What is Cardioembolic Stroke (Stroke)?
In the history of societal advancement, we’ve seen a trend of diseases changing – non-infectious diseases have replaced infections as major health concerns. Strokes are a prime example of these non-communicable diseases. It’s important to highlight that strokes are a significant health issue, especially in lower-to-middle income countries. Around 26 million people have a stroke each year, which makes it a major factor in both death rates and long-term disabilities. Roughly two-thirds of these strokes are ischemic, or caused by a blockage of blood flow.
About a quarter of all ischemic strokes are estimated to be caused by cardioembolic events, meaning they originate from the heart. Even though they make up a small percentage of all ischemic strokes, cardioembolic strokes are especially significant because they are often more severe and more likely to reoccur.
Cardioembolic strokes can result from several specific heart conditions, such as irregular heart rhythms, blood clots in the left ventricle of the heart, heart tumors, valve infections, and unusual blood clots. Generally, these types of strokes can be prevented with appropriate care and management.
What Causes Cardioembolic Stroke (Stroke)?
Cardioembolic strokes, which are strokes caused by a blood clot that forms in the heart, can happen due to various heart-related issues that lead to the damaging of blood vessel lining, slowed down or stopped blood flow, and blood clumping together (forming clots).
Several common causes include:
• Heart rhythm problems: Atrial fibrillation, a heart condition that causes irregular and fast heart rate, is often the cause of cardioembolic strokes. This condition often affects people who are 65 and older, and is usually caused by diseases that affect the blood vessels in your heart or high blood pressure. Overactive thyroid or heavy drinking can also contribute. The risk of having a stroke is significantly higher in people with this specific condition, especially those with heart valve disease. There’s a tool doctors use, called the CHADS2, to predict the risk of stroke in patients with atrial fibrillation.
A condition known as sick sinus syndrome, characterized by a slow or fast heartbeat, can also increase the risk of stroke.
• Structural heart disease: Conditions like a patent foramen ovale (a hole in the heart that didn’t close after birth) can increase the risk of stroke. However, it’s still not clear if this is a direct cause or simply a passageway for clots formed elsewhere in the body to reach the brain.
Even without rhythm problems, a structural heart disease like valvular heart disease can increase the risk of stroke. Examples of this include:
- Rheumatic valvular disease, which is very likely to cause stroke if not treated with medication that prevents clot formation.
- Infective endocarditis, an infection of the heart’s inner lining, which results in stroke in about 10% of cases. There is a higher risk of stroke in the two weeks after starting antibiotics. Stroke survivors are usually started on blood thinners a week after the stroke.
- Non-infective endocarditis, such as marantic endocarditis (an inflammation of the heart valves).
Calcification or hardening of heart valves, especially the mitral valve, can also increase stroke risk.
• Problems with heart ventricles: Conditions like ventricular aneurysms, septal aneurysms, and weakened heart muscles that don’t pump well(help maintain circulation known as general ventricular hypokinesia) can increase stroke risk. The worse the heart’s ability to pump, the higher the risk of stroke. If you’ve had a heart attack, your risk of stroke will also be higher. Factors like the extent of heart damage, the presence of abnormal bulging (aneurysm) in the heart’s walls or clots on the walls, and irregular heart rhythms can make this risk even higher. People recovering from a heart attack face a particularly high risk in the first four weeks afterward and over the six years following their heart attack.
Risk Factors and Frequency for Cardioembolic Stroke (Stroke)
Cardioembolic strokes, which are a type of stroke, are more common as people get older. Studies show that while they make up roughly 14.6% of stroke cases in people younger than 65, this number increases to 36% in people who are 85 or older. In total, about 20% of all strokes are cardioembolic, and the risk of having one increases with age.
Signs and Symptoms of Cardioembolic Stroke (Stroke)
A cardioembolic stroke is a type of stroke that happens suddenly. This means that severe symptoms develop almost instantly and then start to slowly get better.
Like all strokes, the symptoms depend on the area and severity of the damage in the brain’s blood vessels. However, one key feature of a cardioembolic stroke is a sudden change in consciousness. Additionally, if a person was straining or holding their breath (known as a Valsalva-like maneuver) when the stroke occurred, it might point towards a cardioembolic stroke. This type of stroke can also cause more seizures due to the lack of blood reaching the far areas of the brain.
The common signs of a cardioembolic stroke and related cardiac findings are as follows:
Key signs of a cardioembolic stroke:
- Sudden decrease in mental clarity
- Change in consciousness
- Appearance of neurological symptoms
Possible signs of heart problems:
- Irregular heartbeat (atrial fibrillation)
- The presence of a heart murmur
- Signs of heart failure
- Recent heart attack
- Recent diagnosis of a heart valve infection (endocarditis)
Testing for Cardioembolic Stroke (Stroke)
The first step in checking someone’s heart health includes checking both the heart’s electrical and physical function. This is usually done by using a 12-lead EKG and a heart ultrasound, known as transthoracic echocardiography.
The EKG can help identify heart rhythm problems and provide clues about previous or current damage to the heart muscle. However, some heart rhythm abnormalities, such as irregular heartbeats that come and go, might not be detected with an EKG. For a more continuous monitoring of the heart’s rhythm, a Holter monitor, which records heart activity for a full day, is often used.
If longer monitoring is required, a device known as an implantable loop recorder (ILR) can be used. It can record heart activity for up to three years. This device has helped to identify several cases of a common heart rhythm disorder known as atrial fibrillation that were previously missed.
On the other hand, transthoracic echocardiography serves as the main tool to evaluate the heart’s structure and function. It can identify issues in the heart muscles and valves. However, it has limitation in visualising certain areas of the heart, such as the left atrial appendage. Where necessary, a more invasive type of ultrasound known as transesophageal echocardiography can be used. This offers higher resolution imaging and can identify smaller issues that might not be visible with a regular echocardiogram. However, due to its steep learning curve and limited availability, its use is not as widespread.
When it comes to evaluating the brain, the imaging tool used can vary depending on how much time has passed since the stroke symptoms started. MRI scans are generally the best for assessing the brain tissue. In particular, 3T MRI devices have unmatched image clarity. MRI scans can help us identify the affected area in the brain and estimate when the stroke happened, even if the patient’s history is unclear. However, a major constraint is they take a relatively long time to complete, which is not ideal for unstable patients. CT scans, on the other hand, are faster and can easily show signs of bleeding. The downside is that they may not be as sensitive in detecting smaller strokes.
Angiography, either through MRI or CT, helps to visualize the blood vessels in the brain for any issues. While MR angiography is preferred in patients with kidney issues, CT angiography is generally the investigation of choice, unless the patient has kidney problems.
Lastly, while its use is debated, checking for high levels of a substance called homocysteine in the blood can be relevant in certain cases, like in patients who are vegan. Homocysteine levels can be increased due to a deficiency of vitamin B12, which is common in people who follow a vegan diet, and it could potentially contribute to strokes.
Treatment Options for Cardioembolic Stroke (Stroke)
Managing stroke caused by blood clots often calls for the use of blood thinning drugs, known as anticoagulants, to help prevent more clots from forming. At the same time, it’s not clear exactly when to start anticoagulation therapy. This is because the therapy needs to balance two critical risks: further blood clots and a higher risk of serious bleeding in the brain.
Current guidelines suggest delaying blood thinning treatment for two weeks after a stroke. These recommendations rely mainly on data from studies using heparin, a specific type of anticoagulant.
Traditionally, oral anticoagulants, such as warfarin, have been used. The impact of these drugs is monitored through regular tests measuring clotting time and the international normalized ratio (INR), a standardized measure for clotting time. The ideal INR target is between 2.0 and 3.0, although this increases to 2.5 to 3.5 for those with certain types of artificial heart valves. The less predictable effects of these drugs, their likelihood of interacting with other drugs, and their reliance on strict diet control all present challenges.
Newer oral anticoagulants, known as Direct Oral Anticoagulants (DOACs), aim to overcome these issues. DOACs, including apixaban, rivaroxaban, dabigatran, and edoxaban, are assumed to have more predictable effects and require less regular testing. Initially, a critical drawback of these drugs was the absence of a ‘reversal agent’ that could quickly cancel out their effects if needed. However, the FDA has now approved reversal agents for several DOACs.
There are also approved devices aiding in stroke prevention, like the “WATCHMAN”, which closes off a small part of the heart (left atrial appendage) to lower the risk of stroke-causing blood clots, particularly useful for patients unable to take blood thinners.
Closing patent foramen ovale, a small hole in the wall between the two upper chambers of the heart, is gaining acceptance as a critical tool for preventing stroke recurrence. It has shown clear advantages over antiplatelet therapy, while performing at least as well as anticoagulation therapy. Therefore, it’s advisable to check for patent foramen ovale in any patient who had a stroke caused by a clot, who is under 60 years old.
Finally, for patients suffering from dangerous blood clots in the heart’s main pumping chamber, combined with a heart attack, we typically advise taking anticoagulants for at least three months due to the risk of clots breaking off and causing a stroke.
What else can Cardioembolic Stroke (Stroke) be?
- Strokes caused by plaque-induced clots (atherothrombotic strokes)
- Strokes caused by bleeding in the brain (hemorrhagic stroke)
- ‘Mini-strokes’ that temporarily block blood flow (transient ischemic attack)
- Conditions that mimic the symptoms of a stroke (stroke mimic syndromes)
What to expect with Cardioembolic Stroke (Stroke)
If not handled properly, cardioembolic strokes are more likely than atherothrombotic strokes to recur both in the early and late stages.
Possible Complications When Diagnosed with Cardioembolic Stroke (Stroke)
Bleeding transformations, either naturally occurring or after blood thinning treatment, can lead to serious outcomes from this condition. It can also cause long-term disability, and complications from prolonged bed rest, like bed sores. However, these complications depend on how severe and widespread the nerve damage is.
Preventing Cardioembolic Stroke (Stroke)
It is helpful for individuals to avoid drinking too much alcohol and to consider adopting diets like the Mediterranean or DASH (Dietary Approaches to Stop Hypertension) diet. These choices can help fight against high blood pressure and also eliminate triggers of a condition called atrial fibrillation, which affects the heart rhythm. These lifestyle changes are likely to provide health benefits.
People who are taking a medicine called warfarin should be aware of the foods they’re eating. Certain foods, such as avocados and broccoli, contain a substance called vitamin K. Vitamin K can interfere with the effectiveness of warfarin. So, it’s a good idea for patients to have a list of foods containing vitamin K to ensure their medication works well.
