Rate of Late Venous Thromboembolism Events In High-Risk Medical Patients
Authors: Hull Russell , Bates Duane , Brocklebank Cynthia , Komari Nelly , Merali Tazmin 
Published: October 2019

Abstract
Abstract 82

Background:
Current guidelines recommend that venous thromboembolism (VTE) prophylaxis should be given to high-risk medical inpatients based on evidence of reduced VTE events and reduced mortality. However, current guidelines do not specify the appropriate length of VTE prophylaxis in this population, especially after discharge. The EXCLAIM study showed a 90 day VTE incidence of 4.2% in those patients who received enoxaparin for 10 days in the hospital, with 1.1% being symptomatic VTE. However, real world data is needed to understand the risk of VTE for this patient population after they are discharged from acute care and the prevalence of symptomatic VTE.

Objective:
To determine the incidence of late VTE events in high-risk medical patients in every day clinical practice and in the absence of systematic screening for VTE.

Methods:
Charts from 1134 consecutive high-risk medical patients who were hospitalized in the Calgary region and discharged between January and February 2008 were abstracted using standardized case record forms. All hospitals in the region use a common unique patient identifier number, thus enabling the tracking of subsequent patient visits to the emergency room, inpatient admissions or outpatient visits occurring anywhere in the region's acute care system. High-risk medical patients were defined as age > 60 years and having at least one of the following risk factors: malignancy, respiratory illness, neurological illness, inflammatory bowel disease, previous VTE, acute infection or heart failure.
Records excluded were those of patients who were admitted for VTE or to rule out VTE, those receiving chronic anticoagulation, those with acute coronary syndromes, patients whose hospital stay was ≤ 3 days, surgical patients, orthopedic patients, and pregnant patients. Data was collected on patient risk factors, thromboprophylaxis received in hospital and at discharge, VTE related events for up to 100 days post discharge.

Results:
989 patients met criteria over the review period. 74% (733/989) of all patients received mechanical or pharmacological prophylaxis in hospital: 28% (281) received unfractionated heparin, 28% (281) received LMWH and 4% (40) received mechanical prophylaxis and 13% (131) received a combination of modalities. The prevailing medical risk factors were malignancy (46%), respiratory illness (44%), neurological illness (15%), inflammatory bowel disease (6%), previous VTE (4%), acute infection (17%), heart failure (9%). Only 2% (95% CI, 1.6% to 3.6%) of all patients received anticoagulation prophylaxis at discharge.
Twenty one percent of patients in the population studied received medical care for symptoms associated with VTE. Of these, 4% (95% CI, 2.7% to 5.2%) had confirmation of VTE by diagnostic testing while the other 17% (95% CI, 15.0% to 19.8%) had diagnostic tests that were negative or inconclusive. The mean length of time to confirmed VTE was 34.1 days post hospital admission.

Conclusion:
This study demonstrates that in a real life setting 21% of high-risk patients would develop symptoms of VTE requiring a health professional's attention with 4% having VTE confirmed by diagnostic testing. These events occurred despite prophylaxis in hospital and suggest that the risk of symptomatic VTE could be higher in real life compared to that reported in randomized clinical trials where patients are screened for asymptomatic VTE. These findings show that the prevalence of VTE warrants consideration of extended thromboprophylaxis in selected high-risk medical patients, as the benefits of extended prophylactic therapy may outweigh the risks in this population.

Disclosures:
Hull: sanofi-aventis Canada Inc: Consultancy, Research Funding. Brocklebank:sanofi-aventis Canada Inc: Honoraria; Bayer, Inc.: Honoraria; Leo Pharma: Honoraria. Komari:sanofi-aventis Canada Inc: Employment. Merali:sanofi-aventis Canada Inc: Consultancy, Research Funding.