For at least 30 years, cardiologists have recommended patients with atrial fibrillation be placed on blood thinners, ie. anticoagulants. The reason for that is that patients with atrial fibrillation have a high rate of embolic stroke. An embolic stroke is one that occurs when a blood clot formed within the heart breaks loose and travels up a carotid artery and lodges in the brain where it blocks the flow of blood and oxygen to the brain tissue. Blockage of blood and oxygen causes a cerebral infarct which is permanent, irreversible damage to the brain tissue. Stroke symptoms then occur, and the symptoms depend on what part of the brain is affected.
Why do atrial fibrillation patients develop blood clots in the heart? There are two major reasons. One is atrial fibrillation is an erratic, irregular rhythm that greatly slows the flow of blood through the heart, allowing it to stagnate and pool in certain areasj. These areas pump the blood poorly during a normal rhythm, but very poorly, or not at all, during atrial fibrillation.
The second reason is that one of those stagnating areas is a pocket in the left atrium called the left atrial appendage. Blood pools in the appendage and coagulates forming clots. If a clot gets big enough, pieces of it break loose and flow to the brain with tragic consequences. Anticoagulation, thinning of the blood, prevents pooled, stagnate blood from forming clots, as such reduces the risk of embolic stroke.
For years, doctors had only heparin and oral warfarin for blood thinning. Heparin was inconvenient requiring injections several times a day, and warfarin required blood test monitoring to gauge the thinness of the blood. Plus, both had the potential to cause bleeding if the level of anticoagulation got out of control.
Then, along comes a new class of drugs called direct oral anticoagulants (DOAC), or direct thrombin inhibitors (DTI’s). These drugs (Eliquus, Pradaxa, Xarelto) work by directly inhibiting thrombin from forming blood clots rather than interrupting the usual mechanism called the coagulation cascade, or clotting cascade. DOAC’s drastically reduce the frequency of adverse events caused by atrial fibrillation with a reduced risk of bleeding.
Medscape.com reports on a study from South Korea involving 1803 atrial fib patients. They were divided into 3 groups: one-third took Xarelto, one-third Pradaxa, and one-third took no anticoagulant. Over 24 months of observation only 4 patients on a DOAC had a major CV event, while 13 patients not on an anticoagulant, had a major CV event. Three of the 4 on anticoagulant had a stroke. Abnormal, nonmajor bleeding occurred in 22 DOAC patients and in 14 non-anticoagulation patients. So, there is a bleeding tendency with DOAC’s which is mentioned as one advantage of the DOAC class.
Dr.G’s Opinion: The drug class direct oral anticoagulation is a prime example of how marketing and salesmanship can create a need where none exists. While it’s true that the advertised advantages of not needing blood test monitoring and “one dose fits all,” are compelling, bleeding episodes still do occur. They are minimized by the manufacturer, but do occur. After my wife’s partial knee replacement, and also after a total knee replacement, she had spontaneous bleeding into her knee on three separate occasions. That never happened when she was on warfarin and has not happened again since returning to warfarin. I think the only advantage of these drugs is to make money for the drug companies. That’s not a valid reason for taking them. Plus they are expensive. I would recommend warfarin and continue monitoring the anticoagulation level (INR) regularly.
Reference: McCall B. SINGLE-AF: DOAC’s Cut Clinical Events in AF Patients at Intermediate Stroke Risk. medscape.com 2026 August 28.
