Charles Matouk, MD, Vice Chair of Neurosurgery and Chief of Neurovascular Surgery at Yale School of Medicine talks about how direct carotid puncture (DCT) is an improvement in stroke treatment that could ultimately save more lives.
What are the traditional ways you treat stroke patients?
Dr. Matouk: For many years, the only treatment we had to treat patients with acute strokes was a clot-busting medication administered intravenously through the veins which is called TPA. We still use TPA today and it remains the standard of care. The problem with intravenous TPA is the time window. The amount of time from when you have a stroke and when you must administer the medication for it to be safe and effective is exceedingly small. In the U.S. we say about 4 1/2 hours from the onset of a stroke and its symptom. The type of symptoms that somebody might have are weakness or paralysis on one side of the body, an asymmetric smile, or having trouble finding words or understanding people, and maybe vision loss in one eye. Those types of problems that indicate that a stroke is happening makes the timer start and you must get a patient to a hospital, get a CAT scan, and then have a neurologist and someone that can administer the intravenous TPA available at that hospital 24/7 for the medication to be effective. So, you can imagine the number of people that were eligible for this therapy was small, especially in rural communities or in dense cities like New York where it is difficult to get from A to B during the day. So that is one disadvantage of the intravenous TPA. The second disadvantage was that the medicine was much more effective at breaking up small blood clots that were stuck in smaller blood vessels and it was less effective at breaking up bigger blood clots that got stuck in bigger blood vessels. So, it was better for the small strokes and maybe not as effective for the big strokes or the types of big strokes that would leave someone disabled. It remains available and it is highly effective for many. But again, the number of folks that were eligible for this type of treatment was relatively small. In 2015, there were a series of papers that were published, about randomized-controlled trials on different continents and in different countries that showed if you can mechanically remove a clot from a person’s blood vessel, especially for bigger strokes which is the type that IV TPA is not as effective against, that patients did much better and that is what the papers in 2015 demonstrated. It really changed the standard of care in the U.S. and around the world for how we manage acute stroke patients, because now we have another therapy that is potentially of tremendous benefit to patients. The other advantage of this therapy is for select patients you have a longer window of opportunity to act. So, in the right patients you can have up to 24 hours after stroke onset as opposed to only 4 1/2 hours for the intravenous medication. That really increases the number of folks that are eligible for this type of treatment. So, it really is a watershed moment in acute stroke care. Those extended window papers were published in 2018 and now, in 2020, we are having to react as a medical system to this new reality and the public must be aware. Now, we must connect to the public that if you are having stroke symptoms, there is something that can be done about it, but the treatments are time sensitive and you need to get to a hospital that can treat the stroke.
Can you talk about the procedure and how it is done?
Dr. Matouk: First, let me describe how a typical procedure is performed. 90% of the time, we navigate to the blood clot in your head from the groin. That is our standard access, and it has been our standard for years. So, it is a large and forgiving blood vessel so that if there is a problem it can be corrected, and you do not have some major problem associated with it. So, you can get big devices in through that blood vessel and we navigate using an X-ray machine to guide our catheters and wires up through the body from the leg into the blood vessels in the neck and then all the way up into the blood vessels in the brain. We can either use an aspiration catheter, which literally sucks the clot out like a vacuum-type system, or we can deploy a stent. The stent sort of grabs on to the blood clot and when we pull the stent out, hopefully the blood clot comes with it. So that is the standard approach that majority of folks are using all around the world. That approach was validated in those big clinical trials in 2015 and then again in 2018. So, a lot of folks that have strokes are older and in their 80s and 90s and we know this type of treatment can be effective at making potentially big strokes and some smaller strokes easier to recover from. The problem is as we get older, our blood vessels become more twisted and they become more difficult to navigate and in some it is impossible to get from the leg through all the blood vessels in the abdomen and chest, and to the blood vessels in the neck to remove the blood clot. It is a shame when you must give up the procedure or the procedure takes hours and you have lost time and the procedure is time sensitive. So, a few years ago we decided to bring back an old technique of catheter angiography. It was done by neurosurgeons and it was typically done by a direct puncture in the neck and we moved away from that because if you damage the blood vessel in the neck which supplies the brain that could lead to a stroke in and of itself. But with all the advances in catheter and access technology we thought that by bypassing all the twists and turns in the patient’s body and going directly through the neck it would be a much shorter distance to the clot and that would be beneficial to the patient. That is essentially what our paper showed. When we started doing this, we knew based on the preoperative imaging that it was not going to be possible. When we quickly converted to direct puncture of the carotid artery and then put our stroke tools directly through the artery, patients did much better than if we gave up and did not try. That is the major finding of the paper that we just published in the Journal of Neurosurgery.
How many patients did you look at?
Dr. Matouk: We looked at about 20 patients with a direct carotid puncture method and we compared them to a population that came in with strokes that we tried to go up from the leg, but then aborted because we could not do it. So, when we compared these two groups, there was a clear benefit to trying, even though it is a riskier procedure because it is a more delicate blood vessel than the one on your leg.
Who are the patients that would benefit the most from this procedure?
Dr. Matouk: It is important to note that we are not advocating that this should be the way this procedure is performed. This procedure is well suited for folks that are older and have a more diseased vascular anatomy. For example, there are folks that have no blood vessels because the big blood vessels in their legs have collapsed or they are occluded because of disease. For those folks, they would not be eligible for a standard access route. There are other folks that have overly complex aneurysms or even occluded aortas which is the big blood vessel in your abdomen and chest. So, for them the traditional way of doing it would not be available. For those patients this would be one of the only alternatives.
What percentage of patients would this be appropriate for?
Dr. Matouk: It is about 10 percent, which is a significant number.
You said this is a riskier procedure, so what are the risks?
Dr. Matouk: The major risk is when we take the catheter out, how do you plug the hole? We have had one patient that died after a successful procedure because she had bleeding from that side. We have since learned that the best way to plug the hole is by holding pressure. If you hold pressure for 20 minutes, that seems to do the trick. We do this while the patient is asleep and with a breathing tube in their mouth. The advantage of that is they can stay still overnight and give their blood vessel chance to heal. So that is the protocol that we have adopted and published in this recent publication.
Are there other medical centers or research centers that are using this procedure?
Dr. Matouk: In extreme situations many of the large academic centers will do this. The University of Buffalo, which is a large neurosurgical center, has published in the past about this technique. What makes what we are proposing particularly novel is we have modifications of the technique itself that is integrated into our standard workflow. So, it is not only for patients where their leg vessels are completely occluded, but it is also for patients where we know it is going to be a difficult to get from the leg up into the head and we know that this is exponentially safer and faster than struggling for an hour or two trying to get there from the groin.
Are there cases where with an aborted procedure you tried the carotid and that did not work?
Dr. Matouk: We had one patient where we aborted the procedure early on. There was a bit of a learning curve to understand how to get the catheters in safely. Those patients would fall into the category of folks that we would have given up going from the groin. Some doctors are now trying from the arm but that has their own issue. But again, it is nice to have options. So, when one way does not work, there are other options.
You mentioned that Yale does this a bit differently than the other centers.
Dr. Matouk: One of the ways that we are different is that we only spend 10 to 15 minutes from the groin before deciding that we are not going to pursue this technique anymore. Then we do a trans-carotid technique which is one of the main differences. The second difference is the integration into our standard workflow. This is not something where we are scrambling to get the right equipment, we have a protocol of when to decide to do it, what equipment to use and the actual technique. So, we puncture in the same place every time and it is something that we have given a lot of thought and consideration to. For example, the carotid artery bifurcates so it divides into two in the middle of your neck and one artery goes up to your face and the other one goes up to your brain. So, we puncture much lower down where it is a larger vessel, and it is like the border of two muscles that attach to your breastbone and your proximal collarbone. That creates a very convenient space where you are going to miss all the nerves and veins through your neck and gives us easy access to the carotid artery. So that is one thing we have introduced as a standard technique when we are doing these types of procedures.
How quickly can you get up to the clot?
Dr. Matouk: From puncturing to accessing the clot, it can be anywhere from five to 15 minutes in a procedure that would have taken more than an hour or two.
Is there anything I did not ask you about this procedure that you would want people to know?
Dr. Matouk: The big thing is we have a procedure that can remove clots from the brain very efficiently. So, the technology is advanced to a point now where 80% to 90% of the time we are going to be able to remove the blood clot from your brain and potentially make a big stroke into a little stroke. We are proposing one more option so that patients that cannot benefit from the mechanical thrombectomy are now eligible for the procedure and that increases the number of folks that will get better after having a stroke.
Could describe for me what vessel wall imaging is?
Dr. Matouk: It is a technique to look at the blood vessels, in particular blood vessels in the brain. The traditional ways that we look at blood vessels is with a CT angiogram, MR angiogram or a diagnostic catheter angiogram, which is an invasive procedure. All these techniques essentially look at the inside of the blood vessel – so the lumen of the blood vessel. What we are really interested in looking at is what is diseased in the wall of the blood vessel. Until about 10 years ago, we were not able to image the wall of a blood vessel in a dedicated way, and that is because the blood vessel wall is very thin and because the blood vessels in the brain take a lot of twists and turns, which makes it difficult for imaging to deal with, especially when you are focusing on the vessel wall. About 10 years ago, two groups came up with protocols on how to image the vessel wall, and one of those groups was Johns Hopkins University led by radiologist Bruce Wassermann and the other group was from the University of Toronto, led by a diagnostic radiologist named David Mickolus. Both wonderful and bright people. They started to look at several different disease processes using vessel wall imaging, and what they were most interested in was atherosclerotic disease which affects your heart, blood vessels in your legs and blood vessels in your brain. I trained there as a neurosurgeon and as an interventional neuroradiologist and was exposed to some of the research going on. When I started at Yale back in November 2011, we adapted that technique and looked at my neurosurgical interest, which was brain aneurysms. No one had looked at brain aneurysms using vessel wall imaging and when we did, we were shocked by some of the results that we saw in the sense that things that looked the same using traditional imaging techniques can look vastly different on vessel wall imaging. The reason that is of interest in the aneurysm community is that aneurysms are quite common. About one in 100 folks walking around have a small brain aneurysm. The risk of a small brain aneurysm bleeding and being catastrophic and even potentially fatal, is exceedingly small. So small aneurysms have a small risk of bleeding whereas bigger aneurysms have a higher risk of bleeding. But there is a paradox and that is when folks come in with ruptured aneurysms, the overwhelming majority are small and small ruptured aneurysms have a low risk of bleeding, but most ruptured aneurysms are small, and so there is a disconnect. So, the question is, can we identify which small aneurysms are most at risk of bleeding, and which are the most unstable? The research that we and others have conducted over the last 10 years have started to build a story that vessel wall enhancement can be taken up by the aneurysm wall in unstable aneurysms whereas stable aneurysms tend not to show that vessel wall enhancement. That concept is really coming into maturity, as many groups now around the country are studying it. Good examples are the University of California at San Francisco, Johns Hopkins, University of Toronto, University of Iowa and there is a group in Paris that have really pushed this storyline.
How would it work?
Dr. Matouk: You come into the hospital and we would use your clinical grade and the usual magnetic resonance imaging of your brain. There are two MRIs that are in clinical use. One is called a 1.5 Tesla magnet, which is a low-strength magnet, and the other is a three Tesla magnet. It must be done on a three T magnet because you need a stronger magnet to help resolve that very thin wall, but it is the same magnet that is available at most hospitals across the U.S. The nice thing about this technique is it can be universally available to any hospital that has a three T magnet, which is the majority in the U.S.
Would patients have something injected prior to going in?
Dr. Matouk: You would get an IV placed. Before the scan is conducted you get an image without anything being injected, and then you get dye injected into your hand. The dye can be seen on the MRI scan and then you are rescanned. This all happens when you are in the magnet itself. So, you do not have to a different room or anything. But again, this is a standard technique that is done for all different kinds of brain pathology. But the physics that MR sequence employs is really geared to looking at the vessel wall, and then you can detect the enhancement. So, the dye that has been injected in an IV in your hand will get picked up in the wall of this very tiny two or three-millimeter aneurysm in your brain.
When you are looking at the image, is it evident?
Dr. Matouk: It looks like a light bulb. When you look at an MRI scan it is black and some shades of grey and then it will look like a little bright white sort of glowing rim, almost like a halo around the aneurysm. It is very conspicuous and very evident to the naked eye.
So, the ones that light up tell you what?
Dr. Matouk: We think it has something to do with inflammation, but we do not know for sure yet. What we do know is if you have evidence of bleeding in your brain and have multiple aneurysms and you do not know which aneurysm bled, it turns out that this technique is extremely useful in figuring that out because the aneurysm that bled almost always enhances and glows like a light bulb. That is extremely helpful in the clinical context because you are going to target the right aneurysm to treat. In the case of enraptured aneurysms, it is very unusual for a small and ruptured aneurysm in the brain to bleed but also to enhance. Only a ridiculously small fraction of these enhance. We have looked at thousands of aneurysms all over the world so that phenotype is unusual. There are studies ongoing and studies that have been published that have shown that it is more likely to have an enhancing aneurysm if you come into the emergency department with a very severe headache but there is no evidence of blood, which is interesting because that probably means that the aneurysm is acting up. When we look over time at enhancing versus unenhancing aneurysms, enhancing aneurysms are more likely to grow. When we look at the shape of aneurysms enhancing aneurysms are more likely to be bumpy as opposed to smooth, which the field has always thought has been a high-risk feature of aneurysms, potentially making them have higher risk of rupture.
What is the implication for having the tool?
Dr. Matouk: The treatments for aneurysms, unfortunately, are not benign. Whenever you are in someone’s brain, whether it is through the blood vessels or by opening the skull bad things can happen. So, you do not want to put people in harm’s way during a procedure if the risk of the aneurysm bleeding is low. So, the implication is if we do not see enhancement and the aneurysm is small and most small aneurysms do not bleed, then maybe they can be safely watched. Whereas if you have a small aneurysm but it enhances, that at least informs us that maybe this is one of the rare small aneurysms that has a higher risk of acting up and we already know from some studies that they have a higher risk of growing over time, and they might even have a higher risk of rupture. So, this is information that can help color the conversation with your surgeon about whether the risk of a procedure is warranted.
Interview conducted by Ivanhoe Broadcast News.
END OF INTERVIEW
This information is intended for additional research purposes only. It is not to be used as a prescription or advice from Ivanhoe Broadcast News, Inc. or any medical professional interviewed. Ivanhoe Broadcast News, Inc. assumes no responsibility for the depth or accuracy of physician statements. Procedures or medicines apply to different people and medical factors; always consult your physician on medical matters.
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