In patients with baseline atrial fibrillation (AF) who are hospitalized with COVID-19, individuals who are receiving preadmission oral anticoagulation (OAC) have lower rates of death, as well as arterial and venous thrombotic events, and have less severe SARS-CoV-2 infection. These findings were published in the The American Journal of Cardiology.

A retrospective cohort study was conducted among patients with a history of AF admitted to the hospital between March 1, 2020, and December 31, 2020, with a diagnosis of COVID-19. Investigators sought to explore whether the use of preadmission OAC for AF is associated with a reduced incidence of in-hospital death or thrombotic events in patients with COVID-19.

The primary study outcome was a composite of in-hospital all-cause mortality or arterial/venous thrombotic events. Arterial events included acute coronary syndrome, transient ischemic attack, acute ischemic stroke, acute limb ischemia, and acute mesenteric ischemia. Venous thromboembolism included acute deep vein thrombosis and acute pulmonary embolism.

A total of 630 individuals with preexisiting AF and a hospitalization diagnosis of COVID-19 were enrolled in the final study cohort, with all patients stratified based on preadmission OAC use. Among the participants, 57.3% of them had been prescribed outpatient OAC. Of those receiving preadmission OAC, 73% were taking a direct OAC and 27% were taking a vitamin K antagonist. Of those receiving a direct OAC, 72% were on apixaban, 25% were on rivaroxaban, and 3% were on dabigatran. Among participants who were not receiving preadmission OAC, therapeutic and nontherapeutic anticoagulation was started in 38.3% and 49.8% of individuals, respectively.

The primary composite outcome event was reported in 35.6% of all patients, 27.1% of those receiving preadmission OAC, and 46.8% of those not receiving preadmission OAC (P <.001). Following adjustment for multiple covariates, treatment with preadmission OAC was associated with a 63% significantly decreased likelihood of all-cause mortality or thrombotic complications (odds ratio, 0.37; CI, 0.25-0.53; P <.0001).

Additionally, in patients receiving vs those not receiving OAC, secondary study outcomes, including all cause-mortality (16.3% vs 24.9%, respectively; P =.007), admission to an intensive care unit (14.7% to 29.0%, respectively; P <.001), intubation (6.4% vs 18.6%, respectively; P <.001), and use of noninvasive ventilation (18.6% vs 27.5%, respectively; P =.007), were reported significantly less often, and length of hospital stay was significantly shorter (6 days vs 7 days, respectively; P <.001).

A higher CHA₂DS₂-VASc risk score was associated with an increased risk for thrombotic events.

Limitations of the study include that it is not possible to rule out the possibility of residual confounding or bias, in spite of the use of multivariable adjustment. Further, the researchers are unable to confirm participant adherence to outpatient OAC prior to hospitalization. Routine screening for thrombotic complications was not performed in the study cohort.

“Further investigation is needed to establish the safety and efficacy of OAC in ambulatory patients with symptomatic COVID-19 who are at elevated thrombotic risk,” the study authors wrote.