Fiix-prothrombin time monitoring improves warfarin anticoagulation outcome in atrial fibrillation: a systematic review of randomized trials comparing Fiix-warfarin or direct oral anticoagulants to standard PT-warfarin

BACKGROUND

Monitoring warfarin with Fiix-prothrombin time (Fiix-PT), which is only affected by coagulation factors II and X, stabilizes anticoagulation and reduces thromboembolism compared to PT/INR monitoring. We compared outcome in nonvalvular atrial fibrillation (NVAF) patients treated with Fiix-warfarin, direct oral anticoagulants (DOACs), or PT-warfarin.

METHODS

A systematic efficacy and safety assessment by retrieving data from the Fiix trial and the four major phase III DOAC trials in NVAF. Prespecified outcomes included stroke and systemic embolism (SSE), SSE and myocardial infarction (MI), major bleeding (MB), composite major vascular events (SSEMI and MB; CMVE), and deaths. We calculated relative risk, 95% CI, and 95% confidence limits (CL) for each outcome and performed meta-analysis using fixed- and random-effects modeling.

RESULTS

There were 613 and 628 observation years with Fiix-warfarin and PT-warfarin in the Fiix trial, and 70 628 and 57 962 with DOACs and PT-warfarin in DOAC trials. Populations were comparable although death rates were lower in the Fiix trial. Compared to pooled PT-warfarin, Fiix-warfarin reduced SSE (RR 0.54;95% CI 0.26-1.10/95% CL <1.00), SSEMI (0.51;0.26-0.99/<0.90), MB (RR 0.63;0.37-1.07/<0.99), and CMVE (RR 0.66;0.43-1.00/<0.94). Vascular death was lower (RR 0.13;0.04-0.47/<0.42). Compared to pooled DOACs, Fiix-warfarin consistently had lower point estimates for the RR for efficacy and safety, but only significant for lower death rates (vascular death RR 0.14;0.04-0.49/<0.43). Meta-analysis comparing Fiix-warfarin and DOACs with PT-warfarin consistently found Fiix-warfarin to have the lowest point estimates for efficacy.

CONCLUSION

Monitoring warfarin with Fiix-PT reduces risk of vascular events in NVAF patients as much as DOACs. Warfarin monitored with Fiix-PT is an improved anticoagulant.

During warfarin induction, the Fiix-prothrombin time reflects the anticoagulation level better than the standard prothrombin time

Essentials Fiix-prothrombin time (PT) monitoring of warfarin measuring factor (F) II and X, is effective. Plasma obtained during warfarin induction and stable phase in Fiix-trial was assayed. Fiix-PT stabilized anticoagulation earlier than monitoring with traditional PT-INR. FVII had little effect on thrombin generation that was mainly determined by FII and FX.

SUMMARY

Background The prothrombin time (PT) is equally prolonged by reduction of each of the vitamin K-dependent (VKD) factors (F) II, VII and X. The Fiix-PT is only affected by FII and FX, the main contributors to thrombin generation (TG). Objective To test the hypothesis that variability in warfarin anticoagulation is reduced early during monitoring with the normalized PT-ratio calculated from Fiix-PT (Fiix-International Normalized Ratio [INR]) compared with traditional PT-INR monitoring. Also, that because of its insensitivity to FVII, Fiix-PT more accurately reflects TG when Fiix-INR and PT-INR are discrepant. Methods Samples from Fiix-trial participants monitored with either Fiix-PT or PT were used. VKD coagulation factors and TG were measured in samples from 40 patients during stable anticoagulation and in serial samples obtained from 26 patients during warfarin induction. TG was assessed in relation to selective reduction in single VKD factors. Results During Fiix-warfarin induction full anticoagulation measured as FII or FX activity was achieved at a similar rate to that with PT-warfarin but subsequently stabilized better. Fiix-INR but not PT-INR mirrored total TG during initiation. During induction, FII (R2 = 0.66) and FX (R2 = 0.52) correlated better with TG and with a steeper slope than did FIX (R2 = 0.37) and in particular FVII (R2 = 0.21). In vitro, FII and FX were the main determinants of TG at concentrations observed during VKA anticoagulation, whereas FVII and FIX had little influence. Conclusions Fiix-PT monitoring reduces anticoagulation variability, suggesting that monitoring FVII has a limited role during VKA management. TG is better reflected by Fiix-PT.

Monitoring of Therapy for Deep Vein Thrombosis Using Magnetic Resonance Imaging

Magnetic resonance imaging using limited-flip-angle, gradient refocused pulse sequences has been used to monitor the course of anticoagulant or fibrinolytic therapy for deep vein thrombosis in two patients. The findings demonstrate the capacity of this technique to delineate the extent of thrombosis and characterize changes in size in response to treatment. Advantages of this approach include high anatomic resolution, speed of examination and non-invasiveness, properties that make it well-suited to following the progress of therapy with potentially significant implications for improving treatment.

A single test to assay warfarin, dabigatran, rivaroxaban, apixaban, unfractionated heparin, and enoxaparin in plasma

Essentials Simple and fast assaying of different anticoagulants (ACs) is useful in emergent situations. We used highly diluted prothrombin time (dPT) or highly diluted Fiix-PT (dFiix-PT) to assay ACs. Both tests could quantify target specific anticoagulants and warfarin anticoagulation. Improved results were consistently observed with the dFiix-PT compared with the dPT.

SUMMARY

Background Assaying anticoagulants is useful in emergency situations or before surgery. Different specific assays are currently needed depending on the anticoagulant. Objectives We hypothesized that levels of warfarin, dabigatran, rivaroxaban, apixaban, and heparins could be measured with use of the diluted prothrombin time (dPT) and diluted Fiix-PT (dFiix-PT), using highly diluted thromboplastin (TP). The latter test is affected only by reduced levels of active factors II and X but corrects test plasma for other deficiencies Methods Increasing TP dilutions were used to identify suitable dilutions to measure dabigatran, rivaroxaban, apixaban, unfractionated heparin (UFH), and enoxaparin. Calibrators containing known amounts of direct oral anticoagulants (DOACs) were used to make standard curves. Citrated plasma samples were obtained from patients taking warfarin or DOACs with known drug concentrations as determined by specific assays. Results The dFiix-PT at a TP dilution of 1:1156 could be used to measure all of the drugs tested at therapeutic concentrations except for fondaparinux. The dPT achieved the same but required two TP dilutions (1:750 and 1:300). The warfarin effect could be assessed by using dFiix-PT at 1:1156 with a PT ratio identical to the international normalized ratio. Six different TPs yielded similar results, but two were less sensitive. Dabigatran, rivaroxaban, and apixaban could be accurately measured in patient samples using both dilute PT assays, but a better correlation was consistently observed between the dFiix-PT and specific assays than with the dPT. Conclusion The dFiix-PT using a single dilution of TP may be suitable to assess the anticoagulant effects of warfarin, dabigatran, rivaroxaban, apixaban, heparin, and enoxaparin.

Treatment of venous thromboembolism in cancer patients with dalteparin for up to 12 months: the DALTECAN Study

BACKGROUND

Treatment of venous thromboembolism (VTE) in patients with cancer has a high rate of recurrence and bleeding complications. Guidelines recommend low-molecular-weight heparin (LMWH) for at least 3-6 months and possibly indefinitely for patients with active malignancy. There are, however, few data supporting treatment with LMWH beyond 6 months. The primary aim of the DALTECAN study (NCT00942968) was to determine the safety of dalteparin between 6 and 12 months in cancer-associated VTE.

METHODS

Patients with active cancer and newly diagnosed VTE were enrolled in a prospective, multicenter study and received subcutaneous dalteparin for 12 months. The rates of bleeding and recurrent VTE were evaluated at months 1, 2-6 and 7-12.

FINDINGS

Of 334 patients enrolled, 185 and 109 completed 6 and 12 months of therapy; 49.1% had deep vein thrombosis (DVT); 38.9% had pulmonary embolism (PE); and 12.0% had both on presentation. The overall frequency of major bleeding was 10.2% (34/334). Major bleeding occurred in 3.6% (12/334) in the first month, and 1.1% (14/1237) and 0.7% (8/1086) per patient-month during months 2-6 and 7-12, respectively. Recurrent VTE occurred in 11.1% (37/334); the incidence rate was 5.7% (19/334) for month 1, 3.4% (10/296) during months 2-6, and 4.1% (8/194) during months 7-12. One hundred and sixteen patients died, four due to recurrent VTE and two due to bleeding.

CONCLUSION

Major bleeding was less frequent during dalteparin therapy beyond 6 months. The risk of developing major bleeding complications or VTE recurrence was greatest in the first month of therapy and lower over the subsequent 11 months.

Challenges of rare disease research: limited patients and competing priorities

Rare disease research is increasingly challenging. For those with haemophilia, this is an exciting time, with the promise of new therapies at the bench and in early phase clinical trials. Yet, it is also a time for critical assessment and planning to assure the success of the clinical research effort. As successes at the bench have enabled transition of novel peptides, longer-acting factor products and gene therapy to clinical trials, clinicians face the challenges of limited number of patients, competing priorities and strained resources. To solve these problems and assure the success of the clinical research effort, it is essential that the research process be enabling and the dialogue be global, involving academia with industry, and physicians with patients. This is a critical juncture in the process, especially with new national initiatives in clinical research at hand. Needs must be assessed and priorities must be set to assure that despite the challenges, exciting new therapies will ultimately translate into safe, effective therapies for patients. Finally, these challenges are by no means restricted only to rare disease research. With the evolution of genetic medicine, it is likely that the general medical disease research of the future will include small clinical trials of new agents for small subsets of patients with certain disease mutations. Thus, the milestones we achieve in this ongoing process will hopefully not only enable clinical trials research in a rare disease, but also in many medical genetic disease of the future.

Low-molecular-weight heparin for venous thromboprophylaxis in ambulatory cancer patients: A meta-analysis

9537

Background: Patients with cancer have an increased risk of venous thromboembolism (VTE). However, routine VTE prophylaxis is generally not recommended in ambulatory cancer patients. Several randomized controlled trials (RCTs) of low-molecular-weight heparin (LMWH) in ambulatory cancer patients have been reported with inconclusive results. Methods: A systematic review of RCTs of LMWH in ambulatory cancer patients without a VTE diagnosis was conducted. Included trials had to report VTE as primary or secondary outcome. An extensive electronic database search was conducted, including Medline, EMBASE, Cochrane Library along with abstracts from major meetings. Dual-blinded data extraction was performed. Meta-analysis was conducted using Mantel and Haenszel method to estimate relative risk (RR) and absolute risk difference (ARD) ± 95% CI. Primary outcomes in this analysis were all reported VTE and major bleeds. Most trials did not require VTE screening by imaging, precluding a separate analysis of asymptomatic VTE events. Results: Six RCTs were identified with a total of 2,648 patients including 1,525 receiving LMWH and 1,123 controls. No significant heterogeneity was observed across trials. Among patients receiving LMWH, the crude incidence of VTE was 2.95% compared to 5.25% among control patients. LMWH reduced the RR of VTE by 36% compared to controls (RR=0.64 [0.44 - 0.94], P=0.021), and reduced the ARD by 1.8% [0.2% - 3.4%]. Major bleeding events were reported in 1.57% LMWH patients compared to 0.98% in controls. The non-significant RR increase by LMWH for major bleeding was 1.85 [0.923 - 3.68], P=0.081, with an ARD of 0.9% [0.0% - 1.8%]. Results were comparable in the analysis limited to studies with VTE as primary outcome. Conclusions: While patients experienced a 36% relative risk reduction in VTE with LMWH, the absolute risk reduction was small, and concerns remain about the potential increase in major bleeding. Therefore, routine VTE prophylaxis in ambulatory cancer patients cannot be recommended at this time. Additional research is needed to identify cancer outpatients at high risk for VTE, in whom prophylaxis may have a more favorable risk-benefit ratio.

[Table: see text]

15-deoxy-Delta12,14 prostaglandin J2-induced heme oxygenase-1 in megakaryocytes regulates thrombopoiesis

BACKGROUND

Platelet production is an intricate process that is poorly understood. Recently, we demonstrated that the natural peroxisome proliferator-activated receptor gamma (PPARgamma) ligand, 15-deoxy-Delta(12,14) prostaglandin J(2) (15d-PGJ(2)), augments platelet numbers by increasing platelet release from megakaryocytes through the induction of reactive oxygen species (ROS). 15d-PGJ(2) can exert effects independent of PPARgamma, such as increasing oxidative stress. Heme oxygenase-1 (HO-1) is a potent antioxidant and may influence platelet production.

OBJECTIVES

To further investigate the influence of 15d-PGJ(2) on megakaryocytes and to understand whether HO-1 plays a role in platelet production.

METHODS

Meg-01 cells (a primary megakaryoblastic cell line) and primary human megakaryocytes derived from cord blood were used to examine the effects of 15d-PGJ(2) on HO-1 expression in megakaryocytes and their daughter platelets. The role of HO-1 activity in thrombopoiesis was studied using established in vitro models of platelet production.

RESULTS AND CONCLUSIONS

15d-PGJ(2) potently induced HO-1 protein expression in Meg-01 cells and primary human megakaryocytes. The platelets produced from these megakaryocytes also expressed elevated levels of HO-1. 15d-PGJ(2)-induced HO-1 was independent of PPARgamma, but could be replicated using other electrophilic prostaglandins, suggesting that the electrophilic properties of 15d-PGJ(2) were important for HO-1 induction. Interestingly, inhibiting HO-1 activity enhanced ROS generation and augmented 15d-PGJ(2)-induced platelet production, which could be attenuated by antioxidants. These new data reveal that HO-1 negatively regulates thrombopoiesis by inhibiting ROS.

Fibrinogen synthesized by cancer cells augments the proliferative effect of fibroblast growth factor-2 (FGF-2)

BACKGROUND

Fibroblast growth factor (FGF)-2 is a critical growth factor in normal and malignant cell proliferation and tumor-associated angiogenesis. Fibrinogen and fibrin bind to FGF-2 and modulate FGF-2 functions. Furthermore, we have shown that extrahepatic epithelial cells are capable of endogenous production of fibrinogen.

OBJECTIVE

Herein we examined the role of fibrinogen and FGF-2 interactions on prostate and lung adenocarcinoma cell growth in vitro.

METHODS

Cell proliferation was measured by (3)H-thymidine uptake and the specificity of FGF-2-fibrinogen interactions was measured using wild-type and mutant FGF-2s, fibrinogen gamma-chain (FGG) RNAi and co-immunoprecipitation. Metabolic labeling, immunopurification and fluorography demonstrated de novo fibrinogen production.

RESULTS

FGF-2 stimulated DU-145 cell proliferation, whereas neither FGF-2 nor fibrinogen affected the growth of PC-3 or A549 cells. Fibrinogen augmented the proliferative effect of FGF-2 on DU-145 cells. The role of fibrinogen in FGF-2-enhanced DNA synthesis was confirmed using an FGF-2 mutant that exhibits no binding affinity for fibrinogen. FGG transcripts were present in PC-3, A549 and DU-145 cells, but only PC-3 and A549 cells produced detectable levels of intact protein. RNAi-mediated knockdown of FGG expression resulted in decreased production of fibrinogen protein and inhibited (3)H-thymidine uptake in A549 and PC-3 cells by 60%, which was restored by exogenously added fibrinogen. FGF-2 and fibrinogen secreted by the cells were present in the medium as a soluble complex, as determined by coimmunoprecipitation studies.

CONCLUSIONS

These data indicate that endogenously synthesized fibrinogen promotes the growth of lung and prostate cancer cells through interaction with FGF-2.

A meta-analysis of anticoagulants as cancer treatment: Impact on survival and bleeding complications

9071

Background: There is substantial laboratory evidence that anticoagulants, in particular the low-molecular-weight heparins (LMWH), exert an antitumor effect, while clinical trials have reported conflicting results. This study represents the first comprehensive systematic review and meta-analysis of the evidence from randomized controlled trials (RCTs) evaluating specifically the impact of anticoagulants on survival and safety in cancer patients without venous thromboembolism (VTE). Methods: An exhaustive systematic literature review of RCTs was performed without language restrictions, including a comprehensive search of electronic databases through May 2006 with subsequent weekly updates to the end of 2006 (Medline, EMBASE, Cochrane Database of Systematic Reviews, CENTRAL, DARE, and major conference proceedings) and relevant article references. Two reviewers extracted the data independently. Primary study outcomes were 1-year overall mortality and all bleeding complications. Major and fatal bleeding complications were secondary outcomes. The meta- analysis was performed utilizing the Mantel-Haenszel method. Results: All identified 11 RCTs were performed in solid tumor patients. Anticoagulation significantly decreased overall mortality across all studies with a relative risk (RR) of 0.905 (95%CI: 0.847–0.967; p=0.003). The survival improvement appears not to be due to the prevention of fatal VTE. All bleeding complications (RR=2.309; 95%CI: 1.928–2.764; p<0.0001) and major bleeding events (RR=2.598; 95%CI; 1.936–3.488; p<0.0001) occurred more frequently with anticoagulation. The relative risk for mortality was 0.877 (95%CI: 0.789–0.975; p=0.015) with LMWH, compared to warfarin (RR=0.942; 95%CI: 0.854–1.040; p=0.239). Warfarin resulted in higher rates for all and major bleeding complications compared to LMWH (p<0.0001, respectively). Conclusions: Anticoagulants significantly improved overall survival in cancer patients while increasing the risk of bleeding complications. Despite these encouraging findings, given limitations of available data and the potential for life-threatening complications, the use of anticoagulants as antineoplastic therapy cannot be recommended until additional RCTs confirm these results.

No significant financial relationships to disclose.

Increasing risk for venous thromboembolism among hospitalized cancer patients

9009

Background: Venous thromboembolism (VTE) contributes to morbidity and mortality in cancer patients and is a frequent complication of anti-cancer therapy. We examined the frequency, risk factors and trends associated with VTE among hospitalized US cancer patients. Methods: We conducted a retrospective cohort study using the discharge database of the University Health System Consortium. This included all 1,824,316 hospitalizations of cancer patients between 1995 and 2003 at 133 United States medical centers. To avoid overestimation, only a single randomly chosen hospitalization was included for patients with multiple admissions. Results: Among 1,015,598 individual cancer patients, 34,357 (3.4%) were diagnosed with deep venous thrombosis and 11,515 with pulmonary embolism (PE) (1.1%) for an overall VTE rate of 4.1%. Subgroups of cancer patients with highest rates included Black ethnicity (5.1% per hospitalization) and those on chemotherapy (4.9%). Sites of cancer with the highest rates of VTE included pancreas (8.2%), kidney (5.7%), ovary (5.6%), lung (5.1%) and stomach (4.9%). Amongst hematologic malignancies, myeloma (5%), non-Hodgkin’s lymphoma (4.8%) and Hodgkin’s disease (4.6%) had the highest rates of VTE. The rate of VTE rose from 3.6% per hospitalization in 1995–96 to 4.6% in 2002–03, an increase of 28%, including a near-doubling of PE rates from 0.8% to 1.5% (P<0.0001). Among patients receiving chemotherapy, rates of VTE rose from 3.9% per hospitalization to 5.7%, an increase of 47% (P<0.0001). In contrast, patients undergoing surgery for breast, head and neck, pancreatic or spinal cancers, experienced no significant change in the rate of VTE. Use of diagnostic procedures for VTE also did not increase over the study period. Conclusions: The rate of VTE, including PE, among hospitalized cancer patients has increased significantly in recent years. Black patients, those on chemotherapy and those with certain types of cancer are disproportionately at increased risk. The rise in VTE does not appear to be attributable to an increased utilization of diagnostic procedures. Further efforts to increase thromboprophylaxis compliance during hospitalization are needed.

No significant financial relationships to disclose.

Effects of pioglitazone on fasting and postprandial levels of lipid and hemostatic variables in overweight non-diabetic patients with coronary artery disease

OBJECTIVES

To evaluate the effects of pioglitazone on insulin sensitivity and levels of biomarkers associated with thrombotic risk in overweight and obese, non-diabetic subjects with coronary artery disease.

BACKGROUND

Little information is available regarding the effects of thiazolidinediones in the absence of diabetes. Further, although postprandial hyperlipemia is a risk factor for cardiovascular diseases, there is limited information about the postprandial effects.

METHODS

Twenty overweight and obese, non-diabetic patients with coronary artery disease were enrolled in a randomized, placebo-controlled, double-blind study. Subjects were on atorvastatin for the duration of the study and received either placebo or pioglitazone (45 mg day(-1)) for 12 weeks and then crossed over to the alternative therapy for an additional 12 weeks. Insulin sensitivity, fasting and postprandial levels of lipid, hemostatic, and inflammatory variables were measured, and endothelial function was assessed.

RESULTS

Insulin sensitivity improved from 0.03 micromol kg(-1) x min pM(-1) on placebo to 0.04 on pioglitazone (P = 0.0002), and there were decreases in fasting levels of factor (F) VII:C (102 +/- 17% to 92 +/- 18%, P = 0.001), FVII:Ag (68 +/- 12% to 60 +/- 14%, P = 0.01) and in von Willebrand factor (VWF) (174 +/- 94% to 142 +/- 69%, P = 0.01). Pioglitazone lowered postprandial levels of FVII:Ag, FVII:C, plasminogen activator inhibitor-1, VWF, and triglycerides, and increased high-density lipoproteins (+9%, P = 0.02).

CONCLUSIONS

Pioglitazone improves insulin sensitivity and favorably modifies fasting and postprandial lipid, hemostatic and inflammatory markers of the metabolic syndrome in overweight and obese non-diabetic patients with coronary artery disease.

A prediction model for chemotherapy-associated thrombocytopenia in cancer patients

8616

Background: Thrombocytopenia (TP) can lead to serious complications, however, little is known about the incidence and risk factors for chemotherapy-associated TP. A prospective, nationwide cohort study was undertaken to better define the impact of TP in cancer treatment. Methods: 2,842 patients with cancer of the breast, lung, colon, ovary or lymphoma initiating a new chemotherapy regimen have been prospectively enrolled at 115 randomly selected US community oncology practices between 2002 and 2005. Risk factors for chemotherapy-associated TP were identified, a multivariate logistic regression model based on pretreatment characteristics was developed, and test performance characteristics were estimated. Results: Over a median of 3 cycles of chemotherapy, minimum recorded platelet counts were: ≥150K in 53% of patients; 100–150K in 26%; 75–100K in 8%; 50–75K in 6% and <50K in 7%. Significant independent predictive factors for platelets <75K include type of cancer (P<.0001), type of chemotherapy including gemcitabine-based (P<.0001), anthracycline-based (P<.0001) and platinum-based (P<.0001) regimens, prior chemotherapy (P<.0001) or surgery (P=.005), age (P=.015), Caucasian ethnicity (P=.022), body surface area (P=.0001), planned relative dose intensity ≥85% (P=.082), diabetes (P=.018), pulmonary disease (P=.011), abnormal baseline platelets (P<.0001), hematocrit (P=0.030), alkaline phosphatase (P=.072) or albumin (P=.017). Model fit was good (Chi-square, P<.0001), R2 = 0.735 and c-statistic = 0.816 [95% CI: 0.792–0.840, P<.0001]. Model test performance characteristics [95% CI] at a ≥20% risk of TP include: sensitivity 56% [51–61]; specificity 88% [87–89]; likelihood ratio positive 4.63 [4.02–5.33]; likelihood ratio negative 0.50 [0.45–0.57]; and diagnostic odds ratio 9.22 [7.23–11.75]. Validation of the model is underway. Conclusions: This prediction model based on pretreatment factors identifies with high specificity patients at risk for clinically important chemotherapy-associated thrombocytopenia early in the treatment course. It may provide a valuable tool for guiding chemotherapy and new supportive care measures.

[Table: see text]

Tissue factor, angiogenesis and thrombosis in pancreatic cancer

4001

Background: Coagulation proteins are commonly activated in pancreatic cancer and are closely linked to regulation of angiogenesis. We investigated tumor cell expression of tissue factor (TF), the prime initiator of coagulation, and its association with parameters of angiogenesis, venous thromboembolism (VTE) and survival. Methods: Tissue cores from a bi-institutional retrospective series of patients consecutively resected between January 1994 and February 2002 and followed for a median period of 16 months were used to build a pancreatic cancer tissue microarray. TF expression was graded semiquantitatively using immunohistochemistry (IHC)(grade 0:negative, grade 1: 1- 33% positive, grade 2: 34- 66% positive and grade 3: > 66% cells positive) in pancreatic intraductal dysplasia (n=5) and resected pancreatic cancer (n=122). Study endpoints included correlation of TF with VEGF expression by IHC, microvessel density (MVD), clinical VTE and survival in resected patients. Patients with history of VTE, on anticoagulation or with inadequate follow-up were excluded from analysis of VTE outcomes (n=33). Results: TF expression was observed in all specimens with intraductal dysplasia and 108 resected pancreatic cancers (89%) but not in uninvolved pancreas. Sixty-six patients (54%) with resected pancreatic cancer were found to have high TF expression (defined as ≥ grade 2, the median score), and 56 patients (46%) had low or no TF expression. Tumors with high TF expression were more likely to also express VEGF (80% versus 27% with low TF expression, p<0.0001). Tumors with high TF expression had a higher median MVD (8 versus 5/tissue core with low TF expression, p=0.01). Resected patients with high TF expression had a VTE rate of 20% compared to 5.5% in patients with low TF expression (p=0.04). Median survival in tumors with high TF was 17.9 months versus 12.6 months in those with low TF (p=0.16). Conclusions: TF expression appears to occur early in pancreatic cancer pathogenesis. This is the first report describing an association of TF expression with VEGF expression, increased MVD and clinical VTE in resected pancreatic cancer, confirming the linkage of thrombosis and angiogenesis. Targeting TF in pancreatic cancer could affect both neoplastic and thrombotic outcomes.

No significant financial relationships to disclose.

Direct Thrombin Inhibitors for Treatment of Heparin Induced Thrombocytopenia, Deep Vein Thrombosis and Atrial Fibrillation

Thrombin is a central enzyme in hemostasis, exerting potent procoagulant effects and activating platelets. Recently, several small molecule direct thrombin inhibitors (DTI's) with important clinical applications have been developed. Both lepirudin and argatroban are effective in treatment of heparin-induced thrombocytopenia resulting in rapid normalization of platelet counts and a reduction in thrombotic events. Because of differences in clearance mechanisms, argatroban is preferable in patients with renal insufficiency and lepirudin if there is hepatic impairment. DTI's have also been evaluated in treatment of venous thromboembolism. Small studies with recombinant hirudin have shown promise. Ximelagatran is a new DTI in late-stage clinical trials with advantages for treatment of venous thromboembolism including oral administration and fixed dosing, making it convenient for long-term treatment. A Phase III trial demonstrated that ximelagatran was superior to placebo for preventing recurrent thrombosis in patients who had undergone six months of standard anticoagulant therapy for venous thromboembolism. Another large trial compared ximelagatran to standard treatment with enoxaparin and warfarin for treatment of symptomatic deep vein thrombosis in a Phase III trial of 2,528 patients. The results showed that ximelagatran administered twice daily was as effective as standard treatment in preventing recurrence with no increase in bleeding complications. Ximelagatran has also been evaluated in two Phase III trials in patients with atrial fibrillation. The primary analysis of both showed that ximelagatran was non-inferior to warfarin for preventing stroke and other embolic events with no increase in bleeding complications. Unexpectedly, elevated serum transaminase levels were observed in 5-10% of patients receiving ximelagatran for over 1 month, and routine monitoring may be necessary. The introduction of DTIs represents an important advance in treatment of heparin-induced thrombocytopenia. The oral direct thrombin inhibitor, ximelagatran, shows promise in providing simplified, effective therapy for venous thromboembolism and atrial fibrillation.

Fibrinogen binding potentiates FGF-2 but not VEGF induced expression of u-PA, u-PAR, and PAI-1 in endothelial cells

Endothelial cell responses at sites of injury occur in a fibrin matrix and are regulated by growth factors including those of the FGF and VEGF families. The pericellular proteolytic balance is important in these responses, and FGF-2 and VEGF up-regulate endothelial cell u-PA, u-PAR and PAI-1. Because both VEGF and FGF-2 bind to fibrinogen, we have examined the capacity of fibrinogen to modulate the up-regulation of these proteins by FGF-2 and VEGF. Confluent cultures of endothelial cells were exposed to FGF-2, VEGF, and fibrinogen or to combinations of growth factors with fibrinogen. Changes in mRNA levels of u-PA, u-PAR and PAI-1 were measured by Northern blot. FGF-2 increased u-PA, u-PAR, and PAI-1 mRNA, but there was a significantly greater induction when fibrinogen was added to FGF-2 at all concentrations. The potentiation by fibrinogen was particularly evident at an FGF-2 concentration of 0.1 ng mL(-1), which resulted in non-significant change in transcript levels by itself, but significantly increased up to 2.6-fold with fibrinogen. VEGF also increased endothelial cell expression of u-PA, u-PAR and PAI-1, but this effect was not potentiated by fibrinogen. Addition of LM609, a monoclonal antibody to alphaVbeta3, significantly inhibited induction of u-PA mRNA and activity by fibrinogen-bound FGF-2 compared to FGF-2. A monoclonal antibody to FGFR1 also inhibited u-PA mRNA expression induced by fibrinogen-bound FGF-2. We conclude that fibrinogen increases the capacity of FGF-2, but not of VEGF, to up-regulate u-PA, u-PAR, and PAI-1 in endothelial cells and that fibrinogen-bound FGF-2 requires alphaVbeta3 binding to up-regulate endothelial cell u-PA.

Effects of lipids and lipid-lowering therapy on hemostatic factors in patients with myocardial infarction

BACKGROUND

The risk of cardiovascular disease (CVD) is associated with specific hemostatic markers and lipid profiles, and evidence indicates that there are associations between lipid profiles and the levels of certain hemostatic factors. The disturbances in hemostasis and the risk of CVD can be ameliorated by lipid-lowering therapy.

OBJECTIVE

We investigated the associations of lipid profiles with factor (F)VIIa, von Willebrand factor (VWF), D-dimer and plasminogen activator inhibitor-1 (PAI-1), and examined whether lipid-lowering statin therapy would affect the levels of these hemostatic markers.

PATIENTS AND METHODS

This cross-sectional study analyzed 1045 postmyocardial infarction patients.

RESULTS

In multivariate regression analyses (without adjusting for clinical covariates) HDL-cholesterol (HDL-C) and HDL size were independent and significant predictors of FVIIa; HDL size was a predictor of VWF; HDL size, HDL-C and LDL size were predictors of D-dimer; and triglyceride and HDL size were predictors of PAI-1. After adjusting for clinical covariates, HDL-C, lipoprotein (Lp)(a), apolipoprotein B (apoB) and warfarin were independent and significant predictors of FVIIa; HDL size, age, diabetes mellitus, insulin, race and warfarin were predictors of VWF; HDL-C, HDL size, LDL size, age, warfarin, hypertension and gender were predictors of D-dimer; and triglyceride, HDL size, body mass index, insulin and hypertension were predictors of PAI-1. Patients on statin therapy had significantly lower levels of D-dimer than those who were not on this therapy.

CONCLUSION

There are significant associations of lipid profiles with hemostatic factors, the directions of which suggest novel pathways by which dyslipidemia may contribute to coronary heart disease.

Low-intensity ultrasound increases endothelial cell nitric oxide synthase activity and nitric oxide synthesis

Low-intensity ultrasound (US) increases tissue perfusion in ischemic muscle through a nitric oxide (NO)-dependent mechanism. We have developed a model to expose endothelial cells to well-characterized acoustic fields in vitro and investigate the physical and biological mechanisms involved. Human umbilical vein endothelial cells (HUVEC) or bovine aortic endothelial cells (BAEC) were grown in tissue culture plates suspended in a temperature-controlled water bath and exposed to US. Exposure to 27 kHz continuous wave US at 0.25 W cm(-2) for 10 min increased HUVEC media NO by 102 +/- 19% (P < 0.05) and BAEC by 117 +/- 23% (P < 0.01). Endothelial cell NO synthase activity increased by 27 +/- 24% in HUVEC and by 32 +/- 16% in BAEC (P < 0.05 for each). The cell response was rapid with a significant increase in NO synthesis by 10 s and a maximum increase after exposure for 1 min. By 30 min post-exposure NO synthesis declined to baseline, indicating that the response was transient. Unexpectedly, pulsing at a 10% duty cycle resulted in a 46% increase in NO synthesis over the response seen with continuous wave US, resulting in an increase of 147 +/- 18%. Cells responded to very low intensity US, with a significant increase at 0.075 W cm(-2) (P < 0.01) and a maximum response at 0.125 W cm(-2). US caused minor reversible changes in cell morphology but did not alter proliferative capacity, indicating absence of injury. We conclude that exposure of endothelial cells to low-intensity, low-frequency US increases NO synthase activity and NO production, which could be used to induce vasodilatation experimentally or therapeutically.

Comparison of ximelagatran, an oral direct thrombin inhibitor, with enoxaparin for the prevention of venous thromboembolism following total hip replacement. A randomized, double-blind study

BACKGROUND

Prophylaxis is recommended following total joint replacement because of the high risk of venous thromboembolism (VTE). Postoperative low-molecular-weight heparin (LMWH) reduces the incidence of venographically detected deep vein thrombosis (DVT) to about 10-15% in total hip replacement (THR) patients. Ximelagatran is a novel, oral direct thrombin inhibitor that selectively and competitively inhibits both free and clot-bound thrombin. We compared the efficacy and safety of ximelagatran with those of enoxaparin for the prevention of VTE in patients undergoing THR.

METHODS

This was a prospective, randomized, multicenter, double-blind study conducted principally in the USA and Canada. Patients received fixed-dose oral ximelagatran 24 mg bid or subcutaneous enoxaparin 30 mg bid and matched placebo for 7-12 days; both regimens were initiated the morning after surgery. The incidence of VTE (by postoperative day 12) included thrombosis determined by mandatory venography of the leg on which surgery was performed and symptomatic, objectively proven DVT or pulmonary embolism (PE). VTE and bleeding events were interpreted by an independent central adjudication committee for primary analysis.

RESULTS

Of the 1838 patients randomized, 1557 had either adequate venography or symptomatic, proven VTE (efficacy population). Overall rate of venography acceptable for evaluation was 85.4%. Overall rates of total VTE were 7.9% (62 of 782 patients) in the ximelagatran group and 4.6% (36 of 775 patients) in the enoxaparin group, with an absolute difference of 3.3% and a 95% confidence interval for the difference of 0.9% to 5.7%. Proximal DVT and/or PE occurred in 3.6% (28 of 782 patients) in the ximelagatran group and 1.2% (nine of 774 patients) in the enoxaparin group. Major bleeding events were observed in 0.8% (seven of 906) of the ximelagatran-treated patients and in 0.9% (eight of 910) of the enoxaparin-treated patients (P > 0.95). Non-inferiority of ximelagatran 24 mg bid based on a prespecified margin of 5% was not met, resulting in superiority of the enoxaparin regimen.

CONCLUSIONS

Both ximelagatran and enoxaparin decreased the overall rate of VTE compared with that reported historically. However, in this study, enoxaparin 30 mg bid was more effective than ximelagatran 24 mg bid for prevention of VTE in THR. Oral ximelagatran was used without coagulation monitoring, was well tolerated, and had bleeding rates comparable to those of enoxaparin. Further refinement by testing a higher dose of ximelagatran in the patients undergoing THR is warranted.

FGF-2 but not FGF-1 binds fibrin and supports prolonged endothelial cell growth

Endothelial cell viability and growth are dependent on both polypeptide growth factors, and integrin-mediated matrix interactions. We have now examined the ability of fibrin-binding and non-binding growth factors to support long-term endothelial cell growth in the presence or absence of the soluble form. Endothelial cells were cultured on a fibrin surface, with or without FGF-1 or FGF-2, and proliferation was determined by (3)H-thymidine incorporation. Cells cultured on fibrin with no growth factor showed minimal proliferation up to 96 h. In contrast, when FGF-2 was incorporated into fibrin, proliferation was increased 6.5 +/- 0.6-fold, equal to growth on a fibrin surface with FGF-2 continually present in the medium. Thymidine incorporation was similar when cells were cultured on a fibrin surface that had been incubated with FGF-2 and then the growth factor removed (8.6 +/- 0.5-fold). In contrast to results with FGF-2, a surface of fibrin exposed to FGF-1 supported minimal growth, whereas growth was comparable to either FGF-1 or FGF-2 present in the medium. Comparable results were observed when proliferation was quantitated by cell counting at times up to 48 h. Binding studies demonstrated no high-affinity interaction of FGF-1 with fibrinogen or fibrin. We conclude that FGF-2 bound to fibrin supports prolonged endothelial cell growth as well as soluble FGF-2, whereas FGF-1 does not bind to fibrin and can support endothelial cell growth only if continually present in soluble form. Fibrin may serve as a matrix reservoir for FGF-2 to support cell growth at sites of injury or thrombosis.

Plasmic degradation modulates activity of fibrinogen-bound fibroblast growth factor-2

Fibroblast growth factor-2 (FGF-2) binds to fibrin(ogen) with high affinity, and fibrinogen potentiates FGF-2-stimulated proliferation of endothelial cells. Because plasmin degrades fibrin(ogen) physiologically and could liberate growth factor from fibrin deposits or alter its activity, we have now investigated the effect of plasmic degradation on the activity of fibrin(ogen)-bound FGF-2. Fibrinogen with bound FGF-2 was incubated with plasmin, the products characterized by SDS-PAGE, and the proliferative activity determined by (3)H-thymidine incorporation into endothelial cells. Before plasmin exposure, proliferation was increased 3.7 +/- 0.6-fold with fibrinogen-bound FGF-2 compared with medium alone (P < 0.005). Plasmic degradation resulted in progressive decrease in the proliferative capacity, with the 60-min digest showing predominantly fragment D1 and E and (3)H-thymidine uptake of only 1.2 +/- 0.2-fold, significantly less than the activity of an equal concentration of free FGF-2 (P < 0.02). However, further degradation increased activity, and proliferation with a 90-min digest increased to 2.6 +/- 0.5-fold, significantly greater than the 60-min digest (P < 0.02). Plasmic degradation in the presence of 10 mm calcium chloride prevented degradation of D1 to D2 and D3, and the activity did not increase with extended degradation. Immunoprecipitation of the digests with antifibrinogen antibody showed 70 +/- 8% of fibrinogen-bound FGF-2 in the presence of calcium but only 15 +/- 4% in its absence, indicating that cleavage of D1 to D2 and D3 is critical in binding. Fragment D1 and D2, but not D3, bound to a column containing immobilized FGF-2, indicating that a binding site is lost upon degradation to D3. The results demonstrate that plasmic degradation of fibrinogen modulates the activity and binding of FGF-2 that involves a site near the carboxyl terminus of the gamma chain.

Protein S declines during winter respiratory infections

There is an increase in cardiovascular and cerebrovascular morbidity and mortality in the older adult population during the winter that could be related to prothrombotic changes caused by seasonal effects or acute respiratory tract infections. Therefore, a prospective cohort study was conducted to assess the effect of acute winter respiratory infection on hemostatic parameters including complement 4b-binding protein (C4-BP), functional protein S, total protein S, free protein S, and the inflammatory marker, interleukin-6 (IL-6), in younger and older adults. The changes in the levels of hemostatic and inflammatory markers during winter respiratory infections in the younger and older adults were compared with matched, non-infected controls. In younger and older adults (combined), total protein S increased from 83% [95% confidence interval (CI); 77-88] to 98% (95% CI; 91-106, P < 0.001) while free protein S decreased from 100% (95% CI; 95-105) to 70% (95% CI; 66-75, P < 0.001). There were no significant changes in C4-BP (P = 0.622), functional protein S (P = 0.061) or IL-6 (P = 0.651) from baseline. In a multivariate analysis, only total protein S and free protein S showed significant association with seasonal change after adjusting for the effect of infection. The estimated effect of season on total protein S was 15 +/- 4%, P < 0.001 and on free protein S was -27 +/- 3%, P < 0.001. After adjusting for seasonal effect, only functional protein S showed a significant association with infection, with the estimated effect of -17 +/- 5%, P < 0.001. The results in the younger and older adults were similar to those in the combined groups. Seasonal and infection-related changes in hemostatic parameters including an increase in fibrinogen and a decrease in free protein S, observed in this study, may contribute to thrombotic risk and excess vascular disease morbidity and mortality in older populations in the winter season.

Neuropathologic findings in a Guillain-Barré patient with strokes after IVIg therapy

Strokes have been rarely associated with immunoglobulin G (IVIg) therapy. A 70-year-old woman with stable polycythemia vera developed Guillain-Barré syndrome and received IVIg, 8 days following which she became comatose due to bilaterally symmetric cerebral infarcts. Autopsy showed intravascular aggregates of fibrin-IgG but also platelets and a necrotizing microangiopathy in the infarcts.

Ultrasound and thrombolysis

Thrombolytic therapy and mechanical interventions are frequently used in the treatment of both arterial and venous thrombotic disease. Limitations to these approaches include failure to achieve reperfusion and complications including bleeding and vessel wall damage. Increasing evidence indicates that the use of ultrasound offers potential therapeutic advantages. This review considers two distinct approaches which include the use of high intensity ultrasound to mechanically fragment clots and also the use of low intensity ultrasound to augment enzymatic fibrinolysis. High intensity ultrasound can be delivered via catheter or transcutaneously to disrupt clots in vitro or in animal models into small fragments. Initial clinical studies demonstrate potential clinical value in peripheral and coronary arterial thrombosis and occluded saphenous vein bypass grafts treated with the catheter approach. Studies in vitro indicate that low intensity ultrasound accelerates enzymatic thrombolysis through non-thermal mechanisms involving improvement in drug transport. The effect is larger at low frequencies, which also offer better tissue penetration and less heating. The ability to accelerate thrombolysis has been confirmed in animal models demonstrating markedly increased reperfusion and minimal toxicity. The use of ultrasound to mechanically disrupt occlusive thrombi or to accelerate enzymatic thrombolysis offers a new approach to treating occlusive thrombotic disease.

Fibrin degradation products, fibrin monomer and soluble fibrin in disseminated intravascular coagulation

Disseminated intravascular coagulation (DIC) is characterized by activation of hemostasis and fibrinolysis resulting in the formation of thrombin and plasmin, and the characteristic effects of these enzymes on plasma fibrinogen can be useful in diagnosis. Thrombin cleaves fibrinopeptides from fibrinogen, forming fibrin monomer that rapidly polymerizes to form a clot. Small amounts can circulate in plasma as "soluble fibrin," which may have a complex composition and include fibrinogen and a variable amount of cross-linking. Plasmic degradation of cross-linked fibrin forms a heterogeneous group of degradation products reactive in assays for D-dimer, and their levels provide a measure of the amount of fibrin formation and lysis. Caution should be exercised in comparing quantitative results using different assays because of problems with standardization and variable reactivity with different molecular forms. Marked elevations of fibrin(ogen) degradation products are a constant finding in experimental animal models of DIC. In human models of DIC resulting from endotoxin infusion, D-dimer is elevated early and high levels persist, reflecting lysis of microvascular fibrin deposits. Elevated levels of D-dimer and soluble fibrin are very sensitive for the diagnosis of DIC, and a normal level has a high negative predictive value. Serial monitoring of soluble fibrin or D-dimer assays may be of value in evaluating the response to therapy and possibly in identifying at-risk patients.

Comparison of the oral direct thrombin inhibitor ximelagatran with enoxaparin as prophylaxis against venous thromboembolism after total knee replacement: a phase 2 dose-finding study

BACKGROUND

Up to one third of patients who undergo total knee replacement develop deep vein thrombosis after surgery despite receiving low-molecular-weight heparin prophylaxis. Ximelagatran is a novel direct inhibitor of free and clot-bound thrombin.

METHODS

We performed a randomized, parallel, dose-finding study of 600 adults undergoing elective total knee replacement at 68 North American hospitals to determine the optimum dose of ximelagatran to use as prophylaxis against venous thromboembolism after total knee replacement. Patients received either ximelagatran twice daily by mouth in blinded fixed doses of 8, 12, 18, or 24 mg or open-label enoxaparin sodium, 30 mg, subcutaneously twice daily, starting 12 to 24 hours after surgery and continuing for 6 to 12 days. We measured the 6- to 12-day cumulative incidence of symptomatic or venographic deep vein thrombosis, symptomatic pulmonary embolism, and bleeding.

RESULTS

A total of 594 patients received at least 1 dose of the study drug; 443 patients were evaluable for efficacy. Rates of overall venous thromboembolism (and proximal deep vein thrombosis or pulmonary embolism) for the 8-, 12-, 18-, and 24-mg doses of ximelagatran were 27% (6.6%), 19.8% (2.0%), 28.7% (5.8%), and 15.8% (3.2%), respectively. Rates of overall venous thromboembolism (22.7%) and proximal deep vein thrombosis or pulmonary embolism (3.1%) for enoxaparin did not differ significantly compared with 24-mg ximelagatran (overall difference, -6.9%; 95% confidence interval, -18.0% to 4.2%; P=.3). There was no major bleeding with administration of 24 mg of ximelagatran twice daily.

CONCLUSION

Fixed-dose, unmonitored ximelagatran, 24 mg twice daily, given after surgery appears to be safe and effective oral prophylaxis against venous thromboembolism after total knee replacement.

Timing of initial administration of low-molecular-weight heparin prophylaxis against deep vein thrombosis in patients following elective hip arthroplasty: a systematic review

BACKGROUND

Perioperative and postoperative venous thrombosis are common in patients undergoing elective hip surgery. Prophylactic regimens include subcutaneous low-molecular-weight heparin 12 hours or more before or after surgery and oral anticoagulants. Recent clinical trials suggest that low-molecular-weight heparin initiated in closer proximity to surgery is more effective than the present clinical practice. We performed a systematic review of the literature to assess the efficacy and safety of low-molecular-weight heparin administered at different times in relation to surgery vs oral anticoagulant prophylaxis.

METHODS

Reviewers (A.F.M. and S.M.M.) identified studies by searching MEDLINE, reviewing references from retrieved articles, scanning abstracts from conference proceedings, and contacting investigators and pharmaceutical companies. Randomized trials comparing low-molecular-weight heparin administered at different times relative to surgery with oral anticoagulants in patients undergoing elective hip arthroplasty, evaluated using contrast phlebography, were selected. Two reviewers (A.F.M. and S.M.M.) extracted data independently.

RESULTS

The literature review identified 4 randomized trials meeting predefined inclusion criteria. The results indicate that low-molecular-weight heparin initiated in close proximity to surgery resulted in absolute risk reductions of 11% to 13% for deep vein thrombosis, corresponding to relative risk reductions of 43% to 55% compared with oral anticoagulants. Low-molecular-weight heparin initiated 12 hours before surgery or 12 to 24 hours postoperatively was not more effective than oral anticoagulants. Low-molecular-weight heparin initiated postoperatively in close proximity to surgery at half the usual dose was not associated with a clinically or statistically significant increase in major bleeding rates (P =.16).

CONCLUSIONS

The timing of initiating low-molecular-weight heparin significantly influences antithrombotic effectiveness. The practice of delayed initiation of low-molecular-weight heparin prophylaxis results in suboptimal antithrombotic effectiveness without a substantive safety advantage.

Posttransfusion purpura secondary to an alloantibody reactive with HPA-5a (Br(b))

BACKGROUND

Posttransfusion purpura (PTP) is characterized by severe thrombocytopenia following blood transfusion that results from alloimmunization to platelet-specific alloantigens. Most cases involve antibodies against HPA-1a in homozygous HPA-1b persons.

CASE REPORT

A patient developed PTP after cardiopulmonary bypass associated with a platelet-specific antibody with strong reactivity against HPA-5a (Br(b)). Geno-typing confirmed that the patient was homozygous for HPA-5b.

CONCLUSION

This is the first well-documented occurrence of PTP associated with isolated allosensitization to HPA-5a or Br(b). The case highlights the importance of maintaining a high level of suspicion for PTP in the appropriate clinical setting, even in an atypical patient.

Ultrasound-enhanced thrombolysis

Problems with current thrombolytic therapy include slow and incomplete thrombolysis and frequent bleeding complications. Increasing evidence from in vitro, animal, and initial patient studies indicates that application of ultrasound as an adjunct to thrombolytic therapy offers unique potential to improve effectiveness and decrease bleeding complications. Numerous studies in vitro demonstrate that low intensity ultrasound increases enzymatic fibrinolysis through mechanisms that include improving drug transport, reversibly altering fibrin structure, and increasing tPA binding to fibrin. These observations have been confirmed in animal models that demonstrated that ultrasound delivered transcutaneously or with an endovascular catheter accelerates thrombolysis in models of venous, arterial, and small vessel thrombosis. Ultrasound delivered at higher intensities using either an endovascular vibrating wire or transcutaneously in conjunction with stabilized microbubbles can cause mechanical fragmentation of thrombus without administration of plasminogen activator. Recent studies indicate that ultrasound at lower frequencies in the range of 20-40 kHz has a greater effect on thrombolysis with improved tissue penetration and less heating. These studies form the basis for clinical trials investigating the potential of ultrasound as an adjunct to improve thrombolytic therapy.

Response of C-reactive protein and serum amyloid A to influenza A infection in older adults

Influenza epidemics are associated with significant morbidity and mortality in the elderly, with a substantial proportion of deaths due to cardiovascular events. Elevations of acute-phase proteins have been associated with an increased risk of atherosclerotic events. Therefore, serum amyloid A (SAA) and C-reactive protein (CRP) were measured during influenza illness and 4 weeks later in 7 young persons, 15 elderly outpatients, and 36 hospitalized adults. Striking elevations were seen in mean acute SAA and CRP levels in all groups, but hospitalized patients had the highest levels (SAA, 503 vs. 310 microg/mL [P=.006]; CRP, 120 vs. 34 microg/mL [P<.001]). The presence of dyspnea, wheezing, and fever was also associated with high CRP levels. Influenza infection is associated with significant elevations of SAA and CRP levels in elderly patients, especially those who require hospitalization. It is possible that direct effects of CRP may exacerbate preexisting atherosclerotic lesions and may help explain cardiovascular events associated with acute influenza.

Prothrombotic changes in hemostatic parameters and C-reactive protein in the elderly with winter acute respiratory tract infections

Mortality rates attributable to cerebrovascular and ischemic heart disease increase among older adults during the winter. Prothrombotic changes in the hemostatic system related to seasonal factors, such as ambient temperature changes, and winter acute respiratory tract infections, may contribute to this excess seasonal mortality. A prospective nested case-control study was conducted to assess the impact of winter acute respiratory tract infections on fibrinogen, factor VII, factor VIIa, D-dimer, prothrombin fragment 1.2, PAI-1, soluble P-selectin and C-reactive protein (CRP) in older adults. The change in laboratory parameters from baseline (fall) to the time of infection in both middle-aged and elderly individuals was compared with matched non-infected controls. In older adult participants with winter acute respiratory tract infections, significant increases occurred in fibrinogen and C-reactive protein, but not in any other markers. The mean fibrinogen increased 1.52 g/L (38%) and the mean CRP increased 37 mg/L (370%) over baseline (both p <0.001). In a multivariate analysis, both infection and season were associated with the increase in fibrinogen, but only infection was associated with the CRP increase. Old age magnified the increase in CRP but not in fibrinogen. Winter acute respiratory tract infections induce an exaggerated inflammatory response in older adults. The associated increase in fibrinogen, an independent risk factor for ischemic heart disease, may be partly responsible for the excess winter vascular mortality.

Vascular endothelial growth factor binds to fibrinogen and fibrin and stimulates endothelial cell proliferation

Vascular development and response to injury are regulated by several cytokines and growth factors including the members of the fibroblast growth factor and vascular endothelial cell growth factor (VEGF) families. Fibrinogen and fibrin are also important in these processes and affect many endothelial cell properties. Possible specific interactions between VEGF and fibrinogen that could play a role in coordinating vascular responses to injury are investigated. Binding studies using the 165 amino acid form of VEGF immobilized on Sepharose beads and soluble iodine 125 ((125)I)-labeled fibrinogen demonstrated saturable and specific binding. Scatchard analysis indicated 2 classes of binding sites with dissociation constants (K(d)s) of 5.9 and 462 nmol/L. The maximum molar binding ratio of VEGF:fibrinogen was 3.8:1. Further studies characterized binding to fibrin using (125)I-labeled VEGF- and Sepharose-immobilized fibrin monomer. These also demonstrated specific and saturable binding with 2 classes of sites having K(d)s of 0.13 and 97 nmol/L and a molar binding ratio of 3.6:1. Binding to polymerized fibrin demonstrated one binding site with a K(d) of 9.3 nmol/L. Binding of VEGF to fibrin(ogen) was independent of FGF-2, indicating that there are distinct binding sites for each angiogenic peptide. VEGF bound to soluble fibrinogen in medium and to surface immobilized fibrinogen or fibrin retained its capacity to support endothelial cell proliferation. VEGF binds specifically and saturably to fibrinogen and fibrin with high affinity, and this may affect the localization and activity of VEGF at sites of tissue injury. (Blood. 2000;96:3772-3778)

Anticardiolipin antibodies and recurrent coronary events: a prospective study of 1150 patients. Thrombogenic Factors, and Recurrent Coronary Events Investigators

BACKGROUND

The association of anticardiolipin (aCL) antibodies with coronary artery disease has been shown in several studies but remains controversial. We evaluated the association of aCL and anti-beta(2)-glycoprotein I (abeta(2)GPI) antibodies with the risk of recurrent cardiac events in postinfarction patients.

METHODS AND RESULTS

The study population consisted of 1150 patients with acute myocardial infarction. Levels of IgG and IgM aCL and abeta(2)GPI antibodies were determined on sera collected before hospital discharge. There were 131 recurrent cardiac events (nonfatal myocardial infarctions or cardiac deaths) over a mean follow-up period of 24.6 months. Patients with elevated IgG aCL antibodies had a higher event rate than patients with low levels (P:=0.05). Multivariate Cox analysis after adjustment for relevant clinical covariates showed that elevated levels of IgG aCL (hazard ratio=1. 63; P:=0.01) and low levels of IgM aCL (hazard ratio of 1.76; P:=0. 02) antibodies contribute independent risks for recurrent cardiac events. Patients with elevated IgG aCL and low IgM aCL antibody levels had a 3-fold higher risk of recurrent cardiac events than patients with low IgG aCL and elevated IgM aCL antibody levels (P:<0. 001). There was no significant association of the abeta(2)GPI antibodies with recurrent cardiac events.

CONCLUSIONS

In postinfarction patients, elevated IgG aCL and low IgM aCL antibodies are independent risk factors for recurrent cardiac events. Patients with both elevated IgG aCL and low IgM aCL antibodies have the highest risk. These findings shed additional light on the mechanistic role of aCL antibodies in coronary artery disease in patients without autoimmune diseases.

Cavitational mechanisms in ultrasound-accelerated thrombolysis at 1 MHz

Inertial cavitation is hypothesized to be a mechanism by which ultrasound (US) accelerates the dissolution of human blood clots when the clot is exposed to a thrombolytic agent such as tissue plasminogen activator (t-PA). To test this hypothesis, radiolabeled fibrin clots were exposed or sham-exposed in vitro to 1 MHz c.w. US in a rotating sample holder immersed in a water-filled tank at 37 degrees C. Percent clot dissolution after 60 min of US exposure was assessed by removing the samples, centrifuging, and measuring the radioactivity of the supernatant fluid relative to the pelletized material. To suppress acoustic cavitation, the exposure tank was contained within a hyperbaric chamber capable of pneumatic pressurization to 10 atmospheres (gauge). Various combinations of static pressure (0, 2, 5, and 7.5 atm gauge), US (0 or 4 W/cm(2) SATA), and t-PA (0 or 10 microg/mL) were employed, showing statistically significant reductions in thrombolytic activity as static pressure increased. To gain further insight, an active cavitation detection scheme was employed in which 1-micros duration tonebursts of 20-MHz US (< 1 kPa peak negative pressure, 1 Hz PRF) were used to interrogate clots subjected to US and static pressure. Results of this cavitation detection scheme showed that scattering from within the clot and broadband acoustic emissions that were both present during insonification were significantly reduced with application of static pressure. However, only about half of the acceleration of thrombolysis due to US could be removed by static pressure, suggesting the possibility of other mechanisms in addition to inertial cavitation.

Effect of 40-kHz ultrasound on acute thrombotic ischemia in a rabbit femoral artery thrombosis model: enhancement of thrombolysis and improvement in capillary muscle perfusion

BACKGROUND

We have shown previously that 40-kHz ultrasound (US) at low intensity accelerates fibrinolysis in vitro with little heating and good tissue penetration. These studies have now been extended to examine the effects of 40-kHz US on thrombolysis and tissue perfusion in a rabbit model.

METHODS AND RESULTS

Treatment was administered with either US alone at 0.75 W/cm(2), streptokinase alone, or the combination of US and streptokinase. US or streptokinase resulted in minimal thrombolysis, but reperfusion was nearly complete with the combination after 120 minutes. US also reversed the ischemia in nonperfused muscle in the absence of arterial flow. Tissue perfusion decreased after thrombosis from 13. 7+/-0.2 to 6.6+/-0.8 U and then declined further to 4.5+/-0.4 U after 240 minutes. US improved perfusion to 10.6+/-0.5 and 12.1+/-0. 5 U after 30 and 60 minutes, respectively. This effect was reversible and declined to pretreatment values after US was discontinued. Similarly, tissue pH declined from normal to 7.05+/-0. 02 after thrombosis, but US improved pH to 7.34+/-0.03 after 60 minutes. US-induced improvement in tissue perfusion and pH also occurred after femoral artery ligation, indicating that thrombolysis did not cause these effects.

CONCLUSIONS

40-kHz US at low intensity markedly accelerates fibrinolysis and also improves tissue perfusion and reverses acidosis, effects that would be beneficial in treatment of acute thrombosis.

Fibrinogen and fibrin protect fibroblast growth factor-2 from proteolytic degradation

We have recently reported that fibrinogen and fibrin bind to fibroblast growth factor-2 (FGF-2) and potentiate its ability to stimulate proliferation of endothelial cells. In the present report, we have investigated the potential of fibrinogen and fibrin to protect FGF-2 from proteolytic degradation. FGF-2 was incubated with trypsin or chymotrypsin in the presence or absence of fibrinogen or fibrin and proteolysis of FGF-2 was assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting. In the absence of fibrinogen there was progressive tryptic degradation of FGF-2, but in the presence of fibrinogen, FGF-2 was completely protected from trypsin with no evidence of degradation. The degree of protection was maximum at a molar ratio of FGF-2 to fibrinogen 1:2. Fibrinogen afforded similar protection from degradation by chymotrypsin. Polymerized fibrin provided partial protection of FGF-2 from tryptic degradation, with intact FGF-2 present for up to 360 min. Fibrin provided nearly complete protection from chymotrypsin. These observations indicate that binding of FGF-2 to fibrinogen or fibrin provides protection from proteolytic degradation, and this may modulate its cell proliferative activity.

Reactivity of soluble fibrin assays with plasmic degradation products of fibrin and in patients receiving fibrinolytic therapy

The ability to identify the products of thrombin and plasmin action on fibrinogen is important in patients with thrombotic and fibrinolytic disorders. New assays have been developed for "soluble fibrin" which represents soluble derivatives other than fibrinopeptides formed from fibrinogen by thrombin. These assays are either immunological, using antibodies for fibrin-specific neoepitopes, or functional and based on the cofactor activity of soluble fibrin in the tissue plasminogen activator (t-PA)-mediated conversion of plasminogen to plasmin. As plasmic derivations of fibrin share structural features with soluble fibrin, they may be reactive with assays for soluble fibrin. Therefore, we prepared plasmic digests of fibrin and determined the degree of reactivity with four soluble fibrin assays. Three assays used Mabs directed toward the fibrin-specific neoepitopes at alpha17-23 (A), gamma312-324 (B) and alpha17-78 (D). A fourth (C) was based on t-PA co-factor activity. Tests A and C demonstrated marked crossreactivity with fibrin degradation products, and digests containing the largest derivatives showed greatest reactivity. Plasmic derivatives of crosslinked fibrin had greater reactivity than those of non-crosslinked fibrin. Tests B and D demonstrated minimal reactivity with plasmic derivatives of crosslinked or of non-crosslinked fibrin. Samples from patients with lower limb peripheral arterial occlusion were assayed for soluble fibrin, D-dimer and fibrinogen at presentation and eight hours after thrombolytic therapy. Variable results were seen at presentation with elevations in 13, 1, 0 and 4 of 19 patients using Tests A, B, C and D, respectively. After fibrinolytic therapy, marked increases in soluble fibrin levels were observed up to 600-fold above normal. A strong correlation between baseline levels was observed with Test B and Test D, which showed the least cross-reactivity with plasmic derivations. After thrombolytic therapy there were either weak or no correlations among the different assays. The results demonstrate that assays for soluble fibrin may react with plasmic derivatives of fibrin and this must be considered in interpreting clinical results.

Thrombolytic therapy for arterial thrombosis

The major development in the field of intra-arterial thrombolytic therapy over the past year was the publication of the phase II results of the Thrombolysis or Peripheral Arterial Surgery study, which compared the safety and efficacy of catheter-directed thrombolysis and surgery as the initial treatment of acute arterial occlusion. The results are consistent with those of the prior two studies, showing little or no difference between surgery and thrombolysis in the most important endpoints of survival and amputation rate. Patients receiving thrombolysis needed fewer interventions, but this benefit was balanced by increased bleeding complications. Additional studies have, therefore, been aimed at identifying subsets of patients with acute arterial occlusion who are most likely to benefit from thrombolysis. These studies have refined the selection criteria for use of thrombolytic therapy over the past year. In addition, studies have been published evaluating new drug doses and regimens aimed at broadening the scope of thrombolytic therapy in patients with acute arterial occlusion.