Trial supports full-dose anticoagulation to prevent blood clots in COVID-19 patients


Treatment of critically ill COVID-19 patients with full-dose anticoagulation lowers the risk of venous and arterial clotting complications by 44% compared with the standard dose, according to late breaking research presented in a Hot Line session at ESC Congress 2022 (Aug. 26–29) in Barcelona, Spain. The addition of clopidogrel did not provide further protection.

The COVID-PACT trial evaluated whether a higher intensity of anticoagulation and/or the use of antiplatelet therapy prevents blood clots with an acceptable safety profile in patients with severe COVID-19 infection. COVID-PACT was a 2×2 factorial, randomized controlled trial in critically ill patients with COVID-19 conducted at 34 sites in the U.S. Patients requiring ICU-level care (invasive mechanical ventilation, non-invasive positive pressure ventilation, high-flow nasal cannula, or vasopressors) were randomized to either full-dose or standard-dose prophylactic anticoagulation.

Use of unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH) for either regimen was at the discretion of the managing clinicians. In patients without another indication for antiplatelet therapy, there was an additional randomization to either the antiplatelet clopidogrel or no antiplatelet therapy. Patients were assessed clinically and with lower extremity venous ultrasounds 10 to 14 days after randomization and followed until hospital discharge or for 28 days, whichever occurred first.

The primary efficacy outcome was the hierarchical composite of death due to venous or arterial thrombosis, pulmonary embolism, clinically evident deep vein thrombosis (DVT), type 1 myocardial infarction, ischemic stroke, systemic embolic event or acute limb ischemia, or clinically silent DVT, through hospital discharge or 28 days. Primary efficacy analyses included an unmatched win ratio and a time-to-first event analysis during treatment.

A total of 390 patients were randomized (390 to an anticoagulation strategy and 292 to an antiplatelet strategy). In the primary efficacy analysis of anticoagulation, a greater proportion of wins occurred with the full dose (12.3%) versus standard dose (6.4%; win ratio 1.95, 95% confidence interval [CI] 1.08–3.55, p=0.028). Results were consistent in the time-to-event analysis (19 [9.9%] events on the full dose vs. 29 [15.2%] on the standard dose; HR 0.56, 95% CI 0.32–0.99, p=0.046).

The primary safety outcome of fatal or life-threatening bleeding occurred in four patients (2.1%) on full-dose anticoagulation and one patient (0.5%) on standard-dose anticoagulation (p=0.19); all of these were life-threatening bleeds and there were no fatal bleeding events. There was no difference in all-cause mortality between groups (HR 0.91, 95% CI 0.56–1.48, p=0.70).

In the antiplatelet analysis, there were no differences in the risks of clotting complications or of fatal or life-threatening bleeding in patients treated with clopidogrel compared with no antiplatelet therapy.

David Berg, MD, a cardiologist from Brigham and Women’s Hospital and Harvard Medical School in Boston, said: “COVID-19 treatment guidelines recommend full-dose anticoagulation for hospitalized patients outside the ICU and the standard dose for those in the ICU. This discordant advice has left many clinicians confused about what to do, particularly in COVID-19 patients at the border-zone of needing ICU-level care. The recommendation for ICU patients is largely based on a trial which found that full-dose anticoagulation, compared with the standard dose, did not decrease the number of days alive without organ support in critically ill patients with COVID-19. COVID-PACT shows that full-dose anticoagulation more effectively prevents the clotting complications of COVID-19, which may be a more appropriate focus for antithrombotic therapy as a preventive intervention, and is the basis for anticoagulation recommendations in ICU patients without COVID-19.”


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