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Popular blood thinner warfarin no longer recommended for certain heart arrhythmia cases

Posted: 1:41 PM, Jan 28, 2019
Updated: 2019-01-28 14:44:47-05

The anti-clotting drug warfarin, commonly known by the brand name Coumadin, is no longer recommended for the treatment of atrial fibrillation except for a select subset of patients, according to guidelines released Monday by the American College of Cardiology and the American Heart Association.

Instead, doctors and patients are encouraged to use drugs called "novel oral anticoagulants," or NOACs, that have been developed and approved during the past decade by the US Food and Drug Administration.

Although many of the latest recommendations for atrial fibrillation or Afib remain the same as the last version, issued in 2014, other key changes in the 2019 update include starting anticoagulants at lower stages of the disease and focusing on lifestyle changes such as weight reduction.

Chaotic electrical signals

Three million to 6 million Americans have some form of Afib. According to the Centers for Disease Control and Prevention, about 2% of people younger than 65 and 9% of those above 65 experience symptoms of the condition, making it the most common type of heart arrhythmia.

"It becomes an even bigger problem as people age into their 70s and 80s," said University of Wisconsin cardiologist Dr. Craig January , who was the lead writer for both the 2014 and 2019 guidelines. "So the numbers of people affected by Afib will go up a great deal in our society as the population of baby boomers age."

People with Afib describe the sensation as a flutter in their chest, as if the heart is quivering instead of beating. For some people, the heart might do an uncomfortable flip-flop, like a trapped fish. Often, it skips a beat and then races for what might seem like forever.

Those sensations occur when the upper chambers of the heart receive disordered electrical signals and begin to shudder. As a result, the connection to the lower chambers of the heart is bombarded by impulses, which causes that area to beat more rapidly as well, but out of sync with the rest of the heart. In the midst of an attack, the heart rate can range from 100 to 175 beats a minute. For comparison, a normal heart rate is between 60 and 100 beats a minute.

But while it's beating rapidly, January said, the heart also doesn't contract properly, allowing blood to pool in the left atrial appendage. That's a small ear-shaped sac in the muscle wall of the left upper chamber of the heart. The pooling can allow blood to thicken, and when it's released, it can produce a clot that can travel dangerously throughout the body. Often, the clot ends up in the brain, causing a stroke. People with Afib are up to five times more likely to have a stroke than those without the condition.

Use of anticoagulants is key

The new guidelines continue to stress the use of anticoagulants for Afib, but with a major change.

"In 2014, we recommended the use of warfarin and NOACs, but we didn't prioritize one over the other," January said. "We are now saying that in some patients, NOACs are better than warfarin."

Because of a lack of research on the effects of NOACs vs. warfarin, the guidelines suggest that patients with mechanical heart valves and moderate to severe mitral stenosis (a narrowing of the mitral value opening in the heart), should continue on warfarin.

For other patients, the use of novel oral anticoagulants are encouraged. Those include dabigatran (Pradaxa), rivaroxaban (Xarelto), apixaban (Eliquis) and edoxaban (Savaysa).

"NOACS are better at preventing stroke and have fewer side effects," January said. "NOACs are not free of side effects, but compared to warfarin, it's easier to manage."

Warfarin, which was first developed as a rat poison, has been used since 1954 to reduce the risk of blood clotting. Often called a blood thinner, warfarin does not actually thin the blood. Instead, it works by blocking the formation of vitamin K-dependent clotting factors, reducing the blood's ability to clot.

Marketed under the names Coumadin, Jantoven, Marevan, Lawarin and Waran, warfarin is highly effective at reducing the risk of stroke and has long been the most widely used anticoagulant in the world.

Dosage can be affected by a person's weight loss or gain, level of alcohol intake and infections or other illness. Some over-the-counter medications, like those for colds and cough, contain stimulants that can also increase the heart rate.

Because so many factors can affect warfarin's impact, those using the drug must be monitored via blood tests on a regular basis, usually every three months, to avoid the risk of excessive bleeding or clotting. As people age, those interactions become more common, and blood draw frequency can rise to once a week.

The newer forms of anticoagulants don't require such intensive monitoring, January said.

"With NOACs, you don't measure or draw blood," January said. "Once a year, you do a kidney and liver function test, because that's where they are metabolized."

In addition, January said, there are FDA-approved reversal agents available for most of the NOACs that will rapidly reduce their anti-coagulation effects in cases of severe bleeding.

Risk factors

There are many causes of atrial fibrillation. It could run in the family, or you could be born with an abnormality to your heart's structure, such as abnormal heart valves. Conditions like high blood pressure, overactive thyroid, lung disease, viral infections and a malfunction of the heart's pacemaker can also contribute. So can heart attacks, heart surgery, sleep apnea and exposure to stimulants such as caffeine, tobacco and alcohol, as well as some medications.

Risk factors for Afib also include diabetes and obesity. That's why, for the first time, the guidelines have a section on weight management, January said.

Research has shown that eating a heart-healthy diet , such as the Mediterranean diet , is a key factor to improving heart health. Numerous studies have found that the Mediterranean diet can reduce the risk of diabetes, high cholesterol , dementia , memory loss , depression and breast cancer. Meals from the sunny Mediterranean region have also been linked to stronger bones , weight loss and longer life .

A heart-healthy lifestyle includes more than diet. Increasing physical activity, avoiding smoking, limiting caffeine and alcohol, and reducing bad stress, such as intense anger and frustration, that can affect the heart's rhythm, are also protective.