Times have changed in the treatment of patients with atrial fibrillation (AF).
First some background: The first of the four pillars of AF care is stroke prevention. The only proven means to protect patients with AF from stroke is use of drugs that block clotting factors–or anticoagulants.
Some people call these drugs blood thinners. I don’t. That’s because they don’t thin the blood. They inhibit proteins in the blood that form clots; viscosity of the blood is not affected. Blockade of clotting factors works because static blood in the fibrillating (non-contractile) atria increases the probability of clots, which can break off, travel north and cause stroke.
A study just published in the Journal of the American College of Cardiology reported changing patterns in the use of clot-blocking drugs. It was a registry study in which doctors across the world entered patients with AF into a data bank. Then researchers tallied up the number of patients who took the drugs and which type of drugs were used.
The major finding of the study is something I see happening in my practice: the choice of clot-blocking drugs is moving strongly away from warfarin (Coumadin) and towards the new oral anticoagulant drugs (NOAC), such as dabigatran (Pradaxa), rivaroxaban (Xarelto) and apixaban (Eliquis).
In the registry study, prescriptions for NOAC drugs outnumbered warfarin–48% to 32%.
Since this comes up so often, I will offer three reasons for this trend.
First is that the NOAC drugs are easy to use. The NOAC effect on clotting is immediate. With warfarin, the effect on clotting is delayed. And the convenience continues past the initiation phase. NOAC drugs don’t require frequent testing; they don’t require attention to dietary patterns and they have fewer interactions with other drugs.
I see convenience as important because less time spent being a patient is more time spent enjoying normal life. Convenience also means patients are more apt to take the drugs. Studies show adherence to NOACs is greater than warfarin.
The second reason for increased use of NOAC drugs is that they provide reliable effects. This is important–and the issue comes up all the time in questions from patients: “Doc, how do you know how thin my blood is? With warfarin, you measure the effect but with these new drugs, you don’t?”
The answer is that NOAC drugs have predictable metabolism. That means when I take 20 mg of rivaroxaban it produces the same blood levels of the drug that it would in you. This is not the case with warfarin. Warfarin is broken down by liver enzymes that vary in strength from person to person. My dose of warfarin might be 1 mg daily and yours might be 10 mg daily. Most drugs are like NOACs. Oral antibiotics, for instance, are dosed by standard milligrams. So are ulcer drugs and even aspirin.
The third reason NOAC drugs are taking off is that we aren’t seeing a lot of problems. This brings up another FAQ: “Doc, what are the side effects of NOAC drugs?”
My answer here is almost none. Patients tolerate the drugs well. Dabigatran can cause a bit of reflux and stomach burning–but this side effect simply requires changing to another agent.
Notice I did not list bleeding as a side effect. Bleeding is part of the stroke-prevention equation; it’s almost an effect rather than a side effect.
When you take a clot-blocking drug, you are making a gamble. You take the drug because numerous studies show that they reduce the probability of a future stroke. That’s good. But the drugs also increase the odds of having a bleed. That’s bad. Note this all about probability.
Doctors like this trade in most cases because strokes are worse than bleeds. I tell patients that strokes can cause permanent disability–or said another way, strokes can steal part of what makes us human. Things like thinking, speech, movement, swallowing, etc. Bleeds, on the other hand, are scary and dangerous, but most patients leave the hospital with their human functions intact.
The problem is that doctors don’t ever see patients for strokes prevented. These patients don’t come to the emergency room or our office and say–“look, I didn’t have a stroke.”
We only see the bad outcomes. You also may know someone who had a bleeding outcome with a clot-blocking drug.
It’s important to recognize this as availability bias. A bad case of bleeding can trick our brains into ignoring the actual statistics.