Lower Extremity Deep Venous Thrombosis Research Articles

Risk assessment scales to predict risk of lower extremity deep vein thrombosis among multiple trauma patients: a prospective cohort study

BackgroundDeep vein thrombosis (DVT) is a common complication in orthopedic patients. Previous studies have focused on major orthopedic surgery.There are few studies with multiple trauma. We aimed to describe the prevalence of DVT and compare the predictive power of the different risk assessment scales in patients with multiple trauma.MethodsThis prospective cohort study involved multiple trauma patients admitted to our hospital between October 2021 and December 2022. Data were prospectively collected for thrombotic risk assessments using the Risk Assessment Profile for thromboembolism(RAPT), the DVT risk assessment score (DRAS), and the Trauma Embolic Scoring System (TESS), respectively. The receiver operation characteristic (ROC) curve and the area under the curve (AUC) were evaluated to compare the predictive power. The whole leg duplex ultrasound of both lower extremities Doppler ultrasound was used to determine DVT incidence.ResultsA total of 210 patients were included, and the incidence of DVT was 26.19%. Distal DVT accounted for 87.27%; postoperative DVT, 72.73%; and bilateral lower extremity thrombosis, 30.91%. There were significant differences in age, education degree, pelvic fracture, surgery, ISS, D-dimer level, length of hospital stay and ICU stay between the thrombosis group and the non-thrombosis group. The AUCs for RAPT, DRAS, and TESS were 0.737, 0.710, and 0.683, respectively. There were no significant differences between the three ROC curves.ConclusionsThe incidence of DVT was relatively high during hospitalization. We prospectively validated the tests to predict risk of DVT among patients with multiple trauma to help trauma surgeons in the clinical administration of DVT prophylaxis.

Incidence and risk factors for inferior vena cava filter thrombosis detected at time of filter retrieval in patients with lower extremity deep vein thrombosis: a multicenter retrospective cohort study.

Inferior vena cava filter (IVCF) thrombosis is an uncommon complication of IVCF utilization. The aims of this study were to investigate inferior vena cava (IVC) venography before filter retrieval to determine the incidence relative to filter dwell time and risk factors of IVCF thrombosis based on the clinical data and imaging findings in patients with lower extremity deep vein thrombosis (LEDVT). The clinical data from a multicenter randomized trial conducted between October 2017 and March 2019 were reviewed to determine the incidence of IVCF thrombosis in preretrieval venography and the associated risk factors. The correlation between filter dwell times (within 90 days) and incidence was assessed. Baseline demographics, LEDVT presentation, laboratory examination, thrombus characteristics, concurrent pulmonary embolism (PE), comorbidities and risk factors for LEDVT, and IVCF-relevant information were analyzed using the independent samples t-test, chi-squared test, Fisher exact test, and regression analysis to determine the univariable and multivariable associations in assessing the risk factors of IVCF thrombosis. A total of 178 eligible patients were included, of whom 58 were in the IVCF thrombosis group and 120 were in the IVCF nonthrombosis group, and the mean filter dwell time was 22.07±27.91 days (range, 4-190 days). The overall incidence of IVCF thrombosis in patients with LEDVT who received IVCFs was 32.58% (58/178). The incidence of IVCF thrombosis was 35.25% (49/139) in the first 30 days after the IVCF placement and decreased to 22.73% (5/22) between 30 to 60 days of dwell time and to 18.18% (2/11) between 60 and 90 days of dwell time, indicating a decreasing trend within the first 90 days. The risk factors for the occurrence of IVCF thrombosis were concurrent PE [odds ratio (OR) =2.59; 95% confidence interval (CI): 1.27-5.28; P=0.01], rheumatic diseases of the immune system (OR =14.42; 95% CI: 1.52-136.41; P=0.02), IVC:filter radial ratio >0.587 (OR =0.25; 95% CI: 0.10-0.65; P<0.01), and percutaneous angioplasty (PTA) (OR =2.50; 95% CI: 1.09-5.70; P=0.03). The incidence of IVCF thrombosis at the time of filter retrieval appears to decrease with dwell time within 90 days. Concurrent PE, rheumatic diseases of the immune system, and PTA were taken into account as risk factors. An IVC:filter radial ratio of 0.587 was a protective factor against developing IVCF thrombosis. These findings require further validation in a well-designed study since the present study lacked a close follow-up.

Recurrent Thromboembolism in Patients with Congenital Heart Disease and Prior Thromboembolism: A Prospective Cohort Study

Introduction: Patients with congenital heart disease (CHD) are at increased risk of thromboembolism (TE) due to changes in blood flow, type of cardiac lesion, exposure to cardiopulmonary bypass, and cardiac catheterization. There are limited data describing the rate of and risk factors associated with recurrent TE in pediatric patients with CHD and prior TE. Therefore, the primary aim of this study was to describe the rate of recurrent TE in pediatric patients with CHD and a prior episode of TE. Secondary aims included: characterize the type of index and recurrent TE and site, as well as compare characteristics and risk factors of patients with CHD and history of index TE who developed recurrent TE versus to those who did not develop a recurrent TE. Methods: Patients in this study were enrolled and prospectively followed in the Johns Hopkins All Children's (St. Petersburg, FL) Institution-wide Prospective, Inception Multi-Cohort Study of Pediatric TE anytime between 2013 to present. For this analysis, patients were eligible for inclusion if they were &amp;lt;21 years of age, presented with an index TE, and had a diagnosis of CHD. Data collection included patient characteristics, clinical laboratory testing, radiologic results, type and site of TE, acute and chronic risk factors, and treatment agents. Frequencies/proportions were compared between groups by chi-squared or Fisher's exact test, as appropriate. Results: Thirty patients with CHD and index TE were included in this study. Of these, 11 (36.7%) patients had a total of 23 recurrent TEs. Five (45.5%) patients had one recurrent TE, 3 (27.3%) had two recurrent TEs, and another 3 patients had &amp;gt;2 recurrent TEs. Of the 23 recurrent TE, 3 events (13%) were arterial and 20 (87%) were venous. All 3 (100%) arterial TEs were provoked, and catheter related. Of the 20 venous TEs, 16 (80) were provoked and of these, 15 (93.8%) were catheter related. When compared to those who did not develop recurrent TE, patients who developed recurrent TE were more likely to have immobility (p=0.005), an arterial TE (p=0.041), or a lower extremity deep venous thrombosis (p=0.045) at the time of index TE. A greater proportion of patients with recurrence had a central catheter-associated TE compared to those with no recurrent TE but this difference was not statistically significant (73% vs 55%, p=0.057). Conclusions: In this single center prospective cohort we describe a high rate of recurrent TE (37%) among children with CHD and history of prior TE, and identified risk factors for TE recurrence. The vast majority of recurrent TE was provoked and catheter associated. Identified risk factors include immobility, and type and location of the index TE. Future multicenter prospective cohort studies are needed to validate these findings and identify additional risk factors.

Thromboprophylaxis with Intermediate Dose Low Molecular Weight Heparin in Adults Undergoing Induction with L-Asparaginase for Acute Lymphoblastic Leukemia

Introduction Adolescents and young adults (AYA, defined as age 15-39 years) with acute lymphoblastic leukemia (ALL) have a poorer prognosis than their pediatric counterparts. To replicate the success of ALL treatment in children, pediatric-inspired regimens have been incorporated into the treatment of AYA and often include the use of L-asparaginase. Rates of thrombosis in adults receiving L-asparaginase for treatment of ALL have been reported to be as high as 34%, compared to only about 5% in pediatric patients. The risk of thrombosis is elevated primarily during the induction phase of treatment. Several strategies have been studied in adults, including antithrombin III replacement, fresh frozen plasma replacement, and prophylactic dosing of anticoagulation, however no clear guidelines exist on how to prevent thrombosis in these high-risk patients. To prevent L-asparaginase-induced thrombotic events, our institution implemented a standard practice of 1mg/kg/day of low molecular weight heparin (LMWH), a dose in-between prophylactic and therapeutic dosing, administered to all adults with ALL who were treated with L-asparaginase during induction chemotherapy. In this current study, we report data from patients who have been treated with this strategy from 2012 to present, focusing on the antithrombotic efficacy and safety of 1mg/kg/day LMWH in this population. Methods This retrospective chart review included 62 patients who received prophylactic anticoagulation with the LMWH enoxaparin (1mg/kg/day) while undergoing induction chemotherapy with L-asparaginase for ALL at the Oregon Health &amp; Science University from 2012 to present. Anticoagulation with enoxaparin was initiated with the first dose of L-asparaginase and continued until the day of discharge or day 30 of induction. The primary outcome was the incidence of thrombosis within the first 30 days of L-asparaginase administration. Minor and major bleeding events, as defined by the International Society of Thrombosis and Haemostasis (ISTH), were recorded. Statistical analysis with univariate regression models was performed to evaluate the association of thrombotic events with demographic, disease and treatment variables. Results Sixty-two patients received 1mg/kg/day LMWH prophylaxis during ALL induction between January 2012 and June 2023 (43 with B-ALL and 19 with T-ALL). Median age at induction was 25.7 years (range 18-39 years). A majority of patients (83.9%) received the maximum dose of 2500mg/m 2 of L-asparaginase. Four patients (6.5%; 95% CI 1.8%-15.7%) experienced a thrombotic event within the first 30 days of induction with L-asparaginase; 3 of the events were catheter-associated and were treated supportively or with catheter removal, and 1 patient developed a distal lower extremity deep vein thrombosis related to myositis. Median time to thrombosis was 13.5 days (range 11-22 days). There were no significant associations between development of thrombotic events with age, gender, B- or T-cell precursor, or dose of L-asparaginase. No thrombosis-related deaths or major bleeding events occurred. Conclusions Prophylactic anticoagulation with intermediate dose 1mg/kg/day LMWH in adults with ALL undergoing induction chemotherapy with L-asparaginase is a safe and an effective strategy to prevent serious thrombotic events. Our institutional rate of 6.5% of patients experiencing thrombotic events during induction with L-asparaginase, with all of the events being clinically low risk, compares favorably to historically reported rates in adults and approaches the low rates reported in children. Further prospective research is warranted.

Predictors and Timing of Venous Thromboembolism in Lung Cancer

Introduction Venous thromboembolism (VTE) is a common complication in lung cancer, but its risk factors and incidence have not been fully characterized. While prophylactic anticoagulation is recommended for some patient with cancer to prevent VTE, the thrombosis-risk prediction Khorana score considers lung cancer intermediate risk for development of VTE and combines all subtypes of lung cancer into a single entity. There are also limited data on the impact of therapy-type on VTE risk in patients with lung cancer. This study aimed to identify the incidence of VTE and its associated risk factors in patients with lung cancer at our university cancer center. Methods Using data from our tumor registry, we identified patients diagnosed with lung cancer between 2018 and 2022 who received first therapy beyond surgery alone after date of first contact. Using automated text search from our electronic medical record (EPIC®) combined with natural language processing review, VTE events were identified from 90-days before and up to one year(y) after initiation of systemic therapy. VTE events, including lower extremity deep vein thrombosis (DVT) or pulmonary embolism (PE), were captured by physician investigators, with final, secondary adjudication by one of us (GAS). We report time to event analysis and survival analysis using Kaplan-Meier curve. The study was censored at one year. Univariate and multivariate analyses were performed using COX-regression model. We evaluated the effect of lung cancer subtype, stage, age, sex, race, ethnicity, white blood cell count, hemoglobin, and platelet count. Results A total of 635 lung cancer patients were included in the study with a median age of 65 years. The median white blood cell count (WBC) was 8.8 × 109/L, median hemoglobin (Hgb) was 12.7 g/dL, and platelets (Plt) was 284 × 109/L. Other patient characteristics can be seen in Table 1. The overall 12-month incidence of VTE (lower extremity DVT and/or PE) was 10.1% (n=64). Of the 64 VTE events, 20 were identified before the start of therapy. Univariate analysis revealed that age &amp;lt;60 and WBC &amp;gt;= 11 were associated with a higher risk of VTE (p&amp;lt;0.05), which remained significant after multivariate analysis including age, stage, WBC, and surgery. There was a trend towards a higher risk of VTE in patients receiving chemoimmunotherapy, compared with chemotherapy alone, (HR 1.22), although this trend did not reach significance. Targeted therapy was associated with a lower trend (HR = 0.89), but that also was not significant. The median overall survival was 18 months. Univariate analysis showed that VTE was associated with an increased risk of death (HR 2.05, p&amp;lt;0.001). Other parameters associated with reduced Overall Survival (OS) were age &amp;gt;=60, male sex, stage III-IV, WBC, Hgb, and Plt. After multivariate analysis considering age, sex, stage, lung cancer histology, Hgb, Plt, WBC, surgery, therapy type, and VTE, age &amp;gt;=60, stage III-IV, WBC &amp;gt;=11, Hgb &amp;lt;10, and VTE remained significant predictors of death. Discussion In a retrospective study of more than 600 patients with lung cancer, there was a significant risk of VTE. Every subgroup of patients analyzed in this study retained a high risk of VTE after multivariate analysis. The only hematologic parameter from the Khorana score significantly associated with VTE after multivariate analysis was WBC. WBC and Hgb were associated with increased risk of death. Age &amp;lt;= 60 was associated with increased risk of VTE, while age &amp;gt;60 was associated with increased mortality. There was a trend towards a higher risk of VTE in patients receiving chemoimmunotherapy compared with chemotherapy alone. There were too few immunotherapy-only patients to allow for any interpretation. The development of thrombosis was associated with a significantly decreased overall survival, although we do not have data on the potential contribution of VTE to death. These findings were derived from a single-center data set, and further validation using independent data sets is warranted. If confirmed, a prospective study re-evaluating the risk of VTE and benefits of prophylactic anticoagulation specifically in contemporary patients with lung cancer receiving systemic therapy regardless of histology, treatment, or other factors described here may be indicated. Our findings do not support limiting any such study to any specific sub-group of patients with lung cancer.

Thrombosis Rates and Use of Thromboprophylaxis after Discharge from Gynecologic Cancer-Related Surgery

Background: Cancer and major abdominopelvic surgeries pose significant thrombosis risks, making cancer-related surgery highly susceptible to venous thromboembolism (VTE) despite prophylaxis. Without post-operative thromboprophylaxis (TPX), VTE risk can reach 29% in the weeks following major surgeries. National Comprehensive Cancer Network (NCCN) guidelines recommend anticoagulation for up to 4 weeks after such surgeries, primarily using low molecular weight heparin (LMWH) for 28 days postoperatively. This study aimed to determine VTE rates linked to various gynecologic cancer-related surgeries and explore TPX utilization in a large cancer-center cohort. Additionally, we sought to further understand the necessity for post-discharge TPX in this setting. Methods: Patients (pts) diagnosed with gynecologic cancer between January 1st, 2012, through September 15th, 2022, at our institution were identified through our tumor registry. Using an in-house automated text search tool from our electronic medical record (Epic®), combined with natural language processing review, venous thromboembolism (VTE) events were identified, with secondary adjudication by the study leader (GAS). VTE was defined as either lower extremity deep vein thrombosis (DVT), or pulmonary embolism (PE) diagnosed from the day of surgery until 90 days after the first day of surgery. Logistic regression was performed on binary outcomes for the presence of VTE and TPX use at discharge. Kaplan-Meier curves and Cox regression were used for overall survival analysis. Results: 801 pts who underwent gynecologic cancer-related surgeries were identified. Patient demographics and surgery types are described in Table 1. VTE occurred in 1.9% (n=15) of the overall population but was unequally distributed. The number of VTE in those undergoing minimally invasive surgery (MIS), vulvovaginal surgery, and biopsies collectively was low (0.57%, n=3), even when considering that only 11.1% of those pts received TPX at discharge. VTE was more commonly diagnosed in patients who underwent open surgery (4.3%, n=12), with 5 pts (1.8%) diagnosed before discharge and 7 pts (2.5%) after discharge. In multivariable logistic regression analysis, during the full study period, open procedures were associated with a higher risk of thrombosis, (relative risk 7.5, p &amp;lt; 0.001) and higher use of post-discharge TBX (RR 4.55, p &amp;lt; 0.001). Notably, only 50% (139 of 279) of pts who underwent open surgery received TPX at the time of discharge. Within the open surgery cohort, the rate of post-discharge VTE correlated with the use of post-discharge TPX. Of pts on TPX, 0.7% (n=1) were diagnosed with VTE compared to 4.3% (n=6) of pts who did not receive TPX (RR=0.17, p= 0.12). There was no difference in overall survival in pts who received TPX and those who did not after open surgery up to 36 months after the surgery. Conclusions: Our findings suggest a tiered risk of post-operative VTE after gynecologic cancer surgery, with a clinically relevant risk observed only in women undergoing open surgery. Our gynecologic oncology practice already reflects this, as post-operative TPX is not routinely prescribed for lower-risk procedures. In patients who underwent open surgery, TPX at discharge showed a trend towards a protective effect, although this result did not reach statistical significance, probably due to sample size, it supports the need for a targeted prospective study. If this trend towards benefit holds in a prospective study, the number needed to treat to avoid one clinically detected post-operative VTE would be 28 pts. The relatively high fraction of post-op VTE events during the inpatient hospital stay also supports efforts for early TPX, as has been done with a prophylactic dose of pre-operative unfractionated heparin or LMWH in other high-risk cancer surgery settings (Selby et al, J Am Coll Surg. 2016). The limitations of this study include being conducted at a single institution, retrospective and non-randomized.

Predictors and Timing of Venous Thromboembolism in Lymphoma

Introduction Cancer associated thrombosis (CAT) is common in lymphoma, but the risk is not well characterized. While prophylactic anticoagulation is recommended in certain solid tumors, routine prophylaxis is not practiced in hematologic malignancies. The Kohrana CAT risk score considers lymphoma a single entity. We aimed to identify the incidence rate of venous thromboembolism (VTE) and risk factors in lymphoma patients at our institution. Methods Patients diagnosed with lymphoma between 2018 and 2022 were identified through our institution's tumor registry. Using automated text search from our electronic medical record (EPIC®) combined with natural language processing review, VTE events were identified from 90 days before and up to one year(y) after initiation of chemotherapy initiation, or diagnosis date if no chemotherapy was administered. VTE events included lower extremity deep vein thrombosis (DVT) or pulmonary embolism (PE). Events were reviewed and adjudicated manually by us. We report time to event analysis and survival analysis using Kaplan-Meier curve. The study was censored at one year. Univariate and multivariate analyses were performed using COX-regression model. We evaluated the effect of indolent versus aggressive lymphoma, stage, age, sex, race, ethnicity, white blood cell count, hemoglobin, and platelet count. Results We identified 879 patients(pts) with lymphoma; of those, 378 pts had indolent lymphoma (I-Lym) and 501 pts had aggressive lymphoma (A-Lym). Median age was 61y. 464 pts (52.8%) were above 60 y, 477 pts (54.3%) were males, and 325 pts (37.0%) were Hispanic. Race was distributed as follows: 89.5% white, 9.1% Black, and 1.4% other. 56.9% had advanced stage lymphoma. VTE occurred in 4.9% (n=43) of the overall population within 12 months. The incidence was higher in A-Lym (7.2%, n=36) compared with I-Lym (1.9%, n=7), p&amp;lt;0.001. For both A-Lym and I-Lym, 32.6% of the VTE events occurred prior to diagnosis or initiation of chemotherapy. Among patients who developed thrombosis after the chemotherapy start date, the median time to thrombosis was 39 days. In a univariate analysis (Table 1) for thrombosis-free survival, age&amp;gt;60, receiving chemotherapy and A-Lym, were all associated with higher risk of thrombosis (p&amp;lt;0.05). In the multivariate analysis, only, age&amp;gt;60, and A-Lym remained significant in predicting thrombosis (HR: 3.48, 95%CI: 1.41, 8.61, p=0.007). Hemoglobin &amp;lt;10, platelet count &amp;gt;350, white blood cell count &amp;gt;11, advanced stage, and chemotherapy administration were not significant risks of thrombosis. In multivariate analysis for overall survival (Table 2), development of VTE was associated with increased risk of mortality (HR: 2.59, 95%CI: 1.38, 4.87, p=0.003). This relationship of VTE and mortality was observed independently in both I-Lym and A-Lym. As expected, A-Lym, age&amp;gt;60, male sex, and advanced stage all predicted worse survival in our lymphoma population (p&amp;lt;0.05 for all). Of note, hemoglobin &amp;lt;10 and white blood cell count &amp;gt;11, did not predict VTE in lymphoma but did predict poor OS. Conclusion Lymphoma is associated with a clinically relevant rate of CAT, but incidence is significantly higher in A-Lym compared with I-Lym with a third of events occurring prior to chemotherapy. The hematologic parameters of the Khorana Score (WBC, Hgb, platelet count) did not correlate with incidence of CAT in lymphoma, neither did chemotherapy. Development of CAT during therapy, in multivariate analysis for both A-Lym and I-Lym, was associated with a marked reduction in OS. These points suggest that the thrombotic risk is an inherent property of lymphoma biology in at least some cases, leading to an increased risk of CAT as well as reduced OS. We do not propose that CAT-related mortality is driving the reduced OS, but more likely a marker of poorer prognosis. Limitations: This was a single center/ single dataset and these findings should be considered a derivation cohort, and should be verified with independent additional datasets. If our findings are verified, prospective studies to assess benefit of prophylactic anticoagulation in aggressive lymphoma may be warranted.

Overall Survival of Warfarin Compared to LMWH/Doacs in Cancer-Associated Venous Thromboembolism: VA Cohort Study

Background: Warfarin has been shown in pre-clinical models to have anti-neoplastic activity. In a population-based study using the SEER-Medicare Linked Database warfarin was associated with improved survival compared to low molecular weight heparin (LMWH) or direct oral anticoagulants (DOACs) in the treatment of cancer-associated thrombosis (CAT). To assess whether the observed survival advantage is consistent in other large cohorts, we performed a matched cohort study utilizing the Veterans Affairs (VA) database. The VA is a large, integrated health care system with comprehensive data for their patients at the individual level, which provides the optimal observational cohort to confirm the novel hypothesis warfarin confers a mortality benefit over LMWH. Method: Using the retrospective data from the VA health care system from 2000-2021, we identified patients with CAT who were &amp;gt; 18 years, had available prescription data for anticoagulation within 30 days of venous thromboembolism (VTE), and survived &amp;gt; 14 days after the index VTE event. Patients were excluded if they had prior diagnosis of VTE or had any anticoagulation prescription prior to the first coded VTE event. The primary outcome was overall survival (OS). Patients were matched 1:1 using nearest neighbor matching on the propensity score. The matching variables included cancer site, cancer stage, date of cancer diagnosis, date of VTE diagnosis, age at VTE diagnosis, gender, race, BMI, Elixhauser-based weighted comorbidity score, and rurality of residential status. Cox proportional-hazards regression was performed to estimate hazard ratios (HR) and 95% confidence intervals. Log-rank test was utilized to estimate the p-value. Subgroup analyses were performed in the largest groups of cancer available in the data set including prostate cancer, lung cancer, gastrointestinal cancer (excluding hepatobiliary cancer), and malignant hematologic neoplasms (including myeloid malignancy, lymphoid malignancy, and multiple myeloma). Finally subgroup analysis was also performed on localized cancer and metastatic disease based on AJCC stage grouping. Result: There were a total of 20,078 patients that met the inclusion and exclusion criteria without missing data. The warfarin cohort consistent of 8383 patients while non-warfarin cohort comprised 11696 patients. Among the non-warfarin cohort, 54% of the patients were prescribed LMWH exclusively and 38% of the patients were prescribed DOAC exclusively within 30days of the VTE diagnosis. The most common malignancies in the cohort included prostate (29.4%), lung (20.9%), gastrointestinal (15.7%) and hematologic malignancies (10.3%). Of patients with solid tumors, 22% had metastatic cancer. Among the VTE events, 33.3% were acute lower extremity deep vein thrombosis, 48.4% were acute pulmonary embolism, and 18.3% were acute upper extremity deep vein thrombosis. After propensity score matching, 8,383 patients were included in the warfarin arm and 8,383 patients in the non-warfarin arm. The median age at VTE diagnosis of the matched cohort was 69 [IQR 63 - 75] and the majority of the patients (96.7%) were male. Warfarin was associated with a significant improvement in OS compared to non-vitamin K antagonists (median OS, 1204 days [95% CI, 1137-1276 days] vs 703 days [95% CI, 665-747 days]; HR 0.79 [95% CI 0.76 - 0.82]; p-value &amp;lt;2x10 -16) (Figure1). The difference was also preserved in gastrointestinal malignancy (HR 0.8 v95% CI 0.73-0.87), lung cancer (HR 0.8, 95% CI 0.79-0.92) and prostate cancer (HR 0.71, 95% CI 0.65-0.77). The survival advantage was preserved in patients with metastatic (HR 0.86, 95% CI 0.78-0.83) and localized cancer (HR 0.80, 95% CI 0.76-0.84) (Figure 2). Conclusion and Relevance: In a population level propensity matched study, warfarin for the treatment of CAT was associated with significantly improved survival over non-vitamin K antagonist anticoagulation in CAT. These provocative finding confirm the previous observation in SEER-Medicare database and have important implications on patient care and health care costs. Further investigation into the biological basis of these findings could potentially lead to biomarker and drug discovery for cancer therapies and prognostication.

Spontaneous Iliac Artery Dissection in a 66-Year Old Male Complicated By Hemorrhage, GI Bleeding, and Bilateral DVT/PE

Spontaneous iliac artery dissection (IAD) is a rare medical condition with only a few cases being reported in the medical literature. Dissections typically involve the aorta and are not localized to the iliac arteries. Patients with spontaneous IAD typically present with symptoms that resemble peripheral artery disease, and cases are typically associated with connective tissue diseases such as Marfan syndrome and Ehlers-Danlos syndrome or high-risk states such as pregnancy and extreme athletics. There are some case reports that showed an association with hyperlipidemia, hypertension, and tobacco use. The most frequent complication of spontaneous IAD is rupture, and cases are typically treated endovascularly but may be treated with classical surgery such as in the case of rupture. Some cases have reportedly been treated with conservative management alone. In this case, we discuss a 66-year-old male with a past medical history of hyperlipidemia, hypertension, and tobacco use with no known diagnosis of connective tissue disease, and not in a high-risk state, who was found to have a spontaneous iliac artery dissection. He initially presented with sudden onset back pain that he described as a shooting pain that radiated into his head. He was also having right lower extremity discomfort. Initial vital signs were significant for tachycardia and hypertension, and physical exam was significant for tachycardia and diminished right posterior tibial and dorsalis pedis pulses. Laboratory workup was significant for a leukocytosis of 10.06 and creatinine of 1.52, consistent with acute kidney injury. Labs were otherwise unremarkable. Computed tomography angiogram (CTA) of the head and neck was negative for acute pathology, but CTA chest/abdomen/pelvis demonstrated arterial dissection that began at the origin of the right common iliac artery extending down to the right common femoral artery and also demonstrated a left renal infarct. A bare metal stent was placed by Interventional Radiology and the patient was started on dual antiplatelet therapy (DAPT) with a heparin drip and clopidogrel. Connective tissue disease workup was later performed including antinuclear antibody, rheumatoid factor, cyclic citrullinated peptide, and extractable nuclear antigen antibodies panel, which were all negative. Hospital stay was complicated by development of subarachnoid hemorrhage, intraventricular hemorrhage, subdural hematoma, and intradural hematoma that required laminoplasty and evacuation by Neurosurgery. DAPT was discontinued and the patient was later restarted on aspirin only. The patient then developed a cecal bleed that required clipping by Gastroenterology. Aspirin was discontinued and he then developed bilateral lower extremity deep venous thromboses and pulmonary emboli. He was started on enoxaparin with the assistance of Hematology and was later transitioned to apixaban with no complications. This case supports comorbidities as risk factors for spontaneous IAD and raises the need for formal screening and surveillance guidelines for these patients, as there are currently no guidelines in place. This case also demonstrates the complications that can occur with DAPT and anticoagulants and provides a manner in which to cautiously initiate anticoagulation in patients with high risk of bleeding while also preventing the development of further thrombi.

May-Thurner Syndrome Should be Explored As a Possible Existing Risk Factor in Pediatric Patients Presenting with Non-Central Venous Line Associated Deep Vein Thrombosis

Background: The compression of the left common Iliac vein (LCIV) by the right common iliac artery is called May-Thurner Syndrome (MTS). The incidence of this anatomic variance is unknown, though it is estimated to be 18-49%. It is currently established that the chronic compression of the iliac vein outflow results in various clinical symptoms including edema, pain, discoloration, skin ulcers and venous thromboembolism. Deep vein thrombosis (DVT) of the LCIV is the most reported presentation of MTS in pediatrics. DVTs in pediatric patients are rare and often provoked by a central venous line (CVL). Patients without a CVL in the context of left lower extremity (LLE) DVT often do not undergo MTS work-up if the DVT does not include the LCIV. To assess if MTS is a risk factor for LLE DVT distally to the LCIV, we describe an institutional incidence of MTS in two pediatric patient populations: those with non CVL-associated LLE DVTs and a control group composed of pediatric patients undergoing imaging that includes the LLE vasculature for unrelated reasons. Methods: This was a single center retrospective study. We identified patients with a non CVL-associated LLE DVT seen at our institution using ICD-10 codes as well as a cohort of patients who received imaging of the LLE vasculature for reasons other than DVT using radiology MRI protocol codes.Electronic medical records were reviewed for demographic variables such as age and gender. Patients without DVTs had imaging reviewed for the incidental finding of MTS. Those with DVTs had information collected regarding clinical characteristics such as coagulation panels, thrombosis risk factors (thrombophilic states, oral contraceptive use, obesity), and therapy received. All images were reviewed by a pediatric radiologist. Results: A total of 35 patients with non CVL-associated LLE DVTs, and 752 patients without CVL and without LLE DVTs were identified. Of those with LLE DVTs, 19 (54%) were found to have MTS. Of these 19 patients, 5 (26%) were obese, 14 (74%) were on oral contraceptive pills, and 8 (42%) reported prothrombotic risks (7 heterozygous for Factor V Leiden, 1 heterozygous for protein C deficiency). Two patients (10%) had no additional risk factors for thrombosis. Of those without LLE DVTs, 6 patients (0.01%) were incidentally diagnosed with MTS. Interestingly we also described one patient with non CVL-associated LLE DVT distally to the LCIV with MTS. Conclusions: In our study, the presence of MTS was significantly higher in the non CVL-associated LLE DVT group than in the control group. This study suggests that MTS should be considered, and associated imaging performed, in pediatric patients with a non CVL-associated LLE DVT, considering the incidence revealed by this single institutional case series. The presence of MTS in pediatric patients may significantly impact the life-long risk of DVT recurrence. Given that aging adversely impacts lower limb venous return (exacerbated by central obesity, sedentary lifestyle, and other risk factors) and that pregnancy is a known trigger of DVT in patients with MTS, knowledge of prior MTS may impact patient care over the lifespan.

May Thurner Syndrome: Diagnostic and Therapeutic Outcomes in an Institutional Setting

Introduction: May-Thurner syndrome (MTS), a chronic compression of left common iliac vein (CIV) against the lumbar vertebrae by overlying common iliac artery is an underappreciated contributor to left leg deep venous thrombosis. Even though the estimated prevalence of MTS is high in left-leg deep vein thrombosis (DVT) cases per autopsy studies, the clinical association remains low. Since the screening for MTS in patients with recurrent left-leg DVTs is not a common practice, diagnosis can either be incidental or a combination of clinical presentation and objective testing. Diagnosis is challenging via ultrasound (US) due to the deep anatomical location of iliac veins; therefore, invasive imaging including Contrast venography (CTV) is needed for confirmation. The management of MTS has been reformed over the years with the advances in minimally invasive therapeutic tools. We sought to review the management and outcomes of the MTS adult population by conducting a retrospective review to identify all adult cases of MTS at our academic safety net hospital between 2010 and 2022. Methods: Data was extracted and analyzed for baseline parameters including age, gender, ethnicity, and body mass index (BMI). Presenting symptoms, imaging used for MTS diagnosis (including US Doppler, magnetic resonance venography or CTV), and interventional approaches (catheter or systemic thrombolysis, thrombectomy, balloon angioplasty and/or stent placement) were additionally documented. SAS v9.4 (Cary, NC) was used for statistical analysis. Results: A total of 19 cases, predominantly females 68% (13/19), with a median age of 48 years and a mean BMI of 28.84 kg/m 2 diagnosed with MTS were identified. The predominant initial presentation was left lower extremity edema and pain 36% (7/19) later found to have a DVT, followed by non-healing venous ulcer 15% (3/19) and pelvic congestion syndrome 0.05 % (1/19). Whereas 42% (8/19) of the patients were diagnosed with MTS while undergoing evaluation for chronic and recurrent DVTs. All patients were diagnosed following CTV using transvenous pressures with the formation of collateral veins and a pressure gradient of more than 2 mm Hg across iliofemoral stenosis at rest. Sixteen patients (84%) underwent endovascular stent placement, while one patient underwent Balloon Angioplasty only. One patient refused any intervention for MTS however underwent great saphenous vein ablation for chronic venous wounds. In view of anticoagulation therapy, the initial choice in the most cases was low molecular weight heparin (LMWH), which was later transitioned to other choices, 81 % (10/16) were switched to direct oral anticoagulants, (apixaban= 10, rivaroxaban=3) due to ease of administration and compliance, while 19 % (3/16) were continued on LMWH for patient preference and pregnancy. Post-intervention complications consisted of stent failure in 25% (4/16) patients; related to stent thrombosis and Post-thrombotic Syndrome (PTS) in 12.5 % (2/16) patients. No bleeding complications were seen post any case of endovascular stent placement. Conclusion: This review was a highly educational experience giving us insight into this unacknowledged syndrome. Multiple factors could be contributing to this underdiagnosis, including invasive gold standard imaging for MTS, more easily recognizable risk factors for DVTs that can overshadow MTS, and a smaller number of data and studies. Some authorities have advocated a need to rule out MTS in young women with acute left lower extremity DVT, a clear female predominance was also noted (68%) in our analysis. Post-stent placement, systemic anticoagulation for 3-6 months is recommended, in our review, all patients (100%) who underwent stent placement were started on anticoagulation for at least 3 months. A small sample size, patients lost to follow-up (poor outcomes and complications could have been missed) and a single institutional review were some limitations of our study, however with a rare disease such as MTS with 2-3% prevalence it is difficult to conduct a large size, multi- institutional analysis. This study contributes to the limited literature available on MTS.

Correlation analysis of serum MMP-1 and MMP-2 levels with lower extremity deep venous thrombosis after operation for lower limb fracture

To investigate the relationship between serum matrix metalloproteinase-1(MMP-1) and matrix metalloproteinase-2(MMP-2) and the formation of deep venous thrombosis(LDVT) in lower extremity patients after surgery for lower extremity fracture, and to analyze the value of MMP-1 and MMP-2 in predicting the occurrence of LDVT after lower extremity fracture. From June 2018 to December 2021, 352 patients who planned to receive surgical treatment of lower limb fracture in our hospital were selected as the research objects. Venous blood was collected at 1, 2 and 3 days after surgery, respectively, and serum MMP-1 and MMP-2 levels were detected. The incidence of LDVT during hospitalization was analyzed, and the risk factors of postoperative LDVT in patients with lower limb fracture surgery and the predictive value of MMP-1 and MMP-2 for LDVT were analyzed. LDVT occurred in 40 patients (LDVT group), the incidence of LDVT was 11.36%, and 312 patients did not occurred(no occurred group). The serum levels of MMP-1 and MMP-2 in LDVT group increased gradually after surgery; the serum levels of MMP-1 and MMP-2 in the no occurred group increased slightly after surgery at 2 days and then decreased at 3 days after surgery (P<0.01);the serum levels of MMP-1 and MMP-2 in LDVT group were higher than those in the no occurred group at 2 days and 3 days after surgery (P<0.05). Serum levels of MMP-1 and MMP-2 were positively correlated with serum levels of interleukin-6 (IL-6), IL-8 and tumor necrosis factor -α (TNF-α) in LDVT patients at 2 days and 3 days postoperatively (P<0.05). Operative time, MMP-1 and MMP-2 postoperative 3 days were related to the occurrence of LDVT after lower limb fracture (P<0.01). The area under the curve(AUC) predicted by MMP-1 and MMP-2 postoperative 3 days for LDVT after lower limb fracture was 0.738 and 0.744 respectively, and the AUC predicted by combined MMP-1 and MMP-2 was 0.910, which was higher than that predicted by single indicator(Z=2.819 and 2.025, P<0.05). High levels of MMP-1 and MMP-2 after lower extremity fracture are closely related to the occurrence of LDVT, and 3 d mMP-1 and MMP-2 after surgery maybe used as evaluation indexes for LDVT risk prediction.

Effect of Information/Knowledge/Attitude/Practice Theory-Based Progressive Rehabilitation Care on the Risk of Lower Extremity Deep Venous Thrombosis and Nutritional Status of Patients Undergoing Percutaneous Coronary Intervention for Coronary Heart Disease

Coronary heart disease is one of the cardiovascular disorders with a high risk of morbidity and mortality among older adults. Percutaneous coronary intervention is the most effective treatment for coronary heart disease. However, there are substantial safety concerns for postoperative lower-extremity deep venous thrombosis and nutrient loss. Herein, we randomly divided 112 patients with coronary heart disease into an experimental group who received progressive rehabilitation nursing care based on the information/knowledge/attitude/practice theory and a control group who received conventional nursing care. We found that the experimental group had a lower incidence of deep venous thrombosis, better cardiac function, enhanced physical fitness, and nutritional status than the control group after nursing care. Moreover, we observed better self-care ability, quality of life, and higher nursing satisfaction in the experimental group than in the control group. We demonstrated the importance of information/knowledge/attitude/practice theory-based progressive rehabilitation care in providing a more reliable safety guarantee for deep venous thrombosis and nutritional status for patients with coronary heart disease after percutaneous coronary intervention, as recommended in clinical practice.

Biomimetic platelet-camouflaged drug-loaded polypyrrole for the precise targeted antithrombotic therapy

Lower extremity deep venous thrombosis (LEDVT) affects patient’s quality of life for a long time, and even causes pulmonary embolism, which threatens human health. Current anticoagulant drugs in clinical treatment are hampered by the risk of bleeding due to poor targeting and low drug penetration. Here, we used platelet (PLT)-like biological targeting to enhance the delivery and accumulation of nanomedicines in thrombus and reduce the risk of bleeding. Meanwhile, the parallel strategy of “thrombus thermal ablation and anticoagulation” was applied to increase the permeability of drugs in thrombus and achieve the optimal antithrombotic effect. Polypyrrole (PPy) and rivaroxban (Riv, an anticoagulant drug) were co-assembled into platelet membrane-coated nanoparticles (NPs), PLT-PPy/Riv NPs, which actively targeted the thrombotic lesion at multiple targets in the platelet membrane and were thermally and drug-specific thrombolysed by 808 nm laser irradiation. The combination therapy resulted in up to 90% thrombolysis in a femoral vein thrombosis model compared to single phototherapy or drug therapy. The results showed that the nanoformulation provided a new direction for remote precise and controlled sustained thrombolysis, which was in line with the trend of nanomedicine towards clinical translation.

Intracardiac thrombosis and vascular involvement in Behcet's syndrome: two sides of the same coin?

Abstract Background Behçet’s syndrome (BS) is a complex and relapsing vasculitis that affects vessels of all kinds and sizes. Intracardiac thrombosis (ICT) is a rare but serious complication of the disease, that usually presents with vascular lesions. However, its pathogenesis remains unclear and the link between these manifestations is yet not fully clarified. Objectives Our work aims to describe the clinical characteristics, imaging features, therapeutic management, and outcomes of BS patients with ICT. And secondly, to shed some light on the relation between ICT and the vascular involvement of the disease. Methods We retrospectively conducted a descriptive and monocentric study including 531 BS patients admitted to our department between 2010 and 2022. Results Twelve cases of ICT were enrolled (2%). Patients were mostly males (91.6%), with a mean age of 29 ± 6 years (20 – 41). Past history of lower extremity deep vein thrombosis (DVT) related to BS was frequently reported (41%). ICT was the revealing manifestation of the disease in 50% of the cases. In the other half, it occurred after a median of 4 years following BS onset. Symptoms were dyspnea (50%), chest pain (50%), dry cough (40%), and hemoptysis (30%). Signs of right (33%) and global (17%) heart failure were found. Concomitant noncardiovascular manifestations were mainly mucocutaneous (80%). Inflammatory parameters were always raised with a median ESR of 48 mm/h and CRP of 52 mg/l. Hemostasis parameters were within the normal ranges for all patients. High levels of BNP and Troponin were detected in respectively 50% and 16% of the cases. On echocardiography, ICT was located in the right heart (100%), with an extension to the inferior vena cava (50%). Multiple thrombi were visualized in three cases. The associated cardiac lesions were pericardial effusion (50%), tricuspid (50%) and mitral insufficiency (10%), endomyocardial fibrosis (10%), myocarditis (10%), and ischemic coronaropathy (8%). Pulmonary hypertension (75%) and right dilatation (58%) were frequent, with persevered systolic function (100%). On Chest CTA, pulmonary artery thrombosis (70%) and aneurysms (50%) were observed. Peripheral DVT was also common (41%). All patients were treated with colchicine, glucocorticoids, and immunosuppressants: cyclophosphamide (n=11), and TNF-alpha inhibitor (n=1). Curative anticoagulation was prescribed in half of the cases. Outcomes were: complete remission (n=9), partial remission (n=2), and relapse (n=1). No death was recorded. Conclusion ICT in BS is a life-threatening event that occurs in the first years of the disease onset, among young men with vascular lesions, especially of the pulmonary arteries and vena cava. We believe that this strong association is highly suggestive that, unlike other thrombotic diseases, ICT in BS is a direct consequence of the underlying vasculitis. Hence, prompt and adequate management with immunosuppressive therapy is usually associated with good outcomes.Clinical baseline characteristicsCardiac and vascular manifestations

Abstract 16163: Low Dose Alteplase for Treatment of Pacemaker Lead Associated Thrombosis

Multiple previously published case reports highlighted the thromboembolic risks associated with permanent transvenous pacemaker leads. Even though mostly clinically silent, pacemaker lead associated thrombosis has been linked to fatal outcomes via pulmonary or paradoxical embolism in the case of large mobile RA or RV thrombi formation. There is a lack of consensus on the optimal strategy for managing this condition. Oral and IV anticoagulation, thrombolysis, surgical and percutaneous thrombectomy have been attempted previously with mixed results. A 72 year old gentleman with a history of CAD requiring PCI, paroxysmal atrial fibrillation, and AV node ablation with subsequent biventricular pacemaker implant was admitted to our hospital with a few weeks of worsening dyspnea, now present at rest. Surface echocardiogram showed multiple mobile echo densities in the right ventricle and right atrium, attached to the pacemaker leads, confirmed by TEE, most likely thrombi. The venous duplex was positive for right lower extremity DVT. Bilateral pulmonary emboli with mild right-sided heart strain were noted on CTA chest. The patient was initially treated with IV unfractionated heparin. We subsequently decided to start low-dose tPA infusion for 24 hrs, similar to current off-label protocols for mechanical prosthetic valves or bioprosthetic valve thrombosis. After an initial IV bolus of 5 mg, 1 mg/hour of alteplase was continued for 24 hours. Our team has decided to use percutaneous thrombectomy as a last resort.Follow-up ECHO immediately post tPA infusion showed complete thrombi resolution. The patient was asymptomatic at this point. He was discharged the following day on Lovenox and Coumadin. To our knowledge, this is the first case demonstrating complete resolution of pacemaker lead-associated thrombi by using a 24 hr low dose tPA infusion in addition to IV anticoagulation. This can be entertained as a simple conservative initial strategy in stable patients with pacemaker lead/catheter-associated intracardiac thrombi.

Incidence and Risk Factors for Thrombosis in Cancer Patients with COVID-19

Introduction: Cancer is a leading cause of morbidity and mortality in the United States, and cancer patients infected with COVID-19 are at increased risk of death. Given that cancer and COVID-19 are both risk factors for thrombosis, it has been hypothesized that cancer patients with COVID-19 may be at greater risk for thromboembolic events than patients with COVID-19 alone. This risk could necessitate the need for more vigilant thrombosis prophylaxis. However, studies investigating risk factors for thromboembolic events in this population are limited with mixed results. We aimed to determine the incidence and risk factors for thromboembolic events in patients with cancer and COVID-19. Methods: We performed a retrospective cohort review of all cancer patients hospitalized with COVID-19 at our institution between January 1, 2021 and April 1, 2023. Patients over the age of 18 who had previously been diagnosed with cancer, received treatment within the prior 6 months, and had been hospitalized due to COVID-19 were included in the study. We assessed whether patients had experienced a thromboembolic event during their hospital stay, which included thrombosis of the extracorporeal circuit, distal or proximal lower extremity deep venous thrombosis (DVT), upper extremity DVT, pulmonary embolism, superficial thrombophlebitis, ischemic stroke, or other arterial event. Information regarding comorbidities and clinical course was extracted from the patient's record. Descriptive analysis was performed, and association between qualitative variables was studied with the Chi-squared test and the Fisher Exact test, when appropriate. For quantitative variables, the t-test or the Mann-Whitney U test was performed. Multivariate logistic regression was used to assess variables predictive of thromboembolic events. Results: 456 patients with cancer and COVID-19 were included in the study. The median age was 69 years (IQR 62 - 78) and 55% of patients were male. The majority (85%) of patients were White. Most patients had either lung (19%) or bone marrow (17%) cancer, and 196 (43%) had received chemotherapy in the 6 months prior to hospitalization. 37 patients (8.1%) had thromboembolic events during their hospital stay. Age, race, receipt of chemotherapy, and history of hypertension, heart disease, obesity, and stroke were not predictive of thromboembolic events. Patients with thromboembolic events experienced significantly longer lengths of hospital stay than those without thromboembolic events (9 days vs 12 days, p&amp;lt;0.05). Conclusion: Thromboembolic events affect many cancer patients with COVID-19 and may complicate their treatment course during hospitalization. Patients who experienced a thromboembolic event had prolonged hospital stays, which may lead to increased financial and emotional burden in this patient population. Evidence-based strategies for preventing thrombosis, including pharmacologic and mechanical methods, should be emphasized in hospitalized cancer patients with COVID-19, which may decrease thrombotic complications. Further, methods of secondary thrombosis prophylaxis, such as early detection with screening methods or treatment of subclinical methods, should be encouraged. Future studies should promote risk classification in this patient population and optimal prophylaxis paradigms.

Recurrent Leg Deep Vein Thrombosis in a Female with Atypical Right-Sided Variant of May Thurner Syndrome and Factor V Leiden Mutation

I ntroduction: May-Thurner syndrome (MTS) is a condition in which the right common iliac artery presses on the left common iliac vein, causing it to narrow over time. Right-sided MTS is a rare event. We present this unique case of recurrent right leg deep vein thrombosis in a female with atypical right sided variant of MTS and Factor V Leiden mutation. Case Presentation: A 34-year-old lady with with no signficiant past medical history presented to the hospital with right lower leg edema, tingling, and discolouration. She was taking oral contraceptive pills. Vitals were unremarkable. Doppler studies revealed right lower extremity deep vein thrombosis in the right external iliac vein, common iliac vein and common femoral vein. She was started on an intravenous heparin drip and subsequently had a thrombectomy procedure. She was subsequently discharged home on apixaban anticoagulation. We opted to request a hypercoagulable and vasculitis workup in light of the extensive thrombosis, despite the OCP risk factor, and discovered a heterozygous Factor V Leiden mutation. She returned to the hospital 2 days later with worsening right leg pain. Repeat Doppler studies demonstrated acute right femoral and popliteal deep vein thrombosis. CT angiography of abdomen and pelvis revealed significant right femoral vein DVT that extends into the External iliac vein, common iliac vein, and IVC to at least slightly below renal vein level. Invasive Radiology was consulted and she had a venogram and intravascular ultrasound (IVUS) which showed high-grade right common iliac vein and IVC stenosis (&amp;gt;90%) at L4 superior endplate. Iliac stenting and angioplasty improved iliac and inferior IVC diameters. Patient also underwent thrombectomy &amp; IVC filter placement. The diagnostic venography revealed a popliteal-to-proximal femoral vein rethrombosis. This was treated with tissue plasminogen activator (TPA) by 8 French power pulse AngioJet and a mechanical thrombectomy. This resulted in partial clearing of the common femoral vein with persistent narrowing and thrombosis of the popliteal vein. TPA was infused at 1 mg/hour with a 5 French McNamara lysis catheter over the popliteal region.Patient transferred to ICU for overnight intravenous thrombolysis. The patient was then re-initiated on the heparin drip and then bridged to therapeutic warfarin. Discussion: MTS is a phenomenon commonly described as an acquired stenosis of the left common iliac vein secondary to compression by the right common iliac artery 1. It has been associated with genetic clotting factor abnormalities, repeated pregnancies, postpartum, contraceptive pills, prolonged immobilization, scoliosis, anti-phospholipid syndrome, COVID-19, and recurrent DVT 2. In patients with left lower-limb DVT, the incidence of MTS is about 20-50%. Right lower limb DVT in patients with right sided variant of MTS is rare. Right lower limb DVT with right sided variant of MTS with co-existing Factor V Leiden mutation is even rarer. Ultrasound imaging typically cannot detect the high pelvic abnormalities seen in MTS. Contrast venography, MRI, or IVUS are needed to diagnose MTS 4. As was the case in our patient, venography should be done to evaluate stenosis and iliac vein compression hemodynamics after thrombus removal. Treatment of MTS depends on the presentation, severity of symptoms, and whether the patient has developed DVT. Conservative treatment such as compression stockings can be used for patients who are asymptomatic or have mild symptoms. For patients with moderate symptoms or DVT, endovascular treatment with stenting is recommended 5. Conclusion: This is a very atypical presentation of MTS variation affecting the right lower extremity with limited description in the literature. To our knowledge, this is the first case presentation of right sided MTS resulting in a DVT in a patient with factor V Leiden mutation. MTS is a potentially treatable and often-overlooked pathology. In the era of expanded endovascular management of MTS, recognition of this disease entity is essential for early diagnosis and treatment.

Dynamic Modelling for Cancer-Associated Venous Thromboembolism

Background: Cancer-associated venous thromboembolism (VTE) is an important source of morbidity and mortality. Current risk prediction models for thrombosis are handicapped by static applicability (i.e. one-time evaluation prior to the first cycle of chemotherapy). We hypothesized that event forecasting using time series modelling could account for important changes in clinical state, variations in treatment and aspects of cancer progression over time. Methods: The cohort consisted of adult patients with a solid tumor enrolled in the MSK-IMPACT study between 2014 and 2019. VTE was defined as any symptomatic or asymptomatic pulmonary embolus or lower extremity deep vein thrombosis. We derived time series mixed-effects logistic regression models in order to predict cancer-associated VTE events using baseline patient characteristics (cancer type, time from diagnosis and age) along with time-dependent covariates including total white blood cell count, hemoglobin, platelet count, albumin, creatinine and parenteral chemotherapy type. Time-periods of one month were used and models were fitted to predict the presence or absence of a VTE episode in the following period (time = t+1) based on predictor values in the current period (time = t). The laboratory test result ascribed to a given period could be either the last value in the interval or the mean of all interval-specific values (both approaches tested). Missing laboratory results were imputed using the previously known value when available. Differences in laboratory values between periods t-1 and t were included as predictors in the initial model along with indicators of missingness (see Figure for flow of information between time-period cells). We hypothesized that absence of laboratory testing for a time-period would be a marker of stable medical state and hence associated with a lower risk of VTE. A previously defined training set comprising 80% of the cohort was used and different modelling approaches were evaluated using 5-fold cross-validation. The final selected model was evaluated in a separate dedicated validation set including the remaining 20% of the cohort. Results: The original cohort included 35,391 patients, from which 26,075 individuals with no cancer-associated VTE episode before observation start and sufficient laboratory test information could be included in the analysis, comprising 276,579 months of observation and 1,463 VTE events. The initial logistic regression model including all available predictors was fitted on the training set, revealing associations between predictors and VTE risk largely consistent with data reported by other groups (see Table). After adjusting for multiple comparisons, significant predictors of cancer-associated VTE identified included albumin, cell count result missingness (decreased risk for missing value), treatment with a platinum analogue (increased risk), hemoglobin, white blood cell count, breast cancer (decreased risk) and high-grade glioma (increased risk). Based on model metrics and prior knowledge from published literature, the set of covariates selected for inclusion in the final model consisted of cell counts along with the corresponding missingness indicator, platelet count change over time, albumin and chemotherapy types. The c-index for the final model using 5-fold cross-validation in the training set was 0.77 (95% CI = 0.75-0.80), compared to 0.77 (95% CI = 0.74-0.79) in the validation set. The latter corresponded to a specificity of 0.83 (95% CI = 0.79-0.86) when fixing sensitivity at 50%. Conclusions: A simple mixed-effects logistic regression time series model demonstrated promising potential to estimate the risk of cancer-associated VTE on a dynamic basis using routine laboratory test results and chemotherapy prescription data widely available in most electronic health record systems. Validation of this dynamic VTE risk model has the potential to optimize outpatient thromboprophylaxis during periods of high thrombotic risk.

Development of a Combined Risk Assessment Model for Venous Thromboembolism and Bleeding in Hematopoietic Stem Cell Transplantation Patients

Background: Venous thromboembolism (VTE) and bleeding are common complications amongst allogeneic and autologous hematopoietic stem cell transplant (HSCT) patients. Balancing risk of bleeding and thrombosis in this population is particularly challenging as HSCT patients are concurrently pancytopenic and coagulopathic. However, risk factors for bleeding and thrombosis in HSCT patients are understudied. We aimed to derive a combined bleeding and VTE risk assessment tool to be used in the immediate post-transplant period (90 days). Methods: We conducted a retrospective cohort study of adult patients who underwent allogeneic or autologous HSCT between January 1, 2011 and December 31, 2021 at a tertiary care centre in Canada. The risk models patients were followed from transplant until occurrence of the event of interest with last follow up at Day 90 post-transplant, or death. Primary outcome for VTE was the occurrence of a confirmed thrombosis including proximal upper and lower extremity deep vein thrombosis, pulmonary embolism, or thrombosis of unusual sites, including cerebral and splanchnic. Primary outcome for bleeding was the occurrence of a major or clinically significant non-major bleeding event, not related to anticoagulation, as per the definition of the International Society of Thrombosis and Hemostasis. Group characteristics were compared using chi-square, Fisher's exact, or Student's T-tests as appropriate. Potential predictors for VTE and bleed amongst our patients were evaluated using single variable logistic regression and confirmed with multiple variable logistic regression with forward selection. For continuous variables, optimal cut-off points were estimated using ROC curves. Final VTE and bleed risk scores were derived based on weighted variables and compared using Cox regression with non-parametric bootstrapping used for internal validation. Results: A total of 476 patients (317 autologous, 159 allogeneic) were included. 47 patients (9.8%) suffered from VTE, and 32 patients (6.7%) suffered from bleed unrelated to anticoagulation within 90 days post-HSCT. A VTE risk assessment tool was derived, and internally validated, and it included: second central venous catheter insertion (due to complications from first central line) (2 points), and previous cancer treatment with steroids (1 point). The overall cumulative incidence of VTE was 31.8% in the high-risk group (&amp;gt;2 points) versus 7.6% in the low-risk group (0-1 points). The high-risk group was associated with higher mortality at 90 days (15.9% versus 3.2%, p &amp;lt;0.001; Figure 1). A bleeding risk assessment tool was also derived, and internally validated, and it included: baseline (day 0 of transplant) platelet count of &amp;lt;90 (1 point), and baseline hemoglobin of &amp;lt;96 (1 point). The overall cumulative incidence of bleed was 17.2% in the high-risk group (2 points), versus 4.3% in the low-risk group (0-1 points). The high-risk group was associated with higher mortality at 90 days (12.6% versus 2.6%, p&amp;lt;0.001). Amongst the low-risk bleed group, overall cumulative incidence of VTE was 10.03%, with 31.03% in the high-risk VTE group versus 8.33% in the low-risk VTE group (p&amp;lt;0.001). The positive VTE group was associated with higher mortality at 90 days (10.26% versus 1.72%, p=0.001; Figure 2). Amongst the high-risk bleed group, overall cumulative incidence of VTE was 9.19%, with 33.33% in the high-risk VTE group, versus 4.17% in the low-risk VTE group (p&amp;lt;0.001). The positive VTE group was associated with higher mortality at 90 days (37.5% versus 10.13%, p=0.026). Conclusion: We derived a predictive score, VTE and Bleeding in Marrow Transplant (VBMT) - risk score, for both VTE and bleeding in the immediate post-transplant period (90 days), to be used in conjunction with other criteria for bleeding and thrombosis. Amongst the low-risk bleed patients, we recommend strong consideration of chemical VTE prophylaxis, especially amongst the high-risk VTE group. These risk assessment models will help stratify patients based on bleed and thrombosis risk, and ultimately help guide VTE prophylaxis and surveillance strategies amongst HSCT patients.