0diggsdiggDrano For Clogged Arteries -- In Depth Doctor's Interview
Dr. Bradley Strauss, chief of the Schulich Heart Centre at Sunnybrook Health Sciences Centre in Toronto, Ontario, Canada, tells us about a new way to clear blocked arteries.
We’re talking about an occluded artery called a CTO.
Dr. Bradley Strauss: I think you have to distinguish between an acute abrupt occlusion of an artery, which is typical of a heart attack type, from a chronic total occlusion, which is an artery that has been completely blocked for about six weeks. The presentation is much different than in an acute heart attack and it’s much different to treat. Heart attack tends to be rush to the cath lab to give special drugs to open them, whereas, the chronically occluded artery typically presents with angina or with chest pain, or shortness of breath in exertion. The patient presents to the doctor, gets worked up for it, and at the time of the angiogram the artery is completely blocked, but hasn’t blocked in the way that would cause an acute heart attack.
Can you tell us what the difference is in terms of the blockage?
Dr. Bradley Strauss: In terms of what’s inside the blockage is that an acute heart attack tends to involve a lot of clots and thrombus material whereas an artery that has been blocked for several weeks, and especially several months, becomes a much different type of composition. It becomes much harder material. It contains a lot of material known as collagen. It contains calcium and it contains very little of any clot materials. So, it’s much different to treat and it doesn’t respond to the sort of clot busters that one uses when you are treating a heart attack. It has to be treated in a different way.
Because it a harder material?
Dr. Bradley Strauss: It’s a harder material and it doesn’t have the clot in there that is really the substrate for the clot drugs.
What are the options for treatment now?
Dr. Bradley Strauss: Well, the majority of the patients with chronic total occlusions are treated with medications, angina medications. Some who have a very significant symptoms may undergo bypass surgery, which is one option, and in a selected number of patients we attempt to do coronary osteoplasty on those patients to see if we can open it up with a balloon and then a stent.
If you can’t open it up, what are your options? What do you do for patients that just are not responding?
Dr. Bradley Strauss: First, you have to decide: does the patient need the procedure? And for that, at the present time, indication is some sort of chest pain, angina or shortness of breath, presumably with a positive stress test and then, on an angiogram, you find a blockage. And you have to determine if the other arteries are blocked or not, how old the occlusion is because the older the occlusion is the more difficult it is to cross, and there are certain features when we look at an angiogram that predict the ability to cross it. They’re very common, about 25 to 30% of angiograms have a chronic total occlusion in the angiogram, but only a certain percentage need to be treated. And the part that really dictates it is your ability to sense whether or not you can get through the occlusion with angioplasty. Most of them are not even attempted by angioplasty because the results, to date anyway, have been less than optimal and they are long procedures. They take a lot of contrast and, about 50% of the time, are not successful in opening them and those are the ones that we try. There is even a larger group of them that we don’t even try because we don’t think we’ll get through them.
Is this a case where you can take a wait and see approach, or is there a danger to the patient if you don’t get to it?
Dr. Bradley Strauss: Generally speaking, you don’t have to rush into this decision. You have time to think about it, carefully assess the patient’s symptoms, which I think is a very important part of your selection of patients to treat. And then, if you decide that it is significant enough, and you want to go ahead then you can plan it electively. It is a long procedure. It can take up to a couple of hours, so it uses up a considerable amount of resources in terms of cath lab time, and that’s why many operators are not very enthusiastic about doing it and success rates are much lower than cases where they are not totally occluded.
Is the patient better off not having the arteries opened up as opposed to going to the next step, which is the bypass?
Dr. Bradley Strauss: If you feel that the symptoms are really related to this particular blockage, then in my experience those that you are able to open are the most grateful patients of all, because it can make a considerable improvement in their lifestyle and their ability to do more and have a much more active life. There is some evidence that it may improve left ventricular contractility, or the ability of the heart to pump better. At the present time, we really don’t have the data to suggesting that people will live longer if we open these chronic occluded arteries and that would, of course, depend on the status of the other arteries as well. So, the major indication for doing it now is really symptom benefit and my experience is that patients do tremendous benefits in terms of their ability to live a more satisfying life.
Can you tell me a little bit more about that? You’re talking about quality of life. Is it immediate?
Dr. Bradley Strauss: Yes, in fact some of them say they are breathing better that evening. It can be a very, very satisfying procedure when you’re successful. It can also be extremely frustrating when you’re not, because you can spend a long time and not be successful, not only for yourself, but for the patient. It’s extremely disappointing for them. So, the decision to try it is an important one and when to stop is an important one, and we definitely need better therapies to try and improve ways to open them with angioplasty. If you have multiple arteries blocked and one of them is a totally blocked artery, that often pushes the decision for bypass surgery. But, if we had ways to treat these patients without having to send them to bypass, if we could get through those totally blocked arteries, then it would open up a lot of cases that we are currently sending for bypass because of the occlusion of these chronically total occluded arteries that are difficult to treat.
Tell me what you’re working on.
Dr. Bradley Strauss: What I’ve developed over the last several years is an enzyme-based therapy. My patients frequently ask me ‘why don’t you come up with some material like Drano to try and soften it?’ There’s a lot of wisdom in that comment and I’ve always liked it and so I’ve been working on a type of chemical "Drano" to soften the plaque, to soften the collagen that’s inside the plaque, so then it’s easier to cross with our conventional type of guide wires and equipment. Based on a number of preclinical studies that I’ve done over the years, I now have come up with the therapy that I am about to embark in a human clinical trial that will see whether or not infusion of this enzyme into the coronary arteries will allow me to cross them easier and more frequently with guide-wires so we can do angioplasty.
Tell me a little bit about how the procedure would work? You mention an infusion of this enzyme, how would you get the biological agent into the artery?
Dr. Bradley Strauss: It’s done in a similar fashion to any angioplasty. All the patients will have had to have failed one attempt previously in order to be in the trial. We advance the catheters and the tubes right up to the occlusion. We are going to have a special kind of balloon that has a little tube in the middle of it that we will use to inject the drug through there and we will have the balloon inflated within the catheter so that none of it can leak out. And when we have the balloon up against where the occlusion is, we’re going to infuse the drug and that will take just a minute or so to put it in the space. Then we are going to leave it there for about 40 minutes, allow it to seep into the occlusion, make its way through the occlusion, and then after about 45 minutes we will remove all the equipment. It takes several hours for this to work. In our initial work it looks like it may be an overnight period of time to allow enough time to really soften the plaque, and that will be the basis for our first clinical trial. The patient will go back to the ward, all the equipment will be out of the coronary arteries. We will bring back the patient the next day and then attempt to cross it in the conventional way of doing it.
What are the risks to the patients when you are talking about putting a biological agent in the arteries?
Dr. Bradley Strauss: This enzyme actually comes from a bacteria called clostridium histolyticum. Initially, it’s very interesting that in the first treatment of heart attack we’re using an enzyme from another type of bacteria and that enzyme is known as streptokinase. It has a different substrate; it works on a different material than the collagenase that we are working with, but it’s not the first time that doctors have been using material that comes from bacteria for therapeutic purposes. We don’t think there are going to be problems with allergy because, in general, the patients have not been exposed to this particular enzyme, or any materials from this bacteria, and we will carefully monitor the patients to make sure there is no damage at all effecting the normal tissue because not only does it soften where the plaque is from the occlusion, but, if it was at high enough concentrations, it could weaken some of the wall behind it. We have been very careful based on our pre-clinical studies to limit that and we will carefully monitor the patients to make sure that that’s not the case. It has been used in other clinical situations. There is a problem of thickened tendons in the hand. It’s called Dupuytren’s Contracture. People have injected it into these tendons to see if they can soften the collagen there, and that is at much higher doses than we are going to be using in the coronary arteries. It’s been very well tolerated. And a few other conditions, some orthopedic conditions where it’s been used, so it’s not the first time ever it’s been used in patients. But, will be the first time it will ever be used in coronary arteries.
After the process of the enzyme sitting overnight and being absorbed, tell me what the next step is.
Dr. Bradley Strauss: We bring the patient back the next day and we will just use the conventional approach to angioplasty. We put the catheters into the artery. We take guide-wires, that we are very familiar with, and we use everyday practice, and we are going to attempt to cross the chronic total occlusion and, once we get across, it we will be able to open it up with a balloon, and place the stent. We’ll invite all the patients back in 3 months to do a coronary CT angiogram to make sure that the heart does not have any late effects of the enzyme. We don’t expect it, but for safety purposes that’s what we are going to do. The first trial is really a feasibility and safety trial. We are going to be increasing the dose with each cohort of patients. There will be five patients in a group and, as each group finishes with a good safety record, then we’ll go on to the higher dose. I expect that the dose that will be most efficacious in terms of helping us to cross these occlusions will not be reached until we get to the higher doses of the trial, which will be the third and fourth group that we’re testing.
How many people does this affect? Do you have an estimate of how many times you attempt the traditional way of opening arteries and just can’t do it?
Dr. Bradley Strauss: Well, you just calculate it. I think that there are about 1/3 of cases that have the angiogram can have an occlusion. About 40 to 50% of them would actually have symptoms that could be related to that occlusion, and that’s a very sizable number of patients. You’re talking about 10 or 15% of all the patients who come for a coronary angiogram. So, that’s the denominator that we’re looking at. If it has very good results, I could see it helping one hundred to two hundred thousand patients a year here in the United States. It could have very important ramifications in terms of our therapies.
In terms of patient benefit what’s the recovery time for something like this?
Dr. Bradley Strauss: Well, we expect the patient to go home the next day. In the United States right now, I think, there are about one million cases of coronary angioplasty done every year. About 10% or so, maybe a little bit less, 8% are done for chronic total occlusions, so it’s a relatively small percentage of them. And I expect that at least double that could benefit if we have a therapy, and presumably it could be a much larger group of the patients that go for a coronary bypass surgery that could benefit from this as well. They go home the next day and they resume their lifestyle within the next couple of days. I think it will be a very immediate effect, and hopefully have a very positive effect on their overall life happiness and satisfaction.
And just a point of clarification for viewers: if the occlusions are left long enough is that a possible leading indicator for a heart attack?
Dr. Bradley Strauss: These arteries have already totally occluded, so they’re not going to get any more blocked than they are. And, as I mentioned before, the older the occlusions are, they are much more technically challenging to unblock them. We think, and it hasn’t yet been proven, that the problem may be that as they develop blockages in other arteries having an additional artery blocked will not have an impact on their survival. There is evidence that patients who have chronic total occlusions do worse than those who do not. And, that’s probably based on the fact that they have more disease in their arteries, and don’t tolerate future problems with the heart as well because they are already have a condition presenting some difficulty.
Is there anything I didn’t ask you that you think people need to be aware of?
Dr. Bradley Strauss: I think you have to be extremely careful in terms of patient selection. Not every patient is a candidate. Just because you have a chronic total occlusion does not mean that you need something done for it. I think that the decision, at the present time, is based almost entirely on symptoms. The conventional way of treating these with guide-wires and balloons, etc., is still going to be successful in some cases and in these more complex procedures, we are looking for those that are not successful at the first attempt. Hopefully, it will make it a much more efficient procedure so that you’ll be able to do it faster and that’s where I think it may even apply to ones that we’re successful with. Now, if you can speed it up, and have the patient treated in a much quicker way with higher results, that will work well.
Who could best benefit from this?
Dr. Bradley Strauss: The patients that will best benefit are those who have really significant symptoms in terms of limiting their lifestyle and have an artery in which we can deliver the collagenase directly before. The other point I should make is that I’m only talking about the coronaries, but there is an equal number of patients who are limited by these chronic total occlusions in the arteries in their legs as well. And, at some point in the future, I think that’s another huge area of disease burden that we will address with this therapy, but we are starting first with the coronaries.
Same therapy, same enzyme, just different place?
Dr. Bradley Strauss: Right.
And, the ideal candidate again, you said some with chronic total occlusion would not be candidates?
Dr. Bradley Strauss: Well, in the first part we are limiting it to patients whose occlusions are two years of age or less. We want to have a more homogenous group to start with, and they have to have significant symptoms, and they have one previous attempt that has failed. And then there are specific lesion criteria that we will carefully review to make sure they fit the type of therapy we will want to use.
END OF INTERVIEW
Drano For Clogged Arteries -- In Depth Doctor's Interview | Medical News and Health Information
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.
If you would like more information, please contact:
Laurie Legere, Communications Advisor
Sunnybrook Health Sciences Centre
Toronto, Ontario, Canada
(416) 480-6100 ext. 7351
Laurie.Legere@sunnybrook.ca
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Drano For Clogged Arteries | Medical News and Health Information
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