SAN FRANCISCO – The direct-acting anticoagulants, as a class, were more effective and at least as safe as warfarin in low-weight and very-low-weight patients with atrial fibrillation in an adjusted analysis of real-world outcomes data from more than 21,000 Korean patients.
The analysis also showed that the direct-acting oral anticoagulants (DOACs) had the best safety and efficacy on low-weight patients when used at the labeled dosages, with blunted efficacy and safety at dosages that either exceeded or fell short of labeled levels,, said at the annual scientific sessions of the Heart Rhythm Society.
The overall superiority of DOACs by both efficacy and safety also generally extended to the subgroup of very-low-weight patients, those with weights of less than 50 kg. In this subgroup, which was 28% of the total population studied, the composite adverse event outcome occurred 33% less often among patients treated with a DOAC relative to patients treated with warfarin, a statistically significant difference, said Dr. Lee, a cardiologist at Seoul (South Korea) National University Hospital. Among all patients with weights of 60 kg (132 pounds) or less, the composite outcome occurred 34% less often in the DOAC-treated patients relative to the warfarin-treated patients, also a statistically significant difference.
Dr. Lee and colleagues used a Korean National Health Insurance database that included information on more than 600,000 adults with atrial fibrillation (AFib) as of January 2013. The researchers whittled this down to 21,678 patients who began for the first time treatment with an oral anticoagulant starting during or after January 2014; had no history of a stroke, intracranial hemorrhage, or gastrointestinal bleed; and weighed no more than 60 kg. This cohort included 7,575 (35%) who received warfarin treatment, and 14,103 (65%) who received a DOAC. Within the DOAC-treated group, 42% received rivaroxaban (Xarelto), 26% dabigatran (Pradaxa), 24% apixaban (Eliquis), and 8% edoxaban (Savaysa).
To account for baseline differences in demographics and comorbidities between the patients treated with a DOAC and those who received warfarin, Dr. Lee and her associates did propensity score adjustment, which resulted in similar cohorts of 6,692 patients treated with warfarin and 12,810 patients treated with a DOAC. The average age of these patients was 73 years, a third were men, and the average body mass index was just over 22 kg/m2.
The events that the researchers tallied during follow-up through December 2016 included rates of all-cause death, ischemic stroke, intracranial hemorrhage, hospitalization for GI bleeding, hospitalization for major bleeding, and the composite of these five outcomes.
In the propensity-score adjusted full cohort of all patients who weighed 60 kg or less, the rate of each of these five outcomes, as well as the composite outcome, occurred statistically significantly less often among the DOAC-treated patients than in those on warfarin. The reductions ranged from a 41% lower incidence of ischemic stroke on DOAC treatment compared with warfarin treatment, to an 18% reduced rate of hospitalization for a GI bleed, compared with warfarin-treated patients. In the subgroup of patients who weighed less than 50 kg (110 pounds), the reductions ranged from a 41% cut in ischemic stroke on a DOAC compared with warfarin to a 24% relative reduction in the rate of hospitalization for a major bleed, a difference that just reached statistical significance. The outcome of hospitalization for a GI bleed showed no significant between-group difference among very-low-weight patients, but the rates of intracranial hemorrhage and all-cause death also showed statistically significant lower rates among DOAC-treated patients.
Nearly two-thirds of the patients on a DOAC received the label-appropriate dose of the drug, but 31% received a dosage that was below the labeled level while 4% received a dosage above the labeled level. An analysis that divided the NOAC patients by the appropriateness of their treatment dosages showed that patients on the correct dosages fared best. For example, in the total cohort of patients who weighed 60 kg or less, those on the correct DOAC dosage had a 9.1% rate of the combined endpoint. Patients on a low DOAC dosage did about as well as did the patients on warfarin, with a combined event rate of 11.6% in each of these subgroups. The worst outcomes occurred among the small number of patients on an inappropriately-high DOAC dosage, with a combined event rate of 15.4%. The researchers found a similar pattern among patients who weighed less than 50 kg.
Dr. Lee had no disclosures.
SOURCE: Lee SR et al. HRS 2019, Abstract .