Patterns of Management and Adherence to Venous Thromboembolism (VTE) Treatment Guidelines In a National Prospective Cohort Study of VTE Management In the Canadian Outpatient Setting: Recovery Study

Little is known about patterns and quality of venous thromboembolism (VTE) management in Canadian outpatient settings, including how closely clinicians adhere to evidence based treatment guidelines. Such information could help identify gaps in patient care requiring attention.

To obtain prospective, clinical practice-based data from Canadian outpatient settings on 1) management of VTE; 2) determinants of patterns of VTE management; 3) degree of adherence with ACCP 2008 VTE treatment guidelines; and 4) frequency of bleeding and recurrent VTE during follow-up.

We performed a multi-centre prospective observational study to evaluate physician practice patterns and degree of adherence to ACCP consensus guidelines for VTE treatment. From 2007–2010, we enrolled 915 consecutive patients with objectively confirmed acute symptomatic VTE who received treatment with the low molecular weight heparin (LMWH) enoxaparin alone or with warfarin in the outpatient setting (mainly thrombosis clinics) in 12 Canadian centers. Patients attended an enrolment visit, where data on demographics, site(s) of VTE, VTE risk factors, bleeding risk factors, creatinine clearance and initial treatment were recorded. A follow-up visit occurred when anticoagulant treatment was stopped or at 6 months, whichever occurred first. Indicators of adherence to VTE treatment guidelines included: (1) having received any thromboprophylaxis for VTE associated with transient risk factors (recent medical admission, major surgery or leg immobilization); (2) use of LMWH monotherapy to treat cancer-associated VTE; (3) at least 5 days median duration of LMWH in patients treated with initial LMWH overlapped with warfarin; (4) at least 1 day overlap of LMWH and warfarin once INR was therapeutic. Recurrent VTE, bleeding and adverse events were recorded throughout study follow-up.

At the time of abstract submission, end of study data were available for 747 of 915 enrolled patients. Average age was 56 years, 54% were male and mean body mass index was 28.3 kg/m². Index VTE was lower or upper extremity deep venous thrombosis (DVT) in 511 (68.4%) patients, pulmonary embolism (PE) with or without DVT in 218 (29.2%) patients, and unusual site DVT in 18 (2.4%) patients. VTE was associated with cancer in 70 (9.4%) patients, transient risk factors in 289 (38.7%) patients, hormonal risk factors in 55 (7.4%) patients and was deemed unprovoked in 331 (44.3%) patients. Overall, enoxaparin was prescribed at a dose/frequency of 1.5 mg/kg QD in 85.4% of patients, 1.0 mg/kg BID in 14.6% of patients and 1.0 mg/kg QD for one patient who had creatinine clearance <30ml/min. Among patients with VTE risk factors such as recent medical admission, recent surgery or paralysis, only 37.3% had been prescribed thromboprophylaxis. Among patients with cancer-related VTE (n=70), 61.4% were prescribed LMWH monotherapy, a majority received 1.5 mg/kg once daily, and 42.9% received such treatment for >3 months. Among patients treated with initial LMWH overlapped with warfarin (n= 667; 89.3%), median duration of LMWH was 8 days (IQR 6–10 days), median duration of warfarin was 182 days (IQR 115–190) and median overlap with LMWH once INR was therapeutic was 1 day (IQR 1–2 days). However, 48 (7.2%) patients received <5 days LMWH and 99 (15%) patients had overlap <1 day. During follow-up, 16 (2.1%) patients had recurrent VTE, at a median of 71 days follow-up; rate of recurrent VTE was highest (8.6%) and occurred earliest (median, 49 days) in cancer patients. Major bleeding events (primarily GI or GU) occurred in 10 (1.3%) patients at a median of 23 days; at the time of bleed, 2 patients were receiving LMWH alone, 3 patients, LMWH and warfarin, and 5 patients, warfarin alone.

Our study provides useful information on clinical features of patients, management of VTE and rates of recurrence and bleeding in Canadian outpatients. Our results suggest that there are important gaps in (1) use of thromboprophylaxis to prevent VTE and (2) use of LMWH monotherapy to treat VTE in cancer patients. Conversely, in patients treated with combination LMWH/warfarin therapy, adherence to recommendations regarding minimum duration of LMWH and minimum overlap of LMWH and warfarin once INR was therapeutic was quite good.

Kahn:Sigvaris: Research Funding; sanofi-aventis: Advisory Board, Research Funding; Boehringer Ingelheim:. Schulman:Sanofi Aventis: Honoraria.