Bailey, Kent R.

Abstract Introduction: Diabetes mellitus is often cited as a VTE risk factor. However, persons with diabetes are frequently hospitalized for medical illness or undergo surgery, both major VTE risk factors. Thus, the association of VTE with diabetes independent of surgery or hospitalization is uncertain. Methods: Using longitudinal, population-based Rochester Epidemiology Project resources, we identified all Olmsted County, MN residents who met objective criteria for incident VTE over the 25-year period, 1976–2000 (n=1922), and one to two controls per case, matched on age, gender, Olmsted County residency, and length of medical history (n=2115). For cases and controls, we reviewed their complete medical history in the community for baseline characteristics previously identified as independent VTE risk factors, including clinically-diagnosed diabetes mellitus. We tested diabetes as a potential VTE risk factor both alone and after adjusting for other baseline characteristics, and in the subset of cases with idiopathic VTE, using conditional logistic regression. Results: Among all cases and controls, 231 (12%) and 199 (9.4%) had diabetes, respectively. Univariately, diabetes was associated with overall VTE (odds ratio [OR]=1.32; 95% CI: 1.07, 1.62; p=0.009). However, after controlling for body mass index (OR=1.04, p<0.001), hospitalization with major surgery (OR=25.2, p<0.001) or hospitalization for medical illness (OR=7.3, p<0.001), active cancer (OR=8.3, p<0.001) and varicose veins (OR=1.3, p=0.003), diabetes was no longer associated with VTE (OR=1.09; 95% CI: 0.85, 1.41; p=0.49). Among 458 idiopathic VTE cases and 518 matched controls, 43 (9.4%) and 46 (8.9%) had diabetes, respectively. Diabetes was not associated with idiopathic VTE (OR=1.07, 95% CI: 0.69, 1.67; p=0.76). Conclusions: Diabetes mellitus is not an independent risk factor for overall or idiopathic incident VTE.

Abstract If the observed dramatic increase in VTE incidence with advancing age is due to increased VTE risk factor exposure (i.e., secondary VTE), the incidence of idiopathic VTE should not vary with age or calendar year. Objective: To estimate the incidence of idiopathic and secondary VTE by age and by calendar year. Methods: Using the resources of the Rochester Epidemiology Project, we identified the inception cohort of Olmsted County, MN, residents with a first lifetime VTE during the 30-year period, 1966–1995 (n=2761). For each case, we reviewed the complete medical records in the community for 48 baseline clinical characteristics that are commonly-accepted risk factors for VTE. We categorized VTE cases as idiopathic (n=305) if no such characteristics were present; the remaining cases were categorized as secondary. Age- and sex-specific incidence rates were calculated using idiopathic or secondary VTE cases as the numerator, and age-, sex- and calendar year-specific estimates of the population of Olmsted County as the denominator. Results: The incidence of both idiopathic and secondary VTE increased exponentially with age for both men and women (p<0.001). Over the 30-year study period, the age-adjusted incidence of idiopathic VTE was essentially constant among men (from 19.0 to 17.1 per 100,000 men-years for 1966–70 and 1990–95, respectively), but decreased markedly among women (from 18.5 to 3.6 per 100,000 woman-years for 1966–70 and 1990–95, respectively; p=0.005 for the interaction). Conclusions: The dramatic increase in VTE incidence with age likely reflects the biology of aging, although as yet unidentified VTE risk factors cannot be excluded. The reason for the decreased incidence of idiopathic VTE over the last 30 years among women is unclear.

Abstract Abstract 1241 Background: Hospitalization (with or without surgery) is a major risk factor for incident venous thromboembolism (VTE); however, the contribution of interim hospitalization to risk of recurrent VTE is unknown. Objective: To estimate risk of recurrent VTE related to interim hospitalization by conducting a population-based longitudinal review of provider-linked detailed medical records. Methods: We performed a nested case-cohort study. The cohort consisted of all Olmsted County residents with incident VTE 1988–2000 and ≥1 day follow-up. Cases were cohort members with recurrent VTE. Subjects were followed for all interim hospitalizations and warfarin use from incident VTE until earliest of emigration, death, recurrent VTE, or 12/31/2005. Data were analyzed using Cox proportional hazards and time dependent covariates to test for the effects of interim hospitalization and prophylaxis on VTE recurrence, adjusting for gender and age at incident VTE. Analyses were limited to subjects who survived free of death and recurrent VTE for ≥ 6 months. Results: Of 1262 incident VTE events (cohort), there were 309 VTE recurrences (cases). We randomly sampled 272 subjects from the cohort and 163 cases. Of the random samples, 210 incident events and 83 cases survived ≥ 6 months free of death and recurrent VTE and form our analysis population. The rate of secondary (interim) prophylaxis was approximately 50% for both incident events and cases, and was not predictive of recurrence (p=0.73). Male gender and interim hospitalization were associated with increased VTE recurrence even after adjusting for age at incident VTE and use of secondary warfarin prophylaxis. The hazard of recurrent VTE was nearly 10-fold higher for subjects with interim hospitalization versus those with none (HR: 9.6; 95% CI: 6.6, 13.8); men had a 1.5-fold increased recurrence rate compared with women (HR: 1.5; 95% CI: 1.1, 2.1). Conclusions: Our results, for the first time, show the importance of interim hospitalization as a predictor of VTE recurrence. Disclosures: No relevant conflicts of interest to declare.

Abstract Active cancer is an independent VTE risk factor (overall 6- to 9-fold increased risk) and accounts for almost 20% of all VTE in the community, but which cancer patients are at risk for VTE is largely unknown. Reportedly, VTE risk varies by tumor site, and cancer of the ovary, pancreas, colon, stomach, lung, prostate, and kidney convey particularly high VTE risk. Objective: To estimate VTE risk by tumor site. Methods: We enumerated observed cancers by tumor site for Olmsted County, MN active cancer patients with incident VTE over the seven-year period, 1991–1997 (n=152). We used 1991–1997 State Surveillance, Epidemiology, and End Results (SEER) data for Iowa to estimate the expected age-specific prevalence of cancer by tumor site in Olmsted County. VTE risk ratios (RR) for each tumor site were estimated by dividing the observed number of cancers by the expected number (calculated as the product of the SEER prevalence and the number of incident VTE cases in the age stratum). Results: For our population of 1991–1997 VTE cases, all tumor sites had RR > 5.0 (range 5.2 to 37.3, all p-values<0.05). Compared to published overall VTE odds ratios of 6–9 for active cancer compared to no cancer, the RR for some tumor sites were particularly increased. A Chi-squared test of heterogeneity of the RR across sites was highly significant (p-value<0.001). Three rare cancer sites - pancreatic cancer, lymphoma, and brain cancer - had unusually high RR (all RR>25). The high number of VTE cases with lymphoma was not due to catheter-related arm vein thrombosis. Liver, leukemia, other gastrointestinal (esophagus, small intestine, gallbladder, other biliary) and other gynecologic (primarily cervical) cancers had over twice the baseline risk (i.e., RR>17.0). On the other hand, the RR for many common cancers (breast, colorectal, ovary, lung, prostate) were essentially the same as the overall baseline risk (all had 9.5<RR<12.0). Conclusions: In contrast to previous reports, pancreas, lymphoma, brain, liver, leukemia, other gastrointestinal, and other gynecologic cancers have the highest VTE risk. Prior estimates of VTE risk by tumor site may have been biased by studies of prevalent cancers among patients hospitalized in tertiary care centers.

Abstract If the incidence of VTE varies by season, then the etiology of VTE could be related to seasonal exposures. However, the few studies that estimated VTE incidence by season reached conflicting conclusions. Objective: To estimate the incidence of VTE by month and by season of the year. Methods: Using the resources of the Rochester Epidemiology Project, we identified the inception cohort of Olmsted County, MN, residents with a first lifetime VTE over the 30-year period, 1966–1995 (n=2761). For each case, we reviewed the complete medical records in the community for the date of VTE onset, date of birth, gender and 48 baseline clinical characteristics commonly accepted as risk factors for VTE. We categorized cases as idiopathic (n=305) if no such characteristics were present; remaining cases were categorized as secondary. Incidence rates were calculated using the number of overall, idiopathic or secondary VTE cases by month of onset as the numerator, and age- and sex-specific estimates of the monthly population of Olmsted County as the denominator (yearly population estimates divided by 12). Results: The incidence of VTE did not vary appreciably by month of the year for overall, idiopathic or secondary VTE (all p-values >0.2). However, the overall incidence of VTE was higher in the 3 summer months (June, July, August) compared to the 3 winter months (December, January, February; 132.6 vs. 116.9 per 100,000 person-years, respectively, both age- and sex-adjusted to year 2000 U.S. Whites; p-value = 0.026). The same general pattern was true for both idiopathic and secondary VTE, but separately neither was statistically significant (p-value=0.48 and 0.15, respectively). Conclusions: The incidence of VTE is higher in the summer compared to the winter months, suggesting the hypothesis that vector-borne (e.g., mosquito, tick) and/or enteroviral infection may play a role in the etiology of VTE.

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 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 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.

Abstract Abstract 2984 Poster Board II-960 In previous studies of venous thromboembolism (VTE) among all residents of Olmsted County, MN, the odds of VTE associated with surgery, medical hospitalization, or active cancer were extremely high (Univariate odds ratio [OR] =14.6; 4.6, and 8.4 respectively). We also showed that nursing home (NH) residency was an independent risk factor for VTE (OR =5.6). From a clinical practice perspective, it is important to identify which NH residents are at risk of VTE. While it might be assumed that, similar to estimates for the population generally, surgery, medical hospitalization, and cancer are associated with increased risk of VTE within the NH population, the answer remains unclear. We took advantage of the previous identification of all Olmsted County, MN residents who met research criteria for incident VTE 1998-2005 (N=1168). We then determined which individuals were resident of a local NH at time of symptom onset, regardless of location of symptom onset (i.e., for purposes of this study, individuals whose VTE occurred in-hospital having been admitted from a NH were considered NH residents). For each such NH VTE case (N=96), we identified 2 same sex Olmsted County residents of similar age and duration-of-medical-history who were resident of a local NH at the time of the case's VTE event (i.e., index date) (N=192). The detailed provider-linked medical records of NH VTE cases and NH non-VTE controls were reviewed for 3 months before index for surgery or medical hospitalization and for 6 months surrounding index for active cancer. Using conditional logistic regression, we tested and estimated the odds ratio associated with each of these potential risk factors. The proportions of NH VTE cases and NH non-VTE controls with surgery (33%, 28%), medical hospitalization (44%, 46%), and active cancer (12%, 9%) were similar. Univariate odds ratios (95% confidence intervals) and p values for surgery, medical hospitalization, and active cancer were 1.5 (0.7-3.1), p=0.30; 1.1 (0.6-2.1), p=0.74; and 1.4 (0.6-3.2), p=0.46 respectively. Compared to the entire Olmsted County population, the odds of VTE associated with surgery, hospitalization, and cancer are surprisingly much lower for NH residents. Additional investigation is needed to characterize the subset of NH residents at increased risk of VTE. Disclosures: No relevant conflicts of interest to declare.

Abstract Background: Venous stasis syndrome (VSS) is a relatively common long-term sequelae of deep vein thrombosis (DVT), although it frequently is noted in individuals with no prior history of DVT. Objective: To evaluate whether: (1) venous stasis syndrome (VSS) is associated with a prior history of DVT; (2a) venous outflow obstruction (VOO) and/or (2b) venous valvular incompetence (VVI) are associated with DVT; and (3) VSS is associated with VVI and/or VOO. Design: Case-control study nested within a population-based inception cohort study. Population: 230 residents of Olmstead County, MN (OCM) with a first lifetime VTE over the 25-year period, 1966 – 1990 (cases), and 135 age, gender and year of incident VTE-matched OCM residents without prior history of VTE (controls). Measurements: Physical examination and patient questionnaire for symptoms or signs of VSS, and strain gauge outflow plethysmography, continuous wave venous Doppler ultrasound, and passive venous drainage and refill testing for VOO and VVI performed between 1996 – 1998. Results: Of the 365 study participants, 43 (12%) had VOO, 136 (37%) had VVI, and 265 (73%) had VSS. In multivariate logistic regression analyses: (1) age at the follow-up visit [OR Δper 10 years: 1.70 (1.41, 2.04)], prior DVT in the affected limb [OR: 4.03 (2.32, 7.01)], and presence of prior varicose veins [OR: 4.36 (1.84, 10.31)] were significantly associated with VSS; (2a) age at the follow-up visit [OR Δper 10 years (95% CI): 1.84 (1.39, 2.44)] and prior DVT in the affected limb [OR: 5.01 (2.61, 9.63)] were significantly associated with VOO; (2b) prior DVT in the affected limb (OR: 3.91 (2.56, 5.97)], presence of prior varicose veins [OR: 2.19 (1.32, 3.63)] and symptoms of VSS prior to incident DVT [OR: 3.42 (1.46, 8.00)] significantly increased the odds for VVI; and (3) VOO (p=0.004) and VVI (p<0.0001) were highly associated with VSS. Having a DVT in the left leg was associated with a greater odds of developing VOO, VVI or VSS in that leg when compared to their association with right leg DVT (OR: 6.69 vs. 3.65; 4.82 vs. 3.09; 4.71 vs. 3.97, respectively). Interestingly, prior DVT in the opposite leg was associated with an increased odds of subsequent VVI [OR: 2.00 (1.28, 3.10) and VSS [OR: 2.20 (1.31, 3.70)], but not VOO, in the test leg. Conclusions: Prior DVT imparts an increased risk for subsequent VSS, likely due to VOO and/or VVI. The odds of VOO or VSS increases with age. Presence of varicose veins increases the odds for VVI and VSS. We speculate that the increased odds of left sided VOO, VVI and VSS in patients with prior DVT may be secondary to May-Thurner syndrome. The increased odds of VVI and VSS in the limb opposite to the one affected by prior DVT could reflect occult DVT in the test limb, inferior vena cava thrombosis, or other mechanisms leading for VVI and VSS.