Background: While there is a consensus on the need for chemoprophylaxis to reduce the rates of postoperative VTE, there is wide variation in choice of agents recommended. Aspirin, while cheap and widely available, has never been directly compared with a direct oral anticoagulant in randomized, controlled trials.
Study design: Multicenter, double-blind, randomized, controlled noninferiority trial.
Setting: 15 university-affiliated health centers in Canada from January 2013 through April 2016.
Synopsis: 3,224 patients who received daily rivaroxaban for 5 days following joint arthroplasty were randomized to either receive aspirin 81 mg daily or continue daily rivaroxaban. Duration of therapy was determined by type of surgery (9 days for knee, 17 days for hip). The primary effectiveness outcome was defined as symptomatic pulmonary embolism or proximal deep venous thrombosis diagnosed in the 90-day follow-up period. The primary outcome results met the predetermined criterion for noninferiority with similar rates of symptomatic VTE in the aspirin and rivaroxaban group (0.64% vs. 0.7%; P less than .001). There was no significant difference in bleeding rates between the groups. Given that patients with prior VTE, morbid obesity, or cancer were not well represented in this study, these results should not be extrapolated to those populations felt to be at highest risk for VTE.
Bottom line: For thromboprophylaxis after joint arthroplasty, rivaroxaban followed by aspirin may be noninferior to extended rivaroxaban.
Citation: Anderson D et al. Aspirin or rivaroxaban for VTE prophylaxis after hip or knee arthroplasty..
Dr. Abdallah is a hospitalist at Beth Israel Deaconess Medical Center, and instructor in medicine, Harvard Medical School, Boston.