Venous Thromboembolism

As the risk of VTE increases steeply with age, our population’s aging demographic portends a rising incidence of VTE. The health care burden of VTE is already quite substantial: the cost to treat an individual case of acute VTE is more than $10,000, and the estimated total cost of VTE and its complications in Canada is at least $600 million per year^8,9. Important indirect costs such as loss of productivity that affects patients, families, and society at large are also considerable^10,11.

Twenty percent of symptomatic VTE is “provoked”, which means its cause can be linked to a known risk factor such as limb fracture or plaster cast, hospitalization with confinement to bed for 3 days, or use of general anesthesia, each within the previous 3 months.  Thirty percent of symptomatic VTE is associated with cancer¹², emphasizing the importance of efforts to prevent VTE in high-risk settings and patient education to ensure early diagnosis. The remaining 50% of patients have “unprovoked” VTE, which means its cause is not linked to a known risk factor.  Patients with suspected VTE present in a wide variety of settings including primary care offices, emergency rooms, inpatient medical and surgical wards and intensive care units. While awaiting diagnostic imaging to confirm VTE, guidelines strongly recommend that patients with suspected VTE should be started on anticoagulant therapy (blood thinners) as the mortality of untreated PE is as high as 1% within 24 hours¹³. Hence, all health care providers require basic knowledge of VTE prevention, VTE diagnosis and principles of VTE treatment.

Anticoagulants are the mainstay of VTE treatment; they are very effective at preventing VTE extension and VTE recurrence, with relative risk reductions greater than 80%. Anticoagulants are also the leading drug class linked to drug-related adverse events (e.g. life-threatening bleeding)¹⁴ and impose patient burden from the need for injections, frequent laboratory monitoring, and lifestyle or dietary modifications. VTE treatment needs to be individualised to optimally balance efficacy and safety. Individualisation increases treatment complexity, which poses knowledge translation (KT) challenges that can be met by developing and validating clinical decision rules to guide clinicians and patients. A number of new oral anticoagulants to prevent and treat VTE have been approved in the last few years, and others are in the development or testing phases¹⁵.  The long term efficacy, safety, cost-effectiveness, and comparative effectiveness of these drugs are unknown, and many hospital and community physicians have limited experience with their use. Also, only selected patients were included in the trials that led to regulatory approval of these drugs, leaving key knowledge gaps about the role of new therapies in many important subgroups (obese patients, those with renal dysfunction, pregnant or lactating women, and cancer patients) for the research community to address.

Other important knowledge gaps include inadequately understood causal factors for first and recurrent VTE, inconsistent use of proven measures to prevent VTE, limited community expertise in diagnosing and managing VTE and its complications, and limited knowledge of VTE among the general public.

Taken together, it is evident that VTE is a significant cause of death, short-term sickness, long-term disability and economic burden to the Canadian population, and that further clinical research, from early phase studies to KT, is needed to address important knowledge gaps and improve patient outcomes. With the rising incidence of VTE and, for the first time in 60 years, the availability of numerous new oral drug options besides warfarin to treat VTE, it is an opportune time to take action to address this important public health issue in a focused, highly organized and patient-centred manner. For this reason, we have created the Canadian Venous Thromboembolism Clinical Trials and Outcomes Research (CanVECTOR) Network.