Retrospective evaluation of venous thromboembolism: Are all transient provoking events the same?
OBJECTIVE
Venous thromboembolism (VTE) provoked by transient risk factors has traditionally been classified as a single entity with lower risk of recurrence. We evaluated the association between different categories of transient provoking factors and the relative risk of recurrence.


METHODS
Retrospective evaluation of VTE events in non-cancer patients from July 2011 to December 2012 at two tertiary institutions in Australia with a minimum follow-up of 24 months.


RESULTS
A total of 747 VTE cases were identified, and following exclusion of cases with mortality within 30 days of presentation (n=26), unprovoked cases (40.2%) had a higher risk of recurrence (4.6 vs 2.3/100 event-years, P=.01). Provoking factors included surgery (40.4%), injury (16.7%), medical-related factors including non-surgical hospitalisation or active infection (22.0%), travel (13.2%) and oestrogen related (6.5%). Air travel had the highest recurrence rate of 5.9/100 event-years, comparable to unprovoked VTE. VTE provoked by surgery showed lower recurrence rate at 1.8/100 event-years (P=.03). 62.5% of patients with provoked VTE recurred with an unprovoked event.


CONCLUSIONS
Transient provoking factors for VTE are heterogeneous with varying potency and should not be considered a single entity. The high recurrence rate after travel-provoked VTE suggests that it is a "minor," if not negligible provoking factor with higher thrombotic predisposition.
Austin Health, Heidelberg, Melbourne, Vic., Australia.
Chong Chyn
CC
Chua
Austin Health, Heidelberg, Melbourne, Vic., Australia.|Northern Health, Epping, Melbourne, Vic., Australia.
Hui Yin
HY
Lim
Northern Health, Epping, Melbourne, Vic., Australia.|University of Melbourne, Parkville, Vic., Australia.
Mark
M
Tacey
Australian Centre for Blood Diseases, Monash University, Melbourne, Vic., Australia.|Monash University, Clayton, Vic., Australia.
Harshal
H
Nandurkar
Austin Health, Heidelberg, Melbourne, Vic., Australia.|Northern Health, Epping, Melbourne, Vic., Australia.|University of Melbourne, Parkville, Vic., Australia.|Australian Centre for Blood Diseases, Monash University, Melbourne, Vic., Australia.
Prahlad
http://orcid.org/0000-0002-1373-7437
P
Ho
D000368:Aged; D000369:Aged, 80 and over; D001315:Australia; D019468:Disease Management; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009026:Mortality; D012008:Recurrence; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D054556:Venous Thromboembolism / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology* / Q000628:therapy
clot recurrence; epidemiological studies; provoking factors; travel; venous thromboembolism