There is no question that COVID-19 infection increases the risks of serious thromboembolic events, including pulmonary embolism (PE), but it also increases the risk of bleeding, complicating the benefit-to-risk calculations for anticoagulation, according to a review of data at the virtual Going Back to the Heart of Cardiology meeting.
“Bleeding is a significant cause of morbidity in patients with COVID-19, and this is an important concept to appreciate,” reported Rachel P. Rosovsky, MD, director of thrombosis research, Massachusetts General Hospital, Boston.
At least five guidelines, including those issued by the American College of Cardiology, International Society on Thrombosis and Haemostasis (ISTH), and the American College of Chest Physicians, have recently addressed anticoagulation in patients infected with COVID-19, but there are “substantive differences” between them, according to Dr. Rosovsky. The reason is that they are essentially no high quality trials to guide practice. Rather, the recommendations are based primarily on retrospective studies and expert opinion.
The single most common theme from the guidelines is that anticoagulation must be individualized to balance patient-specific risks of venous thromboembolism (VTE) and bleeding, said Dr. Rosovsky, whose group published a recent comparison of these guidelines (Flaczyk A et al. Crit Care 2020;24:559).
Although there is general consensus that all hospitalized patients with COVID-19 should receive anticoagulation unless there are contraindications, there are differences in the recommended intensity of the anticoagulation for different risk groups and there is even less is less consensus on the need to anticoagulate outpatients or patients after discharge, according to Dr. Rosovsky
In her own center, the standard is a prophylactic dose of low molecular weight heparin (LMWH) in an algorithm that calls for dose adjustments for some groups such as those with renal impairment or obesity. Alternative forms of anticoagulation are recommended for patients with a history of thrombocytopenia or are at high risk for hemorrhage. Full dose LMWH is recommended in patients already on an oral anticoagulant at time of hospitalization.
“The biggest question right now is when to consider increasing from a prophylactic dose to intermediate or full dose anticoagulation in high risk patients, especially those in the ICU patients,” Dr. Rosovsky said.
Current practices are diverse, according to a recently published survey led by Dr. Rosovsky (Rosovsky RP et al. Res Pract Thromb Haemost. 2020;4:969-83). According to the survey, which had responses from more than 500 physicians in 41 countries, 30% of centers escalate from a prophylactic dose of anticoagulation to an intermediate dose when patients move to the ICU. Although not all answered this question, 25% reported that they do not escalate at ICU transfer. For 15% of respondents, dose escalation is being offered to patients with a D-dimer exceeding six-times the upper limit of normal.
These practices have developed in the absence of prospective clinical trials, which are urgently needed, according to Dr. Rosovsky. The reason that trials specific to COVID-19 are particularly important is that this infection also engenders a high risk of major bleeding.
For example, in a multicenter retrospective study of 400 hospital-admitted COVID-19 patients the rates of major bleeding was 4.8% or exactly the same as the rate of radiographically confirmed VTE. At 7.6%, the rates of VTE and major bleeding were also exactly the same for ICU patients (Al-Samkari H et al. Blood 2020;136:489-500).
“An elevated D-dimer was a marker for both VTE and major bleeding,” reported Dr. Rosovsky, who was the senior author of this study. On the basis of odds ratio (OR), the risk of VTE was increased more than six-fold (OR, 6.79) and the risk of major bleeding by more than three-fold (OR, 3.56) when the D-dimer exceeded 2,500 ng/mL.
The risk of VTE from COVID-19 infection is well documented. For example, autopsy studies have shown widespread thrombosis, including PE, in patients who have died from COVID-19 infection, according to Dr. Rosovsky.
There is also evidence of benefit from anticoagulation. In an retrospective study from China undertaken early in the pandemic, there was no overall mortality benefit at 28 days among those who did receive LMWH when compared to those who did not, but there was a 20% absolute mortality benefit (52.4% vs. 32.8%; P = .017) in those with a D-dimer six-fold ULN (Tang N et al. J Thromb Haemost 2020;18:1094-9).
These types of data support the use of anticoagulation to manage VTE risk in at least some patients, but the reported rates of VTE across institutions and across inpatient and outpatient settings have varied “dramatically,” according to Dr. Rosovsky. The balance of VTE and major bleeding is delicate. In one retrospective study, the mortality advantage for therapeutic versus prophylactic dose of LMWH did not reach statistical significance, but the rate of major bleeding was nearly doubled (3.0% vs. 1.7%) (Nadkarni GN et al J Am Coll Cardiol 2020;76:1815-26).
Because of the many variables that might affect risk of VTE and risk of major bleeding in any individual patient, the benefit-to-risk calculation of anticoagulation is “complex,” according to Dr. Rosovsky. It is for this reason she urged clinicians to consider entering patients into clinical trials designed to generate evidence-based answers.
There is large and growing body of retrospective data that have helped characterize the risk of VTE and bleeding in patients with COVID-19, but “there is no substitute for a well-controlled clinical trial,” agreed Robert A. Harrington, MD, chairman of the department of medicine, Stanford (Calif.) University.
He and the comoderator of the session in which these data were presented agreed that anticoagulation must be administered within a narrow therapeutic window that will be best defined through controlled trial designs.
“There is a significant risk of doing harm,” said Fatima Rodriguez, MD, assistant professor of cardiology at Stanford University. She seconded the critical role of trial participation when possible and the need for clinical trials to better guide treatment decisions.
The meeting was sponsored by MedscapeLive. MedscapeLive and this news organization are owned by the same parent company.