Usefulness of Fluorine-18 Positron Emission Tomography/Computed Tomography for Identification of Cardiovascular Implantable Electronic Device Infections
What is the clinical utility of fluorodesoxyglucose fluorine-18 (18F-FDG) positron emission tomography and computed tomography (PET/CT) for the diagnosis of infection of a cardiovascular implantable electronic device (CIED)?
Patients with either pacemakers or defibrillators (CIED) were studied with 18F-FDG PET/CT. Patients were divided into three groups. Group A consisted of 42 patients with suspected CIED infections, Group B included 12 patients without clinical evidence of infection who underwent study 4-8 weeks post-implant, and Group C included 12 patients implanted >6 months prior to study who had no evidence of clinical infection. A positive PET/CT was defined as abnormal uptake along a portion of the cardiac device including the leads.
PET/CT was positive in 32 of 42 Group A patients with suspected CIED infection, 24 of whom underwent complete device extraction. At the time of extraction, there was excellent correlation between results of PET/CT and anatomical location extent of infection. Vegetations were seen on the leads in 7, on valves in 2, and both in 3 of the 22 patients who underwent transesophageal echocardiography. Abnormal PET/CT was noted in the same anatomical site in only 6 patients. Complete clinical evaluation including blood cultures, findings at the time of extraction, etc., established a diagnosis of CIED infection in 35 patients in Group A, 18 of whom were treated with antibiotics only. Cultures were positive in 24 (57%) of the Group A patients, including 10 with positive blood cultures, 11 with preoperative wound cultures, and 6 with positive cultures on surgical specimens. In Group A, abnormal uptake was noted around the generator in 18, over the leads in 18, in superficial skin tissue in 13, in subcutaneous tissue in 13, and within the heart in 2 patients. Uptake was limited to superficial tissues without contact of the generator leads in 6 patients who were treated as superficial skin infections and had no evidence of recurring infection at 9.1 ± 6.6 months. Ten patients with negative PET/CT were treated with antibiotics, none of whom had symptoms of relapse at 12.9 ± 1.9 months. In Group B, patients with recent device implantation, either no uptake or mild uptake seen only at the level of the connector was noted. No patient in Group C with a remotely-implanted device had abnormal uptake.
The authors concluded that 18F-FDG PET/CT is a useful adjunct for differentiating between CIED infection and post-implant changes, and may identify a lower risk group of patients who may be treated more conservatively compared to those for whom a device extraction is required.
Infection of implantable devices such as pacemakers and defibrillators occurs with an estimated prevalence of 1.9 cases/1,000 implants per year. Typically, extraction of all components of the infected device is recommended as standard therapy, but is associated with major complications in 1.5-2% and a mortality of 0.8%. Patients with cardiovascular devices often present with a febrile illness, and consideration of device infection needs to be undertaken. Obviously, in instances of frank pocket erosion, the diagnosis is easily established. However, subjects with fairly recently implanted devices and mild wound erythema, the diagnosis of infection versus inflammation may be problematic. This study nicely demonstrates the role that 18F-FDG PET/CT can play in separating nonspecific inflammation from actual device infection. Furthermore, this study suggests that patients with evidence of infection, but no significant activity at the device may in many instances be treated conservatively as a superficial skin infection, rather than requiring explantation of the cardiac device. The description of a relatively small number of patients with recently implanted devices also provides valuable guidance to the anticipated appearance of devices with PET/CT at varying time points remote from immediate implantation. Patients with known or suspected device infections are often elderly and debilitated, and morbidity and mortality for device extraction are not inconsequential. Additionally, the cost of prolonged hospitalization with complex antibiotic combinations is costly, and consumes valuable hospital resources. If metabolic imaging with 18F-FDG PET/CT can be confirmed in larger populations to accurately exclude device infection, and furthermore, identify a subset of patients with superficial infections which can successfully be treated with antibiotics alone, this would have significant implications for management of these often challenging and difficult patients, as well as implications for resource utilization.
Keywords: Inflammation, Defibrillators, Fluorodeoxyglucose F18, Subcutaneous Tissue, Echocardiography, Positron-Emission Tomography
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