Venous thromboembolism: diagnostic advances and unaddressed challenges in management.

PURPOSE OF REVIEW: This review summarizes recent advances in developing targeted diagnostics for venous thromboembolism (VTE) and unaddressed knowledge gaps in patient management. Without addressing these critical data needs, the morbidity in VTE patients will persist. RECENT FINDINGS: Recent studies investigating plasma protein profiles in VTE patients have identified key diagnostic targets to address the currently unmet need for low-cost, confirmatory, point-of-care VTE diagnostics. These studies and a growing body of evidence from animal model studies have revealed the importance of inflammatory and vascular pathology in driving VTE, which are currently unaddressed targets for VTE therapy. To enhance the translation of preclinical animal studies, clinical quantification of thrombus burden and comparative component analyses between modeled VTE and clinical VTE are necessary. SUMMARY: Lead candidates from protein profiling of VTE patients' plasma offer a promising outlook in developing low cost, confirmatory, point-of-care testing for VTE. Additionally, addressing the critical knowledge gap of quantitatively measuring clinical thrombi will allow for an array of benefits in VTE management and informing the translatability of experimental therapeutics.

Role of platelet count in a murine stasis model of deep vein thrombosis.

Platelets are core components of thrombi but their effect on thrombus burden during deep vein thrombosis (DVT) has not been fully characterized. We examined the role of thrombopoietin-altered platelet count on thrombus burden in a murine stasis model of DVT. To modulate platelet count compared to baseline, CD1 mice were pretreated with thrombopoietin antisense oligonucleotide (THPO-ASO, 56% decrease), thrombopoietin mimetic (TPO-mimetic, 36% increase), or saline (within 1%). Thrombi and vein walls were examined on postoperative days (POD) 3 and 7. Thrombus weights on POD 3 were not different between treatment groups (p = .84). The mean thrombus weights on POD 7 were significantly increased in the TPO-mimetic cohort compared to the THPO-ASO (p = .005) and the saline (p = .012) cohorts. Histological grading at POD 3 revealed a significantly increased smooth muscle cell presence in the thrombi and CD31 positive channeling in the vein wall of the TPO-mimetic cohort compared to the saline and THPO-ASO cohorts (p < .05). No differences were observed in histology on POD 7. Thrombopoietin-induced increased platelet count increased thrombus weight on POD 7 indicating platelet count may regulate thrombus burden during early resolution of venous thrombi in this murine stasis model of DVT.

Deep vein thrombosis (DVT) is a pathology in which blood clots form in the deep veins of our body. Usually occurring in the legs, these clots can be dangerous if they dislodge and travel to the heart and are pumped into the lungs. Often these clots do not travel and heal where they formed. However, as the body heals the clot it may also cause damage to the vein wall and predispose the patient to future clots, i.e., the biggest risk factor for a second clot is the first clot. DVT can also cause symptoms of pain, swelling, and redness in the long-term, leading to post-thrombotic syndrome where the initial symptoms of the clot persist for a long time. All blood clots have common components of red blood cells, white blood cells, platelets, and fibrin in varying concentrations. Humans maintain a platelet count between 150 and 400 thousand platelets per microliter of our blood. However, diseases like cancer or medications like chemotherapy can cause a change in our body's platelet count. The effect of a changing platelet count on the size (clot burden) of DVT clot and how platelet count could affect DVT as the clot heals is not fully understood. Studying this might help us develop better targets and treat patients with a wide range of platelet counts who experience DVT. In this study, we intentionally decreased, left unchanged, and increased platelet counts in mice and then created a DVT to study what the effect of low, normal, and high platelet counts, respectively, would be on the clot burden. We observed that mice with higher platelet counts had a higher clot burden during the early part of the healing process of the clot. Within this study, we can conclude that higher platelet counts may lead to higher clot burden in DVT which furthers our understanding of how platelet count affects clot burden during DVT.

Discovery and Characterization of Antibody Probes of Module 2 of the 6-Deoxyerythronolide B Synthase.

Fragment antigen-binding domains of antibodies (Fabs) are powerful probes of structure-function relationships of assembly line polyketide synthases (PKSs). We report the discovery and characterization of Fabs interrogating the structure and function of the ketosynthase-acyltransferase (KS-AT) core of Module 2 of the 6-deoxyerythronolide B synthase (DEBS). Two Fabs (AC2 and BB1) were identified to potently inhibit the catalytic activity of Module 2. Both AC2 and BB1 were found to modulate ACP-mediated reactions catalyzed by this module, albeit by distinct mechanisms. AC2 primarily affects the rate (kcat), whereas BB1 increases the KM of an ACP-mediated reaction. A third Fab, AA5, binds to the KS-AT fragment of DEBS Module 2 without altering either parameter; it is phenotypically reminiscent of a previously characterized Fab, 1B2, shown to principally recognize the N-terminal helical docking domain of DEBS Module 3. Crystal structures of AA5 and 1B2 bound to the KS-AT fragment of Module 2 were solved to 2.70 and 2.65 Å resolution, respectively, and revealed entirely distinct recognition features of the two antibodies. The new tools and insights reported here pave the way toward advancing our understanding of the structure-function relationships of DEBS Module 2, arguably the most well-studied module of an assembly line PKS.

Myeloid p53 regulates macrophage polarization and venous thrombus resolution by inflammatory vascular remodeling in mice.

Deep venous thrombosis (DVT) remains a common and serious cardiovascular problem with both fatal and long-term consequences. The consequences of DVT include the development of postthrombotic syndrome in 25% to 60% of DVT patients. Despite the clinical importance of venous thrombus resolution, the cellular and molecular mediators involved are poorly understood, and currently there is no molecular therapy to accelerate this process. Several lines of evidence suggest that a complex and interrelated array of molecular signaling processes are involved in the inflammatory vascular remodeling associated with the resolution of DVT. Here, we have identified a role for the tumor suppressor gene p53 in regulating venous thrombus resolution. Using the stasis model of venous thrombosis and resolution in mice, we found that genetic deficiency of p53 or pharmacologic inhibition by pifithrin impairs thrombus resolution and is associated with increased fibrosis and altered expression of matrix metalloproteinase-2. The effect of p53 loss was mediated by cells of the myeloid lineage, resulting in enhanced polarization of the cytokine milieu toward an M1-like phenotype. Furthermore, augmentation of p53 activity using the pharmacological agonist of p53, quinacrine, accelerates venous thrombus resolution in a p53-dependent manner, even after establishment of thrombosis. Together, these studies define mechanisms by which p53 regulates thrombus resolution by increasing inflammatory vascular remodeling of venous thrombi in vivo, and the potential therapeutic application of a p53 agonist as a treatment to accelerate this process in patients with DVT.

Venous thrombosis in unusual sites: A practical review for the hematologist.

Thrombosis of unusual venous sites encompasses a large part of consultative hematology and is encountered routinely by practicing hematologists. Contrary to the more commonly encountered lower extremity venous thrombosis and common cardiovascular disorders, the various thromboses outlined in this review have unique presentations, pathophysiology, workup, and treatments that all hematologists should be aware of. This review attempts to outline the most up to date literature on cerebral, retinal, upper extremity, hepatic, portal, splenic, mesenteric, and renal vein thrombosis, focusing on the incidence, pathophysiology, provoking factors, and current recommended treatments for each type of unusual thrombosis to provide a useful and practical review for the hematologist.

Arterial thrombosis in unusual sites: A practical review.

While cardiovascular disease is common, occasionally hematologists and other practitioners will encounter patients with arterial thrombosis/infarction in unusual sites, without clear cause or obvious diagnostic and treatment paradigms. Contrary to the more commonly encountered cerebrovascular accident and cardiovascular disorders, the various infarctions outlined in this review have unique presentations, pathophysiology, workup, and treatments that all hematologists should be aware of. This review outlines the current literature on arterial thrombosis, with consideration given to anatomic sources and hypercoagulable associations, while focusing on the epidemiology, pathophysiology, provoking factors, and current recommended treatments for intracardiac thrombus, primary aortic mural thrombus, visceral infarctions, and cryptogenic limb ischemia to provide a useful and practical review for the practitioner.

Venous Conduits Have Superior Patency Compared with Prosthetic Grafts for Femorofemoral Bypass.

BACKGROUND: The objective of the study was to compare the outcomes of externally supported polytetrafluoroethylene (PTFE) grafts and femoral vein as conduits for femorofemoral crossover grafts. METHODS: This is a retrospective review of consecutive femorofemoral crossover grafts at our institution between January 2005 and March 2016. Patient demographics, indications, complication rates, patency rates, and survival rates were compared between femorofemoral grafts created with either PTFE or femoral vein conduits, autogenous or cryopreserved. RESULTS: One hundred nineteen femorofemoral crossover bypasses (89 PTFE, 30 vein [18 autogenous and 12 cryopreserved femoral veins]) were performed. Most patients underwent isolated femorofemoral bypass alone (76% isolated femorofemoral bypass versus 24% axillobifemoral bypass). A greater proportion of patients who received vein grafts were female (PTFE 37% vs. vein 60%, P = 0.028) and had prior bypasses (PTFE 33% vs. vein 73%, P < 0.001). PTFE bypasses were performed primarily for chronic limb ischemia (61.8%), while most venous bypasses were for infections (80%, P < 0.001). Femoral vein conduits were used in cases of infected aortic or extra-anatomical grafts (N = 20) or groin infection (N = 5). The 30-day complication rate was 38.7% and was not different between groups (36% for PTFE, 44.4% for autologous vein grafts and 50% for cryovein, P = 0.33) with wound complications being most frequent (18% PTFE, 27.8% autologous vein, 16.7% cryovein, P = 0.25). Patients receiving vein grafts were more likely to receive blood transfusion (34.8% PTFE vs. 70% vein, P = 0.001). Overall, median follow-up was 9.8 months (range 0-107). Primary patency rates at 1, 2, and 3 years were 83.7 %, 73.7% and 69.8%, respectively, for PTFE bypasses, and 100% for all time points for venous grafts, respectively (log rank, P = 0.03). Primary-assisted and secondary patency rates were not significantly different between the 2 groups (log rank, P = 0.16). Survival rates at 1, 2, and 3 years were 82%, 76.4% and 69.7%, respectively, for patients with PTFE grafts versus 76.7%, 73.3%, and 55%, respectively, for patients with vein grafts, respectively (log rank, P = 0.17). CONCLUSIONS: While the indications for procedure differed in this series, femoral veins in femorofemoral bypasses have overall superior primary patency and similar complication rates compared with PTFE grafts. Based on this series, femoral vein, either autologous or cryopreserved, appears to be a suitable conduit for femorofemoral bypasses, and in some cases, it may be the preferred conduit.

Comparison of Nonpenetrating Titanium Clips versus Continuous Polypropylene Suture in Dialysis Access Creation.

BACKGROUND: Nonpenetrating titanium surgical clips (clips) offer a theoretical advantage of inducing less intimal hyperplasia at an anastomosis because of less endothelial injury. Whether this translates into improved outcomes when used in the creation of arteriovenous fistulas (AVFs) remains unclear. We sought to compare the maturation, patency, and failure rates of anastomoses created using traditional continuous polypropylene suture and clips. METHODS: All primary AVF created at a single Veterans Administration Medical Center were reviewed over a 6-year period. Anastomoses were created with either clips or suture based on surgeon preference. Patient characteristics and surgical outcomes were collected. Comparisons were made between the 2 groups. RESULTS: Over a 6-year period, 334 fistulas were created (29% suture and 71% clips) in 326 patients. The mean age was 64.8 ± 11 years with 98% males. Comorbidities included diabetes (70%), hypertension (96.1%), and tobacco use (52.9% previous or current). Approximately half the patients were predialysis. Comparison of patient characteristics showed no differences between the suture and clip groups. There was no significant difference in maturation rate (suture 79% versus clips 72%, P = 0.25), median time to maturation (suture 62 ± 35 versus clips 71 ± 13 days, P = 0.07), 1 year primary patency rate (suture 37.4% versus clips 39.6, P = 0.72), 1 year assisted primary patency rate (suture 82.4% versus clips 76.3%, P = 0.31), or overall failure rates (suture 62% versus clips 58%, P = 0.56). Median time to initial failure or reintervention was not significantly different in the clip group (suture 615 [range, 239-991] versus clips 812 [range, 635-989] days, P = 0.72). CONCLUSIONS: Compared to traditional polypropylene suture creation of upper extremity AVFs, nonpenetrating clips had equivalent maturation, 1-year patency, and overall failure rates. Neither clips nor suture offers any clear advantage in the creation of AVF.

Factors associated with lack of clinical improvement after vein ablation in the vascular quality initiative.

BACKGROUND: Insurance companies have adopted variable and inconsistent approval criteria for chronic venous disease (CVD) treatment. Although vein ablation (VA) is accepted as the standard of care for venous ulcers, the treatment criteria for patients with milder forms of CVD remain controversial. This study aims to identify factors associated with a lack of clinical improvement (LCI) in patients with less severe CVD without ulceration undergoing VA to improve patient selection for treatment. METHODS: We performed a retrospective analysis of patients undergoing VA for CEAP C2 to C4 disease in the Vascular Quality Initiative varicose veins database from 2014 to 2023. Patients who required intervention in multiple veins, had undergone prior interventions, or presented with CEAP C5 to C6 disease were excluded. The difference (Δ) in venous clinical severity score (VCSS; VCSS before minus after the procedure) was used to categorize the patients. Patients with a ΔVCSS of ≤0 were defined as having LCI after VA, and patients with ≥1 point decrease in the VCSS after VA (ΔVCSS ≥1) as having some benefit from the procedure and, therefore, "clinical improvement." The characteristics of both groups were compared, and multivariable regression analysis was performed to identify factors independently associated with LCI. A second analysis was performed based on the VVSymQ instrument, which measures patient-reported outcomes using five specific symptoms (ie, heaviness, achiness, swelling, throbbing pain, and itching). Patients with LCI showed no improvement in any of the five symptoms, and those with clinical improvement had a decrease in severity of at least one symptom. RESULTS: A total of 3544 patients underwent initial treatment of CVD with a single VA. Of the 3544 patients, 2607 had VCSSs available before and after VA, and 420 (16.1%) had LCI based on the ΔVCSS. Patients with LCI were more likely to be significantly older and African American and have CEAP C2 disease compared with patients with clinical improvement. Patients with clinical improvement were more likely to have reported using compression stockings before treatment. The vein diameters were not different between the two groups. The incidence of complications was overall low, with minor differences between the two groups. However, the patients with LCI were significantly more likely to have symptoms after intervention than those with improvement. Patients with LCI were more likely to have technical failure, defined as vein recanalization. On multivariable regression, age (odds ratio [OR], 1.01; 95% confidence interval [CI], 1.00-1.02) and obesity (OR, 1.47; 95% CI, 1.09-2.00) were independently associated with LCI, as was treatment of less severe disease (CEAP C2; OR, 1.82; 95% CI, 1.30-2.56) compared with more advanced disease (C4). The lack of compression therapy before intervention was also associated with LCI (OR, 6.05; 95% CI, 4.30-8.56). The analysis based on the VVSymQ showed similar results. CONCLUSIONS: LCI after VA is associated with treating patients with a lower CEAP class (C2 vs C4) and a lack of compression therapy before intervention. Importantly, no significant association between vein size and clinical improvement was observed.

Pharmacologic targeting of coagulation factors XII and XI by monoclonal antibodies reduces thrombosis in nitinol stents under flow.

BACKGROUND: Cardiovascular implantable devices, such as vascular stents, are critical for the treatment of cardiovascular diseases. However, their success is dependent on robust and often long-term antithrombotic therapies. Yet, the current standard-of-care therapies often pose significant bleeding risks to patients. Coagulation factor (F)XI and FXII have emerged as potentially safe and efficacious targets to safely reduce pathologic thrombin generation in medical devices. OBJECTIVES: To study the efficacy of monoclonal antibody-targeting FXII and FXI of the contact pathway in preventing vascular device-related thrombosis. METHODS: The effects of inhibition of FXII and FXI using function-blocking monoclonal antibodies were examined in a nonhuman primate model of nitinol stent-related thrombosis under arterial and venous flow conditions. RESULTS: We found that function-blocking antibodies of FXII and FXI reduced markers of stent-induced thrombosis in vitro and ex vivo. However, FXI inhibition resulted in more effective mitigation of thrombosis markers under varied flow conditions. CONCLUSION: This work provides further support for the translation of contact pathway of coagulation inhibitors for their adjunctive clinical use with cardiovascular devices.

Mitochondrial heat shock protein-90 modulates vascular smooth muscle cell survival and the vascular injury response in vivo.

The healing response of blood vessels from the vascular injury induced by therapeutic interventions is characterized by increased cellularity and tissue remodeling. Frequently, this leads to intimal hyperplasia and lumen narrowing, with significant clinical sequelae. Vascular smooth muscle cells are the primary cell type involved in this process, wherein they express a dedifferentiated phenotype that transiently resembles neoplastic transformation. Recent studies have highlighted the role of mitochondrial proteins, such as the molecular chaperone heat shock protein-90 (Hsp90), in promoting cancer cell survival, which leads to new candidate chemotherapeutic agents for neoplastic disease. Herein, we identify mitochondrial Hsp90 as a key modulator of the vascular injury response. Hsp90 expression is up-regulated in injured arteries and colocalizes with the apoptosis inhibitor, survivin, in vascular smooth muscle cell in vitro and in vivo. By using a proteomic approach, we demonstrate that targeted disruption of mitochondrial Hsp90 chaperone function in vascular smooth muscle cell leads to loss of cytoprotective client proteins (survivin and Akt), induces mitochondrial permeability, and leads to apoptotic cell death. Hsp90 targeting using a cell-permeable peptidomimetic agent resulted in marked attenuation of neointimal lesions in a murine arterial injury model. These findings suggest that mitochondrial Hsp90 chaperone function is an important regulator of intimal hyperplasia and may have implications for molecular strategies that promote the long-term patency of cardiovascular interventions.

Patients with body mass index ≥25 kg/m2 as a target population for improvement of rate of follow-up duplex venous ultrasound examinations following initial incomplete examinations.

OBJECTIVE: Obesity is highly prevalent and a major risk factor for deep vein thrombosis (DVT) and chronic venous disease. It can also technically limit duplex ultrasound evaluations for lower extremity DVT. We compared the rates and results of repeat lower extremity venous duplex ultrasound (LEVDUS) after an initial incomplete and negative (IIN) LEVDUS in overweight (body mass index [BMI] ≤25-30 kg/m2) and obese (BMI ≥30 kg/m2) patients with those of patients with a BMI <25 kg/m2 to evaluate whether increasing the rate of follow-up examinations in overweight and obese patients might facilitate improved patient care. METHODS: We performed a retrospective review of 617 patients with an IIN LEVDUS study from December 31, 2017 to December 31, 2020. Demographic and imaging data of the patients with an IIN LEVDUS and the frequency of repeat studies performed within 2 weeks were abstracted from the electronic medical records. The patients were divided into three BMI-based groups: normal (BMI <25 kg/m2), overweight (BMI 25-30 kg/m2), and obese (BMI ≥30 kg/m2). RESULTS: Of the 617 patients with an IIN LEVDUS, 213 (34.5%) were normal weight, 177 (29%) were overweight, and 227 (37%) were obese. The repeat LEVDUS rates were significantly different across the three weight groups (P < .001). After an IIN LEVDUS, the rate of repeat LEVDUS for the normal weight, overweight, and obese groups was 46% (98 of 213), 28% (50 of 227), and 32% (73 of 227), respectively. The overall rates of thrombosis (both DVT and superficial vein thrombosis) in the repeat LEVDUS examinations were not significantly different among the normal weight (14%), overweight (11%), and obese (18%) patients (P = .431). CONCLUSIONS: Overweight and obese patients (BMI ≥25 kg/m2) received fewer follow-up examinations after an IIN LEVDUS. Follow-up LEVDUS examinations of overweight and obese patients after an IIN LEVDUS study have similar rates of venous thrombosis compared with normal weight patients. Targeting improving usage of follow-up LEVDUS studies for all patients, but especially for those who are overweight and obese, with an IIN LEVDUS through quality improvement efforts could help minimize missed diagnoses of venous thrombosis and improve the quality of patient care.

Vascular Graft Implantation Using a Bilateral End-to-Side Aortoiliac Preclinical Model.

Arterial bypass grafts are a standard preclinical model for evaluating physiology and pathophysiology at graft-material interfaces. Implantations of vascular grafts are commonly done as end-to-end grafts in small animal models. Here we detail bilateral end-to-side aortoiliac graft implantation, which requires open surgery and the creation of vascular anastomoses between the graft material and the infrarenal aorta and iliac artery in a nonhuman primate model. In this model, the aortoiliac graft configuration is created using two 4 mm inner diameter vascular grafts (e.g., ePTFE). After exposure and control of the infrarenal aorta and bilateral common iliac arteries and heparinization, the proximal aortic-graft anastomosis is sewn on the lateral wall of the aorta, and subsequently the distal graft-common iliac anastomosis is sewn on the anterior wall of the common iliac artery with one tube graft. Another tube graft is sewn on the contralateral side in the same manner.

Mortality and Conversion to Transfemoral Amputation After Transtibial Amputation in the Veterans Affairs Health System.

INTRODUCTION: Transtibial below-knee amputation (BKA) is associated with considerable morbidity, particularly in the vasculopathic population. The purpose of this study was to determine the cumulative probability of undergoing transfemoral above-knee amputation (AKA) conversion within 5 years of BKA and associated risk factors while accounting for the competing risk of death. METHODS: This is a retrospective, national database study with structured query of the Veterans Affairs (VA) database for patients who underwent BKA from 1999 to 2020, identified by Current Procedural Terminology codes. Above-knee amputation conversion was identified using Current Procedural Terminology codes in combination with natural language processing to match procedure laterality. After internally validating our patient identification method, risk factors were collected. Competing risk analysis estimated the cumulative incidence rate of AKA conversion and associated risk factors with death as a competing risk. RESULTS: Our query yielded 19,875 patients (19,640 men, 98.8%) who underwent BKA with a median age of 66 years (interquartile range, 60 to 73). The median follow-up was 951 days (interquartile range, 275 to 2,026). The crude cumulative probabilities of AKA conversion and death at 5 years were 15.4% (95% confidence interval [CI], 14.9% to 16.0%) and 47.7% (95% CI, 46.9% to 48.4%), respectively. In the Fine and Gray subdistribution hazard model, peripheral vascular disease had the highest AKA conversion risk (hazard ratio [HR] 2.66; 95% CI, 2.22 to 3.20; P < 0.001). Other factors independently associated with AKA conversion included urgent operation (HR 1.32; 95% CI, 1.23 to 1.42), cerebrovascular disease (HR 1.19; 95% CI, 1.11 to 1.28), chronic obstructive pulmonary disease (HR 1.15; 95% CI, 1.07 to 1.24), and previous myocardial infarction (HR 1.10; 95% CI, 1.02 to 1.19) (All P < 0.02). DISCUSSION: Within this predominantly male, VA population, BKA carries a high risk of conversion to AKA within 5 years, without reaching a steady risk of AKA conversion within 5 years. Peripheral vascular disease, chronic obstructive pulmonary disease, cerebrovascular disease, previous myocardial infarction, and urgent BKA increase the risk of AKA conversion. LEVEL OF EVIDENCE: Level III.

Pharmacological reduction of coagulation factor XI reduces macrophage accumulation and accelerates deep vein thrombosis resolution in a mouse model of venous thrombosis.

BACKGROUND: Deep vein thrombosis (DVT) and post-thrombotic syndrome (PTS) remain highly prevalent despite modern medical therapy. Contact activation is a promising target for safe antithrombotic anticoagulation. The anti-factor XI (FXI) monoclonal antibody 14E11 reduces circulating levels of FXI without compromising hemostasis. The human recombinant analog, AB023, is in clinical development. The role of FXI in mediation of inflammation during DVT resolution is unknown. OBJECTIVES: Investigate the effects of pharmacological targeting of FXI with 14E11 in an experimental model of venous thrombosis. METHODS: Adult wild-type CD1 mice were treated with subcutaneous anti-FXI antibody (14E11, 5 mg/kg) versus saline prior to undergoing surgical constriction of the inferior vena cava (IVC). Mice were evaluated at various time points to assess thrombus weight and volume, as well as histology analysis, ferumoxytol enhanced magnetic resonance imaging (Fe-MRI), and whole blood flow cytometry. RESULTS: 14E11-treated mice had reduced thrombus weights and volumes after IVC constriction on day 7 compared to saline-treated mice. 14E11 treatment reduced circulating monocytes by flow cytometry and macrophage content within thrombi as evaluated by histologic staining and Fe-MRI. Collagen deposition was increased at day 3 while CD31 and smooth muscle cell actin expression was increased at day 7 in the thrombi of 14E11-treated mice compared to saline-treated mice. CONCLUSION: Pharmacologic targeting of FXI enhances the early stages of experimental venous thrombus resolution in wild-type CD1 mice, and may be of interest for future clinical evaluation of the antibody in DVT and PTS.

RNA interference-mediated survivin gene knockdown induces growth arrest and reduced migration of vascular smooth muscle cells.

Survivin (SVV) is a multifunctional protein that has been implicated in the development of neointimal hyperplasia. Nuclear SVV is essential for mitosis, whereas in mitochondria SVV has a cytoprotective function. Here, we investigated the effects of RNA interference (RNAi)-mediated SVV knockdown on cell cycle kinetics, apoptosis, migration, and gene expression in primary cultured vascular smooth muscle cells (VSMCs) from the human saphenous vein. Primary Human VSMCs were obtained from saphenous veins and cultured under standard conditions. SVV knockdown was achieved by either small interfering RNA or lentiviral transduction of short hairpin RNA, reducing SVV gene expression by quantitative PCR (>75%, P < 0.01) without a loss of cell viability. Subcellular fractionation revealed that RNAi treatment effectively targeted the nuclear SVV pool, whereas the larger mitochondrial pool was much less sensitive to transient knockdown. Both p53 and p27 protein levels were notably increased. SVV RNAi treatment significantly blocked VSMC proliferation in response to serum and PDGF-AB, arresting VSMC growth. Cell cycle analysis revealed an increased G(2)/M fraction consistent with a mitotic defect; 4',6-diamidino-2-phenylindole staining confirmed an increased frequency of polyploid and abnormal nuclei. In a transwell assay, SVV knockdown reduced migration to PDGF-AB, and actin-phalloidin staining revealed disorganized actin filaments and polygonal cell shape. However, apoptosis (DNA content and annexin V flow cytometry) was not directly induced by SVV RNAi, and sensitivity to apoptotic agonists (e.g., staurosporine and cytokines) was unchanged. In conclusion, RNAi-mediated SVV knockdown in VSMCs leads to profound cell cycle arrest at G(2)/M and impaired chemotaxis without cytotoxicity. The regulation of mitosis and apoptosis in VSMC involves differentially regulated subcellular pools of SVV. Thus, treatment of VSMC with RNAi targeting SVV might limit the response to vascular injury without destabilizing the vessel wall.

Improving follow-up of incomplete lower extremity venous duplex ultrasound examinations performed for deep and superficial vein thromboses.

OBJECTIVE: A lower extremity venous duplex ultrasound (LEVDUS) examination is the standard diagnostic test to evaluate patients for lower extremity deep vein thrombosis (DVT). However, some studies will be incomplete for a variety of reasons, including patient-related factors such as pain, edema, a large leg circumference, or the presence of overlying bandages or orthopedic devices. We previously reported that the frequency of obtaining a follow-up examination after an incomplete and negative (I/N) LEVDUS examination was low but that the rates of DVT found on the follow-up studies of initially I/N LEVDUS studies were similar to the rates of DVT found with initially complete LEVDUS examinations. Therefore, we recommended process improvements to increase follow-up LEVDUS studies after an I/N LEVDUS examination. In the present study, we have described the results of appending a recommendation to obtain a follow-up LEVDUS study to preliminary and final reports of I/N LEVDUS. METHODS: Starting in January 2019 through December 2019, a recommendation to obtain a repeat LEVDUS examination after an I/N study was appended to the preliminary and final reports of all I/N LEVDUS examination of patients who did not, otherwise, have an indication for anticoagulation (group 2). The patients were identified on an ongoing basis through the study period and entered into an Excel database (Microsoft Corp, Redmond, Wash). Group 2 was compared with a previously reported historic control cohort of patients identified from January 2017 to December 2017 (group 1). We compared groups 1 and 2 with respect to the frequency of the repeat studies performed within 4 weeks after an I/N LEVDUS examination and the DVT rates found from the follow-up LEVDUS examinations after an I/N LEVDUS study. RESULTS: Of the patients in groups 1 and 2, 187 and 229 had had I/N LEVDUS examinations, with 28% and 40.2% of group 1 and 2 studies having follow-up LEVDUS examinations (P < .01). Previously unidentified lower extremity thrombi were discovered in 21% of the group 2 follow-up examinations. Also, the rate of new thrombi detected was not different between groups 2 and 1 (historic controls; DVT, 14.3% vs 18.5% [P = .25]; SVT, 6.3% vs 3.3% [P = .15]). A definitive finding of either positive or negative for DVT and SVT with a complete examination in 50% of the group 2 patients with follow-up examinations. CONCLUSIONS: A recommendation to obtain a follow-up examination appended to the preliminary and final I/N LEVDUS reports was associated with an increased rate of follow-up examinations, which revealed many previously undetected DVTs and SVTs or had allowed for definitive exclusion of DVT.

Prospective study comparing the rate of deep venous thrombosis of complete and incomplete lower extremity venous duplex ultrasound examinations.

BACKGROUND: A lower extremity venous duplex ultrasound (LEVDUS) examination positive for deep venous thrombosis (DVT) is an indication for anticoagulation. Incomplete examinations that fail to examine all lower extremity veins in patients not otherwise indicated for anticoagulation may be followed by repeated examination to exclude missed or progressing DVT. This study examined the frequency of incomplete LEVDUS studies, reasons for incomplete studies, veins incompletely examined, and follow-up LEVDUS after incomplete LEVDUS. The incidence of a positive finding of DVT was compared between initial complete LEVDUS and follow-up LEVDUS after an initial incomplete examination to determine whether improving rates of follow-up LEVDUS after an incomplete examination is a reasonable target for quality improvement. METHODS: At a single academic medical center from January 2017 to December 2017, incomplete LEVDUS studies were prospectively identified in patients who did not otherwise have an identified indication for anticoagulation. Rate of DVT in complete LEVDUS was also determined during the same time frame. Incomplete LEVDUS reports were reviewed for clinical setting, patient demographics, examination indication, ordering providers, reasons for incomplete examinations, anatomic locations of veins not visualized, rates of follow-up LEVDUS examinations within 30 days of the initially incomplete study, and rates of DVT identified in follow-up examinations of initially incomplete examinations. RESULTS: Of the 2843 LEVDUS examinations performed in 2017, 341 studies identified DVT and 197 incomplete examinations did not identify DVT. Veins not visualized on incomplete studies included tibial veins (n = 170 [86.3%]), femoral veins (n = 73 [37.1%]), and popliteal veins (n = 76 [38.6%]), with the most common reasons for incomplete studies being bandages or fixation devices (46.2%), intolerance of the patient for the study (14.7%), and body habitus or edema (17.4%). Only a minority of incomplete studies not identifying DVT (27.9%) had a follow-up examination performed. The majority of the repeated examinations were performed after incomplete LEVDUS examinations that were originally performed for high-risk screening (80%) as opposed to clinical suspicion for DVT (20%). There was no significant difference in demographic features of patients with initially incomplete studies who did or did not have a follow-up examination and no significant difference in the rates of DVT (13.1%) in complete LEVDUS examinations compared with the rate of DVT found in follow-up examinations of initially incomplete LEVDUS examinations (9.1%; P = .33). CONCLUSIONS: The majority of patients with incomplete LEVDUS, even those with symptoms or signs suggestive of DVT, do not have a follow-up examination within 30 days of the incomplete study. The rate of DVT detected in initially complete studies was similar to that in patients with follow-up examinations whose initial study was incomplete and did not identify DVT. This suggests that to avoid missing DVT in patients with incomplete LEVDUS studies, quality assurance programs should be initiated to ensure that follow-up LEVDUS studies are performed after an incomplete LEVDUS examination.

Optimizing sequential decisions in the drift-diffusion model.

To make decisions organisms often accumulate information across multiple timescales. However, most experimental and modeling studies of decision-making focus on sequences of independent trials. On the other hand, natural environments are characterized by long temporal correlations, and evidence used to make a present choice is often relevant to future decisions. To understand decision-making under these conditions we analyze how a model ideal observer accumulates evidence to freely make choices across a sequence of correlated trials. We use principles of probabilistic inference to show that an ideal observer incorporates information obtained on one trial as an initial bias on the next. This bias decreases the time, but not the accuracy of the next decision. Furthermore, in finite sequences of trials the rate of reward is maximized when the observer deliberates longer for early decisions, but responds more quickly towards the end of the sequence. Our model also explains experimentally observed patterns in decision times and choices, thus providing a mathematically principled foundation for evidence-accumulation models of sequential decisions.

The role of axillofemoral bypass in current vascular surgery practice.

BACKGROUND: In the era of increasing endovascular approaches for aortoiliac disease, we sought to determine the role of axillofemoral bypass in contemporary practice. METHODS: All axillofemoral bypasses performed at our institution from 2006 to 2013 were reviewed for indication, patency, and survival and compared with our prior published series before the widespread use of endovascular techniques (1996 to 2001). RESULTS: During the study period, 90 bypasses (29 axillofemoral and 61 axillobifemoral) bypasses were performed. The number of procedures performed decreased from an average of 24 to 12 procedures per year in historical and contemporary groups, respectively. Indications have changed significantly with more urgent or emergent procedures. Overall patency at 1 and 2 years was 74.6% and 67.8%, respectively. Median survival was 40.3 months, with overall survival 67.0% and 54.2% at 1 and 2 years, respectively. CONCLUSIONS: Axillofemoral bypass is an increasingly uncommon procedure and more likely performed for limb salvage in urgent or emergent settings.