Improving Awareness and Outcomes Related to Venous Thromboembolism

New Triazole-Based Potent Inhibitors of Human Factor XIIa as Anticoagulants

Factor XIIa (FXIIa) functions as a plasma serine protease within the contact activation pathway. Various animal models have indicated a substantial role for FXIIa in thromboembolic diseases. Interestingly, individuals and animals with FXII deficiency seem to maintain normal hemostasis. Consequently, inhibiting FXIIa could potentially offer a viable therapeutic approach for achieving effective and safer anticoagulation without the bleeding risks associated with the existing anticoagulants. Despite the potential, only a limited number of small molecule inhibitors targeting human FXIIa have been documented. Thus, we combined a small library of 32 triazole and triazole-like molecules to be evaluated for FXIIa inhibition by using a chromogenic substrate hydrolysis assay under physiological conditions. Initial screening at 200 μM involved 18 small molecules, revealing that 4 molecules inhibited FXIIa more than 20%. In addition to being the most potent inhibitor identified in the first round, inhibitor 8 also exhibited a substantial margin of selectivity against related serine proteases, including factors XIa, Xa, and IXa. However, the molecule also inhibited thrombin with a similar potency. It also prolonged the clotting time of human plasma, as was determined in the activated partial thromboplastin time and prothrombin time assays. Subsequent structure-activity relationship studies led to the identification of several inhibitors with submicromolar activity, among which inhibitor 22 appears to demonstrate significant selectivity not only over factors IXa, Xa, and XIa, but also over thrombin. In summary, this study introduces novel triazole-based small molecules, specifically compounds 8 and 22, identified as potent and selective inhibitors of human FXIIa. The aim is to advance these inhibitors for further development as anticoagulants to provide a more effective and safer approach to preventing and/or treating thromboembolic diseases.

Epidemiology and prevention of venous thromboembolism

Venous thromboembolism, that consists of the interrelated conditions deep-vein thrombosis and pulmonary embolism, is an under-appreciated vascular disease. In Western regions, approximately 1 in 12 individuals will be diagnosed with venous thromboembolism in their lifetime. Rates of venous thromboembolism are lower in Asia, but data from other regions are sparse. Numerous risk factors for venous thromboembolism have been identified, which can be classified as acute or subacute triggers (provoking factors that increase the risk of venous thromboembolism) and basal or acquired risk factors (which can be modifiable or static). Approximately 20% of individuals who have a venous thromboembolism event die within 1 year (although often from the provoking condition), and complications are common among survivors. Fortunately, opportunities exist for primordial prevention (prevention of the development of underlying risk factors), primary prevention (management of risk factors among individuals at high risk of the condition) and secondary prevention (prevention of recurrent events) of venous thromboembolism. In this Review, we describe the epidemiology of venous thromboembolism, including the incidence, risk factors, outcomes and opportunities for prevention. Meaningful health disparities exist in both the incidence and outcomes of venous thromboembolism. We also discuss these disparities as well as opportunities to reduce them.

Measurement of the awareness of venous thromboembolism in the Saudi population

BACKGROUND

Venous thromboembolism (VTE) causes significant morbidity and mortality. International studies have suggested poor public awareness of VTE, with a few data from Saudi Arabia. The aim of this study was to investigate the knowledge and awareness of VTE in the Saudi population. Awareness of other important diseases was also investigated to allow contextualization.

METHODS

A cross-sectional survey study was conducted throughout Saudi Arabia from April to June 2021. A nonprobability, purposive, social media-driven, snowballing sampling technique was used to distribute a validated online questionnaire to Saudi adults (aged over 18 years) from the general population.

RESULTS

Of 1226 respondents, 214 were excluded as they were health-care professionals. The majority of the participants were unaware and unconcerned about VTE. They were more aware of other medical conditions such as hypertension. Immobility and old age were frequently recognized as risk factors for VTE. While less than half of the participants were aware that thrombosis is the cause of VTE, most participants correctly identified leg pain and tenderness as symptoms of deep venous thrombosis. The majority of the participants identified chest pain and breathlessness as symptoms of pulmonary embolism. However, leg paralysis and slow, shallow breathing were frequently identified as symptoms of VTE. The majority of subjects disagreed with the statement, "having a blood clot is not considered a medical emergency." Awareness of VTE varied significantly with age.

CONCLUSION

In Saudi Arabia, the public awareness of VTE is poor. To improve outcomes, public health initiatives must increase awareness, introduce preventive measures, encourage early diagnosis, and ensure compliance with treatment.

Active Cancer Patients Presenting to the Emergency Department with Acute Venous Thromboembolism: A Retrospective Cohort Study on Risks and Outcomes

BACKGROUND

There is no prior study that has documented emergency department (ED) outcomes or stratified mortality risks of cancer patients presenting with an acute venous thromboembolism (VTE).

OBJECTIVE

To evaluate ED treatment of these patients, to document their outcomes, and to identify risk factors associated with death.

METHODS

A retrospective cohort study was performed on active cancer patients presenting with deep venous thrombosis or pulmonary embolism to two academic EDs between July 2012 and June 2016. Key outcomes included mortality, ED revisit, and admission within 30 days. The patient cohort was characterized; crosstabs and regression analysis were performed to assess relative risks (RRs) and mitigating factors associated with 30-day mortality.

RESULTS

Of 355 patients, 9% died and 38% had one or more ED revisits or admissions. Recent immobility (RR 2.341, 95% CI 1.227-4.465), poor functional status (RR 2.090, 95% CI 1.028-4.248), recent admission (RR 2.441, 95% CI 1.276-4.669), and metastatic cancer (RR 4.669, 95% CI 1.456-14.979) were major risk factors for mortality. ED-provided anticoagulation reduced the overall mortality risk (RR 0.274, 95% CI 0.146-0.515) and mitigated the risk from recent immobility (RR 1.250, 95% CI 0.462-3.381), especially among patients with good or fair functional status.

CONCLUSION

Immobility and cancer morbidity are key risk factors for mortality after an acute VTE, but ED-provided anticoagulation mitigates the risk of immobility among healthier patients. Eastern Cooperative Oncology Group performance status can help clinicians risk stratify these patients at presentation.

Deep Venous Thrombosis in a Patient with a Moderate Pretest Probability and a Negative D-Dimer Test: A Review of the Diagnostic Algorithms

Modern diagnostic strategies of venous thromboembolism (VTE) have been developed. In this review, the diagnostic algorithms for deep-vein thrombosis (DVT) and their parameters are discussed individually in the context of reporting a case of DVT in a 43-year-old Caucasian female with a moderate pretest probability stratified by Wells’ score and a negative high quality D-dimer test. The patient was on treatment with Xarelto (rivaroxaban), 20 mg PO daily at the time of presentation. The diagnosis was verified through a complete lower limb ultrasound (US). This case highlights the diagnostic challenges and pitfalls of the current algorithms, especially those seen in a subgroup of patients such as patients with cancer, pregnancy, recurrent VTE or are on anticoagulation therapy at the time of presentation. The diagnosis of DVT is less plausible in a patient who is on anticoagulation therapy, but physicians should be aware of such a possibility. Physicians should also know in advance the numerous clinically relevant limitations of D-dimer testing before interpreting the results. Unifying the current diagnostic strategies, modifying the current Wells’ score and using the protocol of a whole-leg compression US instead of the limited US protocol are among the several cautious suggestions that have been proposed based on this review to possibly decrease the incidence of missed DVT.

Prognostic characteristics and body mass index in patients with pulmonary embolism: does size matter?

Objective

The aim of this study was to explore the impact of body mass index (BMI) on prognostic indicators and clinical outcomes in patients with pulmonary embolism.

Methods

Patients with pulmonary embolism from the Hokusai venous thromboembolism (VTE) randomised clinical trial that compared two anticoagulant regimens were followed-up for 1 year (n=1911). Patients were analysed with regard to World Health Organization (WHO) BMI categories at baseline (underweight (<18.5), normal (18.5 to <25), overweight (25 to <30), obese I (30 to <35), obese II (35 to <40), and obese III (≥40)). Clinical and radiological prognostic characteristics for right ventricular dysfunction and adverse events were assessed with normal weight as a reference. Clinical outcomes were mortality, recurrent VTE, hospitalisation, bleeding and overall adverse events.

Results

The relationship between BMI categories and both prognostic parameters and clinical outcomes showed U-shaped curves. Adjusted odds ratios (aORs) were highest in patients who were grade III obese for both clinical parameters (N-terminal pro-brain natriuretic peptide (NT-proBNP) >600 and simplified pulmonary embolism severity index (sPESI)≥1; 2.9 and 1.6), and radiological parameters (pulmonary trunk>29 mm, right-to-left-ventricular ratio>1.0, and central emboli; aOR=4.3, 2.1 and 2.3). Bleeding was observed more frequently in the higher categories of obesity. In patients who were underweight, for NT-proBNP>600 and sPESI≥1 the aORs were 2.6 and 2.5, respectively; however, no major bleeding occurred in this category.

Conclusion

Several clinical and radiological prognostics characteristics and right ventricular dysfunction in pulmonary embolism are not evenly distributed among BMI categories. This is reflected in a trend towards worse outcomes in patients who are overweight and underweight.

Overweight patients with pulmonary embolism have a higher risk of heart dysfunction and worse outcomeshttp://bit.ly/2Pwtln0

Catheter-directed, ultrasound-facilitated fibrinolysis in obese patients with massive and submassive pulmonary embolism

Obesity is a well-established risk factor for pulmonary embolism (PE). However, treatment of PE in obese patients is challenging because of limited outcomes data, especially with advanced therapies such as catheter-based fibrinolysis. We assessed the efficacy and safety of ultrasound-facilitated, catheter-directed fibrinolysis in obese patients with submassive and massive PE enrolled in the SEATTLE II Trial. Eligible patients had a right ventricular-to-left ventricular (RV/LV) diameter ratio ≥ 0.9 on chest computed tomography (CT). The primary efficacy outcome was the change in chest CT-measured RV/LV diameter ratio at 48 h after procedure initiation. The primary safety outcome was GUSTO major bleeding within 72 h. One-hundred and four patients were obese, as defined by a BMI ≥ 30 kg/m², and 44 were non-obese. Mean RV/LV ratio was greater in obese patients at baseline compared with non-obese patients (1.60 vs. 1.43, p = 0.02). Reduction in RV/LV diameter ratio at 48 h was greater in obese patients compared with non-obese patients (absolute reduction: - 0.47 vs. - 0.30, p = 0.01; relative reduction: - 26 vs. - 18%, p = 0.03). Major bleeding occurred in 12 (12%) of obese patients and in 3 (7%) in non-obese patients (p = 0.55). In conclusion, ultrasound-facilitated, catheter-directed fibrinolysis shows promise in obese patients for whom advanced therapy for acute PE is warranted.

Identification of Genetic Interaction with Risk Factors Using a Time-To-Event Model

Background: Certain diseases can occur with and without a trigger. We use Venous Thromboembolism (VTE) as our example to identify genetic interaction with pregnancy in women with VTE during pre- or postpartum. Pregnancy is one of the major risk factors for VTE as it accounts for 10% of maternal deaths. Methods: We performed a whole genome association analysis using the Cox Proportional Hazard (CoxPH) model adjusted for covariates to identify genetic variants associated with the time-to-event of VTE related to pre- or postpartum during the childbearing age of 18–45 years using a case-only design in a cohort of women with VTE. Women with a VTE event after 45 years of age were censored and contributed only follow-up time. Results: We identified two intragenic single nucleotide polymorphisms (SNPs) at genome-wide significance in the PURB gene located on chromosome 7, and two additional intragenic SNPs, one in the LINGO2 gene on chromosome 9 and one in RDXP2 on chromosome X. Conclusions: We showed that the time-to-event model is a useful approach for identifying potential hazard-modification of the genetic variants when the event of interest (VTE) occurs due to a risk factor (pre- or post-partum).