People with irregular heartbeat due to a condition called atrial fibrillation, are often prescribed blood thinners to reduce the risk of blood clots that can cause a stroke.

One reason: patients on dialysis are routinely excluded from clinical trials, which test utility and safety of treatments, says Konstantinos Siontis, M.D., first author of new research in Circulation. Siontis' new observational study is the first to reveal that one anticoagulant, apixaban (also known as Eliquis), may be safer for this patient population.

"These are the first data to show that apixaban is potentially safer than warfarin in dialysis patients with atrial fibrillation," said Siontis, who recently completed a cardiovascular fellowship at Michigan Medicine's Frankel Cardiovascular Center.

"We found patients on apixaban had a significantly lower risk of major bleeding with no difference in stroke, which is what we try to prevent by prescribing these anticoagulants," said Siontis.

A complicated calculation

If blood is not completely pumped out of the heart due to atrial fibrillation, it can pool into clots and cause a stroke, leading clinicians to prescribe blood thinners to reduce the clotting risk.

The anticoagulation landscape for all patients continues to change as new agents, including apixaban, become more popular, while mainstay warfarin (also known as Coumadin) is still widely used in the general population. Warfarin is difficult to manage, though, and comes with the risk of major bleeding.

Siontis says there is uncertainty about whether adding dialysis to the mix means an anticoagulant is still a good idea for someone with Afib, given the safety and bleeding concerns.

Of the four novel anticoagulants, two (dabigatran/Pradaxa and rivaroxaban/Xarelto) have already been associated with higher bleeding rates in dialysis patients compared to warfarin, leaving researchers to focus mainly on apixaban in their push to come up with an alternative, safer anticoagulation plan for these patients.

Need for more data

Although clinical trials have investigated use and outcomes of anticoagulants in atrial fibrillation, the most common form of heart arrhythmia, their findings cannot be applied to people on dialysis in the same way as other patients.

Siontis said the comorbidities and other worse outcomes associated with kidney failure and dialysis lead most researchers to exclude this population from clinical trials.

"Patients on dialysis are one of the most challenging populations because they have many comorbid conditions, are often on many prescription drugs and are at significant risk of kidney failure associated and treatment-related adverse events," said senior co-author Rajiv Saran, M.D., a nephrologist at Michigan Medicine. "Dialysis patients were excluded from all randomized trials that established the utility of the newer anticoagulants including apixaban."