*2.6.3 Imaging*

*Advanced Concepts in Endocarditis - 2021*

*2.6.2 Microbiological evidence*

antibiotic treatment.

presentation.

documented.

microorganism.

CIED.

account:

reactivate late with delayed handling.

and pus from a generator pocket wound. **Blood sample extraction** [6, 21].

the start of empirical antimicrobial therapy.

not be assumed unless proven otherwise.

specific media for slow-growing organisms.

the progression to systemic disease faster than in the case of germs such as S Epidermidis or *Propionibacterium acnes*, in which it can be latent and even

We have already discussed the main agents involved, now we will address how and when microbiological samples should be collected and processed. Appropriate microbiological samples include: culture of blood, lead fragments (ideally distal and proximal), lead vegetation (proximal and distal tips), generator pocket tissue

• Should be collected as soon as possible, and whenever possible before starting

• Collection of multiple samples increases diagnostic sensitivity: three sets of aseptically collected, optimally filled blood cultures should be taken from peripheral sites with ≥6 h between them, especially in patients with non-acute

• To avoid an undesirable delay in patients with suspected IE-CIED and severe sepsis or septic shock at the time of presentation, two sets of optimally filled blood cultures should ideally be taken at different times within 1 h and prior to

• Follow -up blood cultures should be obtained 48 to 72 h after antimicrobial therapy is begun, and every 48–72 hours until clearance of bacteremia is

• Blood cultures should be taken 48–72 h after removal of an infected

Regarding blood culture, the following considerations must be taken into

• In a variable percentage, around 10%, it will not be possible to grow any

• The interpretation of a single positive culture for an organism, common contaminant of the skin flora, should not be interpreted systematically as bacteremia and should be evaluated within the overall clinical context.

• All cultured samples must be processed in different culture media and in

• When interpreting the results of the cultured electrodes, it should be considered their potential contamination when extracted through the explant area.

• In case of bacteremia originated at a clear distant infectious focus (abdominal, urinary, respiratory) and due to germs that do not frequently cause endocarditis on devices (enterobacteria, pneumococci), affectation of the device should

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Different imaging techniques are used for the diagnosis of IE – CIED and, therefore, we will speak of Multimodal imaging when referring to them [21, 22].

First line technique, due to its availability and safety, is echocardiography. Initially, an echocardiogram should be performed in all patients with CIED infection, either local or systemic. Transthoracic echocardiogram (TTE) will allow us to globally assess all the structures of the heart as well as their function (**Figure 3**). Despite the advantage of the proximity of the right cavities to the thoracic wall, the presence of metallic electrodes generates artifacts that make it difficult to assess associated vegetations. Occasionally, images compatible with vegetations can be identified, associated with the electrodes, the valves or the endocardium; although their absence does not exclude the diagnosis, since sensitivity is low.

Regardless of the result of the TTE, a Transesophageal echocardiography (TOE) should be performed in all patients with CIED infection suspected of systemic involvement, and probably in carriers of intracardiac devices in the presence of S Aureus bacteremia (**Figure 4**). Even though the sensitivity is higher than in ETT, it is still less than 100% in the case of devices. The reasons for the low sensitivity include: the small part visualized of the cava, the difficulty to assess electrodes in the coronary sinus, or the lesser proximity to the transducer. Three-dimensional (3D) echo, if available, can provide information about vegetation's morphology and size (**Figure 5**). On the other hand, there are images that are difficult to interpret as they may correspond to fibrin strands or small thrombi adhering to the surface of the leads, more frequent in the right cavities due to a slower flow.

In some centers, intracardiac echo (ICE) is also used for the diagnosis of vegetations based on electrodes, with greater sensitivity for the detection of vegetations in the case of high suspicion without diagnostic images. As drawbacks, it is an invasive and expensive technique [23].

In the case of uncertain diagnosis and high suspicion of endocarditis in the absence of diagnostic criteria or doubts about the extent of a local infection,

**Figure 3.** *Lead vegetation TTE.*

**Figure 4.** *Lead vegetation TOE.*

**Figure 5.** *Lead vegetation 3D echo.*

Nuclear Medicine or hybrid technique can be used, based on the detection of metabolic or inflammatory activity.

Positron Emission Tomography-CT (PET-CT) is generally performed using a single acquisition (generally at 1 h) after administration of 18F-FDG, which is actively incorporated in vivo by activated leucocytes, monocytes, macrophages and CD4+ T-lymphocytes accumulating at the sites of infection. Its limitations are the low resolution for foci smaller than 5 mm, its price, the high radiation and the early post-implant or post-surgery period, since the isotope uptake can occur in any inflamed tissue or with metabolic activity, including thrombi and tumors. Sensibility of this test it is estimated around 87% and its specificity around 94% (**Figures 6** and **7**).

Scintigraphy (SPECT) with labeled leukocytes can be combined with CT. Compared to PET-CT, it has the disadvantages of a lower availability, a longer duration -since it requires 2 separate acquisitions (2 and 24 hours)- and the use of blood products. On the other hand, it is cheaper, has greater utility in the postimplantation/postoperative period, exposes less radiation and a greater specificity is reported, close to 100% (except for non-pyogenic agents such as Candida or Coxiella, rarely implicated in CIED infection) [24, 25].

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**Figure 7.** *PET-TAC+.*

**Figure 6.** *PET-TAC-.*

Beyond imaging techniques focused on evaluating of vegetations and inflammatory activity, a chest radiograph in 2 projections or even a CT should be performed to assess the type of device (sometimes unknown), the presence of breakage, torsion or dislocation of the electrodes or the generator displacement, and to assess

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

**Figure 6.** *PET-TAC-.*

*Advanced Concepts in Endocarditis - 2021*

Nuclear Medicine or hybrid technique can be used, based on the detection of

Positron Emission Tomography-CT (PET-CT) is generally performed using a single acquisition (generally at 1 h) after administration of 18F-FDG, which is actively incorporated in vivo by activated leucocytes, monocytes, macrophages and CD4+ T-lymphocytes accumulating at the sites of infection. Its limitations are the low resolution for foci smaller than 5 mm, its price, the high radiation and the early post-implant or post-surgery period, since the isotope uptake can occur in any inflamed tissue or with metabolic activity, including thrombi and tumors. Sensibility of this test it is estimated around 87% and its specificity around 94%

Scintigraphy (SPECT) with labeled leukocytes can be combined with CT. Compared to PET-CT, it has the disadvantages of a lower availability, a longer duration -since it requires 2 separate acquisitions (2 and 24 hours)- and the use of blood products. On the other hand, it is cheaper, has greater utility in the postimplantation/postoperative period, exposes less radiation and a greater specificity is reported, close to 100% (except for non-pyogenic agents such as Candida or

Coxiella, rarely implicated in CIED infection) [24, 25].

metabolic or inflammatory activity.

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(**Figures 6** and **7**).

**Figure 4.**

**Figure 5.**

*Lead vegetation 3D echo.*

*Lead vegetation TOE.*

**Figure 7.** *PET-TAC+.*

Beyond imaging techniques focused on evaluating of vegetations and inflammatory activity, a chest radiograph in 2 projections or even a CT should be performed to assess the type of device (sometimes unknown), the presence of breakage, torsion or dislocation of the electrodes or the generator displacement, and to assess

the pulmonary parenchyma as there may be images suggestive of septic embolism or infectious pulmonary involvement (**Figure 8**).
