New Thoughts on Coronary Artery Stenting
The Wall Street Journal is reporting (July 20, 2007) that the implantation of drug eluting stents has decreased significantly; fewer of the devices were placed in June of this year than in any other month in the last year.
It has been reported since November 2006 that the drug releasing stents have an increased risk of developing blood clots for as long as three years after implantation, especially in certain higher-risk individuals. Ironically the drug-coated stents were made for the very purpose of preventing clot formation within stents, a problem noted with the first devices. When a stent is implanted in an artery the body attaches it to the arterial wall by putting down a layer of new cells, forming a seal that holds the stent in place. Unfortunately the body can go overboard, and in treating the stent like a foreign object, it can form scar tissue and inflammation. This can lead to clotting within the stent, resulting in a recurrence of the problem it was designed to prevent-lack of blood flow through the artery. The drug-coated stents slowly release medication that is designed to prevent scar formation, but they don't always work as designed.
The drug-coated stents were originally tested in a group of individuals with basic, stable coronary artery disease; they were individuals with small blockages in one or two arteries, who did not have other complications to their disease, such as uncontrolled diabetes or hypertension. This was done specifically to control for factors that might make the stents fail such as the body's tendency toward inflammation that is inherent in type 2 diabetes. Gradually interventional cardiologists began placing the drug eluting stents in individuals for whom the stents had not actually been cleared, such as individuals with diabetes or those in acute coronary syndrome (ACS), who were actively having chest pains. Individuals in ACS have dynamic clotting and inflammation going on, placing them at higher risk of clot formation. Analysis of data from post marketing use have indicated that both these higher-risk individuals and others who would not seem to have an obvious risk for clotting are getting clots in their stents, some as long as 3 years after they are placed.
Deepak L. Bhatt, MD, associate director of The Cleveland Clinic's heart center reported to Web MD on his analysis of the clinical studies of the drug releasing stents that those individuals who have them have a 0.5% risk of developing serious blood clots than those who have the bare metal stents implanted. "The absolute risk to an individual patient is less than one in 200," Bhatt says. But "with a million stents going in each year in the U.S. and twice that number worldwide, this is not trivial."
This reanalysis of the data has caused physicians to rethink all stent use, and to seriously consider whether or not a plain, bare-metal stent will be more appropriate than the drug-coated stents in a given individual. In March the New England Journal of Medicine reported on a study that showed that for patients with mild chest pains it might be more appropriate to delay stenting in favor of treatment with medications. Should those medications fail to control chest pain then those individuals could be scheduled for stenting. If stenting is required, cardiologists are recommending that a conscious decision be made between the use of a bare metal versus a drug-coated stent. This represents a major shift in the approach to managing cardiac chest pain, and is good news for the companies who manufacture the plain, bare-metal stents. These devices had essentially been overlooked in favor of the newer drug coated devices when they arrived on the market.
Researchers don't know for certain what all of the risks factors are that may increase individuals' chances of developing a clot in a stent, but a few factors are known. Individuals with diabetes, those with acute coronary syndrome, and those who would not be able to take medications to prevent clotting for more than a year might be better candidates for the bare metal devices. Individuals in the latter group would include those who are at increased risk bleeding on blood thinners, such as the elderly, those with liver disease, and those with a history of bleeding disorders and health problems such as a stomach ulcer or diverticulitis.
Doctors point out that if you have a drug releasing stent it is important to discuss with your provider your risks of clot formation, and to question whether or not you should remain on blood thinners for longer than the typical year that was originally indicated for stent placement. If you are going to have a stenting procedure done, ask the cardiologist to explain their choice of stent type, and be certain that the risk of one type or the other is chosen with your situation in mind.
The process of medical device (and medication) development occurs over many evolutions. Each time the researcher looks at problems with the current device and tries to overcome them. The original stents helped to prevent the recurrence of coronary artery blockages. The next generation of stents that released medications to prevent clot formation within the stents for some individuals, but not others. Like all clinical situations, we learned this information only after they began to be widely implanted, sometimes in individuals for whom this device had not been specifically cleared for use.
Fortunately it appears that several generations of new stents are on the horizon; one version has a drug coating that dissolves and disappears when it is no longer helpful and may be coming to the harmful point that we are now seeing. Another stent is placed but dissolves completely over time. For physicians and patients dealing with coronary heart disease, these developments are eagerly awaited.
Take care,
Laurie
The important thing in science is not so much to obtain new facts as to discover new ways of thinking about them.
Sir William Bragg (1862 - 1942)
Related Topics:
It has been reported since November 2006 that the drug releasing stents have an increased risk of developing blood clots for as long as three years after implantation, especially in certain higher-risk individuals. Ironically the drug-coated stents were made for the very purpose of preventing clot formation within stents, a problem noted with the first devices. When a stent is implanted in an artery the body attaches it to the arterial wall by putting down a layer of new cells, forming a seal that holds the stent in place. Unfortunately the body can go overboard, and in treating the stent like a foreign object, it can form scar tissue and inflammation. This can lead to clotting within the stent, resulting in a recurrence of the problem it was designed to prevent-lack of blood flow through the artery. The drug-coated stents slowly release medication that is designed to prevent scar formation, but they don't always work as designed.
The drug-coated stents were originally tested in a group of individuals with basic, stable coronary artery disease; they were individuals with small blockages in one or two arteries, who did not have other complications to their disease, such as uncontrolled diabetes or hypertension. This was done specifically to control for factors that might make the stents fail such as the body's tendency toward inflammation that is inherent in type 2 diabetes. Gradually interventional cardiologists began placing the drug eluting stents in individuals for whom the stents had not actually been cleared, such as individuals with diabetes or those in acute coronary syndrome (ACS), who were actively having chest pains. Individuals in ACS have dynamic clotting and inflammation going on, placing them at higher risk of clot formation. Analysis of data from post marketing use have indicated that both these higher-risk individuals and others who would not seem to have an obvious risk for clotting are getting clots in their stents, some as long as 3 years after they are placed.
Deepak L. Bhatt, MD, associate director of The Cleveland Clinic's heart center reported to Web MD on his analysis of the clinical studies of the drug releasing stents that those individuals who have them have a 0.5% risk of developing serious blood clots than those who have the bare metal stents implanted. "The absolute risk to an individual patient is less than one in 200," Bhatt says. But "with a million stents going in each year in the U.S. and twice that number worldwide, this is not trivial."
This reanalysis of the data has caused physicians to rethink all stent use, and to seriously consider whether or not a plain, bare-metal stent will be more appropriate than the drug-coated stents in a given individual. In March the New England Journal of Medicine reported on a study that showed that for patients with mild chest pains it might be more appropriate to delay stenting in favor of treatment with medications. Should those medications fail to control chest pain then those individuals could be scheduled for stenting. If stenting is required, cardiologists are recommending that a conscious decision be made between the use of a bare metal versus a drug-coated stent. This represents a major shift in the approach to managing cardiac chest pain, and is good news for the companies who manufacture the plain, bare-metal stents. These devices had essentially been overlooked in favor of the newer drug coated devices when they arrived on the market.
Researchers don't know for certain what all of the risks factors are that may increase individuals' chances of developing a clot in a stent, but a few factors are known. Individuals with diabetes, those with acute coronary syndrome, and those who would not be able to take medications to prevent clotting for more than a year might be better candidates for the bare metal devices. Individuals in the latter group would include those who are at increased risk bleeding on blood thinners, such as the elderly, those with liver disease, and those with a history of bleeding disorders and health problems such as a stomach ulcer or diverticulitis.
Doctors point out that if you have a drug releasing stent it is important to discuss with your provider your risks of clot formation, and to question whether or not you should remain on blood thinners for longer than the typical year that was originally indicated for stent placement. If you are going to have a stenting procedure done, ask the cardiologist to explain their choice of stent type, and be certain that the risk of one type or the other is chosen with your situation in mind.
The process of medical device (and medication) development occurs over many evolutions. Each time the researcher looks at problems with the current device and tries to overcome them. The original stents helped to prevent the recurrence of coronary artery blockages. The next generation of stents that released medications to prevent clot formation within the stents for some individuals, but not others. Like all clinical situations, we learned this information only after they began to be widely implanted, sometimes in individuals for whom this device had not been specifically cleared for use.
Fortunately it appears that several generations of new stents are on the horizon; one version has a drug coating that dissolves and disappears when it is no longer helpful and may be coming to the harmful point that we are now seeing. Another stent is placed but dissolves completely over time. For physicians and patients dealing with coronary heart disease, these developments are eagerly awaited.
Take care,
Laurie
The important thing in science is not so much to obtain new facts as to discover new ways of thinking about them.
Sir William Bragg (1862 - 1942)
Related Topics:
- WebMD Video: Heart Angioplasty and Bypass - Combining Procedures
- WebMD Video: Stent Treatment for Stroke Patients
3 Comments:
My husband had his first heart attack in Jan. 2006 and had 5 stents placed in arteries...
He has since had 10 heart attacks and had open heart in May 2007.
He had the surgery at a medical center out of town and I had the opportunity to talk in detail with the surgeon and he did feel clots forming around the stents caused some of his heart attacks.
Sadly he suffered another heart attack last week and now has 5 stents.
The surgeons opinion that scar tissue formation made it necessary to put in the stents to stop another clot from forming behind the scar tissue...
It is kind of stuck between a rock and a hard place to know you have stents to help with scar tissue and the stents may in fact cause clots!!!!!!
In case a stent gets partially clogged due to formation of a clot inside, why this cannot be cleared with a needle via the angiographic procedure? Just as one cleans a barrel of the gun. What about coating stents with snake (viper) venom, if that dissolves the clot? R.C. YashRoy, Ph.D.
I had 4 drug alluding stents put in my Left Coronary Artery (LCD) in January of 2007. Last week (March, 2008) my cardiologist discovered that one of the four stents was 95% blocked with scar tissue formation and decided to do a triple bypass surgery. After that successful surgery I am reuperating at home now. I wonder how long this graft (CABG) will last??!!
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