PHILADELPHIA – In patients with atrial fibrillation, declining kidney function significantly increased the risk of a major bleed during the first 30 days of warfarin therapy.
Those with the poorest kidney function had an 11-fold increase in the risk of a major bleed during that time, Min Jun, Ph.D., said at a meeting sponsored by the American Society of Nephrology. “After 30 days, the risk was attenuated, but it was still doubled,” compared with that of patients with normal kidney function.
Dr. Jun, a researcher at the University of Calgary (Alta.) retrospectively assessed bleeding incidence among 12,400 older adults with atrial fibrillation who started warfarin therapy from 2003 to 2010. He divided the cohort into six groups according to estimated glomerular filtration rates (eGFR), from normal (90 or more mL/min per 1.73 m2), to extremely poor (less than 15 mL/min per 1.73 m2).
The primary outcome was incident major bleeding (intracerebral, upper or lower gastrointestinal, or any other location). The analysis controlled for comorbidities, antiplatelet and nonsteroidal anti-inflammatory medications, and socioeconomic factors.
Almost 12% of the cohort experienced the primary outcome. The adjusted bleeding rates were highest for those with an eGFR of less than 15 mL/min per 1.73 m2 (66 per 100 person-years) and lowest for those with an eGFR of at least 90 mL/min per 1.73 m2 (5.9 per 100 person-years).
The rates moderated after the first 30 days of treatment, from 3.7 per 100 person-years in the highest eGFR group to 7.9 per 100 person-years in the lowest. But that was still a significant between-group difference.
The incidence ratio showed a clear, linear association with decreasing kidney function. During the first 30 days, it was highest in those patients with the lowest eGFR (11.08, compared with those with the highest eGFR). After 30 days, the ratio moderated; but it remained significantly elevated, compared with patients with the highest eGFR, at 2.09.
Kidney function apparently also influenced gastrointestinal bleeding, Dr. Jun noted. GI bleeding occurred in about 6% of those patients with an eGFR of at least 90 mL/min per 1.73 m2, but in almost 19% of patients with an eGFR of less than 15 mL/min per 1.73 m2. Intracranial bleeds occurred in less than 1% of patients in each group. There were no significant findings in other bleeding types, which were increased in the first 30 days of treatment, but which never exceeded 5% in any group.
Dr. Jun had no financial disclosures.