1. Warfarin therapy in chronic kidney disease patients with atrial fibrillation decreased incidence of death, myocardial infarction and stroke at 1-year follow-up.
2. The severity of kidney disease did not correlate to the rate of these outcomes.
Evidence Rating Level: 1 (Excellent)
Study Rundown: Patients presenting with atrial fibrillation (AF) following myocardial infarction are often prescribed warfarin as a preventative measure against thromboembolic events. A subset of these patients also have chronic kidney disease (CKD) potentially complicating their AF management. While patients with CKD and AF have increased risk of thromboembolic events, studies have yielded ambiguous results regarding complications with warfarin use. This study, conducted with Swedish patient data, provides evidence that warfarin therapy decreases 1-year risk of death, myocardial infarction, or ischemic stroke in AF patients at all stages of CKD. There was also no significant difference found in hemorrhagic events between the warfarin and non-warfarin populations. Of note, poor outcome rates were not associated with severity of CKD.
The study’s strengths lie in the large study population, relative completeness of patient information, and thorough control of confounders. Additionally patients in Scandinavian countries have demonstrated therapeutic INRs about 75% of their time on warfarin. Duration of AF, valvular replacement, pulmonary embolism, and deep venous thromboembolism, potentially confounding factors, were not controlled for in this analysis. Furthermore, the follow-up was limited to 1 year, which may be too short to detect complications. Nonetheless, this study supports warfarin use in patients with AF and CKD.
In-Depth [prospective, observational study]: This study analyzed the occurrence of complications in AF following cardiac events in patients with concomitant CKD. Patient information was collected from the National Inpatient Registry and the System for Enhancement and Development of Evidence Based Care in Heart Disease Evaluated According to Recommended Therapies (SWEDEHEART) registry in Sweden. A total of 24,317 patients were included in the study of which 5,292 were prescribed warfarin for AF treatment. CKD was stratified into four classes. Rates of death, myocardial infarction and stroke were significantly less at all stages of CKD; eGFR≥60 HR 0.73 (CI95%, 0.65-0.81), eGFR30-60 HR 0.73 (CI95%, 0.66-0.80), eGFR15-30 HR 0.84 (CI95%, 0.70-1.02), eGFR<15 HR 0.57 (CI95%, 0.37-0.86%) in the warfarin cohort. There were no significant differences among hemorrhagic outcome.
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