Heit, John A.

Abstract Abstract 491 Introduction: Chronically-anticoagulated patients with active cancer (Ca) often require temporary interruption of warfarin for an invasive diagnostic or therapeutic procedure. While such patients may be at increased risk for periprocedural thromboembolism and bleeding, there are virtually no estimates of these outcomes among Ca patients or the most appropriate periprocedural anticoagulation management. The aims of this study were to estimate rates of these outcomes among Ca patients and to test active cancer and “bridging” low molecular weight heparin (LMWH) as potential predictors of these outcomes. Patients and Methods: In a retrospective cohort study, all chronically-anticoagulated patients referred to the Mayo Clinic Thrombophilia Center for periprocedural anticoagulation management over the 11-year period, 1997-2007, were followed forward in time for the outcomes of venous and arterial thromboembolism (VTE; ATE), major bleeding and vital status within 3 months of consultation. Warfarin was stopped 4-5 days prior to the procedure and patients received bridging LMWH according to the estimated risk of thromboembolism and bleeding. All outcome events were centrally adjudicated using pre specified criteria. Results: The total cohort (n=2517) included 500 patients with Ca. Chronic anticoagulation indications included prior VTE (n=1033), mechanical heart valve (n=669), atrial fibrillation (n=530) and other (mainly vascular bypass; n=285). 65% and 64% of patients with and without Ca received bridging LMWH, respectively. Prior VTE was more common among Ca patients compared to those without CA, both in the bridged (56% vs 37%; p<0.001) and the non-bridged (48% vs 39%; p<0.05) groups. The 3 month rate for the composite of VTE, ATE or bleeding was higher among Ca patients compared to patients without Ca (5% vs 2%; p=0.004) due to higher post procedure rates of VTE (1% vs 0.2%; p<0.001) and major bleeding (4% vs 1.7%; p=0.009); the post procedure ATE rates were low in both groups (0.40% vs 0.45%). For the entire cohort, patients receiving bridging LMWH had a significantly higher rate of post procedure bleeding (5% vs 1%; p<0.05). Finally, there were significantly more deaths in Ca patients compared to non-Ca patients (5% vs. 1%; p<0.001). Conclusions: The three-month rates of VTE, major bleeding and death among patients with Ca in whom anticoagulation is temporarily interrupted for an invasive procedure is significantly higher than in patients without Ca, especially the major bleeding rate. Use of heparin increases this rate even farther, suggesting that bridging should be used with caution in patients with active cancer. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 2305 Background. Recurrent venous thromboembolism (VTE) occurs in ∼30% of patients with spontaneous VTE after completion of a standard course of anticoagulant therapy. D-dimer levels and selected clinical parameters have been used to identify patients at low risk for recurrent VTE, who may safely discontinue antithrombotic therapy. We have used gene expression profiles to distinguish patients with a single VTE from patients with recurrent VTE. The purpose of this study was to extend this initial report and identify unique gene expression patterns from whole blood that correlate with different risk profiles for VTE recurrence. Methods. Patients with ≥1 prior VTE, with the first event occurring at age 18 years or older and >3 months from the most recent event were recruited for this study. Patients were allocated into 4 groups: (1) ‘low-risk’ patients had sustained ≥1 provoked VTE; (2) ‘moderate-risk’ patients had sustained 1 unprovoked VTE (with or without provoked VTE); (3) ‘high-risk’ patients had sustained ≥2 unprovoked VTE and had no evidence for antiphospholipid antibodies; and (4) antiphospholipid syndrome (APS) patients met established consensus criteria for APS. A similar number of individuals with no prior history of VTE were enrolled as a control population. Citrated plasma, serum and PAXgene RNA tubes were collected, processed and stored at −80°C until shipped to the CDC for analysis. Antiphospholipid testing was performed on all participants to confirm correct group distribution. Total RNA was isolated from whole blood drawn into PAXgene tubes. Following sample labeling and normalization, cRNA samples were hybridized to Illumina HT-12 Beadchips to assay whole genome gene expression with over 47,000 probes against human transcripts. Two hundred and twenty six unique samples passed initial quality control measures. Quality assessment of raw data was done using GenomeStudio. The raw data files were converted to a text file using the IlluminaExpression FileCreator in GenePattern and then log transformed, normalized and median-centered using Cluster. Both unsupervised (hierarchical clustering using Cluster) and supervised analyses (SAM) were used to identify genes that were differentially expressed between the groups. GATHER was used to help understand the biological processes and gene ontology of the gene lists generated by Cluster and SAM. Results. A total of 226 participants were enrolled into the study. Characteristics of the patient groups are summarized in the Table. Demographically, the groups were similar except that patients in the high-risk group tended to be older and were more likely male. The number of events per patient, and the proportion on anticoagulant therapy, increased with the risk group. Antiphospholipid antibodies were detected in several patients in each of the 3 non-APS VTE patient groups, but in most cases this was a single test positive; antiphospholipid antibodies were present in the majority of patients with APS, typically with more than one test positive (37 of 45 with complete testing, 82%). Preliminary analysis of the gene expression profiles using an unsupervised clustering by gene on the high-risk and low-risk groups identified multiple genes that distinguished the two groups, including 18 immune response genes identified by GATHER. These two patient groups were also distinguished by SAM analysis, and multiple genes in the MAPK signaling pathway that separated the two groups were identified by the KEGG pathways in GATHER. Additional analyses are being performed on all of the groups. Conclusions. Whole blood gene expression profiling can be used to develop profiles that distinguish patients with VTE who differ based on their risk of recurrent events. Individual genes identified in these profiles may provide biological insights into the molecular basis for recurrent VTE. Disclosures: Heit: Daiichi Sankyo: Honoraria; Ortho-McNeil Janssen: Honoraria; Covidien: Honoraria. Manco-Johnson:Octapharma AG: Consultancy; Bayer: Research Funding.

Abstract Abstract 2295 Background: While interaction between Factor V Leiden and other VTE risk exposures compound VTE risk, whether other gene-environment interactions are associated with VTE is largely unknown. Objective: To test novel gene-environment interactions for an association with VTE. Methods: Genome-wide scan (Illumina 660Q [557,112 SNPs]) and candidate gene (12,551 SNPs in 764 genes within the anticoagulant, procoagulant, fibrinolytic and innate immunity pathways) genotypes from 1270 non-Hispanic adults of European ancestry with objectively-diagnosed VTE (cases; no cancer, venous catheter or antiphospholipid antibodies) and 1302 controls (frequency-matched on case age, gender, race, MI/stroke status) were merged and imputed to 2.5 million SNPs with MACH using HapMap Phase 2 (60 CEU). We tested pairwise interactions between these SNPS and each of 7 exposures (“stress” [defined as ever hospitalized, ever surgery, ever trauma, ever transfemoral procedure or ever leg paresis], ever surgery, ever neurosurgery, ever orthopedic surgery; and among women, ever pregnant, ≥3 pregnancies and ever oral contraceptives/hormone therapy), adjusted for age, gender, MI/stroke status and state of residence, using logistic regression. Results: The mean ± standard deviation case and control ages were 54.4 ± 16.2 and 55.6 ± 15.8 years, respectively and 51% were female. Among the 7 models, a significant interaction was found between stress and A2BP1 (rs735919, OR=0.2, p=2.8E-07), ever surgery and ABCG8 (rs6709904, OR=0.27, p=2.1E-07), orthopedic surgery and SLC24A3 (rs6081599, OR=0.53, p=2.8E-07), neurosurgery and TBC1D4 (rs17064485, OR=8.5, p=3.5E-07), every pregnant and MICALCL (rs11022321, OR=0.17, p=8.3E-07), >3 pregnancies and KLRB1 (rs2536929, OR=0.31, p=1.1E-07) and ever oral contraceptives/hormone therapy and LINGO2 (rs10969259, OR=2.02, p=4.9E-07). A2BP1 plays a role in RBC shape and size, ABCG8 is associated with severe hypercholesterolemia, SLC24A3 is important for intracellular calcium homeostasis, TBC1D4 participates in cell signaling in CD4+/CD45RO+ memory T-cells, MICALCL is an extracellular signal-regulated kinase 2-binding protein, KLRB1 regulates natural killer cell function, and LINGO2 encodes a leucine-rich repeat signaling protein. Our observed interaction of VTE risk factors with these genes to compound the risk of VTE requires replication in future studies. If confirmed, functional studies will be important to determine the roles of these gene products in the causal pathway to VTE. Conclusion: VTE risk factors and SNPs within several novel genes may interact to compound the risk of VTE. Disclosures: Heit: Daiichi Sankyo: Consultancy, Honoraria.

Abstract Abstract 2273 Background: Continuous flow left ventricular assist device (CF-LVAD) recipients have high tendency of post-surgical gastrointestinal (GI) bleeding. We previously described the loss of high molecular weight VWF multimers (HMWM), due to either an accelerated clearance or enhanced cleavage of the HMWM, in most CF-LVAD recipients (Ann Thorac Surg. 90:1263–9). However, besides the tedious plasma VWF multimer analysis, neither VWF ristocetin cofactor nor collagen binding activity assay provides sufficient sensitivity for detecting such an acquired VWF abnormality (AVWA). In this study, we examined a new automated latex particle-enhanced immunoturbidimetric VWF activity assay (VWF:Lx) for its ability of detecting CF-LVAD-AVWA. We also analyzed the VWF pro-peptide (VWF:pp) to explored the potential mechanism of CF-LVAD-AVWA. Design: As part of an on-going prospective multicenter study, pre- and post-CF-LVAD implantation (7, 30 days and 5–7 months) blood samples were collected from 15 LVAD recipients (median age 52 years; 10 male and 5 female; 2008∼2009). Plasma VWF antigen (VWF:Ag), VWF:Lx activity, VWF:pp/Ag ratios were measured; and plasma VWF multimer analyses were performed on all available plasma samples. Standard statistical analyses were employed. Result: Loss of VWF HMWM was observed in 3 patients prior to CF-LVAD implantation and virtually all patients after surgery. VWF:Ag, VWF:Lx or VWF:pp/Ag ratios of the pre- and post-implantation samples were not significantly different (P> 0.1). However, VWF:Lx/Ag ratios of the post-implantation samples were significantly decreased (P<0.05). At a cut off of 0.8, the VWF:Lx/Ag ratio has a 90% sensitivity and specificity for detecting AVWA. Conclusions: VWF:Lx/Ag ratio has excellent sensitivity and specificity in detecting CF-LVAD-AVWA, and its impact on predicting post-surgical bleeding tendency in CF-LVAD recipients is being investigated. The distinct CF-LVAD-AVWA is most likely caused by enhanced cleavage, rather than clearance, of the HMWM. Disclosures: No relevant conflicts of interest to declare.

Abstract Background Recurrent VTE is frequent and may be fatal; the 2-week case fatality rate after recurrent pulmonary embolism is 11%. However, predictors of VTE recurrence remain uncertain. Objective To identify independent predictors of VTE recurrence, including interim exposures, adjusted for baseline characteristics and treatments. Methods Using the resources of the Rochester Epidemiology Project, we identified all Olmsted County, MN residents with objectively-diagnosed incident VTE over the 13-year period, 1988-2000. All patients surviving ≥1 day were followed forward in time for first objectively-diagnosed VTE recurrence, death or other loss to follow-up, or 12/31/2005, whichever came first. VTE recurrence was defined as new thrombosis of a previously uninvolved venous territory or re-thrombosis of a previously involved venous territory after interim clearing of the incident thrombosis. We estimated the cumulative incidence of VTE recurrence using the Kaplan Meier product limit method, both overall and by incident cancer-associated, idiopathic and non-cancer secondary VTE. For all patients with VTE recurrence, and a random sample of all patients with incident VTE, we reviewed the complete medical records in the community and collected demographic and baseline characteristics, treatments (heparin and warfarin [including proportion of time in therapeutic range], IVC filter, aspirin, statins) and interim VTE risk factor exposures. Using a case-cohort study design with Barlow’s weighting scheme, we tested these demographic, baseline and interim characteristics as potential predictors of VTE recurrence using time-dependent Cox proportional hazards modeling. Results Among 1261 incident VTE patients who survived ≥1 day, 306 developed recurrent VTE over 6,485 person-years of follow-up. The cumulative incidence of VTE recurrence at 30 and 180 days, and 1 and 5 years, were 4.5%, 8.2%, 10.5% and 20.3%, respectively. The five-year cumulative recurrence rates among patients with incident cancer-associated, idiopathic and non-cancer secondary VTE were 42.6%, 26.8% and 18.5%, respectively. Among the random cohort of 415 incident VTE cases, 381 (92%) and 359 (87%) received heparin and warfarin therapy for a median (IQR) 5 (4 - 7) and 119 (63 - 194) days, respectively. From multivariable analysis, interim exposure to trauma, major surgery (general, cardiac or gynecologic), infection, hospitalization for acute medical illness or active cancer after the incident VTE were each associated with an increased hazard of VTE recurrence, while use of warfarin and achievement of a therapeutic APTT within the first day of starting heparin were associated with reduced hazards. Although measures of time in therapeutic range while on heparin or warfarin were associated with a reduced risk of recurrence from univariate analyses, these results were not significant when adjusting for other risk factors. Conclusions Among patients with incident VTE, new exposure to trauma, major surgery, infection, hospitalization for acute medical illness or active cancer are independent predictors of VTE recurrence; patients with such exposures should be considered for VTE prophylaxis. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 480 Background: While interaction between Factor V Leiden and other VTE risk exposures (i.e., oral contraceptives, hormone therapy, pregnancy, cancer, minor trauma) compound VTE risk, whether other gene-environment interactions are associated with VTE is largely unknown. Objective: To test gene-environment interactions for an association with VTE. Methods: Cases (n=1488) were Mayo Clinic European-American patients of non-Hispanic ancestry with objectively-diagnosed VTE in the absence of active cancer, venous catheter or antiphospholipid antibodies. Controls (n=1439) were Mayo Clinic outpatients without VTE who were frequency-matched on case age, gender, race, MI/stroke status and state of residence. We selected candidate genes relevant to the anticoagulant, procoagulant, fibrinolytic and innate immunity pathways, focusing on platelet, monocyte, neutrophil and endothelial cell agonists, receptors, ligands, signal transduction and adhesion molecules, granule contents and effectors; plasma proteases and inhibitors; matrix metalloproteases; inflammatory cytokines and receptors; estrogen, progesterone and androgen receptors; co-regulators and enzymes related to estrogen metabolism; important enzymes for catechol, homocysteine, thromboxane A2 and prostacyclin biosynthesis and metabolism; and HMG CoA reductase. For these genes (n=750), we selected all non-synonymous coding single nucleotide polymorphisms (SNPs) with minor allele frequency ≥0.5%; the remaining SNPs were selected using an LD tagging algorithm (Carlson et al. AJHG 2004); 479 ancestry-informative markers were also included (total n=13,241 SNPs). Leukocyte genomic DNA was genotyped using a custom Illumina Infinium iSelect platform, including appropriate controls. We tested all pairwise interactions between 12,483 SNPs (12296 autosomal, 187 chromosome X) that passed quality control and each of seven exposures (ever “stress”[defined as ever hospitalized, ever surgery, ever trauma, ever transfemoral procedure or ever leg paresis], ever surgery, ever neurosurgery, ever orthopedic surgery; and among women, ever pregnant, ≥3 pregnancies and ever oral contraceptives/hormone therapy), adjusted for age, gender, MI/stroke status and state of residence, using logistic regression. False discovery rates (q-value) were calculated to estimate the expected fraction of false positive associations due to multiple statistical tests. Results: The mean ± SD case and control ages were 55.3 ± 16.4 and 56.5 ± 15.9 years, respectively, and 51% were female. Analysis of ancestry-informative markers revealed no evidence of population stratification. Among the seven models, a significant interaction (q≤0.05) was found between ever surgery and two genes located on chromosome 1: USF1 (rs2516840, OR=2.1, p=2.0E-06; q=0.02), and F11R (rs790055 & rs790056; OR∼2.29, p∼4E-06; q=0.02); the two F11R SNPs are in complete linkage dysequilibrium (LD), and the USF1 SNP is in moderate LD with the F11R SNPs (r2∼0.6). USF1 encodes for upstream transcription factor 1 which regulates many genes involved in lipid and glucose homeostasis. F11R encodes for the platelet F11 receptor (JAM [junctional adhesion molecule], a cell adhesion molecule important for platelet adhesion to cytokine-stimulated endothelial cells. Conclusion: Interaction between surgery and SNPs within USF1 and F11R are associated with significantly increased risks for VTE. These potential associations require confirmation in future replication studies. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 4201 Background: Hereditary AT deficiency is classified as type 1 (quantitative) or type 2 (qualitative). Type 2 deficiency can be further subdivided into type 2a (reactive center loop [RCL]), type 2b (heparin binding domain), and type 2c (pleiotropic) based on functional and molecular AT analysis. Patients with heterozygous type 2b AT deficiency are thought to be at a lower risk for venous thromboembolism (VTE). Objectives: 1) To estimate the frequency of type 2 hereditary AT deficiency. 2) To utilize molecular analysis to accurately sub type patients with type 2 defects. 3) To correlate thrombotic and obstetric complications with AT deficiency sub types. Methods: Apparently unrelated Mayo Clinic AT-deficient patients (n=20) were categorized as type 1 or 2 based on plasma AT activity and antigen, or by molecular analysis for previously reported type 2a-c mutations. Demographic and clinical characteristics were abstracted from patient medical records. The SERPINC1 putative promoter region, all exons (n=7) and splice junctions, and the 3′UTR were PCR amplified from leukocyte genomic DNA, and sequenced with nested forward and reverse primers. For patients without identifiable mutations, multiplex ligand-dependent probe amplification (MLPA) was performed. Results: Out of 20 probands tested 7 (35%) had type 2 AT deficiency. The mean patient age at diagnosis was 36 years (range 18–65) and 5 (69%) were women. There were 2 patients with type 2a, 4 with type 2b (including 1 with a homozygous defect), and 1 with type 2c AT deficiency. The mean plasma AT (range) activity/antigen for these patients were 50% (37-67%)/93% (78-103%) [AT activity & antigen normal range=80-130%]. 6 patients had a previously described mutation, whereas 1 had a novel mutation [S380R] affecting the RCL (Table1). All patients with type 2a and type 2c AT deficiency had unprovoked VTE occurring at a young age. All 3 patients with heterozygous type 2b AT deficiency had no VTE or obstetric complications. One patient with a homozygous type 2b defect (AT Vienna) presented with an unprovoked DVT at age 15. One family with AT Toyama (type 2b AT deficiency) had 5 asymptomatic adult family members with the mutation. Background: Molecular testing is important for an accurate subtyping of patients with type 2 AT deficiency. Type 2 defects have a diverse clinical spectrum. Patients with heterozygous type 2b AT deficiency have a low rate of VTE and obstetric complications. Homozygous type 2b AT deficiency can be compatible with adult life. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 476 Background: The burden of VTE among nursing home (NH) residents is known to be high. Yet very little data exist to help determine which NH residents to target for VTE prophylaxis. The need to characterize VTE risk in this population is especially great because the advanced age and high comorbidity that typify NH residents contribute to increased likelihood of adverse consequences from VTE prophylaxis. To compound the problem, results of our prior univariate analyses of certain factors known to contribute substantially to VTE risk in the general population (e.g., major surgery, medical hospitalization, trauma) suggest that impact of these factors on VTE may be less substantial among NH residents. Objective: To use the longitudinal population-based resources of the Rochester Epidemiology Project (REP) to investigate the contribution of multiple clinical characteristics to risk of VTE among NH residents. Methods: We took advantage of the previous identification of all Olmsted County, MN residents who met research criteria for incident VTE 1988 through 2005 (N=2,332). We then determined which individuals were resident of a local NH at time of VTE symptom onset, regardless of location of symptom onset (i.e., individuals whose VTE occurred in-hospital having been admitted from a NH were considered NH residents). For each such NH VTE case (N=269), we identified 2 same sex Olmsted County residents of similar age and duration of medical history who were also resident of a local NH at the time of the case's VTE event (i.e., index date) (N=538). We reviewed the detailed provider-linked medical records of NH VTE cases and NH non-VTE controls for 3 months before index for information on multiple characteristics identified or hypothesized as contributing to VTE risk in studies of the general population and other at-risk subgroups by our group and others (e.g., patient demographics, body mass index, major surgery, hospitalization for acute medical illness, outpatient surgical procedures, trauma/fracture, leg paresis, active cancer, superficial vein thrombosis, varicose veins, infections, diabetes mellitus, coronary artery disease, congestive heart failure, and multiple medications, including anticoagulants, statins, beta-blockers, ACE inhibitors and angiotensin II receptor antagonists). We tested and estimated the odds ratio associated with each factor using step-wise conditional logistic regression. Variables for which <10 cases or <10 controls exhibited the characteristic were excluded from analysis. Results: The first five variables to enter the model were urinary tract infection, active cancer, superficial vein thrombosis, pneumonia, and leg paresis. The respective odds ratios (95% confidence intervals) with all five in the model were 1.7 (1.2, 2.4); 2.1 (1.3, 3.5); 2.1 (1.3, 3.4); 1.9 (1.3, 2.8); 2.3 (1.3, 4.2); each p value was <0.01. Variables associated with high VTE risk in the general population (i.e., surgery, hospitalization for medical illness, trauma/fracture) were not included in the top five risk factors for NH residents. Conclusions: Infection is a potent VTE risk factor among NH residents. Our study results will help inform development of practice guidelines in the NH and stimulate future research on putative VTE mechanisms. REP data afford limited information on cognitive and physical disability, immobility, and need for NH care. Additional investigations are needed that combine information from clinical and NH assessments. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 4219 Background: Clinical characteristics associated with abdominal vein thrombosis (including hepatic, portal, and mesenteric veins; renal veins; and inferior vena cava [IVC]) overlap with characteristics associated with deep vein thrombosis (DVT) in the legs and pulmonary embolism (PE) but also possess unique attributes. These characteristics may differ between adult and pediatric patient groups. Methods: Using a standardized data-collection form, demographic and baseline characteristics were prospectively collected from consecutive consenting patients enrolled within one of seven Thrombosis and Hemostasis Centers over a seven-year period, August 2003 to June 2010. Patients with intra-abdominal venous thrombosis (defined as abdominal and renal veins, and IVC) were divided into pediatric (age <18 years) and adult (age ≥18 years) groups and compared to patients in the same age ranges with lower extremity DVT and/or PE. RESULTS: As of June 2010, the Patient Registry contained a total of 3105 patients with venous thromboembolism (VTE). A total of 270 patients had intra-abdominal thrombosis (9%) compared to 2276 with lower extremity DVT and/or PE (73%). Of the intra-abdominal clots, pediatric patients were more likely to have IVC thrombus (22 of 42; 52%) than adults (38 of 228; 17%; p<0.0001); conversely, pediatric patients were less likely to have hepatic, portal, and mesenteric thrombosis (n=25; 60%) than adults (n=195; 86%, p<.0001). For adult patients, proportionately more women had abdominal thrombosis (157 of 228; 68.9%) than DVT/PE (1306 of 2140; 61%; p=0.02); in contrast, comparable numbers of female pediatric patients had abdominal thrombosis (20 of 42; 47.6%) and DVT/PE (68 of 136; 50%). The mean age for patients having abdominal thrombosis was lower than patients having DVT/PE for both adults (38.3 vs 43.0 yrs; p<0.0001) and pediatric patients (9.0 vs 11.9 yrs; p=0.014). Similarly, the mean body mass index was lower for patients having abdominal thrombosis than patients having DVT/PE for both adults (28.1 vs 30.8; p<0.0001) and pediatric patients (21.5 vs. 24.7; p=0.05). There were no relationships with race, ethnicity, or inherited thrombophilic disorders. In adults, autoimmune conditions (21.9 vs 13.6; p=0.0007) and recent surgery (14.0 vs 9.2; p=0.02) were more common in patients with abdominal thrombosis, whereas, hyperlipidemia was more frequent in patients with DVT/PE (8.3 vs 13.2; p=0.04). None of these relationships were seen in the pediatric patients, but trauma was more frequently seen in pediatric patients with DVT/PE than abdominal thrombosis. Sixty-one adult (26.8%) and 6 pediatric patients (14.3%) had another VTE elsewhere, with most occurring after the initial event (21 DVT and 7 PE). Similar proportions of adult and pediatric patients had arterial thromboembolic events for both abdominal thrombosis and DVT/PE. CONCLUSIONS: Adult patients with abdominal thrombosis are more likely female, have hepatic, portal and/or mesenteric vein thrombosis, and common co-morbid conditions include recent surgery and autoimmune disorders. Pediatric patients are evenly divided between male and female, more commonly have IVC thrombosis, and co-morbid conditions include recent trauma. Both adult and pediatric patients with abdominal thrombosis tend to be younger and have a lower BMI than patients with DVT and/or PE. We also found a high rate of concurrent thrombosis in both adult and pediatric patients with abdominal thrombosis. In summary, patients with abdominal thrombosis display different clinical characteristics when compared to those with DVT/PE, specifically in terms of gender, location of thrombosis, and associated co-morbidities. Some of these differences, such as higher rates of IVC thrombosis in pediatric patients with abdominal thrombosis, might be caused by variance between genetic and anatomic factors. Further studies are warranted to explain these differences. Disclosures: Kulkarni: Novo Nordisk: Membership on an entity's Board of Directors or advisory committees, Participate in clinical trials. Philipp:Baxter: Research Funding; Wyeth: Research Funding; Octapharma: Research Funding. Ortel:Sanofi-Aventis: Consultancy, Research Funding; Ortho-McNeil: Consultancy; GlaxoSmithKline: Research Funding; Eisai: Research Funding; Pfizer: Research Funding.

Abstract Abstract 5118 Background: Increased factor VIII:C (FVIII:C) and hypofibrinolysis are VTE risk factors, and beta-blockers and angiotensin converting enzyme (ACE) inhibitors reduce FVIII:C and enhance fibrinolysis, respectively. Objective: To test the hypotheses that beta-blockers and ACE inhibitors reduce VTE risk. Methods: Using longitudinal, population-based Rochester Epidemiology Project resources, we identified all Olmsted County, MN residents with objectively-diagnosed incident VTE over the 13-year period, 1988–2000 (n=1306), and one to two Olmsted County residents per case matched on age, event year and duration of prior medical history (n=1500). For cases and controls, we reviewed their complete medical history in the community for previously-identified VTE risk factors (e.g., hospitalization with or without surgery, nursing home confinement, trauma/fracture, leg paresis, active cancer, superficial vein thrombosis and varicose veins), as well as body mass index (BMI), coronary artery disease (CAD), congestive heart failure (CHF), and the use of statins, beta-blockers, ACE inhibitors and angiotensin II receptor antagonist drugs. Using conditional logistic regression, we tested beta-blockers and ACE inhibitors/angiotensin II receptor antagonists for an association with VTE, both individually and after adjusting for age, BMI, previously-identified VTE risk factors, CAD, CHF and the use of statins. Results: Among cases and controls respectively, 191 and 173 received beta-blockers, and 171 and 154 received ACE inhibitors/angiotensin II receptor antagonists. Univariately, both beta-blockers (unadjusted OR=1.31; p=0.02) and ACE inhibitors/angiotensin II receptor antagonists (unadjusted OR=1.32; p=0.02) were modestly associated with increased VTE risk. However, after controlling for age, BMI, previously-identified VTE risk factors, CAD, CHF and the use of statins, beta-blockers (OR=1.06; 95% CI: 0.74, 1.51; p=0.75) and ACE inhibitors/angiotensin II receptor antagonists (OR=0.94; 95% CI: 0.65, 1.37; p=0.75) were no longer associated with VTE. Conclusions: Beta-blockers and ACE inhibitors/angiotensin II receptor antagonists do not appear to be protective against VTE. Disclosures: No relevant conflicts of interest to declare.