Warfarin use may be safe following a heart attack in patients with both atrial fibrillation and chronic kidney disease, according to a Swedish study of more than 24,000 patients.
Warfarin use may be safe following a heart attack in patients with both atrial fibrillation (Afib) and chronic kidney disease (CKD), according to a large observational multicenter study in Sweden.
Anticoagulation treatments like warfarin are usually indicated for patients with Afib, however, clinical trials have excluded those patients with CKD. In observational studies, it has been demonstrated that warfarin treatment may increase the risk of death and stroke among patients with renal dyfunction.
Swedish researchers undertook a study to determine the risk of warfarin treatment in relation to kidney function for patients with both cardiovascular disease and Afib. The results were published in the March 5 JAMA edition.
Juan J. Carrero, PhD, of the Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden, and colleagues enrolled more than 24,000 survivors of acute myocardial infarction with Afib and known serum creatinine levels who were in the SWEDEHEART registry, including all 72 hospitals in Sweden. Nearly 22% had been prescribed warfarin following hospital discharge.
The patient outcomes were as follows: 1) death, readmission due to myocardial infarction or ischemic stroke within 1 year after initial discharge, 2) readmission due to bleeding within 1 year after initial discharge, and the aggregate of these two outcomes.
Approximately 5,300 patients received warfarin at hospital discharge, and almost 52% had moderate CKD, defined as eGFR <60 ml/min/1.73 m2.
Patients with CKD who received warfarin had a lower risk of the first composite outcome, no significantly higher risk of bleeding (the second composite outcomes), and lower risk of the aggregate outcome compared with the patients who did not receive warfarin at hospital discharge.
“The number of patients who developed the composite outcomes, bleeding events, and the aggregate of these 2 outcomes increased with the worsening of CKD categories, as did the rate at which these events occurred,” the researchers said.
“Regardless of CKD stage, the number of deaths was lower in patients treated with warfarin compared with patients receiving no warfarin. The rate of readmissions due to myocardial infarction and ischemic strokes were lower in patients treated with warfarin across all renal function strata,” they noted.
The researchers did note that 75% of the patients in this study were within the therapeutic range for international normalized ratio (INR). “Warfarin-associated bleeding in patients with CKD may be more common when INR is not tightly controlled,” they said.
In an accompanying editorial by Wolfgang C. Winkelmayer, MD, and Mintu P. Turakhia, MS, the co-authors suggested that these findings be approached cautiously. They noted that the time in therapeutic range of the INR in the Swedish study of 75% would have to be replicated; otherwise, “the benefit of warfarin is likely to be markedly attenuated and possibly cause harm.”