Ben R. Saleem

Accuracy of FDG-PET–CT in the Diagnostic Work-up of Vascular Prosthetic Graft Infection

OBJECTIVES To investigate the diagnostic accuracy of fluoro-2-deoxy-d-glucose positron emission tomography (FDG-PET) compared with computed tomography (CT) scanning and added value of fused FDG-PET-CT in diagnosing vascular prosthetic graft infection. DESIGN Prospective cohort study with retrospective analysis. MATERIALS Twenty five patients with clinically suspected vascular prosthetic infection underwent CT and FDG-PET scanning. METHODS Two nuclear medicine physicians assessed the FDG-PET scans; all CT scans were assessed by two radiologists. Fused FDG-PET/CT were judged by the radiologist and the nuclear medicine physician. The concordance between CT and FDG-PET and the inter-observer agreement between the different readers were investigated. RESULTS Fifteen patients had a proven infection by culture. Single FDG-PET had the best results (sensitivity 93%, specificity 70%, positive predictive value 82% and negative predictive value 88%). For CT, these values were 56%, 57%, 60% and 58%, respectively. Fused CT and FDG-PET imaging also showed high sensitivity and specificity rates and high positive and negative values. Inter-observer agreement for FDG-PET analysis was excellent (kappa = 1.00) and moderate for CT and fused FDG-PET-CT analysis (0.63 and 0.66, respectively). CONCLUSION FDG-PET scanning showed a better diagnostic accuracy than CT for the detection of vascular prosthetic infection. This study suggests that FDG-PET provides a useful tool in the work-up for diagnosis of vascular prosthetic graft infection.

Conservative treatment of vascular prosthetic graft infection is associated with high mortality

BACKGROUND The aim of this study was to identify patient-related and/or disease-related factors that influence outcomes in patients with vascular prosthetic graft infections. METHODS Through the hospital patient administration system, between January 1997 and December 2007, a total of 44 patients were diagnosed with central prosthetic graft infections. Univariate and multivariate analyses were performed to define factors predictive of mortality. RESULTS Thirty-three men and 11 women (mean age, 71 years) were included. There was considerable comorbidity. Coagulase-negative Staphylococcus and S aureus were isolated in almost 50% of the patients. The mean follow-up duration was 5 years, during which 20 patients (46%) died. The main causes of death were related to vascular disease. Conservative treatment with antibiotics was the only variable with significant predictive value on multivariate analysis (hazard ratio, 3.62; 95% confidence interval, 1.17-11.24; P = .02). CONCLUSIONS Conservative treatment of prosthetic graft infections was associated with high mortality; therefore, it should be limited to a specific group. Patients who are not capable of undergoing open repair may benefit from conservative management. Otherwise, aggressive open treatment seems indicated.

Periaortic endograft infection due to Listeria monocytogenes treated with graft preservation

A 67-year-old man presented to our hospital with general malaise, fever and diffuse abdominal and lower back pain 7 weeks after endovascular aneurysm repair. Blood samples showed a leukocyte count of 10.9 x 10(9)/l and a C-reactive protein of 239 mg/l. The computed tomography (CT)-scan showed fluid collections behind the proximal part of the endovascular graft and dorsal to the aorta. CT-guided translumbar needle aspiration of these collections yielded growth with Listeria monocytogenes. Prosthetic endograft infection is an extremely rare event, especially when it is caused by L. monocytogenes. Given the scarcity of this complication, no consensus has been reached for its treatment. In the described case, radiological drainage and prolonged antibiotic treatment resulted in favourable outcome at midterm follow-up with preservation of the endograft.

Modest utility of quantitative measures in (18)F-fluorodeoxyglucose positron emission tomography scanning for the diagnosis of aortic prosthetic graft infection

BACKGROUND The clinical dilemma in suspected aortic graft infection (AGI) is how to noninvasively obtain a reliable proof of infection. In addition to confirming the presence of infection, obtaining information regarding the extent of infection to select a proper strategy for reoperation is also necessary. Therefore, developing a more reliable noninvasive physiologic approach to detect infected prostheses is required. (18)F-fluorodeoxyglucose positron emission tomography scanning ((18)F-FDG PET) has been suggested to have a pivotal role in the detection of AGI. In this study, we assessed the contribution of two (semi) quantitative parameters-maximal standardized uptake value (SUVmax) and tissue-to-background ratio (TBR)-and of two visual parameters-fluorodeoxyglucose (FDG) distribution patterns and visual grading scale-in the final confirmation of the diagnosis of AGI. METHODS Patients with a central aortic prosthetic graft and symptoms clinically suggestive of AGI were gathered from a prospectively maintained database. Included were those who underwent (18)F-FDG PET scanning combined with computed tomography angiography and in whom periprosthetic samples were taken at some stage in the diagnostic process. AGI was considered proven in case of a positive culture and compared with a group with negative cultures. Positive predictive values (PPVs) and negative predictive values (NPVs) were calculated. Receiver operating characteristics curves were used to assess the ability of SUVmax and TBR to identify the presence and absence of AGI (ie, accuracy). RESULTS In 37 of 77 patients with suspected AGI, (18)FDG-PET and perigraft material for culturing was obtained. The tissue culture was positive in 21 of these 37 patients (56.7%). Mean ± standard deviation SUVmax for proven infection was 8.1 ± 3.7 (range, 3.6-18.5) and TBR was 5.9 ± 2.7 (range, 1.7-13.0). The area under the curve for SUVmax was 0.78 (95% confidence interval, 0.63-0.93). A cutoff value of 8 yielded a PPV of 80% and a NPV of 54%. The area under the curve for TBR was 0.70 (95% confidence interval, 0.52-0.87). A cutoff value of 6 yielded a PPV of 73% and NPV of 52%. The PPVs for the visual grading scale and (18)F-FDG distribution patterns were 75% and 61%, respectively; the NPVs were 77% and 67%, respectively. CONCLUSIONS Our study, performed in a small sample of patients suspected of AGI, showed that the diagnostic abilities of quantitative and visual (18)F-FDG PET parameters are modest.

A comparison of Percutaneous femoral access in Endovascular Repair versus Open femoral access (PiERO): study protocol for a randomized controlled trial

BackgroundAccess for endovascular repair of abdominal aortic aneurysms (EVAR) is obtained through surgical cutdown or percutaneously. The only devices suitable for percutaneous closure of the 20 French arteriotomies of the common femoral artery (CFA) are the Prostar™ and Proglide™ devices (Abbott Vascular). Positive effects of these devices seem to consist of a lower infection rate, and shorter operation time and hospital stay. This conclusion was published in previous reports comparing techniques in patients in two different groups (cohort or randomized). Access techniques were never compared in one and the same patient; this research simplifies comparison because patient characteristics will be similar in both groups.Methods/DesignPercutaneous access of the CFA is compared to surgical cutdown in a single patient; in EVAR surgery, access is necessary in both groins in each patient. Randomization is performed on the introduction site of the larger main device of the endoprosthesis. The contralateral device of the endoprosthesis is smaller. When we use this type of randomization, both groups will contain a similar number of main and contralateral devices. Preoperative nose cultures and perineal cultures are obtained, to compare colonization with postoperative wound cultures (in case of a surgical site infection). Furthermore, patient comfort will be considered, using VAS-scores (Visual analog scale). Punch biopsies of the groin will be harvested to retrospectively compare skin of patients who suffered a surgical site infection (SSI) to patients who did not have an SSI.DiscussionThe PiERO trial is a multicenter randomized controlled clinical trial designed to show the consequences of using percutaneous access in EVAR surgery and focuses on the occurrence of surgical site infections.Trial registrationNTR4257 10 November 2013, NL44578.042.13.

Textural features of (18)F-fluorodeoxyglucose positron emission tomography scanning in diagnosing aortic prosthetic graft infection

BackgroundThe clinical problem in suspected aortoiliac graft infection (AGI) is to obtain proof of infection. Although 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography scanning (PET) has been suggested to play a pivotal role, an evidence-based interpretation is lacking. The objective of this retrospective study was to examine the feasibility and utility of 18F-FDG uptake heterogeneity characterized by textural features to diagnose AGI.MethodsThirty patients with a history of aortic graft reconstruction who underwent 18F-FDG PET/CT scanning were included. Sixteen patients were suspected to have an AGI (group I). AGI was considered proven only in the case of a positive bacterial culture. Positive cultures were found in 10 of the 16 patients (group Ia), and in the other six patients, cultures remained negative (group Ib). A control group was formed of 14 patients undergoing 18F-FDG PET for other reasons (group II). PET images were assessed using conventional maximal standardized uptake value (SUVmax), tissue-to-background ratio (TBR), and visual grading scale (VGS). Additionally, 64 different 18F-FDG PET based textural features were applied to characterize 18F-FDG uptake heterogeneity. To select candidate predictors, univariable logistic regression analysis was performed (α = 0.16). The accuracy was satisfactory in case of an AUC > 0.8.ResultsThe feature selection process yielded the textural features named variance (AUC = 0.88), high grey level zone emphasis (AUC = 0.87), small zone low grey level emphasis (AUC = 0.80), and small zone high grey level emphasis (AUC = 0.81) most optimal for distinguishing between groups I and II. SUVmax, TBR, and VGS were also able to distinguish between these groups with AUCs of 0.87, 0.78, and 0.90, respectively. The textural feature named short run high grey level emphasis was able to distinguish group Ia from Ib (AUC = 0.83), while for the same task the TBR and VGS were not found to be predictive. SUVmax was found predictive in distinguishing these groups, but showed an unsatisfactory accuracy (AUC = 0.75).ConclusionTextural analysis to characterize 18F-FDG uptake heterogeneity is feasible and shows promising results in diagnosing AGI, but requires additional external validation and refinement before it can be implemented in the clinical decision-making process.

Comparison of midterm results for the Talent and Endurant stent graft

Objective: Stent graft evolution is often addressed as a cause for improved outcomes of endovascular aneurysm repair for patients with an abdominal aortic aneurysm. In this study, we directly compared the midterm result of Endurant stent graft with its predecessor, the Talent stent graft (both Medtronic, Santa Rosa, Calif). Methods: Patient treated from January 2005 to December 2010 in a single tertiary center in The Netherlands with a Talent or Endurant stent graft were eligible for inclusion. Ruptured abdominal aortic aneurysms or patients with previous aortic surgery were excluded. The primary end point was the Kaplan‐Meier estimated freedom from secondary interventions. Secondary end points were perioperative outcomes and indications for secondary interventions. Results: In total, 221 patients were included (131 Endurant and 90 Talent). At baseline, the median aortic bifurcation was narrower for the Endurant (30 mm vs 39 mm; P < .001). Median follow‐up was 64.1 ± 37.9 months and 59.2 ± 25.3 months for Talent and Endurant, respectively. The estimated freedom from secondary interventions at 30 days, 1 year, 5 years, and 7 years was 94.3%, 89.4%, 72.2%, and 64.1% for Talent and 96.8%, 89.3%, 75.2%, and 69.2% for Endurant (P = .528). The indication for secondary interventions does differ; more patients required an intervention for a proximal neck‐related complication (type Ia endoleak or migration) in the Talent group (18.2% vs 4.8%; P = .001), whereas more interventions for iliac limb stenosis were seen in the Endurant group (0.0% vs 4.8%; P = .044). In a binomial regression analysis, suprarenal angulation, infrarenal neck length, and type of stent graft were independent predictors of neck‐related complications. Conclusions: Evolution from the Talent stent graft into the Endurant has resulted in significant reduction of infrarenal neck‐related complications; on the other hand, iliac interventions increased. The overall midterm secondary intervention rate was comparable.