Basic mechanisms and pathogenesis of venous thrombosis

Characterization of internal jugular vein region-specific distension and flow patterns during progressive volume shifting

Blood volume shifts during postural adjustment lead to irregular distension of the internal jugular vein (IJV). In microgravity, distension may contribute to flow stasis and thromboembolism, though the regional implications and associated risk remain unexplored. We characterized regional differences in IJV volume distension and flow complexity during progressive head-down tilt (HDT) (0°, -6°, -15°, -30°) using conventional ultrasound and vector flow imaging. We also evaluated low-pressure thigh cuffs (40 mmHg) as a fluid shifting countermeasure during -6° HDT. Total IJV volume expanded 139 ± 95% from supine position (4.6 ± 2.7 mL) to -30° HDT (10.3 ± 5.0 mL). Blood flow profiles had greater vector uniformity at the cranial IJV region (P < 0.01) and became more dispersed with increasing tilt (P < 0.01). Qualitatively, flow was more uniform throughout the IJV during its early flow cycle phase and more disorganized during late flow phase. This disorganized flow was accentuated closer to the vessel wall, near the caudal region, and during greater HDT. Low-pressure thigh cuffs during -6° HDT decreased IJV volume at the cranial region (-12 ± 15%; P < 0.01) but not the caudal region (P = 0.20), although flow uniformity was unchanged (both regions, P > 0.25). We describe a distensible IJV accommodating large volume shifts along its length. Prominent flow dispersion was primarily found at the caudal region, suggesting multidirectional blood flow. Thigh cuffs appear effective for decreasing IJV volume but effects on flow complexity are minor. Flow complexity along the vessel length is likely related to IJV distension during chronic volume shifting and may be a precipitating factor for flow stasis and future thromboembolism risk.NEW & NOTEWORTHY The internal jugular vein (IJV) facilitates cerebral outflow and is sensitive to volume shifts. Concerns about IJV expansion and fluid flow behavior in astronauts have surfaced following thromboembolism reports. Our study explored regional volume distension and blood flow complexity in the IJV during progressive volume shifting. We observed stepwise volume distension and increasing flow dispersion with head-down tilting across all regions. Flow dispersion may pose a risk of future thromboembolism during prolonged volume shifts.

Time-dependent ultrastructural changes during venous thrombogenesis and thrombus resolution

BACKGROUND

Deep vein thrombosis is a common vascular event that can result in debilitating morbidity and even death due to pulmonary embolism. Clinically, patients with faster resolution of a venous thrombus have improved prognosis, but the detailed structural information regarding changes that occur in a resolving thrombus over time is lacking.

OBJECTIVES

To define the spatial-morphologic characteristics of venous thrombus formation, propagation, and resolution at the submicron level over time.

METHODS

Using a murine model of stasis-induced deep vein thrombosis along with scanning electron microscopy and immunohistology, we determine the specific structural, compositional, and morphologic characteristics of venous thrombi formed after 4 days and identify the changes that take place during resolution by day 7. Comparison is made with the structure and composition of venous thrombi formed in mice genetically deficient in plasminogen activator inhibitor type 1.

RESULTS

As venous thrombus resolution progresses, fibrin exists in different structural forms, and there are dynamic cellular changes in the compositions of leukocytes, platelet aggregates, and red blood cells. Intrathrombus microvesicles are present that are not evident by histology, and red blood cells in the form of polyhedrocytes are an indicator of clot contraction. Structural evidence of fibrinolysis is observed early during thrombogenesis and is accelerated by plasminogen activator inhibitor type 1 deficiency.

CONCLUSION

The results reveal unique, detailed ultrastructural and compositional insights along with documentation of the dynamic changes that occur during accelerated resolution that are not evident by standard pathologic procedures and can be applied to inform diagnosis and effectiveness of thrombolytic treatments to improve patient outcomes.

The Association between Obstructive Sleep Apnea and Venous Thromboembolism: A Bidirectional Two-Sample Mendelian Randomization Study

BACKGROUND

 Despite previous observational studies linking obstructive sleep apnea (OSA) to venous thromboembolism (VTE), these findings remain controversial. This study aimed to explore the association between OSA and VTE, including pulmonary embolism (PE) and deep vein thrombosis (DVT), at a genetic level using a bidirectional two-sample Mendelian randomization (MR) analysis.

METHODS

 Utilizing summary-level data from large-scale genome-wide association studies in European individuals, we designed a bidirectional two-sample MR analysis to comprehensively assess the genetic association between OSA and VTE. The inverse variance weighted was used as the primary method for MR analysis. In addition, MR-Egger, weighted median, and MR pleiotropy residual sum and outlier (MR-PRESSO) were used for complementary analyses. Furthermore, a series of sensitivity analyses were performed to ensure the validity and robustness of the results.

RESULTS

 The initial and validation MR analyses indicated that genetically predicted OSA had no effects on the risk of VTE (including PE and DVT). Likewise, the reverse MR analysis did not find substantial support for a significant association between VTE (including PE and DVT) and OSA. Supplementary MR methods and sensitivity analyses provided additional confirmation of the reliability of the MR results.

CONCLUSION

 Our bidirectional two-sample MR analysis did not find genetic evidence supporting a significant association between OSA and VTE in either direction.

Advances in Nano-Functional Materials in Targeted Thrombolytic Drug Delivery

Thrombotic disease has been listed as the third most fatal vascular disease in the world. After decades of development, clinical thrombolytic drugs still cannot avoid the occurrence of adverse reactions such as bleeding. A number of studies have shown that the application of various nano-functional materials in thrombus-targeted drug delivery, combined with external stimuli, such as magnetic, near-infrared light, ultrasound, etc., enrich the drugs in the thrombus site and use the properties of nano-functional materials for collaborative thrombolysis, which can effectively reduce adverse reactions such as bleeding and improve thrombolysis efficiency. In this paper, the research progress of organic nanomaterials, inorganic nanomaterials, and biomimetic nanomaterials for drug delivery is briefly reviewed.

Endothelial PTP1B Deletion Promotes VWF Exocytosis and Venous Thromboinflammation

BACKGROUND

Endothelial activation promotes the release of procoagulant extracellular vesicles and inflammatory mediators from specialized storage granules. Endothelial membrane exocytosis is controlled by phosphorylation. We hypothesized that the absence of PTP1B (protein tyrosine phosphatase 1B) in endothelial cells promotes venous thromboinflammation by triggering endothelial membrane fusion and exocytosis.

METHODS

Mice with inducible endothelial deletion of PTP1B (End.PTP1B-KO) underwent inferior vena cava ligation to induce stenosis and venous thrombosis. Primary endothelial cells from transgenic mice and human umbilical vein endothelial cells were used for mechanistic studies.

RESULTS

Vascular ultrasound and histology showed significantly larger venous thrombi containing higher numbers of Ly6G (lymphocyte antigen 6 family member G)-positive neutrophils in mice with endothelial PTP1B deletion, and intravital microscopy confirmed the more pronounced neutrophil recruitment following inferior vena cava ligation. RT2 PCR profiler array and immunocytochemistry analysis revealed increased endothelial activation and adhesion molecule expression in primary End.PTP1B-KO endothelial cells, including CD62P (P-selectin) and VWF (von Willebrand factor). Pretreatment with the NF-κB (nuclear factor kappa B) kinase inhibitor BAY11-7082, antibodies neutralizing CD162 (P-selectin glycoprotein ligand-1) or VWF, or arginylglycylaspartic acid integrin-blocking peptides abolished the neutrophil adhesion to End.PTP1B-KO endothelial cells in vitro. Circulating levels of annexin V+ procoagulant endothelial CD62E+ (E-selectin) and neutrophil (Ly6G+) extracellular vesicles were also elevated in End.PTP1B-KO mice after inferior vena cava ligation. Higher plasma MPO (myeloperoxidase) and Cit-H3 (citrullinated histone-3) levels and neutrophil elastase activity indicated neutrophil activation and extracellular trap formation. Infusion of End.PTP1B-KO extracellular vesicles into C57BL/6J wild-type mice most prominently enhanced the recruitment of endogenous neutrophils, and this response was blunted in VWF-deficient mice or by VWF-blocking antibodies. Reduced PTP1B binding and tyrosine dephosphorylation of SNAP23 (synaptosome-associated protein 23) resulting in increased VWF exocytosis and neutrophil adhesion were identified as mechanisms, all of which could be restored by NF-κB kinase inhibition using BAY11-7082.

CONCLUSIONS

Our findings show that endothelial PTP1B deletion promotes venous thromboinflammation by enhancing SNAP23 phosphorylation, endothelial VWF exocytosis, and neutrophil recruitment.

Predictors of thrombosis during VV ECMO: an analysis of 9809 patients from the ELSO registry

Venovenous extracorporeal membrane oxygenation (VV-ECMO) is a life-saving therapy for critically ill patients, but it carries an increased risk of thrombosis due to blood interacting with non-physiological surfaces. While the relationship between clinical variables and thrombosis remains unclear, our study aimed to identify which factors are most predictive of thrombosis. The Extracorporeal Life Support Organization Registry was queried to obtain a cohort of VV-ECMO patients aged 18 years and older from 2015 to 2019. Patients who were over 80-years-old, at the extremes of weight, who received less than 24 h of ECMO, multiple rounds of ECMO, or had missing data were excluded. Multivariate logistic regression modeling was used to assess predictors of thrombosis and mortality. A total of 9809 patients were included in the analysis, with a mean age of 47.1 ± 15.1 years and an average ECMO run time of 305 ± 353 h. Thrombosis occurred in 19.9% of the cohort, with circuit thrombosis (8.6%) and membrane lung failure (6.1%) being the most common. Multivariate analysis showed that ECMO runs over 14 days (OR: 2.62, P < 0.001) and pregnancy-related complications (OR: 1.79, P = 0.004) were associated with an increased risk of thrombosis. Risk factors for circuit thrombosis included incremental unit increases in the pump flow rate at 24 h (OR: 1.07 [1.00-1.14], P = 0.044) and specific cannulation sites. Increased body weight (OR: 1.02 [1.00-1.04], P = 0.026) and increased duration on ECMO (OR: 3.82 [3.12-4.71], P < 0.001) were predictive of membrane lung failure. Additionally, patients with thrombosis were at increased likelihood of in-hospital mortality (OR: 1.52, P < 0.001). This study identified multiple thrombotic risk factors in VV-ECMO, suggesting that future studies investigating the impact of pregnancy associated complications and ECMO flow rate on hemostasis would be illuminating.

Effects of hemoglobin concentration on retinochoroidal vascular plexuses: an optical coherence tomography angiography study

PURPOSE

To evaluate retinal and choroidal microvascular structures using optical coherence tomography angiography (OCTA) in patients with anemia and polycythemia vera (PV).

METHODS

In this prospective study, 142 patients (142 eyes) were enrolled and divided into 3 groups: the anemia (n = 56), PV (n = 46), and healthy groups (n = 40, controls). For each patient, 6- × 6-mm macular angiography images were taken using an OCTA system (optovue, Inc., Fremont). For each eye analyzed, the software automatically measured vessel density (VD) in the superficial capillary plexus (SCP), deep capillary plexus (DCP; superior, nasal, temporal, and inferior quadrants), choriocapillaris (CC), and foveal avascular zone (FAZ).

RESULTS

The OCTA analysis revealed that the VD of the DCP was significantly decreased in the superior and inferior hemispheres of the whole area, multiple quadrants of the perifovea, and CC with a 1-mm2 flow area in the anemia group compared with the PV group (p < 0.017), but the VD of the SCP did not show any significant difference in any quadrant between the two groups (p > 0.017). When compared with the healthy group, the anemia and PV groups showed a significant difference in multiple quadrants of the parafovea and temporal quadrant of the perifovea in the VD of the SCP and CC with a 2-mm2 flow area (p < 0.017). The FAZ and non-flow area did not manifest any significant difference between the groups (p > 0.017). The hemoglobin concentrations in the anemia, PV, and healthy groups were 8.11 ± 1.33, 17.5 ± 1.2, and 15.6 ± 0.73 g/dL, respectively, indicating statistically significant differences between the groups (p < 0.001).

CONCLUSION

In this study, quantitative OCTA analysis revealed a higher tendency for retinal and choroidal microvascular morphological changes in patients with anemia and PV. The outcomes of the current investigation can provide new insights into the retinal and choroidal pathophysiologies found in patients with hemoglobin abnormalities.

Venous Thromboembolism in Burn Patients: A 5-Year Retrospective Study

Background and Objectives: Burn patients manifest all components of Virchow's triad, amplifying the concern for venous thromboembolism (VTE). Routine prophylaxis for VTE remains a subject of debate, with the central concern being the occurrence of associated adverse events. Materials and Methods: We conducted a five-year retrospective study on burn patients admitted to our burn center. Demographic data, comorbidities, burn lesions characteristics, surgical interventions, anticoagulant medication, the need for transfusions, the presence of a central venous catheter, length of stay, complications, and mortality were recorded. Results: Of the overall number of patients (494), 2.63% (13 patients) developed venous thromboembolic complications documented through paraclinical investigations. In 70% of cases, thrombosis occurred in a limb with central venous catether (CVC). Every patient with VTE had a Caprini score above 8, with a mean score of 12 points in our study group. Conclusions: Considering each patient's particularities and burn injury characteristics, individualized approaches may be necessary to optimize thromboprophylaxis effectiveness. We suggest routinely using the Caprini Risk Assessment Model in burn patients. We recommend the administration of pharmacologic thromboprophylaxis in all patients and careful monitoring of patients with Caprini scores above 8, due to the increased risk of VTE. Additionally, ongoing research in this field may provide insights into new strategies for managing thrombotic risk in burn patients.

Distinct clinico-molecular arterial and venous thrombosis scores for myeloproliferative neoplasms risk stratification

Current recommended risk scores to predict thrombotic events associated with myeloproliferative neoplasms (MPN) do not discriminate between arterial and venous thrombosis despite their different physiopathology. To define novel stratification systems, we delineated a comprehensive landscape of MPN associated thrombosis across a large long-term follow-up MPN cohort. Prior arterial thrombosis, age >60 years, cardiovascular risk factors and presence of TET2 or DNMT3A mutations were independently associated with arterial thrombosis in multivariable analysis. ARTS, an ARterial Thrombosis Score, based on these four factors, defined low- (0.37% patients-year) and high-risk (1.19% patients-year) patients. ARTS performance was superior to the two-tiered conventional risk stratification in our training cohort, across all MPN subtypes, as well as in two external validation cohorts. Prior venous thrombosis and presence of a JAK2V617F mutation with a variant allelic frequency ≥50% were independently associated with venous thrombosis. The discrimination potential of VETS, a VEnous Thrombosis Score based on these two factors, was poor, similar to the two-tiered conventional risk stratification. Our study pinpoints arterial and venous thrombosis clinico-molecular differences and proposes an arterial risk score for more accurate patients' stratification. Further improvement of venous risk scores, accounting for additional factors and considering venous thrombosis as a heterogeneous entity is warranted.

A computational model-based study on the feasibility of predicting post-splenectomy thrombosis using hemodynamic metrics

For portal hypertensive patients with splenomegaly and hypersplenism, splenectomy is an effective surgery to relieve the complications. However, patients who have undergone splenectomy often suffer from portal venous system thrombosis, a sequela that requires prophylaxis and timely treatment to avoid deterioration and death. The aim of this study is to investigate the feasibility of predicting post-splenectomy thrombosis using hemodynamic metrics based on computational models. First, 15 portal hypertensive patients who had undergone splenectomy were enrolled, and their preoperative clinical data and postoperative follow-up results were collected. Next, computational models of the portal venous system were constructed based on the preoperative computed tomography angiography images and ultrasound-measured flow velocities. On this basis, splenectomy was mimicked and the postoperative area of low wall shear stress (ALWSS) was simulated for each patient-specific model. Finally, model-simulated ALWSS was statistically compared with the patient follow-up results to investigate the feasibility of predicting post-splenectomy thrombosis using hemodynamic metrics. Results showed that ALWSS could predict the occurrence of post-splenectomy thrombosis with the area under the receiver operating characteristic curve (AUC) equal to 0.75. Moreover, statistical analysis implied that the diameter of the splenic vein is positively correlated with ALWSS (r = 0.883, p < 0.0001), and the anatomical structures of the portal venous system also influence the ALWSS. These findings demonstrated that the computational model-based hemodynamic metric ALWSS, which is associated with the anatomorphological features of the portal venous system, is capable of predicting the occurrence of post-splenectomy thrombosis, promoting better prophylaxis and postoperative management for portal hypertensive patients receiving splenectomy.

Intra-abdominal Venous Thromboses and Their Management

While a plethora of articles discuss management of deep venous thromboses in extremities, there is a relative scarcity of literature comprehensively describing intra-abdominal venous thromboses, and their management. Intra-abdominal venous thromboses include iliocaval venous obstruction (ICVO), hepatic venous thrombosis (HVT), portal venous thrombosis (PVT), renal vein thrombosis (RVT), splenic vein thrombosis (SVT), and gonadal vein thrombosis (GVT); each of which provides unique microenvironmental challenges to management. Doppler ultrasound is the first line imaging modality for diagnosis, and computed tomography and magnetic resonance imaging can help define the extent of thrombus burden and aid with interventional planning. Systemic anticoagulation remains the common medical treatment for intra-abdominal venous thrombosis, however, catheter directed thrombolysis and thrombectomy show positive outcomes in ICVO, HVT, PVT, and RVT, with transjugular intrahepatic portosystemic shunt (TIPS) creation especially beneficial in HVT and PVT. In this review article, we describe pathophysiology, clinical features, imaging findings, and current management options for intra-abdominal venous thromboses.

Intra-abdominal pressure increases peri-operatively in patients undergoing deep inferior epigastric perforator flap reconstruction: A prospective study linking high intra-abdominal pressure to non-fatal lung embolism within one patient

BACKGROUND

The deep inferior epigastric perforator (DIEP) flap is the gold standard for autologous breast reconstruction. The procedure and peri-operative period are associated with the risk of severe post-operative complications, like venous thromboembolic events (VTE) and lung embolism. Whether the intra-abdominal pressure (IAP) increases after the closure of the abdominal defect, thereby potentially affecting the venous backflow and the risk of VTE, is currently not known.

AIM

The primary aim is to test if the closure of the abdominal donor site increases the IAP in women undergoing secondary DIEP flap breast reconstruction.

MATERIALS AND METHOD

By using a Unometer, we measured the intravesical pressure as a surrogate marker for the IAP, at baseline, immediately after, and 24 h after abdominal skin closure, for 13 patients.

RESULTS

The mean IAP increased from 6.1 mmHg (95% CI 4.6-7.7) at baseline to 9.0 mmHg (95% CI 8.0-10.0) immediately after skin closure [mean diff. 2.9 (95% CI 1.0-4.8) (p = 0.007)] and further up to 11.7 mmHg (95% CI 9.0-14.5) 24 h after closure [mean diff. 5.3 (95% CI 1.4-9.1) (p = 0.012)]. We found that IAP varies among the patients, regardless of the tightness of abdominal closure or rectus plication (n = 3). Immediately after closure, none of the isolated patients showed abnormal levels of IAP (>12 mmHg), while eight out of 12 isolated patients (67%) showed IAP levels above the normal range after 24 h. One patient developed a non-fatal lung embolism.

CONCLUSION

The mean IAP increases significantly over the post-operative period after DIEP flap reconstruction, although abnormal IAP values are only seen 24 h after the closure of the skin.

Deep vein thrombosis and pulmonary embolism: a prospective, observational study to evaluate diagnostic performance of the Tina-quant D-Dimer Gen.2 assay

Background

D-Dimer testing is a diagnostic tool for exclusion of deep vein thrombosis (DVT) and pulmonary embolism (PE). This study evaluated the diagnostic performance of the Tina-quant® D-Dimer Gen.2 assay (Roche Diagnostics International Ltd, Rotkreuz, Switzerland) in patients with low/intermediate pre-test probability of DVT/PE using standard, age-, and clinical probability-adjusted cut-offs.

Methods

In this prospective, observational, multicenter study (July 2017-August 2019), plasma samples were collected from hospital emergency departments and specialist referral centers. DVT/PE was diagnosed under hospital standard procedures and imaging protocols. A standard D-dimer cut-off of 0.5 µg fibrinogen equivalent units (FEU)/ml was combined with the three-level Wells score; cut-offs adjusted for age (age × 0.01 µg FEU/ml for patients >50 years) and clinical probability (1 µg FEU/ml for low probability) were also evaluated. An assay comparison was conducted in a subset of samples using the Tina-quant D-Dimer Gen.2 assay and the previously established routine laboratory assay, STA-Liatest D-Di Plus assay (Stago Deutschland GmbH, Düsseldorf, Germany).

Results

2,897 patients were enrolled; 2,516 completed the study (DVT cohort: 1,741 PE cohort: 775). Clinical assessment plus D-dimer testing using the standard cut-off resulted in 317 (DVT) and 230 (PE) false positives, and zero (DVT) and one (PE) false negatives. Negative predictive value (NPV) was 100.0% (95% confidence interval [CI]: 99.7%-100.0%) and 99.8% (95% CI: 98.8%-100.0%) for DVT and PE, respectively. After age-adjustment, NPV was 99.9% (95% CI: 99.6%-100.0%) and 99.1% (95% CI: 97.8-99.7) for DVT and PE, respectively. False positive rates decreased (>50%) in clinical probability-adjusted analyses vs. primary analysis. In the assay comparison, the performances of the two assays were comparable.

Conclusion

The Tina-quant D-Dimer Gen.2 assay and standard D-dimer cut-off level combined with the three-level Wells score accurately identified patients with a very low probability of DVT/PE.

Prevalence and Predictors of Venous Stenosis Following First Transvenous Cardiac Implantable Electronic Device Implantation

Objectives

Very few studies have been done on Venous stenosis following the first transvenous cardiac device implantation. We aimed to assess the prevalence and predictors of Venous stenosis/Occlusion following the first transvenous cardiac device implantation with venous angiography at one year of follow-up.

Methods

This study was a single-center prospective, observational study. Demographic, clinical, procedural, and device data was collected. All patients underwent a preimplant contrast and repeated venography at twelve months to look for upper limb venous anatomy, obstruction, or collaterals.

Results

A total of 146 patients were included in the final analysis. 60 (41 %) patients developed some degree of venous stenosis. Most patients had mild to moderate stenosis, and almost all were asymptomatic. Among patient-related factors increasing age (64.66 ± 10.07 vs 60.91 ± 11.94 years p = 0.04), presence of hypertension (50.5 % vs 19.6 % p = 0.0004), diabetes (73 % vs 29.6 % p = 0.000) and dyslipidemia (66.7 % vs 36.3 p = 0.009) were significantly associated with Venous stenosis/occlusion. Among procedure-related factors, larger total lead diameter (3.88 ± 1.09 vs. 3.50 ± 1.03 mm p = 0.03) and implantation of biventricular devices (p = 0.0037) seem to be significantly associated with venous obstruction. In logistic regression analysis, hypertension (p = 0.018), total lead diameter (p = 0.024), and use of CRT-P/CRTD/ICD (p = 0.03) remained significant predictors of severe venous stenosis.

Conclusions

Our study demonstrates venous obstruction in 40 % of cardiac implantable electronic device patients at one-year follow-up. Most patients have mild to moderate stenosis, and almost all are asymptomatic. Increasing age, hypertension, diabetes, dyslipidemia, larger total lead diameter, and implantation of biventricular devices are significantly associated with venous obstruction.

The impact of sleep apnea on primary reverse shoulder arthroplasty for the treatment of glenohumeral osteoarthritis

Introduction

As the prevalence of sleep apnea (SA) increases nationwide, large sample sized studies following primary reverse shoulder arthroplasty (RSA) in SA patients are scarce. Therefore, this study evaluated whether SA is associated with 1) longer in-hospital lengths of stay (LOS) 2) readmissions 3) medical complications and 4) costs.

Methods

A retrospective nationwide Medicare analysis from 2005 to 2014 was performed. Inclusion criteria were patients with SA undergoing RSA for the treatment of glenohumeral osteoarthritis. Study group patients were 1:5 ratio matched to controls yielding 6241 patients in the study and 31,179 in the comparison cohort. Logistic regression was used to calculate odds-ratios (OR) for readmissions and complications. A p-value less than 0.004 was significant.

Results

SA patients had significantly longer in-hospital LOS compared to their counterparts (3-days versus 2-days, p < 0.0001), but similar rates of 90-day readmissions (7.98% vs. 6.54%; OR: 1.00, p = 0.907). Patients with SA had significantly greater incidence and odds of 90-day medical complications (13.36% vs. 7.29%; OR: 1.42, p < 0.0001) and significantly higher 90-day costs ($16,529.16 vs. $14,789.15, p < 0.0001).

Conclusion

Patients with SA undergoing primary RSA for the treatment of glenohumeral OA have longer in-hospital LOS, increased medical complications, and costs of care. Readmissions were not more common.

Level of Evidence

III.

Intravital Imaging of Thrombosis Models in Mice

Intravital microscopy is a powerful tool to study thrombosis in real time. The kinetics of thrombus formation and progression in vivo is studied after inflicting damage to the endothelium through mechanical, chemical, or laser injury. Mouse models of atherosclerosis are also used to induce thrombus formation. Vessels of different sizes and from different vascular beds such as carotid artery or vena cava, mesenteric or cremaster arterioles, can be targeted. Using fluorescent dyes, antibodies, or reporter mouse strains allows to visualize key cells and factors mediating the thrombotic processes. Here, we review the latest literature on using intravital microscopy to study thrombosis as well as thromboinflammation following transient middle cerebral artery occlusion, infection-induced immunothrombosis, and liver ischemia reperfusion.

Incidence of deep vein thrombosis and symptomatic pulmonary embolism in Taiwanese patients with pelvic and/or acetabular fractures: a retrospective study

Venous thromboembolism (VTE) is common in patients with trauma, and thromboprophylaxis has been advocated. However, conflicting results regarding VTE rates in the Asian population following orthopaedic procedures have been presented. We aimed to investigate the VTE incidence in Taiwanese patients with pelvic and/or acetabular fractures and identify the associated risk factors. We included 402 patients who underwent surgery for pelvic and/or acetabular fractures. All patients received mechanical thromboprophylaxis with graduated compression stockings. Duplex scanning was performed postoperatively or during follow-up when signs or symptoms of deep vein thrombosis (DVT) developed. Variables with a significance level of ≤ 0.1 in the univariate analyses were introduced into the multivariate logistic regression analysis to identify DVT risk factors. The overall DVT and symptomatic pulmonary embolism (PE) rate was 3.48% (14/402 patients). Among patients with DVT, 46.1% were asymptomatic. Patients with VTE were significantly older than those without. Multivariate logistic regression analysis revealed that age was a VTE risk factor. The incidence of DVT and symptomatic PE in our cohort was low. Advanced age was a risk factor for VTE. These findings could help clinicians develop appropriate prevention and treatment strategies for VTE in Taiwanese patients with pelvic and/or acetabular fractures.

Fluid flow to mimic organ function in 3D in vitro models

Many different strategies can be found in the literature to model organ physiology, tissue functionality, and disease in vitro; however, most of these models lack the physiological fluid dynamics present in vivo. Here, we highlight the importance of fluid flow for tissue homeostasis, specifically in vessels, other lumen structures, and interstitium, to point out the need of perfusion in current 3D in vitro models. Importantly, the advantages and limitations of the different current experimental fluid-flow setups are discussed. Finally, we shed light on current challenges and future focus of fluid flow models applied to the newest bioengineering state-of-the-art platforms, such as organoids and organ-on-a-chip, as the most sophisticated and physiological preclinical platforms.

Plasminogen Activator Inhibitor-1 and Vitamin D Association in the Overweight and Obese Pediatric Population

BACKGROUND

Childhood overweight and obesity have been described by the World Health Organization as noncommunicable diseases and among the greatest public health threats since they have reached epidemic proportions. A child with obesity risks becoming an adult with obesity and developing metabolic and hemostatic disorders which are the basis for the development of coronary heart diseases. Recently, a number of clinical reports have demonstrated that both an increase in plasminogen activator inhibitor-1 (PAI-1) and a deficiency in 25OH-vitamin D3 (VD) are associated with an increase in thrombotic episodes.

METHODS

PAI-1 and VD levels were measured in 259 clinically overweight and obese children aged between 2 and 18 years enrolled in the Nutritional Education Program of the Bambino Gesù Children's Hospital and Research Institute of Rome (Italy) and 80 normal-weight subjects.

RESULTS

We observed increased HOMA-IR, PAI-1, and other inflammation indices associated with decreased VD levels when compared to normal-weight children.

CONCLUSIONS

Our results demonstrated that overweight and obesity are correlated with higher levels of the inflammation index. Moreover, our patients show high PAI-1 and low VD levels, confirming the high thrombotic risk in our pediatric population.

Soluble endothelial protein C receptor is an independent predictor of venous thromboembolism after severe injury: Secondary analysis of a prospective cohort study

BACKGROUND

Venous thromboembolism is a leading cause of morbidity after trauma. Endothelial cells are essential regulators of coagulation. Although endothelial cell dysregulation is widely reported after trauma, the link between endothelial injury and venous thromboembolism has not been reported.

METHODS

We conducted a secondary analysis of the Pragmatic Randomized Optimal Platelets and Plasma Ratios study. Deaths from hemorrhage or within 24 hours were excluded. Venous thromboembolism was diagnosed by duplex ultrasound or chest computed tomography. Endothelial markers soluble endothelial protein c receptor, thrombomodulin, and syndecan-1 were measured in plasma by enzyme-linked immunosorbent assay and compared over the first 72 hours from admission using the Mann-Whitney test. Multivariable logistic regression assessed the adjusted effects of endothelial markers on venous thromboembolism risk.

RESULTS

Of 575 patients enrolled, 86 developed venous thromboembolism (15%). The median time to venous thromboembolism was 6 days ([Q1, Q3], [4, 13]). No differences were identified in demographics or injury severity. Soluble endothelial protein c receptor, thrombomodulin, and syndecan-1 showed significant increases over time among patients who developed venous thromboembolism compared to those who did not. Using the last available values, patients were stratified into high and low-soluble endothelial protein c receptor, thrombomodulin, and syndecan-1 groups. Multivariable analyses revealed an independent association between elevated soluble endothelial protein c receptor and venous thromboembolism risk (odds ratio 1.63; 95% confidence interval 1.01, 2.63; P = .04). Cox proportional hazards modeling demonstrated a strong yet nonsignificant trend between elevated soluble endothelial protein c receptor and time to venous thromboembolism.

CONCLUSION

Plasma markers of endothelial injury, particularly soluble endothelial protein c receptor, are strongly associated with trauma-related venous thromboembolism. Therapeutics targeting endothelial function could mitigate the incidence of venous thromboembolism after trauma.

Hand grip strength in venous thromboembolism: risk of recurrence and mortality

Background

There is limited information on the relationship between muscle strength and recurrence and mortality after incident venous thromboembolism (VTE).

Objectives

To investigate whether weak hand grip strength (HGS) was associated with risk of recurrence and mortality in patients with VTE recruited from the general population.

Methods

Participants from the Tromsø Study with a first-time VTE (n = 545) were included, and all VTE recurrences and deaths among the participants were recorded in the period 1994 to 2020. Weak HGS was defined as lowest 25th percentile of the general population, and incidence rates for VTE recurrence and mortality according to weak vs normal (>25th percentile) HGS, with 95% CIs, were estimated.

Results

There were 90 recurrences and 350 deaths during a median of 3.7 years of follow-up. The fully adjusted hazard ratio (HR) for overall VTE recurrence for those with weak HGS vs those with normal HGS was 2.02 (95% CI, 1.23-3.30). The corresponding HRs for recurrence were 2.22 (95% CI, 1.18-4.17) in patients with a first deep vein thrombosis and 1.60 (95% CI, 0.72-3.57) in patients with a first pulmonary embolism. The cumulative 1-year survival was 74.9% and 77.8% in those with weak and normal HGS, respectively. For overall mortality after incident VTE, the fully adjusted HR for those with weak HGS was 1.34 (95% CI, 1.04-1.72).

Conclusion

Weak HGS was associated with an increased risk of recurrent VTE, and the association appeared to be particularly pronounced after incident deep vein thrombosis. There was a slightly lower survival probability among those with weak HGS than among those with normal HGS.

The Incident of Multiple Skin Necrosis and Unilateral Vision Loss Post Liposuction: A Case Report

For many years, people with excess weight around specific body parts who wanted to improve their shape or establish symmetry to achieve their ideal body image chose liposuction. As with any intervention, there is a chance of complications and unfavorable outcomes with liposuction. As a late result of the procedure, skin necrosis, infection, and hematoma are some of the known complications of such a procedure. Other known complications include damage to surrounding structures like nerves, vasculature, or perforating body viscera. This study aimed to report an eventful and unwanted result of a common and relatively safe cosmetic procedure. A 31-year-old Saudi female presented to the emergency room (ER) with right unilateral vision loss, bruises, and burning pain involving the upper limbs, thighs, abdomen, back, and flanks after having liposuction and rhinoplasty two weeks ago in a private clinic overseas. Multiple investigations were obtained to investigate her blindness, which showed a right upper branch of retinal vein occlusion. She was treated conservatively with daily wound dressings and analgesics. After five days, the patient returned with infected wounds and clinical deterioration, necessitating multiple excisions, debridement, and grafting. She eventually recovered and was discharged in good health. Herein, we report a rare case of unilateral blindness and multiple skin necrosis following liposuction of the abdomen and thigh. Debridement and skin grafting were the ideal treatment strategies.

Between Scylla and Charybdis: thrombosis in children with hemophilia

Thromboembolism is an infrequent complication in children with hemophilia that has been traditionally associated with the presence of a central venous access device. Novel rebalancing agents have shown promising results as prophylactic therapies to minimize the risk of bleeding but both thromboembolism and thrombotic microangiopathy have been reported as complications. The management of thrombosis in children with hemophilia is particularly challenging given the inherent risk of bleeding. In this paper, we present clinical vignettes to review the literature, highlight challenges, and describe our approach to managing thromboembolism in children with hemophilia.

Exploring the Causal Relationship Between Arterial and Venous Thromboembolism: A Case Series With Review of Literature

Venous thromboembolism (VTE) occurs due to venous stasis or low flow state within the blood vessels, resulting in subsequent fibrin and platelet aggregation leading to thrombosis. Arterial thrombosis affects various arteries including coronaries and is primarily due to platelet aggregation with little fibrin deposition leading to thrombosis. Although both arterial and venous thrombosis are considered as separate entities, some studies have suggested an association between them despite having distinctive causative factors. We retrospectively reviewed patients at our institution who were admitted with acute coronary syndrome (ACS) and underwent cardiac catheterization over a decade between 2009 and 2020 to look for patients who had both venous thromboembolic events and ACS. Here, we report a case series of three such patients who were found to have both VTE and coronary arterial thrombosis. However, it is unclear if having one of venous vs arterial clot increases the risk of having other vascular conditions, and further studies are needed to evaluate this hypothesis in the near future.

Inflammatory stimuli induce shedding of heparan sulfate from arterial but not venous porcine endothelial cells leading to differential proinflammatory and procoagulant responses

Endothelial dysfunction is an early event of vascular injury defined by a proinflammatory and procoagulant endothelial cell (EC) phenotype. Although endothelial glycocalyx disruption is associated with vascular damage, how various inflammatory stimuli affect the glycocalyx and whether arterial and venous cells respond differently is unknown. Using a 3D round-channel microfluidic system we investigated the endothelial glycocalyx, particularly heparan sulfate (HS), on porcine arterial and venous ECs. Heparan sulfate (HS)/glycocalyx expression was observed already under static conditions on venous ECs while it was flow-dependent on arterial cells. Furthermore, analysis of HS/glycocalyx response after stimulation with inflammatory cues revealed that venous, but not arterial ECs, are resistant to HS shedding. This finding was observed also on isolated porcine vessels. Persistence of HS on venous ECs prevented complement deposition and clot formation after stimulation with tumor necrosis factor α or lipopolysaccharide, whereas after xenogeneic activation no glycocalyx-mediated protection was observed. Contrarily, HS shedding on arterial cells, even without an inflammatory insult, was sufficient to induce a proinflammatory and procoagulant phenotype. Our data indicate that the dimorphic response of arterial and venous ECs is partially due to distinct HS/glycocalyx dynamics suggesting that arterial and venous thrombo-inflammatory disorders require targeted therapies.

A Descriptive Analysis of Direct Oral Anticoagulant Drugs Dosing Errors Based on Spontaneous Reports from the EudraVigilance Database

Direct oral anticoagulant drugs (DOACs) interfere with the coagulation process, thus improving patient care for those who require anticoagulant treatment. This study presents a descriptive analysis of adverse reactions (ADRs) attributed to DOAC dosage errors (overdose, underdose, and improper dose). The analysis was performed based on the Individual Case Safety Reports from the EudraVigilance (EV) database. Results show that data reported for rivaroxaban, apixaban, edoxaban, and dabigatran are mostly regarding underdosing (51.56%) compared to overdosing (18.54%). The most dosage error reports were identified for rivaroxaban (54.02%), followed by apixaban (33.61%). Dabigatran and edoxaban had similar percentages (6.26% and 6.11%, respectively) regarding dosage error reports. Since coagulation issues can become life-threatening events, and factors such as advanced age and renal failure can influence the pharmacokinetics of drugs, the correct usage of DOACs is of utmost importance for the management and prevention of venous thromboembolism. Thus, the collaboration and the complementarity of knowledge of physicians and pharmacists may offer a reliable solution for DOAC dose management and improve patient care.

Prevalence of perioperative asymptomatic venous thromboses of the lower extremity in 30 consecutive patients undergoing transsphenoidal surgery for Cushing's disease

Cushing´s disease is a rare endocrinological disorder which is caused by an adrenocorticotropic hormone secreting pituitary adenoma. The condition is associated with an increased risk for venous thromboembolism. While there exist reports on symptomatic venous thromboses complicating Cushing's disease, the prevalence of incidental leg vein thromboses accompanying pituitary surgery for Cushing's disease is yet unknown. 30 consecutive patients (9 male; age 25-77 years) with histologically confirmed Cushing's disease underwent transsphenoidal adenomectomy between October 2018 and September 2019. All patients received perioperative pharmacological thromboprophylaxis. Whole leg compression ultrasound was performed within one week after surgery (median 2 days) to exclude leg vein thromboses (primary endpoint). Preoperative laboratory values including plasma cortisol and various coagulation parameters were evaluated as secondary outcome measures. A comparison was made between patients with and without thrombotic events (p value ≤ 0.05). A total of 2 out of 30 patients (6.7%; CI 0.8-24.1%) presented with asymptomatic perioperative deep vein thromboses of the lower legs. Thrombosis patients differed not significantly from their counterparts with respect to age, sex, and comorbidities, but preoperative morning plasma cortisol was significantly higher in patients with venous thromboses (421.0 ± 49.5 μg/l vs. 188.1 ± 78.2 μg/l; p = 0.01). Moreover, von Willebrand factor activity was markedly increased in one case (409.0%) compared to the mean value obtained from 28 patients without phlebothromboses (146.9 ± 60.7%; p < 0.01). Perioperative asymptomatic leg vein thrombosis can be found with the aid of compression ultrasound in a considerable proportion of patients undergoing transsphenoidal adenomectomy for Cushing's disease despite the administration of pharmacological thromboprophylaxis.

Natural anticoagulant discovery, the gift that keeps on giving: finding FV-Short

The complex reactions of blood coagulation are balanced by several natural anticoagulants resulting in tuned hemostasis. During several decades, the knowledge base of the natural anticoagulants has greatly increased and we have also learned about antiinflammatory and cytoprotective activities expressed by antithrombin and activated protein C (APC). Some coagulation proteins have also been found to function as anticoagulants; e.g., thrombin when bound to thrombomodulin activates protein C. Another example is factor V (FV), which in addition to being a procofactor to FVa has emerged as an anticoagulant. The discovery of APC resistance, caused by FVLeiden, as a thrombosis risk factor resulted in the identification of FV as an APC cofactor working in synergy with protein S in the regulation of FVIIIa in the Xase complex. More recently, a natural anticoagulant FV splice isoform (FV-Short) was discovered when investigating the East Texas bleeding disorder. In FV-Short, the truncated B domain exposes a high-affinity binding site for tissue factor pathway inhibitor alpha (TFPIα), and together with protein S a high-affinity trimolecular complex is generated. The FXa-inhibitory activity of TFPIα is synergistically stimulated by FV-Short and protein S. The circulating FV-Short/protein S/TFPIα complex concentration is normally low (≈0.2 nM) but provides an anticoagulant threshold. In the East Texas bleeding, the concentration of the complex, and thus the threshold, is increased 10-fold, which results in bleeding manifestations. The anticoagulant properties of FV were discovered during investigations of individual patients and follow the great tradition of bed-to-bench and bench-to-bed research in the coagulation field.

The influence of lower-leg injury and knee arthroscopy on natural anticoagulants and fibrinolysis

BACKGROUND

Patients with lower-leg injuries and those undergoing knee arthroscopy are at increased risk of developing venous thromboembolism. The mechanism is unknown, including the influence of lower-leg injury and knee arthroscopy on natural anticoagulant factors and fibrinolysis.

OBJECTIVES

To study the effect of lower-leg injury and knee arthroscopy on plasma levels of anticoagulant and fibrinolytic factors.

METHODS

We applied the following 2 designs to investigate this effect: a cross-sectional study for lower-leg trauma and a before-and-after study for knee arthroscopy. Plasma samples of POT-CAST- and POT-KAST-randomized clinical trial participants (collected shortly after lower-leg trauma or before or after arthroscopy) were analyzed for clot lysis time and levels of antithrombin, tissue factor pathway inhibitor, protein C, free protein S, plasminogen, tissue plasminogen activator, plasminogen activator inhibitor 1, antiplasmin, thrombin activatable fibrinolysis inhibitor, plasmin-antiplasmin, and D-dimer. For the effect of lower-leg injury, samples of 289 patients were compared with preoperative samples of 293 arthroscopy patients, acting as controls using linear regression and adjusting for age, sex, body mass index, comorbidities, and diurnal variation. For the effect of knee arthroscopy, mean changes were calculated for 277 patients using linear mixed models adjusted for diurnal variation. Parameters other than CLT and D-dimer were measured in smaller subsets.

RESULTS

In lower-leg injury patients, most parameters were stable, whereas D-dimer increased. After arthroscopy, most parameters decreased (especially clot lysis time, D-dimer, plasminogen, and anticoagulant factors), whereas tissue plasminogen activator and thrombin activatable fibrinolysis inhibitor slightly increased.

CONCLUSION

In contrast to lower-leg injury, knee arthroscopy was associated with decreased natural anticoagulant factor levels. Neither lower-leg injury nor knee arthroscopy affected in vivo fibrinolysis.

Incidence of Venous Thromboembolism in Patients Receiving Anticoagulation for Foot and Ankle Surgery

Venous thromboembolism (VTE) is a serious medical condition that can be an unfortunate complication arising from foot and ankle surgery. Many factors may predispose a patient to a VTE event including prolonged postoperative immobilization, comorbidities, extended length of tourniquet time, and higher risk surgeries. Unfortunately, there is no clinical consensus for guidelines on VTE prophylaxis following foot and ankle surgery. In this retrospective cohort study, we present our patient population who were prophylactically anticoagulated following foot and ankle surgery along with their incidence of deep vein thrombosis and pulmonary embolism (PE). Included in the study were patients who had undergone elective and traumatic foot and ankle surgery from June 2017 to December 2018. Using retrospective data obtained we compared patient demographics, surgery type, length of tourniquet time, postoperative immobilization, type of VTE prophylaxis, and comorbidities including history of smoking, peripheral vascular disease, bleeding disorders, and patients undergoing dialysis. Five of 425 (1.2%) patients were diagnosed with a deep vein thrombosis and 1 of 425 (0.2%) patients was diagnosed with a pulmonary embolism. Risks factors statistically significant for developing a VTE in our patient population included extended periods of immobilization and an increasing patient age. We were able to conclude that routine prophylaxis for elective and traumatic foot and ankle surgery is both effective and safe for especially in older patients requiring extended immobilization. It's also important to take into consideration comorbidities, smoking history, tourniquet time, and the type of surgery that is being performed.

Measuring the Compression Force Required for Vascular Shortening in Ultrasonic Vascular Models

Background Vascular compression is important for deep vein thrombosis screening. However, pressure analysis of ultrasound vessel models has not been performed. Therefore, we compared the human popliteal vein and several ultrasound vessel models at 50% compression. Methodology Four major ultrasound vascular models used in Japan and the popliteal vein of one subject constituted our measurement targets. Using a pressure-sensitive measuring device, the compressive force required to shorten the vessel diameter by 50% was determined. Results The compression force that shortened the popliteal vein by 50% was measured to be 191 ± 65 g. The blue phantom, ultrasound CV Pad II, ultrasound training block, and UGP-GEL required compression force of 701 ± 8 g, 265 ± 12 g, 697 ± 20 g, and 745 ± 15 g, respectively. The compression force for the ultrasound training block was 2.6 times higher than that for the ultrasound CV Pad II. The gel material around the vessels was the same; however, different vascular tubes required 2.6 times higher compression force. Conclusions This study showed that the objective numerical values of the compressive force were required to compress an ultrasound vascular model. Reproduction of the compressibility of veins required either removing the vascular structure or using thin tubing material.

Factor XI, a potential target for anticoagulation therapy for venous thromboembolism

Venous thromboembolism (VTE) is a common cause of mortality and disability in hospitalized patients, and anticoagulation is an essential therapeutic option. Despite the increasing use of direct oral anticoagulants, complications and adverse drug reactions still occur in patients with VTE. Within 5 years, 20% of patients with VTE experience recurrence, and 50% of patients with deep vein thrombosis develop post-thrombotic syndrome. Furthermore, bleeding due to anticoagulants is a side effect that must be addressed. Therefore, safer and more effective anticoagulant strategies with higher patient compliance are urgently needed. Available epidemiological evidence and animal studies have shown that factor XI (FXI) inhibitors can reduce thrombus size and loosen the thrombus structure with a relatively low risk of bleeding, suggesting that FXI has an important role in thrombus stabilization and is a safer target for anticoagulation. Recent clinical trial data have also shown that FXI inhibitors are as effective as enoxaparin and apixaban in preventing VTE, but with a significantly lower incidence of bleeding. Furthermore, FXI inhibitors can be administered daily or monthly; therefore, the monitoring interval can be longer. Additionally, FXI inhibitors can prolong the activated partial thromboplastin time without affecting prothrombin time, which is an easy and common test used in clinical testing, providing a cost-effective monitoring routine for patients. Consequently, the inhibition of FXI may be an effective strategy for the prevention and treatment of VTE. Enormous progress has been made in the research strategies for FXI inhibitors, with abelacimab already in phase III clinical trials and most other inhibitors in phase I or II trials. In this review, we discuss the challenges of VTE therapy, briefly describe the structure and function of FXI, summarize the latest FXI/activated FXI (FXIa) inhibitor strategies, and summarize the latest developments in clinical trials of FXI/FXIa inhibitors.

The Gab2-MALT1 axis regulates thromboinflammation and deep vein thrombosis

Deep vein thrombosis (DVT) is the third most common cause of cardiovascular mortality. Several studies suggest that DVT occurs at the intersection of dysregulated inflammation and coagulation upon activation of inflammasome and secretion of interleukin 1β (IL-1β) in restricted venous flow conditions. Our recent studies showed a signaling adapter protein, Gab2 (Grb2-associated binder 2), plays a crucial role in propagating inflammatory signaling triggered by IL-1β and other inflammatory mediators in endothelial cells. The present study shows that Gab2 facilitates the assembly of the CBM (CARMA3 [CARD recruited membrane-associated guanylate kinase protein 3]-BCL-10 [B-cell lymphoma 10]-MALT1 [mucosa-associated lymphoid tissue lymphoma translocation protein 1]) signalosome, which mediates the activation of Rho and NF-κB in endothelial cells. Gene silencing of Gab2 or MALT1, the effector signaling molecule in the CBM signalosome, or pharmacological inhibition of MALT1 with a specific inhibitor, mepazine, significantly reduced IL-1β-induced Rho-dependent exocytosis of P-selectin and von Willebrand factor (VWF) and the subsequent adhesion of neutrophils to endothelial cells. MALT1 inhibition also reduced IL-1β-induced NF-κB-dependent expression of tissue factor and vascular cell adhesion molecule 1. Consistent with the in vitro data, Gab2 deficiency or pharmacological inhibition of MALT1 suppressed the accumulation of monocytes and neutrophils at the injury site and attenuated venous thrombosis induced by the inferior vena cava ligation-induced stenosis or stasis in mice. Overall, our data reveal a previously unrecognized role of the Gab2-MALT1 axis in thromboinflammation. Targeting the Gab2-MALT1 axis with MALT1 inhibitors may become an effective strategy to treat DVT by suppressing thromboinflammation without inducing bleeding complications.

Effects of clot contraction on clot degradation: A mathematical and experimental approach

Thrombosis, resulting in occlusive blood clots, blocks blood flow to downstream organs and causes life-threatening conditions such as heart attacks and strokes. The administration of tissue plasminogen activator (t-PA), which drives the enzymatic degradation (fibrinolysis) of these blood clots, is a treatment for thrombotic conditions, but the use of these therapeutics is often limited due to the time-dependent nature of treatment and their limited success. We have shown that clot contraction, which is altered in prothrombotic conditions, influences the efficacy of fibrinolysis. Clot contraction results in the volume shrinkage of blood clots, with the redistribution and densification of fibrin and platelets on the exterior of the clot and red blood cells in the interior. Understanding how these key structural changes influence fibrinolysis can lead to improved diagnostics and patient care. We used a combination of mathematical modeling and experimental methodologies to characterize the process of exogenous delivery of t-PA (external fibrinolysis). A three-dimensional (3D) stochastic, multiscale model of external fibrinolysis was used to determine how the structural changes that occur during the process of clot contraction influence the mechanism(s) of fibrinolysis. Experiments were performed based on modeling predictions using pooled human plasma and the external delivery of t-PA to initiate lysis. Analysis of fibrinolysis simulations and experiments indicate that fibrin densification makes the most significant contribution to the rate of fibrinolysis compared with the distribution of components and degree of compaction (p < 0.0001). This result suggests the possibility of a certain fibrin density threshold above which t-PA effective diffusion is limited. From a clinical perspective, this information can be used to improve on current therapeutics by optimizing timing and delivery of lysis agents.

Predicting the risk of postsplenectomy thrombosis in patients with portal hypertension using computational hemodynamics models: A proof-of-concept study

BACKGROUND

The high incidence of thrombosis in the portal venous system following splenectomy (a frequently adopted surgery for treating portal hypertension in patients with splenomegaly and hypersplenism) is a critical clinical issue. The aim of this study was to address whether quantification of postsplenectomy hemodynamics has potential value for assessing the risk of postsplenectomy thrombosis.

METHODS

Computational models were constructed for three portal hypertensive patients treated with splenectomy based on their preoperative clinical data to quantify hemodynamics in the portal venous system before and after splenectomy, respectively. Each patient was followed up for three or five months after surgery and examined with CT to screen potential thrombosis.

FINDINGS

The area ratio of wall regions exposed to low wall shear stress was small before splenectomy in all patients, which increased markedly after splenectomy and exhibited enlarged inter-patient differences. The largest area ratio of low wall shear stress and most severe flow stagnation after splenectomy were predicted for the patient suffering from postsplenectomy thrombosis, with the wall regions exposed to low wall shear stress corresponding well with the CT-detected distribution of thrombus. Further analyses revealed that postoperative hemodynamic characteristics were considerably influenced by the anatomorphological features of the portal venous system.

INTERPRETATION

Postoperative hemodynamic conditions in the portal venous system are highly patient-specific and have a potential link to postsplenectomy thrombosis, which indicates that patient-specific hemodynamic studies may serve as a complement to routine clinical assessments for refining risk stratification and postoperative patient management.

Acute Venous Disease Anomalies in Critically Ill COVID-19 Patients

Introduction: Other entities besides deep vein thrombosis (DVT) affecting the venous system, such as superficial vein phlebitis (SVP) and superficial vein thrombophlebitis (SVT), receive poor attention in the literature. However, both entities may propagate proximally into the deep venous system and progress to a DVT. To our knowledge, the relevance of other venous findings such as SVP or SVT in coronavirus disease 2019 (COVID-19) patients has not been evaluated. This work aimed to assess the clinical, biochemical, and hematological variables associated with the incidence of acute venous diseases, such as DVT, SVP, and SVT, in a cohort of 74 critically ill COVID-19 patients and their association with mortality.

Methods: Given the high thrombotic risk, all patients underwent venous imaging with bedside ultrasound. Clinical variables were obtained from medical records. Comparisons were made by the chi-square test or Fisher’s exact test. We constructed Kaplan-Meier curves and used Cox proportional hazard models to calculate hazard ratios for dichotomized risk factors to identify predictors of mortality. SPSS version 21.0 (IBM Corp., Armonk, NY) was used for statistical analysis.

Results: SVP occurred in 28 patients (37.8%), DVT in 22 patients (29.7%), and 28 patients died (37.8%). Elevated D-dimer was associated with DVT but not with SVP. Neither SVP nor DVT was associated with mortality. After adjusting for age, elevated troponins (OR: 2.4, 95% CI: 1.1-5.4), platelets < 244 cell/mm³ (2.4, 1.1-5.6), and IMPROVE (International Medical Prevention Registry on Venous Thromboembolism) bleeding score > 7 (2.8, 1.3-6.3) were predictors of mortality.

Conclusions: Acute venous findings such as SVP and DVT are highly prevalent and independent of mortality in critically ill COVID-19 patients. These entities are not related, although they may occur synchronically. DVT is frequently presented as an asymptomatic distal bilateral finding associated with elevated D-dimer, decreased ferritin, and higher vasoactive drug use but independent from chronic venous disease. Interestingly, elevated troponins, decreased platelets, and a prognostic value > 7 of the IMPROVE bleeding score were predictors of mortality in this group of critically ill COVID-19 patients.

Leukocyte as an Independent Predictor of Lower-Extremity Deep Venous Thrombosis in Elderly Patients With Primary Intracerebral Hemorrhage

Objective

Due to the interaction of leukocytes with platelets and coagulation factors, they may in turn play a role in hemostasis or the formation of thrombi. This study aimed to investigate the association of leukocytosis on admission with an increased risk of acute lower-extremity deep venous thrombosis (LEDVT) in elderly patients with primary intracerebral hemorrhage (ICH).

Methods

This was a single-center, retrospective observational study of consecutive patients observed with spontaneous ICH aged 60 years or above at Lanzhou University Second Hospital from January 2017 to September 2021. Clinical data and demographic information were collected and analyzed. Univariate and multivariate analyses were conducted to identify independent risk factors of acute LEDVT. One-to-one matching was implemented to balance important patient characteristics by the groups' propensity score matching (PSM) analysis.

Results

A total of 371 elderly patients with primary ICH fulfilled requirements for inclusion and exclusion, of whom 33 (8.89%) experienced LEDVT. Leukocyte counts were statistically higher in the LEDVT group compared to the non-LEDVT group [12.89 (8.80–14.61) × 10⁹ cells/L vs. 8.31 (6.60–10.75) × 10⁹ cells /L, p < 0.001]. Multivariate logistic regression models adjusted for several potential confounding factors were performed, and leukocytes were consistently a significant independent predictor of LEDVT. The optimal cut-off value of leukocyte counts calculated from the receiver operating characteristic (ROC) curve to predict LEDVT was 10.22 × 10⁹ cells /L (area under the curve:0.714, 95%CI 0.665–0.759; the sensitivity was 72.73%; the specificity was 71.01%) in elderly patients with primary ICH. After one-to-one PSM, compared to the matched non-LEDVT group, the matched LEDVT group had significantly higher leukocyte counts [11.98 (8.40–13.94) × 10⁹ cells/L vs. 6.12 (4.68–12.00) × 10⁹ cells/L, p = 0.003]. After PSM, the ROC curve was plotted for leukocytes as a predictor of LEDVT, with an AUC of 0.722 (95%CI 0.593–0.828, p = 0.001; the sensitivity was 87.10%, and the specificity was 61.29%). Elevated leukocytes remained independently significant as predictors of LEDVT in elderly patients with primary ICH.

Conclusion

Leukocyte at admission is an independent risk factor of LEDVT in elderly patients with primary ICH.

Age-related immunosenescence in Behçet's disease

Behçet's disease (BD) is a systemic vasculitis of unknown etiology causing recurrent mucocutaneous lesions, ocular involvement, central nervous system involvement, and vascular involvement. The disease is characterized by exacerbations and spontaneous remissions. Prognosis is poor in young men when the vessels are involved. The course is more active and severe in the first years of the disease. One of the most interesting features of BD is that the disease changes to a state of low activity and remission over time. Although the association between aging and lower disease activity is well established, there is limited literature data and research investigating the cause. Similarly, there are not many studies on the late onset of BD and its characteristics. In this regard, understanding the cause of the decline in disease activity over time may open new avenues for pathogenesis and treatment research. In this review, we focus on the immunosenescence caused by chronic inflammation and aging in BD. Based on the effect of testosterone on innate immune cells, we also briefly discussed the potential effects of this hormone on vascular involvement.

Anticoagulant SERPINs: Endogenous Regulators of Hemostasis and Thrombosis

Appropriate activation of coagulation requires a balance between procoagulant and anticoagulant proteins in blood. Loss in this balance leads to hemorrhage and thrombosis. A number of endogenous anticoagulant proteins, such as antithrombin and heparin cofactor II, are members of the serine protease inhibitor (SERPIN) family. These SERPIN anticoagulants function by forming irreversible inhibitory complexes with target coagulation proteases. Mutations in SERPIN family members, such as antithrombin, can cause hereditary thrombophilias. In addition, low plasma levels of SERPINs have been associated with an increased risk of thrombosis. Here, we review the biological activities of the different anticoagulant SERPINs. We further consider the clinical consequences of SERPIN deficiencies and insights gained from preclinical disease models. Finally, we discuss the potential utility of engineered SERPINs as novel therapies for the treatment of thrombotic pathologies.

Incidental pulmonary emboli are associated with a very high probability of progressive malignant disease on staging CT scans

PURPOSE

The link between malignancy and venous thromboembolism (VTE) is well established; the risk has been shown to be higher in certain tumour types and in patients receiving platinum-based chemotherapy regimens. 'Active' cancer is often quoted as being a particular risk factor for VTE, but the definition varies widely and the supporting evidence is weak. This study was conceived to establish whether incidental pulmonary emboli are associated with an increased likelihood of progressive disease on a staging computed tomography (CT) scan.

MATERIALS AND METHODS

All CT scans containing incidental PEs over the course of a year in a large specialist cancer hospital were examined (n = 306). An age-matched control group was assembled. Multivariate logistic regression analysis was performed to establish the relationship of several independent variables, including progressive disease, with the dependent variable of the presence or absence of incidental pulmonary emboli.

RESULTS

Progressive disease was present in 144 of 306 (47.1%) of the patients in the PE group but only 63 of 306 (20.6%) of the control group patients. Progressive disease on the staging CT scan was found to have an odds ratio for incidental PE of 3.46, with a 95% CI of 2.38-5.01. Receiving platinum-based chemotherapy resulted in an odds ratio of 3.89 (2.41-6.28) for PE. Receiving non-platinum-based systemic anti-cancer therapy (SACT) resulted in an odds ratio for PE of 1.71 (1.16-2.50).

CONCLUSION

The detection of an incidental PE on a staging CT scan is associated with a very high risk of progressive malignant disease.

Elevated Risk of Venous Thromboembolism in People Living with HIV

Human immunodeficiency virus (HIV) has been generally considered as a highly adaptive and rapidly evolving virus. It still constitutes a major public health problem all over the world despite an effective outcome in the prevention and reversal of the development and prognosis by using antiretroviral therapy. The salient question lies in the more frequent emergence of a series of comorbidities along with the prolongation of the life, which deeply affects the survival in such group. Venous thromboembolism (VTE) has been recognized to be the third most common cardiovascular condition within people living with HIV (PWH). In terms of its mechanism of action, the occurrence of VTE is quite multifactorial and complex in HIV. Prior exploration concerning the etiology of VTE in PWH identifies general, disease-specific, and miscellaneous factors for explaining its occurrence and development. VTE has constituted an important role in PWH and may increase its all-cause mortality. Therefore, it is quite necessary to understand VTE from the following aspects of epidemiology, pathophysiology, molecular mechanisms, and therapeutic interventions so as to balance the risks and benefits of anticoagulation and optimize corresponding treatment.

Obstructive Sleep Apnea as a Risk Factor for Venous Thromboembolism: A Systematic Review

Obstructive sleep apnea (OSA), is a prevalent condition characterized by repeated episodes of pharyngeal airway obstruction resulting in hypopnea and apnea episodes during sleep leading to nightly awakenings. OSA is a major contributor to the healthcare burden worldwide due to its high cardiovascular morbidity and mortality. There is growing evidence to support a pathophysiological link between OSA and venous thromboembolism (VTE). The pro-inflammatory state along with intermittent hypoxia that is invoked in OSA is associated with blood hypercoagulability, venous stasis, and endothelial dysfunction leading to deep vein thrombosis (DVT) and pulmonary embolism (PE). In this systematic review, we aim to analyze and assess the available literature on OSA and VTE (or DVT/PE) to determine whether OSA is an independent risk factor for VTE.

Cerebrovascular Effects of Lower Body Negative Pressure at 3T MRI: Implications for Long-Duration Space Travel

BACKGROUND

Optic disc edema develops in most astronauts during long-duration spaceflight. It is hypothesized to result from weightlessness-induced venous congestion of the head and neck and is an unresolved health risk of space travel.

PURPOSE

Determine if short-term application of lower body negative pressure (LBNP) could reduce internal jugular vein (IJV) expansion associated with the supine posture without negatively impacting cerebral perfusion or causing IJV flow stasis.

STUDY TYPE

Prospective.

SUBJECTS

Nine healthy volunteers (six women).

FIELD STRENGTH/SEQUENCE

3T/cine two-dimensional phase-contrast gradient echo; pseudo-continuous arterial spin labeling single-shot gradient echo echo-planar.

ASSESSMENT

The study was performed with two sequential conditions in randomized order: supine posture and supine posture with 25 mmHg LBNP (LBNP₂₅ ). LBNP was achieved by enclosing the lower extremities in a semi-airtight acrylic chamber connected to a vacuum. Heart rate, bulk cerebrovasculature flow, IJV cross-sectional area, fractional IJV outflow relative to arterial inflow, and cerebral perfusion were assessed in each condition.

STATISTICAL TESTS

Paired t-tests were used to compare measurement means across conditions. Significance was defined as P < 0.05.

RESULTS

LBNP₂₅ significantly increased heart rate from 64 ± 9 to 71 ± 8 beats per minute and significantly decreased IJV cross-sectional area, IJV outflow fraction, cerebral arterial flow rate, and cerebral arterial stroke volume from 1.28 ± 0.64 to 0.56 ± 0.31 cm² , 0.75 ± 0.20 to 0.66 ± 0.28, 780 ± 154 to 708 ± 137 mL/min and 12.2 ± 2.8 to 9.7 ± 1.7 mL/cycle, respectively. During LBNP₂₅ , there was no significant change in gray or white matter cerebral perfusion (P = 0.26 and P = 0.24 respectively) and IJV absolute mean peak flow velocity remained ≥4 cm/sec in all subjects.

DATA CONCLUSION

Short-term application of LBNP₂₅ reduced IJV expansion without decreasing cerebral perfusion or inducing IJV flow stasis.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY STAGE: 1.

Chronic subdural hemorrhage predisposes to development of cerebral venous thrombosis and associated retinal hemorrhages and subdural rebleeds in infants

For infants presenting with subdural hemorrhage, retinal hemorrhage, and neurological decline the "consensus" opinion is that this constellation represents child abuse and that cerebral venous sinus thrombosis and cortical vein thrombosis is a false mimic. This article contends that this conclusion is false for a subset of infants with no evidence of spinal, external head, or body injury and is the result of a poor radiologic evidence base and misinterpreted data. Underdiagnosis of thrombosis is the result of rapid clot dissolution and radiologic under recognition. A pre-existing/chronic subdural hemorrhage predisposes to development of venous sinus thrombosis/cortical vein thrombosis, triggered by minor trauma or an acute life-threatening event such as dysphagic choking, variably leading to retinal and subdural hemorrhages and neurologic decline. These conclusions are based on analysis of the neuroradiologic imaging findings in 11 infants, all featuring undiagnosed cortical vein or venous sinus thrombosis. Subtle neuroradiologic signs of and the mechanisms of thrombosis are discussed. Subarachnoid hemorrhage from leaking thrombosed cortical veins may be confused with acute subdural hemorrhage and probably contributes to the development of retinal hemorrhage ala Terson's syndrome. Chronic subdural hemorrhage rebleeding from minor trauma likely occurs more readily than bleeding from traumatic bridging vein rupture. Radiologists must meet the challenge of stringent evaluation of neuro imaging studies; any infant with a pre-existing subdural hemorrhage presenting with neurologic decline must be assumed to have venous sinus or cortical vein thrombosis until proven otherwise.