Conference Coverage

Full-dose antithrombotic aids selected COVID-19 ICU patients


– Hospitalized patients in the ICU because of an acute COVID-19 infection had significantly fewer thrombotic events and complications when treated with full-dose anticoagulation, compared with patients who received standard-dose anticoagulation prophylaxis, but full-dose anticoagulation also triggered an excess of moderate and severe bleeding events, randomized trial results show.

The new findings from the COVID-PACT trial in an exclusively U.S.-based cohort of 382 on-treatment patients in the ICU with COVID-19 infection may lead to a change in existing guidelines, which currently recommend standard-dose prophylaxis based on results from prior head-to-head comparisons, such as guidelines posted March 2022 from the American Society of Hematology.

The new findings suggest “full-dose anticoagulation should be considered to prevent thrombotic complications in selected critically ill patients with COVID-19” after weighing an individual patient’s risk for both thrombotic events and bleeding, David D. Berg, MD, said at the annual congress of the European Society of Cardiology. Simultaneous with his report at the congress, the results also appeared online in the journal Circulation.

“What the results tell us is that full-dose anticoagulation in critically ill patients with COVID-19 is highly effective for reducing thrombotic complications,” said Dr. Berg, a cardiologist and critical care physician at Brigham and Women’s Hospital, Boston.

The report’s designated discussant agreed with Dr. Berg’s conclusions.

‘Need to replace the guidelines’

“We probably need to replace the guidelines,” said Eduardo Ramacciotti, MD, PhD, MPH, a professor of vascular surgery at Santa Casa School of Medicine, São Paulo. Dr. Ramacciotti praised the study’s design, the endpoints, and the fact that the design excluded patients at high risk for bleeding complications, particularly those with a fibrinogen level below 200 mg/dL (2 g/L).

But other experts questioned the significance of the COVID-PACT results given that the outcomes did not show that full-dose anticoagulation produced incremental improvement in patient survival.

“We should abandon the thought that intensified anticoagulation should be routine, because it did not overall increase the number of patients discharged from the hospital alive,” commented John W. Eikelboom, MBBS, a professor of hematology and thromboembolism at McMaster University, Hamilton, Ont.

“Preventing venous thrombosis is a good thing, but the money is in saving lives and stopping need for ventilation, and we haven’t been successful doing that with an antithrombotic strategy,” said Dr. Eikelboom. “It is useful to prevent venous thrombosis, but we need to look elsewhere to improve the outcomes of [critically ill] patients with COVID-19.”

Reducing thromboembolism is a ‘valid goal’

Dr. Berg took a different view. “It’s a valid goal to try to reduce venous thromboembolism complications,” the major benefit seen in his study, he said. “There is clinical significance to reducing thrombotic events in terms of how people feel, their functional status, and their complications. There are a lot of clinically relevant consequences of thrombosis beyond mortality.”

COVID-PACT ran at 34 U.S. centers from August 2020 to March 2022 but stopped short of its enrollment goal of 750 patients because of waning numbers of patients with COVID-19 admitted to ICUs. In addition to randomly assigning patients within 96 hours of their ICU admission to full-dose anticoagulation or to standard-dose antithrombotic prophylaxis, the study included a second, concurrent randomization to the antiplatelet agent clopidogrel (Plavix) or to no antiplatelet drug. Both randomizations used an open-label design.

The results failed to show a discernable effect from adding clopidogrel on both the primary efficacy and primary safety endpoints, adding to accumulated evidence that treatment with an antiplatelet agent, including aspirin, confers no antithrombotic benefit in patients with COVID-19.

The trial’s participants averaged 61 years old, 68% were obese, 59% had hypertension, and 32% had diabetes. The median time after ICU admission when randomized treatment began was 2.1 days, and researchers followed patients for a median of 13 days, including a median time on anticoagulation of 10.6 days.

The trial design allowed clinicians to use either low molecular weight heparin or unfractionated heparin for anticoagulation, and 82% of patients received low molecular weight heparin as their initial treatment. The prespecified design called for an on-treatment analysis because of an anticipated high crossover rate. During the trial, 34% of patients who started on the prophylactic dose switched to full dose, and 17% had the reverse crossover.


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