If you have atrial fibrillation, preventing stroke is a challenging problem that requires lifelong attention — so it’s good to know that stroke prevention options are changing.
“Mr. Smith, you have atrial fibrillation, and we need to start you on a blood thinner to prevent stroke,” I begin.
Mr. Smith says, “You’re not thinking about putting me on rat poison. I will not take that.”
What Mr. Smith refers to as rat poison is the blood thinner warfarin, which was, in fact, originally developed for use as a rodenticide. Even today, very high doses of warfarin-like drugs are used in rodent poisons.
The warfarin (Coumadin and Jantoven) we use today in people to prevent blood clots — a cause of stroke — is widely used and has been around for more than 70 years. While warfarin-type drugs were the only anticoagulant options for a long time, there are newer options on the market now that work differently.
Another more recent choice for stroke prevention in atrial fibrillation is minimally invasive, nonsurgical closure of the left atrial appendage, an area of the heart where clots often form; this treatment is called left-atrial appendage closure, or LAAC.
How do these treatments compare for real patients?
Warfarin’s Troubling History and Side Effects
When it’s carefully dosed and checked, warfarin is very effective at preventing stroke, but its history as rat poison concerns many people. At very high levels, warfarin can cause fatal bleeding, which is how it kills rodents. In people, we determine the proper dose of warfarin by testing a patient’s blood to find out how quickly it forms a clot. Some people need very few dose adjustments; others need constant dose changes.
Let’s return to Mr. Smith, a few months after he started warfarin treatment, which he eventually agreed to.
“Mr. Smith, how are you doing?” I ask.
“Not so good, Doc,” Mr. Smith says. “Look at my hands and arms. There are bruises all over. I barely hit my arm, and it leaves a bruise. I want to stop my warfarin. What happens if I really cut myself? Will I bleed to death? I also hate to get my blood checked all the time. They charge me each time, and my dose keeps changing.”
Bleeding Risks of Warfarin for Atrial Fibrillation
When Mr. Smith looks at his hands and arms, he notices one of the biggest problems that people with atrial fibrillation have when taking anticoagulants. We want these drugs to work in the heart and prevent blood clots there, but we’d rather they not work anywhere else; in other words, we don’t want for them to cause bruising and bleeding.
Bruises are very minor bleeds. Typically, even if you cut yourself while you’re on a blood thinner like warfarin, the bleeding will be mild. But large and dangerous bleeds in the brain, stomach, bowels, bladder, or kidneys can occur.
With warfarin use, the key to safety is keeping the blood levels of the drug precisely regulated to avoid bleeding. To ensure that the levels are regulated, we tell patients to:
- Eat a similar amount of vitamin K-containing foods (like green leafy vegetables) daily, because vitamin K in your system can affect blood clotting.
- Have their warfarin blood levels checked whenever they’re starting any new medication.
- Tell us about all supplements or vitamins they take, as these can affect warfarin levels.
Newer Blood Thinners Change Stroke Prevention
Four anti-coagulant alternatives to warfarin include Pradaxa (dabigatran), Xarelto (rivaroxaban), Eliquis (apixaban), and Savaysa (edoxaban). Unlike warfarin, these drugs, called direct oral anticoagulants, don’t require frequent blood tests and don’t interact with many common foods.
Although manufacturers help some people with the costs, many of my Medicare patients unfortunately still can’t afford the newer drugs, which are not yet available as generics. So patients in this situation sometimes return to using warfarin.
Bleeding Risks With Direct Oral Anticoagulants
Here’s a new problem I have with people who have atrial fibrillation, and another typical conversation:
“Mrs. Jones, you have atrial fibrillation, and we need to start you on a blood thinner to prevent stroke. We have a lot of options. These include warfarin and blood thinners that are easier to manage and don’t require dietary changes or frequent blood tests.”
Mrs. Jones says, “You mean those drugs on the commercials I see every night? Those drugs are very dangerous. Why would you put me on one of those?”
You may have seen ads from law firms about these newer drugs. They usually say that they’re bad drugs that cause serious internal and fatal bleeding.
It’s true that these newer medications can cause bleeding. We want them to prevent clots only in the heart, but they just don’t act that way. When we prescribe them, we want the benefit in reducing stroke to outweigh the risks of bleeding. The risks and benefits can change over time, so doctors need to constantly readdress anticoagulant use for each patient.
Pradaxa is the only direct oral anticoagulant that has an antidote: Praxbind (idarucizumab), which quickly reverses bleeding. For the other drugs, including warfarin, when serious bleeding occurs, we often given blood-clotting factors (proteins in the blood that help it clot) to stop the bleeding.
So with all of this in mind, are newer anticoagulants “bad drugs”? Absolutely not, the evidence shows.
- In clinical trials, the newer anticoagulants were as effective (or more effective) than warfarin in lowering risk of stroke in people with atrial fibrillation.
- They also lowered a person’s risk of bleeding in the brain compared to warfarin.
Risks of Stroke-Prevention Medication
If a patient stops taking Xarelto abruptly, stroke risk can increase, because the blood-thinning effect of the drug is lost. There’s a warning on this drug label, which was approved by the FDA. But when law firm ads claimed the drug was dangerous, many people abruptly stopped using it before talking with their doctors. Multiple cases of stroke emerged in these people, some of whom who had large blood clots in their lungs and heart chambers, according to research published in May 2016 in Heart Rhythm Case Reports. Many people died, and others suffered debilitating paralysis from strokes.
Before considering stopping an anticoagulant drug, always talk to your physician; these tragedies were preventable. I am hopeful that others will hold accountable those law firms that provided misleading and anxiety-provoking advertisements.
Stroke Prevention With LAAC
Another blood-clot prevention option is the minimally invasive procedure LAAC, a good choice for stroke prevention for some people. In the uppermost part of the left atrium is a small pouch called the left atrial appendage (LAA), which is thought to be the source of most clots that go to the brain and cause disabling strokes in people with atrial fibrillation.
Surgeons recognized the stroke-prevention value of removing the heart’s appendage years ago: Research showed that when the LAA was completely removed, stroke rates were lower and similar to when blood thinners are used very effectively, according to a study published in November 1999 in The Journal of Thoracic and Cardiovascular Surgery.
Recently, a minimally invasive, nonsurgical approach was developed in which physicians position a small device in the heart by going through a patient’s vein. Once the device is inserted in the LAA, small hooks hold it in place, and it seals off the LAA. Blood does not enter it, so blood clots cannot form there. The Watchman (made by Boston Scientific) is the only such LAAC device that is currently FDA-approved.
The Watchman Compared to Warfarin to Prevent Stroke
The Watchman device was compared to warfarin in the PROTECT-AF trial (results of which were published in The Journal of the American Medical Association in November 2014) and in the PREVAIL trial (results of which were published in July 2014 in the Journal of the American College of Cardiology). Researchers found that stroke rates were similar, but bleeding rates were much higher in patients treated with warfarin compared with those who had the Watchman device implanted.
These trials provided the good news that we have another therapy that works directly in the heart and does not increase risk of bleeding elsewhere. But it’s important to remember that Watchman and warfarin stroke rates were similar, so warfarin remains a good drug for lowering stroke risk.
Keep in mind, however, that the newer anticoagulants have been found to be better at reducing stroke risk compared to warfarin. So far, we don’t know how the Watchman device will compare to direct oral anticoagulants. I don’t consider a person a candidate for a Watchman device if they can’t take aspirin, since this drug was used with the Watchman device in all the trials that led to FDA approval.
You may be a candidate for the Watchman device if you:
- Have had bleeding in the stomach, bladder, kidneys, or brain on an anticoagulant
- Have had frequent falls or injuries that increase the risk of major bleeding
- Have difficulty taking warfarin because your blood levels are often too high or low despite frequent blood tests and dose changes
- Engage in a high risk occupation or lifestyle that increase your risk of trauma or injury
If you have atrial fibrillation, talk to your doctor about all of these choices. Hopefully, we will reach a day when we no longer consider stroke the most devastating consequence of having atrial fibrillation, as stroke may become a preventable disease.