Knockout stroke = cardiogenic cerebral embolism. Its cause, prevention and treatment.


English 脳梗塞 脳卒中


Approximately one third of strokes are thought to be caused by blood clots which occur at the heart, creating a blockage.
These strokes, which are caused at the heart, are known as Knockout Strokes.
The medical term is Cardiogenic Cerebral Embolism.
Compared to strokes caused by hardening of the arteries,
It is thought that this type of stroke is associated with greater severity and a higher mortality rates.

As far as this condition is concerned, most people are not familiar with it.
Therefore, we are actively promoting the prevention of this type of stroke by raising awareness.

Cerebral infarction occurs when blood clots are formed, blocking the flow of blood in blood vessel.
Here, we have a rare footage of the moment when a blood vessel gets blocked by a blood clot.

The red color seen in this video is the blood which is flowing through the blood vessel.
Each of these pellets are actually red blood cells.
And these shown on the screen are platelets, the cause of blood clots.
When platelets accumulate, a large cluster forms.
This is a blood clot.
The blood clot drifts as it is carried by the blood stream.
From the bottom left, the blood clot is carried along the blood vessel.
And as the artery narrows, it gets blocked.

This blood clot is blocking a blood vessel in the brain. This is a stroke.
The clot itself is created in order to repair damage which is caused by the hardening of the arteries.
Actually, there are situations where the hardening of the arteries advances further, and the blood vessels become narrower. A blood clot like the one shown earlier, would be carried further down the blood vessel, blocking the blood flow and causing a stroke.


The scariest of strokes, resulting from this mechanism,
is termed a cardiogenic cerebral embolism.

Cardiogenic cerebral embolisms are caused by atrial fibrillations, a form of arrhythmia.
Atrial fibrillations are a form of arrhythmia which causes small vibrations within a chamber of the heart.

In a situation in which small vibrations occur, the blood stagnates and easily hardens. Possibly forming blood clots.
If the blood clot formed in that chamber flows out of the heart, and is carried to the brain, a blood vessel in the brain may be blocked causing cerebral infarction.


Here, a blood clot is formed in the heart.
Compared to a blood clot formed in a blood vessel, this type of clot is often much larger. If, somehow, the clot is dislodged and flows into the body.
In the arteries within the brain, these clots can cause blockages within relatively large blood vessels.
So, an extremely wide-scale infarction may occur, a truly terrifying condition.


【Source: The Japan Stroke Association Yasushi Okada】

This is a CT image from an actual patient.
The dark section is quite spread out. This is the necrosis section.
This shows that the blood vessels at the base got blocked, exerting a massive effect.
The condition itself varies and depends on the circumstances, it may be fatal.
Even if the victim survives, there may be serious complications, leaving the individual bed-ridden or requiring extensive assistance.
The mortality rate of stroke is thought to be 5%.
Recently, the chances of survival have increased favorably.
However, with this condition, the mortality rate is much higher with approximately 1 in 7 or 8 patients losing their life.
Of the survivors, more than half require assistance or remain bed-ridden.
Avoiding such a situation is currently, our biggest mission.

Prevention of Knockout stroke = cardiogenic cerebral embolism.

Approximately 80-90% of cardiogenic cerebral embolism cases are caused by atrial fibrillation, a form of arrhythmia.
Therefore, identifying this condition at an early stage is the most effective form of prevention.

Measure your pulse.
Since this is a form of arrhythmia, the best place to start would be to measure your pulse.
The most common method to measure your pulse is at your wrist. Take the palm of your hand, facing upward or toward yourself. And you'll end und up with some wrinkles here. Then close to your thumb.
If locating the pulse is challenging, move your fingers slightly. Put your fingers somewhat perpendicular, that should help to feel your pulse. Measure the pulse for approximately 30 seconds. Feel the rhythm.
Normally, it is a pretty regular thump, thump, thump, thump. I think the speed of the pulse depends on the individual.
In this case, there is no problem.
But in the case of atrial fibrillation, you may get an irregular pulse like thump-thump, thump, thump-thump-thump.
It you felt that your pulse was irregular, you should discuss this with a physician. An ECG examination would tell you.
Also, arrhythmia and atrial fibrillation occasionally disappear. If there are no pulse irregularities, repeat the measurement at a later time. This way, you might detect an irregular pulse.
Which individuals should show extra care when checking such things?
People who have a background of hardened arteries and the elderly are at a higher risk of arrhythmia and atrial fibrillation.
People over 65, those with lifestyle problems and high blood pressure, and those with identifiable symptoms.
A sudden sense of panic. Or shortness of breath after climbing a flight of stairs. Actual chest pains.
These symptoms alone would warrant a visit to the doctor.
If you have such identifiable symptoms, you should be measuring your pulse on a more regular basis.
If this is performed, the chances of finding atrial fibrillation would be much greater.


Other than this, strokes may also be caused by the hardening of arteries.
These are termed lacunar infarction and atherothrombotic infarction.


Characteristically, lacunar infarctions block thin blood vessels, while atherothrombotic infarctions block larger blood vessels.
Depending on the location of the infarction, each stroke may be minor or serious with various symptoms.
The treatment and prevention of stroke continue to advance.
Please take the appropriate measures for the prevention of stroke.

Stroke Treatment

The key of stroke treatment is to remove the blockage as soon as possible.
Currently, new treatments are gaining attention.

Cerebral infarction occurs when a blood clot blocks a blood vessel in the brain.
The key to treat a stroke is the prompt removal of the clot.

tPA and Intravascular treatment


Recently, a method which has received attention is intravascular treatment.
Nowadays, a thrombolytic agent, tissue plasminogen activator (or tPA) is administered intravenously to dissolve the blood clot. A catheter is inserted into the blood vessel in the brain and the device at the tip removes the clot by directly sucking it out.

There are two methods to treat a stroke.
It has been recently revealed that by simultaneously performing intravascular treatment and administering tPA, you can expect an improvement in the outcome.
Currently, there is a movement in the medical community to make this simultaneous administration of tPA and intravascular treatment available nationwide.

Treatment of stroke has advanced considerably, and tPA was approved for use in the United States in 1996. Thanks to it, the complications of stroke have diminished, showing that the treatment of stroke has truly advanced.
Moreover, recently, many methods are being devised focusing on intravascular treatment, which can lead to brighter prospects in the treatment of stroke.

Let us talk about cerebral infarction and how tPA works.


Cerebral infarction is a condition which occurs when a blood clot blocks a blood vessel in the brain.

How tPA works


Administration is required within 4 and a half hours.

Use of tPA dissolves the blood clot, allowing the blood flow to quickly return to normal, preventing the necrosis of brain cells.
However, administration of tPA is required within 4 and a half hours from the onset of the stroke. Because the danger of a brain hemorrhage increases substantially after that.


In addition, with time, the effectiveness of tPA slowly decreases.
If time passes and necrosis develops, the walls of the blood vessels become brittle.


In this situation, if tPA is administered, the blood clot dissolves and the blood start to flow again. However, hemorrhage may occur through the brittle blood vessels.

As an anti-clotting agent, tPA may cause excessive hemorrhaging. With hemorrhaging occurring in the brain, this would have the same consequences as a brain hemorrhage.

As explained earlier, the effects of the treatment diminish, while the possibility of hemorrhage increases with time. It is thought that 4 and a half hours is the limit.


The initiation of treatment has to be done within 4 and a half hours.
Realistically, the time required to arrive at the hospital, perform tests, and prepare the treatment, may exceed an hour or an hour and a half. Therefore, the time slot for the initiation of treatment becomes 3 and a half hours, resulting in an even more difficult situation.

In Japan today, the number of stroke patients receiving tPA is only about 4-5%. In the past, if treatment wasn't initiated within the 4 and a half hours, nothing could be done.
However, with the development of intravascular treatment, the procedure can be performed a few hours later. Stroke can be treated within 8 hours from its occurrence.
In situations in which tPA did not effectively dissolve the blood clot, use of intravascular treatments permitted the treatment of many more patients from a much wider range.


Intravascular treatment requires the insertion of a catheter at the leg, extending to the blood vessel in the brain.
Using the apparatus at the tip, the blood clot is physically removed.
There is the stent retriever type and the vacuum aspiration type.
This is a demonstration of the use of the stent retriever type.

The circle on the screen shows the blood clot which is blocking the vessel.
The net-like tube takes hold of the blood clot.
Then, the catheter is pulled out, removing the clot with it.
And this is how the vacuum aspiration type removes a blood clot.
The blood clot can be seen within the circle.
The apparatus at the tip sucks the blood clot like a vacuum cleaner, restoring the blood flow.


By combining these two methods (tPA and intravascular treatment), the treatment becomes much more effective. Recent studies show that this is the case.


Treatments using only tPA and treatments using tPA in conjunction with intravascular treatments. This slide shows a comparison of the results for each treatment modality.

The blue color shows cases in which the effects of the stroke are completely remedied. Basically, a full recovery.

The green color shows cases in which some of the effects remain but daily life has not been seriously affected. Almost a full recovery.


Previously, this was practically impossible.

Even with the use of tPA only, the results have been shown to be better than those observed in the past.
With both treatments performed simultaneously, more than half of the patients achieved this favorable outcome. To us, who are familiar with the previous treatment methods, these results are impressive and almost to the point of being unbelievable.
The effects are truly improved with the simultaneous use of these two methods.

Previously, according to the Japanese treatment guidelines, the administration of tPA was recommended.
Recently, based on the excellent results of intravascular treatments, this modality has also become a strongly recommended method.
But, there is a problem、because in Japan, tPA has only been available to approximately 4 or 5% of patients. Part of this is due to time constraints, even the intravascular treatments which provide an extended intervention time are only available in limited locations. And, only a small number of specialists can perform these procedures.
Rectifying this situation is an important task that requires attention.

What do we need to be careful of after treatment?
I think we need to work on preventing stroke recurrence.
Even if treatments and rehabilitation are successful, a relapse may worsen the patient's situation and potentially result in death.
With the current increase in the methods for the prevention and treatment of stroke, patients should continue to take their required medication.

For the prevention of stroke, an anticoagulant agent is administered.
Occasionally, patients forget to take their medication and find that there are no ill effects.
These patients may stop taking the medication.
However, if they suffer another stroke, the damage would be irreversible. Please do not stop taking your medication based on your own perception. Discuss this with your doctor for an effective prevention of stroke and to live a longer life.