A-Fib:When Heart Patients Do Not Benefit From Aspirin

Hundreds of millions of adults who have passed the age of 40 are advised to take a "baby Aspirin" (an 81 mg dose in the US, a 75 mg dose in most of the rest of the world) every day to prevent heart attacks. Sometimes, however, taking Aspirin every day is not a good idea.

Aspirin and Heart Attack Prevention

Aspirin acts as a mild anticoagulant, or "blood thinner." When you bleed, specialized blood cells known as platelets, build up at the site of the wound. These blood cells accumulate to plug the leak so that blood loss is minimal.

The muscle cells in this part of the heart go into hibernation, ceasing to function, and typically "burn out" when the heart is reperfused, when the blood clot eventually breaks up. 

Aspirin in low doses prevents platelets from sticking together to form clots. This reduces the risk of heart attack or stroke, but increases the risk of bleeding. The effects of Aspirin used by itself are usually so mild, however, that the benefit to the heart is thought to outweigh the increased risk of bleeding, especially in people who are known already to have coronary artery disease or who have already had a heart attack.

The Special Case of Atrial Fibrillation

Blood clots don't always form at the sites of injury or in the heart. Blood clots can also form in the brain, causing stroke. And one of the most common causes of blood clots that travel to the brain is an abnormal heart rhythm known as atrial fibrillation.

Atrial fibrillation, known colloquially as A-fib, is an unusually rapid rhythm in the upper chambers of the heart, known as the atria. The heart's rhythm is paced by electrical signals sent out by a nerve known as the sinoatrial node. In a healthy heart, the electrical impulse travels from the sinoatrial node from cell to cell from top to bottom of the heart so that the whole heart beats with a regular rhythm.

In atrial fibrillation, nerves in the pulmonary veins, which bring oxygenated blood back from the lungs to the heart to be pumped throughout the rest of the body, send out "noisy" impulses that cause extra beats in the two upper chambers of the heart. The heartbeat become more rapid, and each beat has less "oomph" to circulate blood through the body.

See Also: Atrial Fibrillation Treatment

As a form of atrial fibrillation treatment people who have A-fib are prescribed anticoagulants such as Plavix (clopidogrel), Coumadin (warfarin), Pradaxa (dabigatran), Xarelto (rivaroxaban), and others. When people who have A-fib are started on Plavix, they usually also are prescribed a baby Aspirin a day. And sometimes patients can't or won't take a prescription anticoagulant and are given just Aspirin. Recent research from Sweden finds that Aspirin alone is not sufficient to prevent stroke.

A-Fib Requires More Than Aspirin Alone

Swedish researchers tracked 182,678 atrial fibrillation patients, 1/3 of whom took only Aspirin, and 2/3 of whom took other oral anticoagulants with or without Aspirin. At the time the study was conducted, European Union guidelines permitted doctors to prescribe Aspirin for the prevention of strokes in people who have atrial fibrillation, although since 2012 Aspirin monotherapy has only been permitted for people who cannot tolerate a combination of clopidogrel (Plavix) and Aspirin or who refuse to take any other oral anticoagulants because of their experiences with increased bruising and bleeding.

If Aspirin actually makes the risk of stroke worse, why had doctors been prescribing it for so long? The use of Aspirin in atrial fibrillation had been based on seven studies conducted in the 1970's and 1980's. Only one of the seven studies found a net positive benefit of Aspirin in preventing blood clotting events in people who have this kind of arrhythmia. There was a 22% reduction in the risk of stroke, but to get the 22% figure in that study, the researchers had to count transient ischemic attacks (TIA's) and "small strokes" as strokes. The benefits of taking Aspirin as the sole medication for A-fib seem to have been limited to minor cerebrovascular events, not the kinds of strokes that can cause permanent disability.

Dutch researchers followed 8,423 people, average age 69 at the beginning of the study, for an average of 13 years. Of this group, 857 developed atrial fibrillation.

When the researchers accounted for smoking, cholesterol, blood pressure, and other cardiovascular risk factors, they found that people who use non-steroidal anti-inflammatory drugs such as Aspirin, Ibuprofen, and Tylenol on a regular basis are 80% more likely to develop atrial fibrillation if they do not already have it.

The lead researcher in the study, Dr. Bruno H. Stricker, a professor of pharmaco-epidemiology at Erasmus University Medical Center in Rotterdam, said these drugs have also been associated with the risk for coronary artery disease and heart attack.

See Also: Supraventricular Tachycardia: Diagnosis & Therapy

“I would really strongly advise that older people be very careful with using these drugs,” he said. “They don’t do anything except relieve pain. Pain is a nuisance, but dying is a nuisance, too.”

You should always rely on your doctor's advice, but it seems like a good idea for everyone to avoid using Aspirin for preventing blood clots unless it is combined with another drug such as Plavix. (Aspirin must not be used with some of the newer anticoagulants, such as Brilinta.) Taking Aspirin to relieve pain on an occasional basis is probably OK, but if you have A-fib, or you are at risk for A-fib, you should not use it as your only anticoagulant medication.