Background: To investigate in vitro how downstream perfusion parameters influence pulsatility index (PI), resistance index (RI) and their constituting Doppler velocities. Materials and methods: We analyzed the influence of resistance, compliance, reflection coefficient and input impedance on PI and RI in an in-vitro model of arterial flow. Results: The nominators of PI and RI were determined by resistance. The numerators were determined by compliance and by the reflection coefficient. There were close relationships of PI and RI with resistance under the condition of constant compliance, but not when compliance was variable. Conclusion: PI and RI consist of velocity terms which are independently influenced by different parameters of impedance: compliance, reflection coefficient and resistance. These findings explain the contradictory results reported for the relationship between the indices and peripheral resistance in studies where compliance and reflection effects were not considered.

Venöse Thrombembolien (= venöse Thrombose + pulmonale Embolie) treten häufig in passageren Risikosituationen, aber auch spontan bei permanent erhöhtem Grundrisiko auf. Sie führen zu respiratorischer und hämodynamischer Beeinträchtigung in einem Ausmaß, das von klinisch stummen Ereignissen zu akut fulminanten Verläufen variieren kann. Die Diagnose kann häufig rationell durch Thrombosenachweis gestellt werden; versagt diese Strategie, ist eine pulmonale Bildgebung erforderlich. Der D-Dimer-Test ermöglicht eine rationelle Patientenselektion für diese Verfahren. Die therapeutische Antikoagulation beginnt sofort mit einem Heparin und wird mit Vitamin-K-Antagonisten fortgesetzt. Darüber hinaus ist über eine systemische Fibrinolysetherapie anhand von Kreislauf- und echokardiographischen Parametern zu entscheiden. Thrombemboliepatienten, bei denen ein Auslöser zu fassen ist, werden einige Monate antikoaguliert; solche mit spontanen oder rezidivierenden Episoden erhalten eine längere oder dauerhafte Antikoagulation.

Mandatory, bilateral, centrally adjudicated venography is currently required to assess the incidence of deep vein thrombosis (DVT) in confirmatory trials of new antithrombotic agents. Non-invasive and less cumbersome methods would be welcomed by both patients and investigators. Centrally adjudicated complete compression ultrasound (CCUS) of all leg veins could become an alternative to venography. Despite the fact that no formal validation of venography has ever been performed, CCUS will have to be externally validated against this 'gold standard' to gain general acceptance and regulatory approval. A substudy of two recent phase IIb trials of a novel, oral anticoagulant for the prevention of venous thromboembolism in patients undergoing elective hip or knee arthroplasty was undertaken to validate CCUS against venography. The studies had similar designs and methodology, and were designed to allow the pooling of data. Mandatory bilateral venography was performed 7±2 days after surgery; CCUS was performed later the same day, with the sonographers blinded to the venography result. All sonographers were required to have completed a training course, and to have obtained personal certification for the standardized examination and documentation procedure. Venograms and CCUS videos were adjudicated centrally by two independent readers at separate locations; discrepancies were resolved by consensus reading. From the 1347 patients participating in the two trials, 870 matching pairs of evaluable venograms and CCUS videos were obtained. Observed prevalences of any DVT, including muscle vein thrombosis, were 19.1% with venography, and 13.0% with CCUS. Sensitivity and specificity values [with 95% confidence intervals (95% CI)] for detecting DVT with CCUS are shown in the table. Although false positives did not severely impair specificity, the small number of true positives detected by CCUS resulted in remarkably low sensitivity, in particular for proximal DVT. Based on these external validation figures, centrally adjudicated CCUS is not a viable technique to replace venography for the screening of DVT early after major orthopaedic surgery in confirmatory trials of novel antithrombotic agents.

Noninvasive diagnosis of deep vein thrombosis (DVT) is based on ultrasound examination of the leg veins, usually restricted to only compression of the proximal veins (CUS). Patients with negative CUS findings require a second examination or a combination with other tests, which impairs clinical efficiency. In this prospective outcome study, 1646 consecutive patients with clinically suspected DVT were examined once by a standardized protocol of complete compression ultrasound comprising all proximal and distal veins (CCUS) as the only diagnostic test. The examination was equivocal in 15 patients' (1% technical failure rate). Another 366 patients (22%) were tested positive for proximal DVT, distal DVT, muscle vein thrombosis, or phlebitis. Of 1265 patients in whom CCUS findings were negative, 242 met exclusion criteria for follow-up (age <18, life expectancy <3 months, other reasons for anticoagulation, postthrombotic lesions of the leg veins, or lack of informed consent). During the 3 months of follow-up, three of 1023 patients with negative CCUS findings experienced a symptomatic venous thromboembolic event (0.3% [95% CI 0.1%-0.8%]). We conclude that the CCUS protocol has a low technical failure rate and is safe with respect to excluding DVT, thereby reducing the diagnostic workup of patients with suspected DVT to a single ultrasound examination.

SummaryUltrasound screening for deep vein thrombosis (DVT) after orthopedic surgery revealed thrombosis in up to 30% of patients, but the clinical impact of screening for distal thrombosis has not been established.Three hundred and forty six patients after hip or knee replacement and postoperative standard prophylaxis of 10 days low molecular weight heparin (LMWH) were randomized to receive either prolonged prophylaxis with LMWH or postoperative ultrasound screening for proximal and distal thrombosis. All thrombosis found in screening was treated. Patients with a negative screening test did not receive any heparin after day 10. The cumulative rate of proximal thrombosis and symptomatic pulmonary embolism until day 35 postoperatively was determined.In 174 screening patients, ultrasound found 55 cases of distal (31.6%) and 9 cases of proximal (5.1%) in-hospital thrombosis. In 108 screening patients without thrombosis at discharge 7 new distal (6.5%) and 6 new proximal (5.6%) thrombotic events occurred by day 35. In 163 patients with prolonged prophylaxis, 33 cases of distal (20.2%) and 7 cases of proximal (4,3%) thrombotic events occurred by day 35. The cumulative rate of proximal events was 8,7% in the screening group and 4.3% in the prophylaxis group (p=0.12).In conclusion, ultrasound screening for thrombosis does not reduce the rate of proximal thrombosis and symptomatic pulmonary embolism 35 days after hip or knee replacement surgery.

BACKGROUND Treatment of venous thromboembolism should consider the influence of thrombophilic disorders on the risk of recurrence. Diagnostic tests should be guided by their expected relevance to therapy. A competent and straightforward clinical approach to venous thromboembolism requires knowledge of the current data regarding stratification of risk of recurrence in thrombophilic patients. METHODS Focusing on clinical management, the current literature on thrombophilia is analyzed. Recommendations are given taking into account the risk of first and recurrent thromboembolism, the bleeding risk under anticoagulation, and validated therapy strategies. A rational diagnostic approach in the light of potential therapies is suggested. CONCLUSION The recurrence risk after triggered venous thromboembolism is low, and anticoagulation does not need to be extended beyond 6 months. Idiopathic or thromboembolism in unusual locations is associated with a higher recurrence risk since underlying thrombophilia is more common in these patients. These cases merit laboratory screening for thrombophilic factors (whose relevance is discussed), and extended anticoagulation is indicated (1 year; in severe thrombophilia several years). In recurrent venous thromboembolism anticoagulation is ideally continued for 4 years, or longer in the absence of complications.

Die Behandlung akuter venöser Thrombembolien (VTE) endetnach einem definierten Intervall. Im Umgang mit danach auftretenden erneutenRisikosituationen bestehen in praxi Unsicherheiten. Aktuelle Daten erlaubenjedoch konkrete Empfehlungen zum Management von Patienten mitfrüheren Thrombosen.

Zusammenfassung. Hintergrund: Bei der Behandlung venöser Thromboembolien ist der Einfluss thrombophiler Störungen auf das Rezidivrisiko zu kalkulieren und gegen Risiken einer Antikoagulanzientherapie abzuwägen. Da die heute bekannten Thrombophilieparameter diesbezüglich unterschiedlichen Stellenwert haben, sollte sich eine rationelle Diagnostik eng an der Erwartung therapeutischer Konsequenzen orientieren. Die klinische Herangehensweise an thrombophile Störungen ist deshalb auf die Kenntnis der heute vorliegenden Daten zur Risikostratifizierung bei Thrombosepatienten angewiesen. Methodik: Unter dem Blickwinkel der praktischen Umsetzung wird die aktuelle Literatur zu thrombophilen Störungen analysiert. In Gegenüberstellung der Risiken von Erkrankung und Therapie und unter Berücksichtigung validierter Therapien werden aktuelle Behandlungsrichtlinien dargestellt. Es werden Empfehlungen zu einer rationellen Diagnostik gegeben, die sich an potentiell abzuleitenden Therapien orientiert. Schlussfolgerung: Das Rezidivrisiko nach klassisch getriggerten venösen Thromboembolien ist so gering, dass eine Antikoagulationsdauer bis zu 6 Monaten ausreichend ist. Idiopathische Thromboembolien oder Thrombosen ungewöhnlicher Lokalisation sind mit einem höheren Rezidivrisiko vergesellschaftet, da häufiger thrombophile Störungen zugrunde liegen. Hier besteht die Indikation zur Bestimmung thrombophiler Faktoren (deren Relevanz im Einzelnen diskutiert wird); eine längere Antikoagulationszeit ist indiziert (1 Jahr, bei schwerer Thrombophilie mehrere Jahre). Rezidivierende venöse Thromboembolien sollten für 4 Jahre behandelt werden, länger bei unproblematischer Führung der Antikoagulation.

Background: Current data allows first recommendations for the management of patients with previous venous thromboembolism (VTE) whose risk of recurrence is transiently increased.Methods: The literature about the risk of VTE recurrence in common clinical situations is analyzed, and recommendations for the diagnostic and therapeutic management and patient counseling are given.Conclusions: Perioperative replacement of oral anticoagulants by low molecular weight heparins (LMWH) is effective and safe in patients treated for VTE. After a triggered first episode of VTE, the same prophylaxis in situations of transient risk is recommended as for patients without previous VTE. Patients with previous VTE who are pregnant or scheduled for hormonal therapy require a detailed exploration, as management is influenced by several factors. In the postpartal period, patients with previous VTE should receive prophylactic over the time of active malignancy; LMWH appear to have a more favorable profile than oral anticoagulants.

Background: Compression ultrasound is considered the preferred test for the diagnosis of deep vein thrombosis of the leg (DVT). Since sensitivity for distal thrombosis is low additional tests are required. We developed a protocol of complete compression ultrasound of all venous segments of the leg (CCUS). A retrospective outcome study was performed to get an estimate of the rate of indeterminate results necessitating repeated testing as well as for the clinical safety of CCUS in a cohort of consecutive, unselected patients.Patients and methods: Case records of all patients referred for clinical suspicion of deep vein thrombosis within a three months period were reviewed. Patients with negative CCUS were followed directly or via the general practitioner in order to know whether an episode of venous thromboembolism had been documented since the initial CCUS.Results: 132 inpatients and 154 outpatients were identified. Clinical probability was high in 50 patients, medium in 142, and low, in 94. The first CCUS was negative in 209 cases. Five patients (1,8%) had repeated CCUS within the next 7 days because of incomplete visualisation of the distal veins and turned out to be negative as well. Of all 214 patients with negative CCUS a clinical follow-up information was obtained after 168 +/- 25 days. Five patients had died, none due to pulmonary embolism. In two patients deep vein thrombosis had been documented (0,9% [95% CI: 0,1-3,3%]) 148 and 172 days after CCUS, respectively.Conclusion: CCUS for diagnosis of DVT needs to be repeated in very few cases only. Clinical safety seems to fall into the same range as with combined algorithms and should be tested in a prospective design. Patients with medium and high probability showed a very low incidence of DVT within three months following CCUS; therefore, they may be included in a prospective outcome study.

Die Vv. gastrocnemiae münden 2 bis 3cm oberhalb des Kniegelenkspalts mit einem gemeinsamen Stamm von medial und lateral in die V. poplitea, nicht selten auch zusammen mit der V. saphena parva des oberflächlichen Venensystems. Meistens liegen zwei, teils auch mehrere Gefäße in den beiden Muskelköpfen vor. Die Venen im tibialen Gastroknemiuskopf sind oft kräftiger als im fibularen ausgebildet (15).