Monitoring anticoagulant therapy with vitamin K antagonists in patients with antiphospholipid syndrome.

Because of the possible interference of antiphospholipid antibodies (APL) with the phospholipid component of thromboplastin reagents, concerns have been raised about the validity of international normalized ratio (INR) testing to monitor anticoagulant therapy with vitamin K antagonists in patients with antiphospholipid syndrome (APS). To investigate the reliability of the INR, we determined the INR using various prothrombin time (PT) assays and compared the results with those of a chromogenic factor X (CFX) assay. The study cohort consisted of 40 APS patients and 100 APL-negative patients who were on anticoagulant therapy for reasons other than APS. The agreement (i.e. the percentage of patients with a difference ≤0.5 INR units) between the PT-derived INR and CFX-derived INR equivalents was only moderate in both patient groups. The best agreement with CFX-derived INR equivalents was observed for the Thromborel S reagent in APS patients (69.1 %) and for Neoplastin Plus in APL-negative patients (72.0 %). Regarding the results for the point-of-care system CoaguChek XS, an agreement between the INR and the CFX-derived INR equivalent was less frequently observed in the APS patients (55.6 vs. 67.8 %; p = 0.050). When considering all 3058 pairs of INR tests within the international sensitivity index (ISI)-calibrated range of 1.5 to 4.5 s, we did not observe a higher variability of INR values in either the APS patient group or the subgroup of APS patients positive for lupus coagulants compared with the APL-negative controls. In conclusion, monitoring vitamin K antagonists (VKA) therapy with laboratory INR measurements seems to be suitable for the majority of APS patients.

Thrombosis of the inferior vena cava and malignant disease.

BACKGROUND: Inferior vena cava thrombosis (IVCT) is a rare event, and studies detailing its underlying aetiologies are scarce. METHODS: One hundred and forty-one IVCT patients (57% females, median age 47 years) were analysed with a focus on malignancy-related thrombosis and compared with 141 age- and sex-matched control patients with isolated lower-extremity deep vein thrombosis. RESULTS: Malignancies were more prevalent among IVCT patients compared with the control group (39% vs. 7.8%; P<0.001). Malignancy-related IVCT more frequently involved the suprarenal and hepatic segments of the IVC and extended more often to the right atrium than IVCT did in non-cancer patients. Among IVCT patients with malignancies, renal cell carcinoma (38%) and other malignancies of the genitourinary tract (25%) were the most common tumours. Analysis of the underlying pathological mechanisms of malignancy-related thrombosis identified external compression of the IVC by tumour masses in 9 cases (16%), and progression of malignancy into the IVC (so-called "tumour thrombosis") in 24 cases (44%). The remaining 22 cases (40%) were attributed to malignancy-related hypercoagulability and the presence of additional venous thromboembolism risk factors, such as previous surgery, immobilisation, or chemotherapy. CONCLUSIONS: Malignancies substantially contribute to the risk of thrombosis involving the IVC. Tumour invasion, especially in cases of renal cell cancer and malignancy-related hypercoagulability are major triggering factors for thrombogenesis.

Late peripheral stent thrombosis due to stent fracture, vigorous exercise and hyporesponsiveness to clopidogrel.

Late peripheral arterial stent thrombosis usually occurs due to haemodynamically relevant in-stent restenosis. However, late stent thrombosis may be multicausal. We report here the well-documented case of a 69-year-old man with acute thrombosis of the stented superficial femoral artery after a long-distance bicycle tour. Catheter-directed thrombolysis revealed a residual stenosis located at a stent fracture site. In addition, platelet function tests revealed an inadequate platelet response to clopidogrel. In conclusion, stent fracture, strenuous exercise and hyporesponsiveness to clopidogrel may have contributed to the development of late peripheral stent thrombosis.