Samy Nitecki

Prosthetic Vascular Graft Infection: The Role of 18F-FDG PET/CT

Graft infection after prosthetic vascular reconstruction is an uncommon but severe complication. The clinical presentation is often subtle and nonspecific and may occur long after surgery. Although defining a prosthetic vascular graft infection can be difficult, early diagnosis and treatment are important because of the relatively high rates of amputation and death. The present study assessed the role of PET/CT using 18F-FDG for the diagnosis of vascular graft infections. Methods: Thirty-nine patients (35 men and 4 women; age range, 44–82 y) with suspected vascular graft infection underwent 18F-FDG PET/CT. The performance of PET/CT for the diagnosis of an infectious process and its localization to the graft or soft tissues was assessed. The final diagnosis was based on histopathologic findings and microbiologic assays obtained at surgery or on clinical and imaging follow-up. Results: PET/CT detected foci of increased 18F-FDG uptake suspected as infection in 27 patients and localized these findings to the graft in 16 patients. Vascular graft infection was confirmed in 14 of these patients (88%). PET/CT excluded graft involvement in 11 patients, and in 10 (91%) of these 11, long-term follow-up further confirmed that the infectious process was limited to surrounding soft tissues only. No abnormal 18F-FDG uptake was found in any of the 12 patients with no further evidence of infection. PET/CT had a sensitivity of 93%, specificity of 91%, positive predictive value of 88%, and negative predictive value of 96% for the diagnosis of vascular graft infection. Conclusion: 18F-FDG PET/CT is a reliable noninvasive imaging modality for the diagnosis of vascular graft–related infection. The precise anatomic localization of increased 18F-FDG uptake provided by PET/CT enables accurate differentiation between graft and soft-tissue infection.

Multidetector CT angiography in the evaluation of acute mesenteric ischemia

The aim of this study was to determine the accuracy of multidetector row CT angiography in the diagnosis of acute mesenteric ischemia. Ninety-three consecutive studies on 91 patients with clinically suspected acute mesenteric ischemia underwent abdominal CT angiography as the first, and usually the sole, diagnostic procedure. CT was performed with a multidetector 16-row CT system from the level of the diaphragm to the pelvis in two phases: early arterial and late portal phase. CT examinations were reviewed by the duty radiologist. Final diagnosis was established by a senior radiologist. CTA was diagnostic in 92 studies. Mesenteric ischemia was diagnosed in 18 patients, 14 of them were of the thromboembolic type and four from the nonocclusive type. Positive CTA findings were confirmed by surgery in 13 patients and by clinical follow-up in three cases. Other reasons for abdominal pain were diagnosed by CT in 38 patients out of the remaining 74. There were two false positive and two false negative CT results, resulting in an overall accuracy of 95.6%. Multidetector CT angiography is a fast and accurate investigation for the diagnosis of acute mesenteric ischemia and in most cases can be used as the sole diagnostic procedure.

18F-FDG Uptake in Noninfected Prosthetic Vascular Grafts: Incidence, Patterns, and Changes over Time

18F-FDG PET/CT is of value in the diagnosis of prosthetic vascular graft infection, but potential pitfalls related to tracer uptake in noninfected implants have been described. The current study assesses the incidence and patterns of 18F-FDG uptake over time in noninfected grafts, in relationship to prosthetic material and location. Methods: A 12-y PET/CT database was retrospectively searched for cancer patients with prosthetic vascular grafts. Data retrieved from patient files included graft location, material, and time from surgery. Images were reviewed by 2 nuclear medicine physicians in consensus, with the presence and patterns (focal, diffuse homogeneous, inhomogeneous) of increased 18F-FDG uptake in grafts recorded. The mean standardized uptake value in grafts (SUV-G) and mediastinum (SUV-M) was measured. The ratio of SUV-G to SUV-M (SUV-G/SUV-M) was calculated for each graft. Results: One hundred seven prostheses were identified in 102 studies in 43 cancer patients. Sixty-seven prostheses were made of Dacron, 33 of Gore-Tex, and 7 were native veins. No increased 18F-FDG uptake was found in 9 grafts (native veins, 4; Gore-Tex, 3; Dacron, 2). There was diffuse homogeneous uptake in 68 and inhomogeneous uptake in 30 grafts. The homogeneous pattern was more prevalent in Gore-Tex whereas the inhomogeneous uptake was seen more in Dacron vascular grafts. None of the grafts demonstrated focal uptake. The SUV-G range was 0.4–6.3 (average, 1.9), and SUV-M range was 0.6–2.4 (average, 1.4). The intensity of uptake was significantly higher in Dacron (SUV-G = 2.35 and SUV-G/SUV-M = 1.72) than in Gore-Tex (SUV-G = 1.09, SUV-G/SUV-M = 0.91) and native vein grafts (SUV-G = 1.07, SUV-G/SUV-M = 0.75) (P < 0.005). Native vein grafts showed a significant decrease in 18F-FDG uptake over time whereas synthetic grafts showed no change in intensity for a follow-up of up to 16 y. Conclusion: Diffuse 18F-FDG uptake was found in 92% of noninfected vascular prostheses, more in Dacron grafts than with other materials. The intensity of 18F-FDG uptake of synthetic grafts did not change over time. With knowledge of the presence, patterns, and persistence of 18F-FDG uptake in noninfected vascular prostheses, misinterpretation of PET/CT studies in patients referred for suspected prosthetic infection and in those assessed for diseases unrelated to their graft status can be avoided.

Human carotid atherosclerotic plaque increases oxidative state of macrophages and low-density lipoproteins, whereas paraoxonase 1 (PON1) decreases such atherogenic effects

Human atherosclerotic plaque contains a variety of oxidized lipids, which can facilitate further oxidation. Paraoxonase 1 (PON1) is a high-density lipoprotein (HDL)-associated esterase (lipolactonase), exhibiting antiatherogenic properties. The aims of the present study were to examine the oxidizing potency of the human carotid plaque lipid extract (LE), and the antiatherogenic role of PON1 on LE oxidation competence. Human carotid plaques were extracted by organic solvent, and the extract was incubated with lipoprotein particles, with macrophages, or with probes sensitive to oxidative stress, with or without preincubation with PON1, followed by oxidative-stress assessment. Our findings imply that the LE oxidized LDL, macrophages, and exogenous probes and decreases HDL-mediated cholesterol efflux from macrophages, in a dose-dependent manner. Incubation of PON1 with LE significantly affects LE composition, reduces LE atherogenic properties, and decreases the extracts total peroxide concentration by 44%, macrophage oxidation by 25%, and probe oxidation by up to 52%. We conclude that these results expand our understanding of how the plaque itself accelerates atherogenesis and provides an important mechanism for attenuation of atherosclerosis development by the antioxidant action of PON1 on the atherosclerotic plaque.

PET/CT Using 2-Deoxy-2-[18F]Fluoro-D-Glucose for the Evaluation of Suspected Infected Vascular Graft

An infected vascular graft was identified using a combined positron emission tomography (PET) and computerized tomography (CT) system. The fusion of 2-deoxy-2-[18F]fluoro-D-glucose (FDG) PET and CT images, acquired in a single session, allowed for the precise localization of the abnormal FDG uptake to the vascular graft and led to the correct diagnosis of prosthetic infection. This hybrid modality, which provides precise registration of metabolic and structural imaging data, may enhance the potential use of FDG in the diagnosis and management of infected vascular grafts.

FDG-PET in Prosthetic Graft Infections

Graft infection following prosthetic vascular reconstruction is an uncommon but severe complication. The clinical presentation is often subtle and nonspecific and may occur long after surgery. Although defining a prosthetic vascular graft infection can be difficult, early diagnosis and treatment are essential for the correct choice of treatment to prevent further complications as well as the high morbidity and mortality associated with repeat surgery and removal of infected grafts. False-positive results may lead to unnecessary surgery while failure to diagnose graft infection may have life-threatening sequels. Scarce literature that is currently available regarding the role of (18)F-labeled fluorodeoxyglucose imaging for assessment of vascular graft infection suggests that this modality may represent reliable noninvasive imaging modality in this specific clinical setting. PET/CT increases the test specificity and thus improves diagnostic accuracy. The precise anatomic localization of increased (18)F-labeled fluorodeoxyglucose PET/CT enables accurate differentiation between graft and adjacent soft tissue infection leading to more accurate diagnosis and subsequent optimized therapeutic strategy.

Percutaneous Ultrasonographically Guided Thrombin Injection of Iatrogenic Pseudoaneurysms in Unusual Sites

Objectives. To evaluate the effectiveness and safety of percutaneous ultrasonographically guided thrombin injection as treatment of unusually positioned and unusually large iatrogenic pseudoaneurysms. Methods. Five patients with iatrogenic pseudoaneurysms were evaluated by color duplex ultrasonography. Two patients had additional digital angiography, and 2 had additional computed tomographic angiography. In 3 of the patients, large, painful iatrogenic pseudoaneurysms located proximal (2 patients) and distal (1 patient) to the arteriovenous hemodialysis fistulas had developed, most likely due to erroneous puncture of the arterial side (brachial artery) or venous side (cephalic vein) of the fistulas. An iatrogenic pseudoaneurysm of the anterior tibial artery had developed in the fourth patient after osteotomy of the fibula, and an iatrogenic pseudoaneurysm of the superficial femoral artery had developed in the fifth patient after erroneous puncture during venous transfemoral angiography. With a sterile technique and color duplex ultrasonographic guidance, a diluted solution of bovine thrombin was slowly injected directly into the iatrogenic pseudoaneurysms until cessation of blood flow was seen. Follow‐up color duplex ultrasonography was performed 24 to 48 hours after the ultrasonographically guided thrombin injection. Results. Four iatrogenic pseudoaneurysms were successfully thrombosed during 1 session. Two large iatrogenic pseudoaneurysms necessitated multiple repositions of the injecting needle and several injections of small amounts of thrombin into the residual patent lumen to induce complete thrombosis without an appreciable increase in the total thrombin dosage. Follow‐up examinations revealed complete and persistent thrombosis without evidence of distal embolization. One iatrogenic pseudoaneurysm involving the cephalic vein, distal to an arteriovenous hemodialysis fistula, recurred after apparently successful initial thrombosis. Conclusions. Most iatrogenic pseudoaneurysms are amenable to ultrasonographically guided thrombin injection as long as they are imaged adequately by color duplex ultrasonography.

Seatbelt injury to the common iliac artery: report of two cases and review of the literature

Blunt trauma to the common iliac artery is rather rare. Moreover, seatbelt injuries to the common iliac artery have not yet been reported. This article presents two cases of seatbelt injury involving the common iliac artery. A deceleration-type mechanism is suggested as the primary cause of injury, resulting in the production of an intimal flap. The diagnosis of such an injury is based on clinical suspicion, a change of pulse, or lower limb ischemia. On arteriotomy the damage is greater than seen on external examination. Once diagnosed prompt treatment should follow to prevent loss of life or limb. The signs, symptoms, and modalities of treatment are reported, as well as a review of the literature.

Effects of Novel Vasopressin Receptor Antagonists on Renal Function and Cardiac Hypertrophy in Rats with Experimental Congestive Heart Failure

Arginine vasopressin (AVP) plays an important role in renal hemodynamic alterations, water retention, and cardiac remodeling in congestive heart failure (CHF). The present study evaluated the acute and chronic effects of vasopressin V1a receptor subtype (V1a) and vasopressin V2 receptor subtype (V2) antagonists on renal function and cardiac hypertrophy in rats with CHF. The effects of acute administration of SR 49059 [(2S)1-[(2R,3S)-5-chloro-3-(2-chlorophenyl)-1-(3,4-dimethoxybenzene-sulfonyl)-3-hydroxy-2,3-dihydro-1H-indole-2-carbonyl]-pyrrolidine-2-carboxamide)] (0.1 mg/kg) and SR 121463B (1-[4-(N-tert-butylcarbamoyl)-2-methoxybenzenesulfonyl]-5-ethoxy-3-spiro-[4-(2-morpholinoethoxy)cyclohexane]indol-2-one, fumarate; equatorial isomer) (0.3 mg/kg), V1a and V2 antagonists, respectively, on renal function, and of chronic treatment (3.0 mg/kg/day for 7 or 28 days, via osmotic minipumps or p.o.), on water excretion and cardiac hypertrophy were studied in rats with aortocaval fistula and control rats. CHF induction increased plasma AVP (12.8 ± 2.5 versus 32.2 ± 8.3 pg/ml, p < 0.05). Intravenous bolus injection of SR 121463B to controls produced dramatic diuretic response (from 5.5 ± 0.8 to 86.3 ± 21.9 μl/min; p < 0.01). In contrast, administration of SR 49059 did not affect urine flow. Likewise, administration of SR 121463B, but not SR 49059, to rats with CHF significantly increased urinary flow rate from 20.8 ± 6.4 to 91.6 ± 26.5 μl/min (p < 0.01). The diuretic effects of SR 121463B were associated with a significant decline in urinary osmolality and insignificant change of Na+ excretion. In line with its acute effects, chronic administration of SR 121463B to CHF rats increased daily urinary volume 2 to 5-fold throughout the treatment period. Both SR 121463B and SR 49059 significantly reduced heart weight in CHF rats when administered for 4 weeks, but not 1 week. These results suggest that V2 and V1a antagonists improve water balance and cardiac hypertrophy in CHF and might be beneficial for the treatment of water retention and cardiac remodeling in CHF.

Vascular endothelial growth factor (VEGF) fails to improve blood flow and to promote collateralization in a diabetic mouse ischemic hindlimb model

BackgroundAngiogenic therapy with vascular endothelial growth factor (VEGF) has been proposed as a treatment paradigm for patients suffering from an insufficiency of collateral vessels. Diabetes is associated with increase in the production of VEGF and therefore additional VEGF may not be beneficial. Accordingly, we sought to determine the efficacy of VEGF therapy to augment collateral formation and tissue perfusion in a diabetic mouse ischemic hindlimb model.MethodsDiabetic and non-diabetic mice were studied in parallel for the efficacy of VEGF administration. Diabetes was induced with streptozotocin. Hindlimb ischemia was produced by severing the left iliac artery. An outlet tube from an osmotic infusion pump with placebo/ 500 micrograms of plasmid-DNA encoding VEGF was fenestrated and tunneled into the left quadriceps muscle.ResultsVEGF induced more rapid and complete restoration of blood flow in normal mice. However, in the setting of diabetes there was no difference between VEGF Vs. placebo in the rate or adequacy of flow restoration. There was a significant increase in smooth muscle actin and Factor-VIII antigen densities in diabetic animals and in animals which received VEGF.ConclusionsAngiogenic therapy with VEGF in the setting of diabetes does not appear to have the beneficial effects seen in the absence of diabetes.