Venous thromboembolism and mortality in a multiethnic population: a report from the Birmingham Black Country VTE registry (BBC-VTE Investigators)

Background

Most epidemiological studies into venous thromboembolism (VTE) are based on the white Caucasian population and unrepresentative of VTE outcomes in non-white ethnicities.

Purpose

Our VTE registry aims to get an insight into the outcomes of VTE patients as applicable to a developed world population with a multi-ethnic background. This will guide clinicians to make appropriate decisions with regards to management and prognosis.

Methods

The Birmingham Black Country VTE Registry (BBC-VTE) is a multi-ethnic cohort of patients in the West Midlands region of the United Kingdom, who suffered a first episode of VTE. In this study we compared baseline characteristics, treatment patterns and outcomes, and secondly, compared these among the different ethnic groups in this region.

Results

Between the years 2012–2014 there was a total of 1615 patients (mean age 65.5; 53.1% female) admitted with a first episode of VTE of whom, 134 (8.3%) were Asian, 92 (5.7%) Black, and 1213 (75.1%) White. Asian patients were younger (mean age 54, SD 19.3) vs Black patients (59, SD 19.7) and White patients (68, SD 17.4); and were less often female (50.7% vs. 55.4% and 53.8%) for Black and White patients respectively. The initial VTE event was a DVT in 680 (42.1%) and a PE±DVT in 935 patients (57.9%). Below-knee and above-knee DVT occurred in 95 (5.9%) and 585 (36.2%) patients respectively. Recurrent DVT occurred in 3.2% of those with an initial below-knee DVT and 12.5% of those with an initial above-knee DVT. Recurrent PE was also more common in those with an initial above knee DVT (4.8%) compared to those with below-knee DVT (3.2%).

After the initial VTE event, 1269 (78.6%) were started on long-term anticoagulation for the prevention of recurrent VTE. Of those, 65.1% stayed on anticoagulation for up to 6 months after the initial VTE event, and 34.9% continued for longer than 6 months, including those on lifelong anticoagulation. Bleeding and major bleeding occurred in 6.8% and 2.5% respectively in those on anticoagulation for 6 or less months, vs. 10.4% and 3.5% in those anticoagulated for longer than 6 months. The most common site of bleeding was gastrointestinal in 42.3% of all bleeds and this site was also responsible for 54.3% of major bleeds.

From evaluating the odds ratio for VTE mortality (see Fig. 1), ethnicity did not have a significant impact. Older age; the presence of diabetes mellitus; history of malignancy; as well as admission laboratory results for C-reactive protein and neutrophil count were all significantly associated with higher odds of mortality in this patient cohort.

Conclusion

BBC-VTE is a contemporary multi-ethnic cohort of patients providing insights into the risk factors among multi-ethnic patients that have developed VTE. Ethnicity did not emerge as an independent risk for VTE mortality.

Funding Acknowledgement

Type of funding sources: None.

The Birmingham Black Country Venous Thromboembolism (BBC-VTE) registry of outcomes of venous thromboembolism patients admitted to hospital

Background

Venous thromboembolism (VTE) is a condition which causes significant morbidity and mortality in hospitalised patients as well as in the community. These are related to adverse outcomes associated with the first incidence of VTE, such as recurrence, major haemorrhage and mortality. These outcomes are difficult to measure and compare among the different regions of the world not least because of varying prevalence of risk factors, paucity of comparable studies and a differing approach to treatment of VTE (1–3).

Purpose

Our VTE registry aims to estimate the above mentioned outcomes as applicable to a developed world population with a multi-ethnic background. Furthermore, our registry has provided a data set to develop and validate a machine learning algorithm in order to predict outcomes in patients admitted to hospital with VTE. This will have profound implications for clinicians who will be able to make evidence-based decisions about which patients are low risk and so can be discharged early as well as those who are high risk and may need more intensive follow up.

Methods

BBC-VTE registry is a retrospective, multi-centre, observational registry. We identified all patients (N=1554) who were admitted with a final radiologically confirmed diagnosis of pulmonary embolism and/or lower limb deep vein thrombosis at three regional hospitals in the UK during the years 2012–2014. Each patient's electronic record was accessed by clinicians to confirm radiological diagnosis of VTE and also collect data on demographics, physical examination findings and laboratory analysis on admission, past medical history, and treatment plan. Outcomes were also recorded including recurrence of VTE, subsequent major bleeding and all-cause mortality.

A simple multivariate analysis (logistic regression) was used to determine risk factors associated with all-cause mortality. Odds ratios (OR) and 95% CI are reported.

Results

The main factors determining higher all-cause mortality were age, a history of diabetes, admission laboratory analysis (c-reactive protein and neutrophil count), and previous malignancy (OR >1) (see Fig. 1). Conversely, hypercholesterolaemia, discharge oral anticoagulation, immobilization, and post-PE syndrome were all significantly correlated with a reduced risk of mortality (OR <1).

Conclusions

BBC-VTE provides unique data on VTE mortality risks in a multi-ethnic cohort. The strengths of our registry are that we are only including radiologically verified VTE patients unlike many of the epidemiological studies to date which rely on clinical coding. We have also shown that it is possible to risk-stratify patients admitted with VTE using simple clinical variables which has implications for their discharge decisions.

Funding Acknowledgement

Type of funding sources: None. Figure 1

On the Sensitivity Analysis of Porous Finite Element Models for Cerebral Perfusion Estimation

Computational physiological models are promising tools to enhance the design of clinical trials and to assist in decision making. Organ-scale haemodynamic models are gaining popularity to evaluate perfusion in a virtual environment both in healthy and diseased patients. Recently, the principles of verification, validation, and uncertainty quantification of such physiological models have been laid down to ensure safe applications of engineering software in the medical device industry. The present study sets out to establish guidelines for the usage of a three-dimensional steady state porous cerebral perfusion model of the human brain following principles detailed in the verification and validation (V&V 40) standard of the American Society of Mechanical Engineers. The model relies on the finite element method and has been developed specifically to estimate how brain perfusion is altered in ischaemic stroke patients before, during, and after treatments. Simulations are compared with exact analytical solutions and a thorough sensitivity analysis is presented covering every numerical and physiological model parameter. The results suggest that such porous models can approximate blood pressure and perfusion distributions reliably even on a coarse grid with first order elements. On the other hand, higher order elements are essential to mitigate errors in volumetric blood flow rate estimation through cortical surface regions. Matching the volumetric flow rate corresponding to major cerebral arteries is identified as a validation milestone. It is found that inlet velocity boundary conditions are hard to obtain and that constant pressure inlet boundary conditions are feasible alternatives. A one-dimensional model is presented which can serve as a computationally inexpensive replacement of the three-dimensional brain model to ease parameter optimisation, sensitivity analyses and uncertainty quantification. The findings of the present study can be generalised to organ-scale porous perfusion models. The results increase the applicability of computational tools regarding treatment development for stroke and other cerebrovascular conditions.

A porous circulation model of the human brain for in silico clinical trials in ischaemic stroke

The advancement of ischaemic stroke treatment relies on resource-intensive experiments and clinical trials. In order to improve ischaemic stroke treatments, such as thrombolysis and thrombectomy, we target the development of computational tools for in silico trials which can partially replace these animal and human experiments with fast simulations. This study proposes a model that will serve as part of a predictive unit within an in silico clinical trial estimating patient outcome as a function of treatment. In particular, the present work aims at the development and evaluation of an organ-scale microcirculation model of the human brain for perfusion prediction. The model relies on a three-compartment porous continuum approach. Firstly, a fast and robust method is established to compute the anisotropic permeability tensors representing arterioles and venules. Secondly, vessel encoded arterial spin labelling magnetic resonance imaging and clustering are employed to create an anatomically accurate mapping between the microcirculation and large arteries by identifying superficial perfusion territories. Thirdly, the parameter space of the problem is reduced by analysing the governing equations and experimental data. Fourthly, a parameter optimization is conducted. Finally, simulations are performed with the tuned model to obtain perfusion maps corresponding to an open and an occluded (ischaemic stroke) scenario. The perfusion map in the occluded vessel scenario shows promising qualitative agreement with computed tomography images of a patient with ischaemic stroke caused by large vessel occlusion. The results highlight that in the case of vessel occlusion (i) identifying perfusion territories is essential to capture the location and extent of underperfused regions and (ii) anisotropic permeability tensors are required to give quantitatively realistic estimation of perfusion change. In the future, the model will be thoroughly validated against experiments.