Postinterventional Assessment after Stent and Flow-Diverter Implantation Using CT: Influence of Spectral Image Reconstructions and Different Device Types.

BACKGROUND AND PURPOSE: CTA provides a noninvasive alternative technique to DSA in the follow-up after endovascular aneurysm treatment to evaluate aneurysm occlusion and exclude intraluminal narrowing after stent or flow-diverter implantation; however, assessability may be impeded by stent material artifacts. The objective of this in vitro study was to compare the visual assessability of different conventional stents and flow diverters as well as different reconstructions of dual-layer CT images. MATERIALS AND METHODS: Four conventional intracranial stents and 4 flow diverters were implanted in identical aneurysm phantoms. Conventional and monoenergetic images (40, 50, 60, 90, 120, 180 keV) were acquired to evaluate attenuation alteration, visible lumen diameter, and SNR. Image quality was rated subjectively by 2 independent radiologists using a 4-point Likert scale. RESULTS: Low kiloelectron volt (40-60 keV) monoenergetic reconstructions showed an improved SNR and an improved lumen density ratio compared with high kiloelectron volt reconstructions (90-180 keV) and conventional reconstructions, however without reaching significance compared with the latter. Assessment of the adjacent aneurysm and subjective evaluation was not affected by the imaging technique and stent type. Artifact susceptibility varied with the device used and increased among flow diverters. CONCLUSIONS: Low kiloelectron volt reconstructions improved the assessment of the stent lumen in comparison with high kiloelectron volt reconstructions. No significant improvement in image quality could be shown compared with conventional images. For some devices, iodine-specific reconstructions led to severe artifacts and are therefore not recommended. There was no relevant improvement in the assessability of the adjacent aneurysm.

Ultrastructural investigations for reducing endothelial cell damage of vein grafts during CABG-operation and practical consequences.

BACKGROUND: In the present study the influence of different storage solutions on endothelial integrity or damage was investigated with direct methods particularly with transmission electron microscopy (TEM), scanning electron microscopy (SEM) and immunohistochemistry. METHODS: Saphenous vein segments of 10 cm in length were taken surgically from 6 male CABG-patients (aged 60-70) under standardized conditions. Each vein segment was cut into rings, which were incubated at room temperature for 45 minutes in different storage solutions, particularly in 0.9% sodium chloride solution and in buffered solution (M 199) with 5% human serum albumin respectively. Then, the vein segments were fixed in 3.5% glutaraldehyde and prepared for scanning and transmission electron microscopy to evaluate the endothelial damage. In addition, immunohistochemical staining (CD34, PECAM and Factor VIII) was performed. RESULTS: When using 0.9% sodium chloride solution, the SEM-examination revealed that 55% of the cell population was destroyed. In comparison to these findings only 26% of the endothelial cell population was damaged when the venous segment was stored in buffered solution with 5% albumin (p<0.01). In immunohistochemistry (CD34, PECAM, Factor VIII) these findings were supported. CONCLUSIONS: This study demonstrates the importance of storage solutions in regard to endothelial integrity. For best preservation of endothelium it is necessary to modify conventional storage methods. So, storage in buffered solution with albumin has shown much better endothelial cell preservation compared with physiological saline which might reduce the obliteration rate of CABG in future.

Changes in coagulation and fibrinolytic parameters caused by extracorporeal circulation.

During cardiopulmonary bypass (CPB) mechanical stress and the contact of blood with artificial surfaces lead to the activation of pro- and anticoagulant systems and the complement cascade, and to changes in cellular components. This phenomenon causes the "postperfusion-syndrome", with leukocytosis, increased capillary permeability, accumulation of interstitial fluid, and organ dysfunction. In this study, we focused on the influence of the extracorporeal circulation, sternotomy, and heparin administration on the activation of coagulation and fibrinolysis. In 15 patients we investigated coagulation parameters before, during and post CPB, i.e., fibrinogen, antithrombin (AT) III, thrombin-antithrombin complex (TAT), prothrombin fragments F1 + 2 (F1 + 2), factor (F) XIIa, tissue factor (TF), and parameters of the fibrinolytic system, i.e., plasmin-antiplasmin-complex (PAP), D-dimer, tissue-plasminogen-activator (tPA), urokinase-type plasminogen activator (uPA), and plasminogen-activator inhibitor type 1 (PAI 1). The results demonstrate distinct alterations in the above mentioned parameters. Despite administration of a high dose of heparin (activated clotting time [ACT] > 450s) combined with a low dose of aprotinin, activation of the coagulation and fibrinolytic pathways was observed. We found this activation was mainly caused by CPB and not by sternotomy. The activation of coagulation was due to foreign surface contact (F XII => F XIIa) as well as to an effect of tissue factor release in the late phase of CPB. The enhanced fibrinolytic activity during CPB was, at least in part, caused by tPA and was followed by PAI 1 release.