SPECT/CT Assessment of Infected Intracardiac Devices With and Without Attenuation Correction

Abstract

Left ventricular assist devices (LVADs) provide the ability to maintain cardiac output and sustain life as a bridge to transplantation, definitive therapy, or a permanent decision. We present a case of LVAD drive infection that was differentiated from pump infection by the use of attenuation-corrected and non-attenuationcorrected CT, along with correlation with the planar images. Clinically, the patient was suspected of having infection; however, the clinician did not know which components of the device were involved. The patient's scan showed abnormal activity along the driveline with and without attenuation correction, whereas the pump showed abnormal activity with attenuation correction only. This finding suggested that the drive line was infected but that the activity within the pump was secondary to overcorrection of attenuation. The driveline was cultured, confirming infection. Thepurposeoft his teaching case study is to demonstrate the use of both attenuation-corrected and non-attenuationcorrected SPECT images when assessing for infection of intracardiac devices, in particular left ventricular assist devices (LVADs). LVADs provide the ability to maintain cardiac output and sustain life as a bridge to transplantation, definitive therapy, or a permanent decision. Potential complications include bleeding, infection, and thromboembolism. The degree and extent of infection can be difficult to discern by clinical measures, leading to imaging. Infections that involve the pump pocket can be particularly worrisome, as the best way to clear the infection would be to remove the pump. We present a case of LVAD drive infection that was differentiated from pump infection by the use of attenuation-corrected and nonattenuation-corrected CT, along with correlation with the planar images. CASE REPORTA 61-y-old man with ischemic cardiomyopathy and New York Heart Association class II congestive heart failure after LVAD placement presented with drainage from his drive line exit site and left upper quadrant pain creating concern about infection. The exudate was cultured, and a 67 Ga scan was ordered to determine the etiology of his left upper quadrant pain and the extent of infection.After administration of 1.9 MBq (5.2 mCi) of 67 Ga, whole-body and multiple planar views were obtained at 48 h. SPECT/CT images of the lower chest and upper abdomen were obtained for better anatomic localization. The planar images demonstrated abnormal curvilinear activity (Fig. 1) along the suspected course of the LVAD drive line site, which was confirmed by SPECT/CT findings showing abnormal activity along the drive line with and without attenuation correction. The SPECT/CT scan also demonstrated intense activity within the LVAD pump. This activity was not expected as it was not seen on the planar images. The nuclear medicine physician reviewed the non-attenuation-corrected images, which showed no abnormal activity within the LVAD pump (Fig. 2). The observations from the SPECT/CT study were interpreted as consistent with infection of the LVAD dr...

Left Ventricular Assist Device Infections

“…Computed tomography (CT) scanning is of limited utility due to the reflective properties of the pump body. However positron emission tomography (PET-CT) [64]; or gallium single photon emission computed tomography (SPECT-CT) [64][65][66], reviewed in [40]) have been used to diagnose infection of LVAD components as well as to assess for metastatic sites of infection often found with prolonged bacteremia with pathogens such as S. aureus and P. aeruginosa (reviewed in [40,67,68]). Erba et al [69] showed that 99m Tc-hexamethypropylene amine oxime labeled autologous white blood cell ( 99m Tc-HMPAO-WBC) SPECT-CT had 94% sensitivity at detecting cardiac implantable electronic device infections, with 95% negative predictive value in patients with other sources of infection.…”