Renal Safety of Intravenous Gadolinium-enhanced MRI in Patients Following Liver Transplantation.

BACKGROUND: Intravenous contrast-enhanced imaging is invaluable in diagnosing pathology following liver transplantation. Given the potential risk of contrast nephropathy associated with iodinated computed tomography contrast, alternate contrast modalities need to be examined, especially in the setting of renal insufficiency. The purpose of this study was to examine the renal safety of MRI with gadolinium following liver transplantation. METHODS: The study involved a retrospective analysis of 549 cases of abdominal MRI with low-dose gadobenate dimeglumine in liver transplant recipients at a single center. For each case, serum creatinine values before and after the MRI were compared. In addition, cases were analyzed for the development of nephrogenic systemic fibrosis. RESULTS: Pre-MRI creatinine values ranged from 0.32 to 6.57 mg/dL (median, 1.28 g/dL), with 191 cases having values ≥1.5 mg/dL (median, 1.86 g/dL). A comparison of the pre- and post-MRI creatinine values showed no significant difference, including those patients with pre-MRI values ≥1.5 mg/dL (mean change of -0.04 [95% confidence interval, -0.07 to -0.01; P = 0.004]). No cases of nephrogenic systemic fibrosis were noted. CONCLUSIONS: Our findings suggest that, irrespective of baseline renal function, MRI with gadobenate dimeglumine is a nonnephrotoxic imaging modality in liver transplant recipients. Importantly, this intravenous contrast-enhanced imaging modality can be considered in those posttransplant patients who have a contraindication to computed tomography contrast due to renal insufficiency.

Treatment allocation in patients with early-stage esophageal adenocarcinoma: Prevalence and predictors of lymph node involvement.

BACKGROUND: In considering treatment allocation for patients with early esophageal adenocarcinoma, the incidence of lymph node metastasis is a critical determinant; however, this has not been well defined or stratified by the relevant clinical predictors of lymph node spread. METHODS: Data from the Surveillance, Epidemiology, and End Results database of the National Cancer Institute were abstracted from 2004 to 2010 for patients with early-stage esophageal adenocarcinoma. The incidence of lymph node involvement for patients with Tis, T1a, and T1b tumors was examined and was stratified by predictors of spread. RESULTS: A total of 13,996 patients with esophageal adenocarcinoma were evaluated. Excluding those with advanced, metastatic, and/or invasive (T2-T4) disease, 715 patients with Tis, T1a, and T1b tumors were included. On multivariate analysis, tumor grade (odds ratio [OR], 2.76; 95% confidence interval [95% CI], 1.58-4.82 [P<.001]), T classification (OR, 0.47; 95% CI, 0.24-0.91 [P =.025]), and tumor size (OR, 2.68; 95% CI, 1.48-4.85 [P = .001]) were found to be independently associated with lymph node metastases. There was no lymph node spread noted with Tis tumors. For patients with low-grade (well or moderately differentiated) tumors measuring <2 cm in size, the risk of lymph node metastasis was 1.7% for T1a (P<.001) and 8.6% for T1b (P = .001) tumors. CONCLUSIONS: For patients with low-grade Tis or T1 tumors measuring ≤2 cm in size, the incidence of lymph node metastasis appears to be comparable to the mortality rate associated with esophagectomy. For highly selected patients with early esophageal adenocarcinomas, the results of the current study support the recommendation that local endoscopic resection can be considered as an alternative to surgical management when followed by rigorous endoscopic and radiographic surveillance. Cancer 2016;122:2150-7. © 2016 American Cancer Society.

Localization of the brachial plexus: Sonography versus anatomic landmarks.

PURPOSE: Interscalene brachial plexus blocks are performed for perioperative management of surgeries involving the shoulder. Historically, these procedures employed anatomic landmarks (AL) to determine the location of the brachial plexus as it passes between the anterior and middle scalene muscles in the neck. In this study, we compared the actual location of the brachial plexus as found with sonography (US) to the anticipated location using AL. METHODS: The location of the brachial plexus was evaluated using US and AL in 96 subjects. The distance between the two locations was measured. A multivariate analysis of variance was used to determine the significance of the difference and a 2 × 2 analysis of variance was used to compare differences in gender, height, and body mass index. RESULTS: The brachial plexus was located on average 1.8 cm inferior (p = 0.0001) and 0.2 cm lateral (p = 0.09) to the location determined with AL. A significant difference was also associated with gender (p = 0.03), but not with height or body mass index. CONCLUSIONS: US is a reliable method that accurately pinpoints the roots of the brachial plexus. The brachial plexus is often located inferior to the location anticipated using AL. © 2016 Wiley Periodicals, Inc. J Clin Ultrasound 44:411-415, 2016.

Renal safety of intravenous gadolinium-enhanced magnetic resonance imaging in patients awaiting liver transplantation.

Renal dysfunction in cirrhosis carries a high morbidity and mortality. Given the potential risk of contrast-induced nephropathy associated with iodinated intravenous contrast used in computed tomography (CT), alternate contrast modalities for abdominal imaging in liver transplant candidates need to be examined. The purpose of this study was to examine the renal safety of magnetic resonance imaging (MRI) with gadolinium in patients awaiting liver transplantation. The study involved a retrospective analysis of 352 patients of abdominal MRI with low-dose gadobenate dimeglumine (MultiHance) (0.05 mmol/kg) in patients with cirrhosis and without renal replacement therapy at a single center during the period from 2007 to 2013. For each case, serum creatinine before and within a few days after the MRI were compared. In addition, the patients were analyzed for the development of nephrogenic systemic fibrosis (NSF), a reported complication of gadolinium in chronic kidney disease. The pre-MRI serum creatinine values ranged from 0.36 to 4.86 mg/dL, with 70 patients (20%) having values ≥ 1.5 mg/dL. A comparison of the pre- and post-MRI serum creatinine values did not demonstrate a clinically significant difference (mean change = 0.017 mg/dL; P = 0.38), including those patients with a pre-MRI serum creatinine ≥ 1.5 mg/dL. In addition, no cases of NSF were noted. In conclusion, our findings suggest that MRI with low-dose gadobenate dimeglumine (MultiHance) is a nonnephrotoxic imaging modality in liver transplant candidates, and its use can be cautiously expanded to liver transplant candidates with concomitant renal insufficiency.

Analysis of in vivo left atrial appendage morphology in patients with atrial fibrillation: a direct comparison of transesophageal echocardiography, planar cardiac CT, and segmented three-dimensional cardiac CT.

PURPOSE: Recent development of percutaneous left atrial appendage (LAA) occlusion devices has underscored the need for an accurate understanding of LAA morphology and the interchangeability of results from differing imaging modalities. The purpose of this study is to assess LAA morphology and location in AF patients, directly comparing transesophageal echocardiography (TEE), planar cardiac computed tomography (CT), and three-dimensional segmented CT reconstructions. METHODS: Fifty-three patients underwent adequate TEE and cardiac CT. Quantitative measurements of maximal LAA orifice diameters, widths, and depths were obtained from each imaging modality. Left atrial and LAA volumes were measured using segmented CT. RESULTS: The mean LAA orifice diameter for segmented CT, planar CT, and TEE was 28.5 +/- 4.5, 26.3 +/- 4.1, and 26.1 +/- 6.4 mm, respectively. CONCLUSIONS: LAA orifice measurements among these imaging modalities are not interchangeable. This difference may be clinically significant because of the need for accurate sizing of LAA occlusion devices. Use of preprocedural segmented CT may improve initial device sizing.

Determinants of lesion sizes and tissue temperatures during catheter cryoablation.

BACKGROUND: Factors which influence lesion size from catheter-based cryoablation have not been well described. This study describes factors which influence lesion size during catheter cryoablation. METHODS AND RESULTS: Cryoablation was delivered to porcine left ventricular myocardium in a saline bath using 4- or 8-mm electrode catheters. Ablation was delivered with the electrodes either vertical or horizontal to the tissue and both with and without superfusate flow over the electrode. The effect of electrode contact pressure was tested. Lesion dimensions were measured. All experiments were duplicated to measure tissue temperatures at 1-, 2-, 3-, and 5-mm deep to the ablation electrode. The 8-mm electrode produced lower tissue temperatures and larger lesion volumes when compared with the 4-mm electrode (all P < 0.05). Superfusate flow slowed the rate of tissue cooling, markedly warmed tissue temperatures, and reduced lesion volume when compared with no flow conditions. By linear regression modeling, lesion sizes and tissue temperatures were related to the presence of superfusate flow, electrode orientation, contact pressure and electrode size, or catheter refrigerant flow rate (r2 for models = 0.90-0.96, all P < 0.001). Electrode temperature predicted lesion size or tissue temperatures only when analyzed independent of electrode size or refrigerant flow rate. CONCLUSIONS: Lesion sizes and tissue temperatures during catheter cryoablation are related to convective warming, electrode orientation, electrode contact pressure, and any of the following: electrode size, catheter refrigerant flow rate or electrode temperature. However, electrode temperature may be a poor predictor of lesion size and tissue temperature for a given catheter size.

Microbubbles during radiofrequency catheter ablation: composition and formation.

OBJECTIVES: The purpose of this study was to measure tissue temperatures associated with microbubble formation during radiofrequency (RF) ablation. BACKGROUND: Microbubble formation visualized by echocardiography has been used to indicate excessive tissue heating during RF pulmonary vein isolation. However, little is known about the tissue temperatures associated with microbubble formation. METHODS: Optical fluorometric thermometry probes were used to record tissue temperatures in isolated porcine atrium overlying either lung or esophageal tissue in a saline bath. RF energy was delivered through an irrigated ablation electrode during echocardiographic monitoring for microbubble formation. RESULTS: The maximal recorded tissue temperatures were 81.0 +/- 5.0 degrees C and 88.3 +/- 8.1 degrees C at the time of intermittent (type 1) microbubble formation for lung and esophageal preparations, respectively. During continuous (type 2) microbubble formation, the temperatures were 91.4 +/- 8.2 degrees C and 99.2 +/- 7.8 degrees C, respectively (both P < .001 vs type 1). Tissue temperatures averaged >100 degrees C at the time of "pops." The maximal recorded temperature occurred up to 4 mm deep in the tissues and frequently occurred external to the atrial tissue. The total RF lesion volumes for lung and esophageal preparations were related to the pattern of microbubble formation but not to total power delivered. After generation of type 1 bubbles, up to 60% reductions in RF energy were needed to restore target tissue temperatures of 65 degrees C. Gas chromatographic analysis of the microbubbles was consistent with steam formation. CONCLUSIONS: Microbubble formation during RF ablation represents excessive tissue heating to the point of steam formation. Maximal tissue heating may occur in the adjacent lung and esophagus during cooled ablation.