Clopidogrel Resistance in Neurovascular Stenting: Correlations between Light Transmission Aggregometry, VerifyNow, and the Multiplate.

BACKGROUND AND PURPOSE: Clopidogrel resistance is blamed for thromboembolic complications in neurovascular stent placement. Platelet-function assays are weakly standardized. The aim of this study was to correlate the results of 3 different platelet-inhibition measurements (from light transmission aggregometry, the VerifyNow P2Y12 test, and the Multiplate analyzer) and their relation to periprocedural thromboembolic complications in elective neurovascular stent placement. MATERIALS AND METHODS: Clopidogrel resistance was determined on the day of the intervention according to predefined platelet reactivity cutoff values. All 3 tests were performed in 103 consecutive neurovascular stent-placement procedures in 97 patients (extracranial, n = 77; intracranial, n = 26). RESULTS: The clopidogrel resistance rates were 47.6% (light transmission aggregometry), 50.5% (VerifyNow), and 35.9% (Multiplate). In 67% of the patients, clopidogrel resistance was present according to at least one method. The correlations of qualitative results that classified a patient as responsive or resistant to clopidogrel were 67.9% for light transmission aggregometry with VerifyNow, 77.7% for light transmission aggregometry with the Multiplate, and 66% for VerifyNow with the Multiplate. Periprocedural thromboembolic complications (n = 9) occurred more frequently in patients who were determined by all 3 methods to be clopidogrel resistant. The difference was most pronounced with light transmission aggregometry (complication rates, 14.4% [clopidogrel-resistant patients] vs 3.7% [clopidogrel-responsive patients]). Sensitivity and specificity rates of clopidogrel resistance in relation to embolic complications were, respectively, 78% and 55% for light transmission aggregometry, 67% and 51% for VerifyNow, and 44% and 67% for the Multiplate. CONCLUSIONS: Clopidogrel resistance is a frequent finding in patients who undergo neurovascular stent placement. The correlations among the different testing methods are only modest and differ considerably. Light transmission aggregometry results seem to correlate with thromboembolic complications more accurately than with VerifyNow and Multiplate point-of-care methods.

The diagnostic value of systolic acceleration time and resistive index as noninvasive modality for detection of graft rejection after orthotopic liver transplantation.

BACKGROUND: Acute cellular and chronic graft rejection are major disorders in the postoperative setting after orthotopic liver transplantation (OLT). An immediate diagnosis and successful therapy are essential for graft survival. We sought to determine whether quantitative and qualitative analysis of Doppler sonography data was predictive and sensitive as noninvasive diagnostic tools for rejection episodes. MATERIALS AND METHODS: We prospectively recorded and retrospectively analyzed the medical records of patients who underwent OLT between January 2000 and November 2011, identifying patients with acute cellular (ACR) and chronic rejection (CR) and the grade classified the activity index according to BANFF criteria. Analyzed parameters included resistive index (R/I), systolic acceleration time (SAT) in the hepatic artery, laboratory values, histopathologic grade and therapy as well as graft and patient survival. RESULTS: Patient follow-up as of December 2011 or to the time of death ranged from 2 to 132 months (median follow- up: 79 months, mean = 83 months). We registered 29 rejection episodes (ACR n = 20 and CR n = 9) in 20 subjects. The majority of patients received a tacrolimus-based immunsuppressive regimen (n = 14, trough level: 7-12 ng/mL) in addition to high-dose corticosteroids, and sometimes a third drug. One patient displayed a corticosteroid-resistant ACR and 4 CR cases, graft loss followed by retransplantation. R/I was calculated for all patients and SA for those who underwent OLT since 2009. As a control group we used subjects with delayed SAT and high R/I without graft rejection. In all patients with a high R/I (>0.7, range: 0.71-0.91) and in all patients who suffered graft rejection since 2009 (n = 14), we observed a delayed SAT (>0.08, range: 0.08-0.18). The sensitivity and specificity for R/I were 82%, and 54.9%; for SAT 100% and 78%, respectively. CONCLUSION: Delayed SAT (>0.08) and high R/I (>0.7) were sensitive indices of graft rejection episode. The limitation of these diagnostic parameters is their specificity, especially in the immediate postoperative period, where early vascular disorders trigger similar sonographic results. Nevertheless SAT and R/I may be considered to be important diagnostic tools, in combination with elevated laboratory liver values they can provide an early diagnosis of graft rejection.

Design of a web portal for interdisciplinary image retrieval from multiple online image resources.

OBJECTIVES: Images play an important role in medicine. Finding the desired images within the multitude of online image databases is a time-consuming and frustrating process. Existing websites do not meet all the requirements for an ideal learning environment for medical students. This work intends to establish a new web portal providing a centralized access point to a selected number of online image databases. METHODS: A back-end system locates images on given websites and extracts relevant metadata. The images are indexed using UMLS and the MetaMap system provided by the US National Library of Medicine. Specially developed functions allow to create individual navigation structures. The front-end system suits the specific needs of medical students. A navigation structure consisting of several medical fields, university curricula and the ICD-10 was created. The images may be accessed via the given navigation structure or using different search functions. Cross-references are provided by the semantic relations of the UMLS. RESULTS: Over 25,000 images were identified and indexed. A pilot evaluation among medical students showed good first results concerning the acceptance of the developed navigation structures and search features. CONCLUSION: The integration of the images from different sources into the UMLS semantic network offers a quick and an easy-to-use learning environment.

Intravascular pressure measurements in feeding pedicles of brain arteriovenous malformations.

Pressure measurements in arterial feeders of arteriovenous malformations (AVMs) can be easily acquired during endovascular treatment procedures. In this study, mean arterial pressure values in arterial feeders (Pfed) of brain AVMs were determined using a pressure measuring system connected to a standard microcatheter. A total of 148 measurements were performed in 139 patients. Mean systemic arterial pressure values were subtracted for correction. The levels of correlation between the pressure values and various clinical parameters (i.e., AVM location, size, previous hemorrhage) and pathoanatomical features of the AVM (e.g., nidus structure, number of draining veins) were determined. Pfed values were 54.5 mmHg on average. Pfed was lower in more distally located AVMs, in larger lesions and in AVMs with multiple drainage veins. Pressure values were significantly higher in patients with previous hemorrhage and in smaller AVMs. Our results support the importance of hemodynamic parameters in determining the presentation of AVMs. More extensive studies using this simple technique may further elucidate these mechanisms and may result in improved criteria for patient selection and reduction of complications.

[Lithium and renal function (author's transl)]. / Lithium et fonction rénale.

Reviewing the literature on the effect of lithium on renal function, the authors summarize the mechanisms involved in the concentration and elimination of lithium by this organ, as well as the urinary modifications in ionic exchanges and concentration capacity induced by this metal. After having mentioned the different factors influencing lithium clearance, the authors emphasize that diuretics should be used with caution with lithium and examine critically the various publications on the eventual nephrotoxicity of this agent. Although they conclude that there is no absolute proof of renal toxicity, they suggest for the time being to consider lithium intoxications and lithium-induced insipid diabetes, without ruling out lithium treatment itself, as risk factors of renal insufficiency. Their importance still needs further evaluation and requires, before and during treatment with this drug, a monitoring of the renal function, some essential element of this surveillance being proposed.

[Lithium and thyroid function. Significance of the TRH test in the diagnosis of lithium-induced thyroid dysfunction]. / Lithium et fonction thyroïdienne. Intérêts du test à la TRH dans le dépistage des dysthyroïdies lithio-induites.

The treatment by lithium is known to involve certain endocrine complications. Those concerning the thyroid function, with risk of a frank hypothyroidy, are the most important. Aiming to appreciate the frequence and the intensivity of the endocrine effects of lithium, the thyroid parameters and the steady state of the hypothalamo-pituitary-thyroid axis were tested using the TRH test in 52 patients with maniaco-depressive psychosis with special attention to TSH, prolactin and growth hormone: 24 out of them were treated for 1 month to 6 years by lithium; the 28 others were considered as controls. The lithium treatment involves a decrease in the free thyroxine index (1.78 +/- 0.09 vs 2.16 +/- 0.09; p less than 0.01), an increase in the mean baseline TSH level (5.80 +/- 1.49 vs 2.70 +/- 0.24 microU/ml; p less than 0.05) and a noteworthy increase in the TSH responsiveness to TRH (22.7 +/- 2.14 vs 9.75 +/- 1.63 microU/ml; p less than 0.005). The TSH supranormal responses were neither correlated with the length of the treatment nor with the age of the patients. They appear as the consequence of a decrease in the thyroidal hormone secretion. The basal and stimulated prolactinemias remain comparable in the two groups of patients and no response of growth hormone occured after TRH. The TRH test must be considered as a useful complement for the surveillance of the patients treated with lithium because it permits to diagnose early the lithio-induced thyroid dysfunction.

[Physical properties and technological problems in the use of xylitol]. / Stoffliche Eigenschaften und technologische Probleme bei der Verwendung von Xylit

Xylitol may be used as a sweetening agent in few cases only, since it appears to be physiologically not so well tolerated as saccharose. From the nutritional viewpoint, it is therefore necessary in many cases to combine sugar substitute, principally to mix xylitol with fructose. Also for technological reasons, new combinations of sugar substitutes for xylitol-containing dietetic foodstuffs must often be found and primarily combinations of sugar substitutes and thickening and gelatinizing agents choose between. It is therefore required that dietetically valuable foodstuffs be developed in line with nutritional requirements and not simply imitate conventional food.