Loss of high-molecular-weight von Willebrand factor multimers mainly affects platelet aggregation in patients with aortic stenosis

Severe aortic stenosis is associated with a haemostatic abnormality that resembles acquired von Willebrand syndrome type 2. It is assumed that high shear conditions render large von Willebrand factor (VWF) multimers accessible to cleavage by ADAMTS-13. However, whether loss of these large multimers affects platelet function by impairing adhesion, aggregate formation, or both has not been evaluated in clinical studies. We prospectively enrolled 47 patients with severe aortic stenosis, and studied them prior to aortic valve surgery and at a median of six months after valve replacement. We investigated levels of large VWF multimers, platelet function under high shear conditions, and residual response to suboptimal concentrations of ADP to express P-selectin. As expected, there was a significant reduction of VWF large multimers before surgery that resolved thereafter in most patients (p<0.0001). The closure time of the ADP cartridge of the PFA-100 was also corrected in most patients after the operation (p<0.0001). We used the cone and plate(let) analyser Impact-R to differentiate between adhesion and aggregation. Both adhesion (p=0.03) and ADP-inducible platelet aggregation (p=0.002) improved considerably after valve replacement. Consequently, ADP-inducible expression of P-selectin was higher after valve replacement (p=0.001). We conclude that reduced levels of large VWF multimers associated with aortic stenosis lead to impairment of both adhesion and, especially, ADP-inducible platelet aggregation.

[Dynamic magnetic resonance tomography (MRI): a follow-up study after femur core decompression and instillation of recombinant human bone morphogenetic protein-2 (rhBMP-2) in avascular femur head necrosis]

OBJECT

The aim of the study was to test the use of dynamic magnetic resonance imaging study with Gd-DTPA-application and the dynamic changes of signal intensity at patients with avascular femoral head necrosis after having installed rhBMP-2 and/or decompressed the core.

MATERIAL AND METHODS

Six patients with avascular necrosis of the femoral head ARCO-stage I- or II-lesions were treated surgically by femoral head core decompression. Three of these patients were additionally treated with rhBMP-2-instillation. The progression or regression could be confirmed by T1- and T2-weighted spinecho-sequences (zero, four, ten, sixteen weeks and 24 months follow up).

RESULTS

Corresponding ARCO-classification with partly more sensitive measurement of vitality signs in comparison to the optical x-ray classification. The objective, quantitative measurement of signal intensity post contrast medium reduces the influence of experience and level of education. The dynamic sequences results are reproducible.

CONCLUSION

The dynamic magnetic resonance imaging study after Gd-DTPA-application and the dynamic changes of signal intensity after Gd-DTPA enhancement in the necrotic areas of the femoral head were the important subject of our study and it seems, that these sequencies and the ascertainment of signal intensity changes will be an efficient method for judgement of vitality, vascularisation and perfusion after therapeutical intervention. Combination of femoral head core decompression and rhBMP-2-instillation for the purpose of osseous regeneration seems to stabilize the affection.

[MRI in the diagnosis and differential diagnosis of radiocarpal diseases and injuries]

Advances in MRI technology have greatly improved visualization of the radio-carpal region. With todays high-resolution imaging, even very small anatomic structures like the triangular fibrocartilage may be seen. Established indications include the osteonecroses (scaphoid and lunate); however, MR images always should be evaluated in conjunction with plain radiographs. By delineating bone marrow edema, MRI is well suited for the detection of microfractures. Visualization of small soft tissue tumors, soft tissue extension of bone tumors and for staging of tumors in general may also be regarded as indications generally agreed upon. Promising indications include pathology of ligaments and similar structures.

MRT in the diagnosis and differential diagnosis of radiocarpal diseases and injuries

Advances in MRI technology have greatly improved visualization of the radio-carpal region. With todays high-resolution imaging, even very small anatomic structures like the triangular fibrocartilage may be seen. Established indications include the osteonecroses (scaphoid and lunate); however, MR images always should be evaluated in conjunction with plain radiographs. By delineating bone marrow edema, MRI is well suited for the detection of microfractures. Visualization of small soft tissue tumors, soft tissue extension of bone tumors and for staging of tumors in general may also be regarded as indications generally agreed upon. Promising indications include pathology of ligaments and similar structures.

[Etiologic factors and incidence of ischemic type biliary lesions (ITBL) after liver transplantation]

Ischemic type biliary lesions (ITBL) are defined as non-ischemic and non-immunological destruction of the graft's biliary tree after liver transplantation. In a retrospective analysis we investigated possible etiological factors and the incidence of ITBL. Differing from previous studies, the incidence of ITBL was low (2.6%) and we did not observe a significant effect of cold ischemic time or initial peak transaminases, as indicator of the reperfusion injury. However, we detected a significant decrease in the incidence of ITBL in self-retrieved organs and in organs preserved with arterial pressure perfusion.

[Initial nuclear magnetic resonance tomography results of the treatment course of avascular femur head necrosis after femoral core decompression]

The vascular femoral head necrosis is a serious illness, especially when appearing in patients aged 30 to 50 years. Many etiologic factors cause a femoral head necrosis such as, for example, high-dose steroids, abuse of alcohol, defect of bone marrow and trauma of the hip. Often the X-ray photograph leads to the diagnosis in the second stage (ARCO 1992) or in the third stage, when the femoral head has begun to collapse. The stage IIc and III shows an evident enhancement in contrast media in MRI. Contrast enhancement is demonstrated by STIR, FATSAT, T1-weighted and dynamic screening sequence. The characteristics of the contrast media enhancement argue for an active concomitant process of destruction and regeneration. This stage has the best chances for a drug or a surgical therapy. The evaluation of the signal intensity by the dynamic screening sequence is considered as an objective contribution for the staging of the femoral head necrosis. This enables one to differentiate between the curable stage IIc and the stage III, showing the beginning of breakdown of the femoral head.