Ask the doctors: Stroke likely not caused by blood thinner, but worth reporting
Q: After getting a pacemaker, my 90-year-old mother was diagnosed with A-fib. She resisted taking a blood thinner for stroke risk but finally agreed. Not 90 minutes after the first pill, she had a major stroke. Who can I notify that this is a possible side effect of the medication?
A: We understand how, due to the timing of the events, it can seem like the blood thinner your mother took contributed to the stroke. In looking at the details of her medical condition and the typical effects of these medications, this is not as simple as it seems.
Blood thinners do not have an immediate effect. Because of this, it is more likely the stroke was related to an underlying condition. That said, it is appropriate for you to report the event so it can be reviewed as a possible adverse reaction. In this column, we will address each of these issues.
Let's begin with the pacemaker your mother received. It is a small device implanted in the body. It uses electrical pulses to regulate abnormal or problematic heart rhythms. As happened in her case, the internal sensors can lead to finding atrial fibrillation, or A-fib. This is an arrhythmia in the upper chambers of the heart, known as atria.
The fluttering, quivering heartbeat of A-fib can cause blood to pool in the atria. This can lead to the formation of blood clots. This puts the person at increased risk of an ischemic stroke, when a clot impedes or completely blocks blood flow to the brain.
To reduce risk of clotting and ischemic stroke, people with A-fib are often prescribed medications known as anticoagulants, or blood thinners. Different anticoagulants work by either slowing or interfering with the cascade of biochemical events that lead to blood clots. Some take three to four hours to begin working. Some can take several days.
But since they prevent the formation of blood clots, anticoagulants are not associated with causing an ischemic stroke. However, data show that blood thinners may increase the risk of a different type of stroke called hemorrhagic stroke. This is when a blood vessel in the brain ruptures and the resulting bleeding disrupts normal blood flow.
Because only about 90 minutes passed between your mother's initial dose of the anticoagulant and the stroke, it is more likely the cause was a preexisting condition rather than an immediate effect of the medication.
Still, because anticoagulants can raise the risk of hemorrhagic stroke, it is impossible to determine the cause. For that reason, you are justified in reporting the event as a possible medication interaction. Reports can be submitted to the U.S. Food and Drug Administration (FDA) through its MedWatch program, either online or by phone.
You can also speak with the doctor who prescribed the medication. Drug manufacturers also maintain help lines to document and review this type of event. Your vigilance is the kind of response that helps improve medication safety for everyone.
• Dr. Eve Glazier is an internist and associate professor of medicine at UCLA Health. Dr. Elizabeth Ko is an internist and assistant professor of medicine at UCLA Health. Send your questions to askthedoctors@mednet.ucla.edu.
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