Atrial Fibrillation and Stroke Prevention: Anticoagulants

Stroke prevention is the cornerstone of AFib treatment.

More than three million Americans treatment. Anticoagulants are 1954. Warfarin (Coumadin) is a have Atrial Fibrillation (AFib), which highly effective at lowering the vitamin K antagonist. is the most common heart rhythm likelihood of ischemic stroke. disorder. AFib is caused by Ⅲ Direct thrombin inhibitors chaotic electrical signals, which What is an Anticoagulant? Thrombin is one of the enzymes in - make the upper chambers of the Anticoagulants, which are some - volved in clot formation. By inhibiting heart (the atria) quiver, instead of times called blood thinners, inter - thrombin, the coagulation cascade properly contracting. During AFib, rupt the blood’s normal clotting is interrupted, so blood clots form blood pools in the atria, which can (coagulation) process. This less readily. Dabigatran (Pradaxa) allow a clot to form. If a blood clot complex system, which is called is a direct thrombin inhibitor. breaks free, it can enter the blood - the coagulation cascade, involves stream and cause a stroke. many cell proteins that work Ⅲ Factor Xa inhibitors together to stop bleeding. Factor Xa is another enzyme in - People with AFib have a stroke risk volved in the coagulation cascade. five times higher than those who do Anticoagulant Types By inhibiting Factor Xa, the coagula - not have AFib. AFib causes approxi - There are several anticoagulant tion cascade is interrupted. Rivarox - mately 120,000 ischemic strokes medications available for patients aban (Xarelto) and Apixaban each year. Ischemic stroke happens with AFib. Anticoagulants target (Eliquis) are Factor Xa inhibitors. when a clot breaks free, lodges in different parts of the coagulation a blood vessel, and blocks the flow cascade so blood clots cannot form. Benefits and Risks of blood and oxygen to the brain. When taken as prescribed, all One out of every 4 strokes is due Ⅲ Vitamin K antagonists anticoagulants significantly reduce to AFib. Because of the adverse Many of the cell proteins involved the risk of ischemic stroke. Patients effects a stroke can have on quality in the coagulation cascade rely on taking anticoagulants are at risk and duration of life, stroke prevention vitamin K for synthesis. Vitamin K for excess bleeding because the is a primary treatment goal in AFib. antagonists (VKAs) interrupt the medications interrupt the coagula - There are a variety of treatments to production of these clotting proteins. tion cascade and prevent clotting. prevent ischemic stroke, but a VKAs have the longest track record Each type of anticoagulant has its medication called an anticoagulant of use in AFib-related stroke preven - own benefits and risks. is the most common “first-line” tion. The first VKA was approved in

did you know AFib-related strokes have double the mortality rate of non-AFib-related strokes. Vitamin K antagonists (VKAs) Direct thrombin inhibitors Factor Xa inhibitors Benefits. Most doctors are experi - Benefits. Direct thrombin inhibitors Benefits. A Factor Xa inhibitor enced with managing patients tak - may be easier for some patients may be easier for some patients ing a VKA. If there is an emergency to use than a VKA. Direct thrombin to use than a VKA. Similar to direct (such as a car accident) or a inhibitors have fewer dietary thrombin inhibitors, Factor Xa planned medical procedure, restrictions and fewer drug-to-drug inhibitors have fewer dietary re - healthcare professionals can interactions than VKAs. Direct strictions and fewer drug-to-drug reverse a VKA so that the body’s thrombin inhibitors do not require interactions than VKAs. Frequent normal clotting abilities return. frequent blood tests. In addition, blood tests are not needed. Factor In addition, VKAs are the least direct thrombin inhibitors have a Xa inhibitors also have a lower risk expensive type of anticoagulant. lower risk of bleeding in the brain of bleeding in the brain compared than VKAs. to VKAs. Risks. Certain foods—particularly green, leafy vegetables—have a lot Risks. There is no approved drug Risks. Healthcare professionals of vitamin K. Eating too many foods to reverse the anticoagulation are less experienced managing that are rich in vitamin K can make effect of direct thrombin inhibitors, patients taking Factor Xa inhibitors VKAs ineffective at stroke preven - and healthcare professionals are in emergency situations, and there tion. In addition, some medications less experienced managing pa - is no approved drug to reverse the also interfere with VKAs. Because tients in emergency situations. anticoagulation effects of Factor of this, patients taking a VKA must Direct thrombin inhibitors offer Xa inhibitors. Similar to direct have their blood tested routinely to stroke protection for a certain thrombin inhibitors, Factor Xa make sure it is adequately thinned, period of time, so patients cannot inhibitors offer stroke protection but not too thinned. The test meas - skip a dose. Direct thrombin for a certain period of time, so it’s ures the International Nor malized inhibitors may also have a higher important to take the medication Ratio (INR), which in gen eral risk of major bleeding in the as prescribed by the doctor and should be maintained between 2.0 gastro-intestinal organs, including not skip doses. and 3.0. If the INR is less than 2, the the stomach and intestines. patient is at risk for an ischemic stroke. If the INR exceeds 3, there is an increased risk of bleeding.

Determining the Appropriate Treatment Stroke prevention is a primary goal of AFib treatment. Patients should discuss their risk of stroke with their electrophysiologist (a doctor who specializes in heart rhythm disorders), cardiologist or primary care physician. If an anticoagulant is needed, patients should discuss the risks and benefits of the differ ent anticoagulants with their doctor and together, determine which treatment is the best choice.

Factor Xa Inhibitors Vitamin K Antagonists Direct thrombin Inhibitors (Rivaroxaban/Xarelto (Warfarin/Coumadin) (Dabigatran/Pradaxa) and Apixaban/Eliquis) Dosing frequency Once/day Twice/day Once or twice/day* Effective at preventing strokes Yes Yes Yes Risk of excess bleeding Yes Yes Yes Time to peak effectiveness Days 0.5-2 hours 2-4 hours Interaction with food Yes No No Interaction with other medications Yes Fewer Fewer Need for frequent blood tests Yes No No Reversal drug for emergencies Yes No** No** Need to stop taking drug before Depends Depends Depends medical procedures *Some Factor Xa inhibitors only need to be taken once a day with the evening meal. Other Factor Xa inhibtiors need to be taken twice a day. **There is currently no approved reversal drug in the US, however, reversal drugs are under development. The type of medical or dental procedure will determine whether anticoagulation medication must be stopped. Patients should discuss the planned procedure with their doctor to determine appropriate anticoagulation dosing before and after.