What Is the Main Idea?

Hemodialysis is a way of treating people with end-stage renal disease (ESRD) after they have experienced kidney failure. In the free-access research article “Warfarin Use, Stroke, and Bleeding Risk among Pre-Existing Atrial Fibrillation US Veterans Transitioning to Dialysis”, published in the journal Nephron, the authors discuss whether it is safe for patients with atrial fibrillation and ESRD to continue to take warfarin, a medication that reduces the risk of blood clots forming, while they transition to regular dialysis treatment.

What Else Can You Learn?

In this blog post, atrial fibrillation and ESRD are discussed, as well as anticoagulant treatments and what they are used for.

What Is End-Stage Renal Disease (ESRD)?

The kidneys help to control blood pressure and make red blood cells, and remove waste products and extra water from the body to make urine. If a person’s kidneys stop working (known as “kidney failure”) they will need kidney replacement therapy, in the form of dialysis or kidney transplant, to survive. Kidney failure treated in this way is referred to as ESRD. During the hemodialysis process, the person’s blood leaves their body, goes through a filter in a machine that removes waste products and excess water, and the purified blood is then returned to their body.

What Is Atrial Fibrillation?

A normal resting heart rate should be between 60 and 100 beats per minute and be regular. Atrial fibrillation is a heart condition that causes a person’s heart rate to be irregular (known as arrhythmia) and often very fast. The heart is divided into four “chambers”: two at the top called atria and two at the bottom called ventricles. Atrial fibrillation occurs if the atria start to beat irregularly in a way that is out of sync with the ventricles, causing the heart to be less efficient. Although some people with atrial fibrillation do not experience any symptoms, others may experience dizziness, heart palpitations (fluttering or irregular heartbeat), chest pain, shortness of breath, tiredness, and weakness. Importantly, atrial fibrillation can lead to blood clots in the heart and increases the risk of stroke, heart failure, and other heart-related complications.

How Is Atrial Fibrillation Treated?

Although not usually life-threatening, atrial fibrillation often requires treatment. Approaches to control the rate or rhythm of the heart include medications, cardioversion (where a controlled electric shock is given to the heart to restore a normal rhythm), and catheter ablation (where radiofrequency energy is used to destroy the area in the heart that’s causing the abnormal rhythm), which is often followed by a person having a pacemaker fitted to help their heart beat regularly. Because of the increased risk of stroke, people may also receive a type of medication called an anticoagulant.

What Is an Anticoagulant?

Coagulation (blood clotting) is the process by which blood clots are formed to stop bleeding. Although blood clots are an essential response to injury, for example preventing too much blood from being lost via a wound, coagulation can become a problem if blood clots form inside the body and stop blood from flowing through blood vessels, potentially starving the affected part of the body from oxygen. Depending on where a blood clot forms, this can lead to serious problems such as heart attack, deep vein thrombosis, and stroke (or mini-stroke, which is also called a transient ischemic attack). Although they are sometimes called “blood thinners”, anticoagulants don’t thin the blood. They work by reducing the blood’s ability to clot. There are three main types of anticoagulant: medicines that prevent the liver from processing vitamin K in a way that enables it to help clot the blood (these are called vitamin K antagonists), direct oral anticoagulants (also known as DOACs), and low molecular weight anticoagulants. The most commonly prescribed anticoagulant is warfarin, which is a vitamin K antagonist.

Is It Safe for Patients with Atrial Fibrillation with ESRD Who Transition to Hemodialysis to Take Anticoagulants?

Although patients with atrial fibrillation are commonly treated with anticoagulants to reduce their stroke risk, patients with ESRD are at greater risk of stroke. The decision of whether or not someone should be treated with an anticoagulant is usually weighed against the person’s risk of bleeding, which is also more common in patients receiving hemodialysis. Several risk scores have been developed to help healthcare practitioners assess this delicate balance, of which the CHA2DS2-VASc score for stroke risk and the HAS-BLED score for bleeding risk are the most widely used. However, neither has been fully assessed for validity in patients receiving dialysis, and it is unclear whether it is safe for patients with atrial fibrillation to continue anticoagulation treatment at the time of transition to hemodialysis. It is unclear whether patients who are about to transition to hemodialysis have similar stroke and bleeding risks compared with those who have received hemodialysis for years, or those who have chronic kidney disease who do not receive dialysis.

In this study, the authors looked at how accurate the CHA2DS2-VASc and HAS-BLED scores are in evaluating the stroke and bleeding risks of patients with atrial fibrillation. They also compared the risks of stroke and bleeding for patients with atrial fibrillation who transition to hemodialysis to assess whether they are likely to benefit from anticoagulation treatment with warfarin.

What Were the Findings of the Study?

The authors studied data relating to veterans of the United States military. Of the 28,620 veterans who had atrial fibrillation before they were transitioned to hemodialysis, 19% were treated with warfarin in the 6 months before transition while 81% didn’t receive any anticoagulation treatment. Of those receiving warfarin at the time of transition, 37% discontinued warfarin treatment after transition. Although the initial analyses showed that the risks of bleeding and stroke were similar between the groups taking or not taking warfarin, the authors went on to use a statistical approach called competing risk analysis to consider the effect of mortality (death). This time, the risk of stroke was 44% greater after transition for those receiving warfarin and the risk of bleeding increased by 38%.

Overall, the study suggests that patients with atrial fibrillation who receive warfarin may not have a lower risk of stroke or increased risk of bleeding compared with those who do not receive it. Importantly, the authors found that patients with atrial fibrillation who transition to hemodialysis who receive warfarin may have significantly higher bleeding and stroke risk than those who do not receive warfarin. The authors suggest that warfarin treatment should be re-evaluated at the time of transition to hemodialysis and should not be used for primary stroke prevention for people receiving hemodialysis with atrial fibrillation. However, newer anticoagulants like direct oral anticoagulants (DOACs) may be safer than warfarin, and studies are needed to assess whether patients with atrial fibrillation who transition to dialysis may benefit from switching treatment to them.

Take-Home Message for Patients

Warfarin treatment to reduce the risk of stroke in people with atrial fibrillation who are transitioning to hemodialysis may not be as safe as treatment with newer anticoagulant medications. People who are concerned should consult their clinical team.

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