin of the thorax (especially *Staphylococcus epidermidis*). *Staphylococcus aureus* is not part of this resident flora, but it can become a persistent colonizer of the nasal mucosa, pharynx, and skin, especially in kidney patients, diabetics, some skin diseases, and hospital workers.
