What is Embolic Stroke (Stroke)?
Stroke is the main cause of long-term disability and the fifth leading cause of death in the United States. There are various underlying factors that can lead to a stroke. Identifying the root cause of the stroke is critical in guiding the most effective treatment options aimed at preventing another stroke, such as blood-thinning medication for irregular heart rhythm, and surgical procedures to improve blood flow in narrowed neck arteries.
In 1993, a study was published that grouped stroke into five categories based on cause. These include large artery atherosclerosis, an issue when the heart sends clot-forming materials, small blood vessel disease, other identified causes like tearing in the artery layers, and unidentified sources. Another classification system groups stroke under different headings — hardened arteries, disease of small blood vessels, heart-related causes, artery tearing, and other factors.
Additionally, stroke can result from clots (embolic strokes) originating from various sources. This could be from the heart, one artery to another, a rare case of clots moving from the vein to the heart in patients with a small opening in the heart (a condition known as patent foramen ovale), clots from the major artery of the body, or clot-driven strokes from unknown sources.
What Causes Embolic Stroke (Stroke)?
An ischemic stroke can happen in three ways: by blood flow getting blocked in a blood vessel, by getting reduced blood flow, or when a clot or other particle moves from elsewhere in the body to block a blood vessel in the brain. When a blood clot or other material moves like this, it’s called an embolic stroke.
The clot or material that causes an embolic stroke can come from a few places, including the heart, aorta, arteries, or veins in the pelvis or lower legs. Sometimes, a clot can even move from the veins to the arteries with the help of a hole in the heart. If a doctor suspects that you’ve had an embolic stroke, they will usually conduct various tests like an echocardiogram, a Holter monitor test, and vascular imaging to find out where the clot came from. This helps them decide what treatment is best and how to prevent another stroke.
Several things can cause clots or other materials to move through the body and cause an embolic stroke. One way is through blood pooling in an enlarged part of the heart, leading to the formation of a clot. Other times, bits of material can detach from damaged heart valves and move through the bloodstream. There’s also the possibility of a clot moving from the veins to the arteries through a hole in the heart, which happens in a condition called Patent Foramen Ovale.
Among all ischemic strokes, those caused by clots that originate in the heart are generally the most severe. This is because these clots can be quite large and block big blood vessels in the brain, resulting in serious strokes with high chances of disability and death. These types of strokes are also more likely to happen again.
There’s a considerable variation in the risk of having an embolic stroke. Common conditions that increase the risk include irregular heart rhythm (atrial fibrillation), recent heart attack, mechanical heart valve, enlarged heart muscle disease, and rheumatic heart disease affecting the mitral valve. Rarer possible causes include bacterial infection of the heart, non-bacterial heart inflammation caused by cancer or autoimmune disease, and a type of heart tumor called left atrial myxoma.
Atrial fibrillation, a type of irregular heart rhythm, is the most common condition that leads to cardioembolic stroke (stroke caused by a clot formed in the heart). Blood tends to pool and form clots within the left part of the heart when people have atrial fibrillation. This increase in clot formation leads to a higher chance of cardioembolic strokes. The likelihood of atrial fibrillation increases with age and is most common in people over 65. High blood pressure is the most common cause of atrial fibrillation in developed countries.
Heart attacks also commonly lead to embolic strokes, mainly because they can cause the left side of the heart to not work as well, leading to blood pooling and clot formation. Heart conditions that reduce the heart’s ability to pump blood increase the risk of embolism (clots moving in the bloodstream). The risk of stroke is higher when the heart can’t pump out as much blood. For example, people are more likely to have a stroke if less than 28% of the blood in their heart gets pumped out with each beat, compared to if more than 35% of the blood gets pumped out.
Heart valve disease can increase the risk of stroke, even if someone doesn’t have atrial fibrillation. People with mechanical heart valves, especially those in the mitral position, are at a significantly higher risk, especially if they cannot maintain a stable level of warfarin, a blood thinning medication. In developing countries, rheumatic heart disease affecting the heart valves is a common cause of embolic stroke in young people.
Septic embolic strokes, caused by bacterial infective endocarditis, are challenging to treat since they have a high risk of transforming into hemorrhagic stroke (stroke caused by a brain bleed) and developing multiple clots. Approximately 10% of those affected will have a stroke, particularly in the early stages of their illness, despite being on antibiotics. This risk is even higher in patients with artificial valve infections caused by staphylococcus aureus bacteria.
Even though they’re rare, myxomas are the most common primary heart tumors. They can cause strokes by forming clots that move to the brain, which is a common way young patients may present clinically. A less common cause of clots are papillary fibroelastomas, another type of primary heart tumor.
The new coronavirus, SARS-CoV-2, which causes COVID-19, has been proven to increase the risk of stroke. This can be due to small vessel disease stroke, caused by disease in the small blood vessels in the brain, or embolic stroke. Strokes related to COVID-19 are associated with high levels of inflammatory markers, causing a hypercoagulable state (increased tendency of the blood to clot). It’s not clear yet whether anticoagulation (medication that prevents blood clots) could decrease the risk of embolic strokes in COVID-19 patients. Additionally, the presence of heart damage due to COVID-19, leading to reduced blood supply, could potentially result in embolic strokes.
Risk Factors and Frequency for Embolic Stroke (Stroke)
Stroke is the leading cause of serious long-term disability and the fifth most common cause of death in the United States. There are several factors that can increase your risk of having a stroke, including high blood pressure, diabetes, an irregular heartbeat known as atrial fibrillation, high cholesterol, smoking, lack of exercise, kidney disease, sleep apnea, and drinking a lot of alcohol. Atrial fibrillation, in particular, can cause a type of stroke known as embolic stroke, and the risk of this increases as you get older. This condition is often the main reason for embolic stroke.
Approximately 25% of strokes in the United States fall into the category of “cryptogenic,” meaning their cause is unknown. Another one-sixth are known as Embolic Strokes of Undetermined Source, or ESUS. This term, coined in 2014, refers to strokes that show up as non-small vessel on brain scans and don’t have signs of atrial fibrillation, narrowing of the carotid artery, or tearing of the blood vessel walls.
- Stroke is the top cause of serious long-term disability and the fifth leading cause of death in the U.S.
- Risk factors for stroke include high blood pressure, diabetes, atrial fibrillation, high cholesterol, smoking, lack of exercise, kidney disease, sleep apnea, and heavy alcohol use.
- As a person ages, the risk of embolic stroke due to atrial fibrillation increases.
- Atrial fibrillation is often the main identifiable cause of embolic stroke.
- About 25% of strokes in the U.S. are cryptogenic, meaning their cause isn’t known.
- One-sixth of strokes are Embolic Strokes of Undetermined Source (ESUS), a term defined in 2014.
- ESUS refers to strokes that appear to not be due to small vessel disease, and there’s no evidence of atrial fibrillation, carotid artery narrowing, or blood vessel wall tears.
Signs and Symptoms of Embolic Stroke (Stroke)
Embolic strokes, a type of stroke caused by a clot or other particle that forms elsewhere and then travels to the brain, can have various symptoms depending on the specific region of the brain that’s affected. Generally, embolic strokes are distinct from those caused by small vessel disease.
Embolic strokes often develop very quickly. Interestingly, they can sometimes drastically improve from initial severe symptoms, a situation sometimes known as a “spectacular shrinking deficit syndrome.” This surprising recovery might be due to the clot shifting and the blocked blood vessel reopening. Altered consciousness has been identified as a more common symptom of this type of stroke than in other kinds.
Specific symptoms associated with this type of stroke include language problems (such as Wernicke’s, Broca’s, or global aphasia), vision issues, a tendency to gaze in a particular direction, and failure to attend to one side. It can also lead to damage in various brain areas and in turn, can cause symptoms of various brain syndromes. Cardioembolic strokes, in particular, may cause issues with vision without related weakness.
- Quick development of symptoms
- Possible fast recovery from severe initial symptoms
- Altered consciousness
- Language problems
- Vision issues
- Concentration on one side
- Problems with ignoring one side of the body
Activities that increase pressure in the upper right heart chamber, such as those provoking the Valsalva maneuver, could also trigger cardioembolic strokes. For example, severe coughing or bending down could cause symptoms to occur, suggesting a right-to-left blood shunt, such as a patent foramen ovale (PFO), leading to a paradoxical embolism.
On the other hand, strokes caused by small vessel disease typically produce different types of symptoms and don’t display any cortical signs. Commonly, these strokes manifest as weakness on one side, sensory issues, balance and coordination problems, combined sensory and motor issues, and the “dysarthria clumsy hand syndrome”.
Testing for Embolic Stroke (Stroke)
In diagnosing a stroke, along with understanding the patient’s medical history and conducting a physical check-up, it’s also important to use a method called ‘neuroimaging’. This involves creating images of the brain to confirm a stroke and figure out what caused it. One specific type of stroke, called a ‘lacunar infarct’, can be identified in these images. These are small strokes (ranging from 0.2 to 15 mm in size) that occur deeper in the brain, caused by a blockage in one of the tiny vessels that branch out from a larger brain artery. The most common risk factor linked to this type of stroke is high blood pressure.
On the other hand, ’embolic strokes’ are a different type. They are larger and can occur in several areas of the brain at the same time, or one after another. They are caused by large clumps of material that flow up to the brain and block larger arteries, like the middle cerebral artery. The symptoms this type of stroke causes are more severe. They also come with a higher risk of turning into a bleeding stroke, especially if the clump blocking the artery came from the heart.
Patients who had a stroke that wasn’t a lacunar infarct, should be watched for a heart rhythm issue called ‘atrial fibrillation’. If there’s no clear cause found even after continuously monitoring the heart rhythm, these patients should be sent home with a device called a ‘Holter monitor’. This device records the heart’s electrical activity for a longer period. The exact duration that’s best isn’t known yet, but the longer the monitoring, the higher the likelihood of catching sporadic episodes of atrial fibrillation. In some cases, this monitoring continues even after the patient leaves the hospital, and can reveal atrial fibrillation in 10 to 25% of patients.
Treatment Options for Embolic Stroke (Stroke)
For those experiencing a stroke, the typical treatment within the first 4.5 hours is an intravenous injection of a medicine called recombinant tissue plasminogen activator (tPA). This treatment is used as long as there are no issues preventing its use, regardless of what caused the stroke in the first place. A clear picture of the brain using a CT scan is crucial to make sure there is no bleeding in the brain.
Sometimes, a stroke is caused by a blockage in a large blood vessel, which can result in more severe symptoms. These patients may benefit from a procedure called mechanical thrombectomy, which can be performed within six hours of the onset of stroke symptoms. In certain cases, this procedure can be performed up to 24 hours after symptoms first appear to save any brain tissue that is still viable (able to function). If this treatment is being considered, a special type of CT scan is recommended that can provide images of the blood vessels in the head and neck. However, treatment with tPA shouldn’t be delayed just for this scan if the patient qualifies for the medication. If a patient presents more than six hours after the onset of stroke symptoms, a specific type of CT scan (known as a CT perfusion scan) of the head is necessary to make the decision about mechanical thrombectomy.
If a patient is found to have a heart condition called atrial fibrillation (AF) during their hospital stay or in monitoring at home after discharge, they should be started on full anticoagulation therapy. This therapy has been shown to decrease the risk of stroke by nearly 70% in people with AF. Warfarin is a good choice for people with heart valve disease, but there are other blood-thinning options such as dabigatran, apixaban, and rivaroxaban for people with non-valvular AF.
Patients who are younger than 60 and have a patent foramen ovale (PFO), a hole in the heart that didn’t close as it should after birth, should be evaluated for the risk of a stroke caused by a blood clot passing through the hole. Closing the PFO may lower the risk of stroke by about 60% in these patients compared to just receiving medicine.
For patients with a kind of stroke whose cause isn’t clear (known as ESUS), two large trials compared treatment with antiplatelet therapy (which helps prevent blood clots) against anticoagulation (which also reduces the risk of clotting). The results did not show a difference in stroke recurrence between the two treatments. As a result, treatment with a single antiplatelet therapy is recommended.
Lastly, ongoing research is looking at whether anticoagulation therapy may benefit patients who have a stroke that might have been caused by a disorder of the upper chamber of the heart, even though they do not have AF.
What else can Embolic Stroke (Stroke) be?
When you go to the emergency department with symptoms that suggest a stroke, doctors have to consider other conditions that can look a lot like a stroke. This is important, as they need to make sure they’re treating the correct problem. They might use a CT scan, which is a type of x-ray, to make sure you don’t have a condition called intracranial hemorrhage. This is when you have bleeding inside your brain, which can happen due to high blood pressure or a condition called amyloid angiopathy. It also includes conditions when blood collects under the covering of the brain, like with subarachnoid and subdural hematomas.
Sometimes, doctors also need to think about other conditions like seizures, which can make one side of your body weak (this is called Todd paralysis). These are usually short and can sometimes leave the person feeling weak for longer. Another condition that can look like a stroke is a type of severe headache called a migraine aura. This can cause neurological symptoms, which could affect your vision and senses. These symptoms are usually slower and develop gradually. Conditions like low blood sugar can also cause symptoms like a stroke, so doctors check your blood sugar levels before giving stroke treatment.
Sometimes, the patient’s symptoms don’t match the test results or physical exam, which could suggest a psychological cause, but this can be hard to pinpoint in an urgent setting. Still, the treatment for stroke should be given if there are no reasons not to.
There are other, less common conditions that can also look like a stroke. These include multiple sclerosis, brain tumors, compression of the spinal cord, problems with nerves due to pressure or position, and toxic metabolic encephalopathy, a type of brain dysfunction. These are especially important to consider when the patient has had a stroke before, as sometimes old symptoms can come back.
What to expect with Embolic Stroke (Stroke)
Certain factors can predict how a person might recover from a stroke caused by a blood clot in the short term, including the person’s age, other health conditions, as well as the size and location of the stroke which can be confirmed through brain scans. Despite these factors, the most critical predictor of long-term outcomes still remains the clinical assessment.
Larger strokes that significantly alter a person’s thinking processes or cause severe physical and visual problems tend to have a less favorable recovery. On a more positive note, research shows that people who regain abilities like finger extension, lifting the shoulder, and releasing their grasp early on, generally have better recovery outcomes after 6 months. Nevertheless, extensive damage to the corticospinal tract, a part of the brain that controls movement, is viewed as a negative sign for recovery.
Possible Complications When Diagnosed with Embolic Stroke (Stroke)
Mortality rates from strokes have been decreasing due to improvements in medical care. The death rate from the first incident of an ischemic stroke, within the first month, is between 16% to 23%. This is also linked to an increase in sickness rates. Stroke is the leading neurological reason for disability in both developing and developed countries.
After 6 months, a stroke caused by a blood clot can cause severe disabilities. These disabilities may include language difficulties, poor vision on one side of the visual field, mental impairment, sensation and movement issues, and problems with walking. All stroke patients should undergo speech and swallowing assessments to screen for difficulty swallowing and prevent the risk of aspiration pneumonia, a potentially deadly condition. We should also screen for depression, infections due to bedsores, and urinary tract infections. A worsening of symptoms early in the course of a stroke is linked to a worse outcome and increased rates of sickness and death.
Recovery from Embolic Stroke (Stroke)
Physical rehabilitation can help speed up recovery and enhance results after a severe stroke. Most of this recovery takes place in the first six months after the stroke occurs. It’s important that everyone who has had an embolic stroke be assessed for possible rehabilitation by a team of experts. Another crucial step is screening all stroke patients for signs of depression. As per the FLAME trial, beginning treatment with fluoxetine soon after a stroke occurs can improve results after three months, particularly in patients with moderate to severe motor deficits.
