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Most Heart Stents Are Placed Imperfectly, Increasing Risk of Heart Attack or Reclosure
S.T.L.L.R. Study Calls for Better Understanding and
Better Technique for Stent Placement

May 30, 2007 -- Could it be that two-thirds of the stents implanted in patients' coronary arteries are not properly placed? Dr. Marco A. Costa of the University of Florida College of Medicine in Jacksonville told Angioplasty.Org:

"It's unbelievable, but it's the reality. Those are the data. Those are the facts.... Based on the criteria that were defined in the S.T.L.L.R. trial, two-thirds of the stents that are placed nowadays are not properly deployed."

Dr. Costa is lead investigator for the S.T.L.L.R. clinical trial, the complete name of which is "The Impact of Stent Deployment Techniques on Clinical Outcomes of Patients Treated With the CYPHER® Stent". In this prospective double-blinded study of almost 1,500 patients, treated with the Johnson & Johnson / Cordis drug-eluting CYPHER stent, the correct placement of the stent was measured and the patients followed up for one year. What were the results for those stents imperfectly placed? States Dr. Costa:

"Three times the increased chance of heart attack. And twice the chance of repeat procedures."

The results of this study, which was funded by stent manufacturer Cordis, are striking. The study is currently undergoing peer review by a major cardiology journal, but the findings were first discussed at last fall's TCT 2006 meeting and were also reported by Avery Johnson and Ron Winslow in yesterday's Wall Street Journal ("Scrutiny of Stent Problems Turns to Doctors"). The article, and accompanying "Health Blog" entry, state that, while the focus has been on the stent devices as a possible cause of late stent thrombosis (blood clots occurring many months or years after implantation) attention may now be shifting to "overconfidence" on the part of interventional cardiologists that has led to "sloppy" and "poor technique".

Dr. Costa disagrees with this characterization and told Angioplasty.Org:

"I didn't say that. That was not my opinion at all. What I said was that we need to learn from S.T.L.L.R. and need to learn more judicious technique. We, as operators, need to pay attention to the S.T.L.L.R. results, understand those results...because we can avoid many of the mistakes. However we need improvement in the device side, we need better devices so we can do our job easier. We need better definition on who is at risk, so we need to learn about the anatomical factors of the patients. And I think we need improvement in our imaging aspect. I think IVUS (intravascular ultrasound) is a great technology that can help us to get it better."

He continued that there had never been a study like S.T.L.L.R. before, showing that this suboptimal placement (or "geographic miss") was so widespread, so this information was not really known.

Stents are tiny metal mesh sleeves that are inserted into blocked areas of the artery and expanded against the artery wall by inflating a balloon. The balloon is then withdrawn, leaving the expanded stent to keep the artery open and the blood flowing. Over a couple of months, cells cover the metallic stent, incorporating it into the arterial wall. The study identified two ways in which stents were not optimally placed. In some cases the stent did not completely cover the diseased surface of the artery -- allowing those areas to build up tissue and "reclose" more often.

However, in an equal number of cases, the problem was that the stent was not fully expanded, leaving a small "pocket" or space between the stent and the wall of the artery. This is a complex issue, because cardiologists don't want to overexpand the stent, for fear of tearing the arterial wall, which is a serious complication.

Another difficulty for the cardiologist is that angiography, the imaging method used in all angioplasties, does not tell the physician the entire story. Many doctors, including Dr. Costa, feel that the addition of intravascular ultrasound (IVUS) imaging can fill that need. One of the pioneers of stenting, Dr. Antonio Colombo of Milan, told Angioplasty.Org, that he now uses intravascular ultrasound in all of his stent cases:

"Because I can verify an optimal implantation with good expansion of the stent which matches the appropriate size of the vessel and the presence of disease in the wall of the vessel. Angiography is not the best tool to evaluate appropriate stent dilatation. Angiography gives incomplete information because we only know the lumen size, but we don’t know exactly the vessel size. And we can’t assess if the stent is adequately dilated and well-apposed to the media; we only know if the stent is apposed to the plaque."

The media is the true arterial wall, and defines the boundary of the vessel. But angiography, which uses X-rays and dye to get a shadow profile image of the artery, only reveals the actual opening, or lumen, which in a diseased or blocked artery may be significantly smaller than the true vessel. By being cautious and only expanding the stent to what can be seen under angiography, the cardiologist may unwittingly be making a "geographic miss" and under-deploying the stent. The implications of an underdeployed stent can be serious, as Dr. Colombo explains:

"Then you have a stent which is in a less optimal contact with the vessel wall. You have more turbulence. You have struts that are not perfectly attached or embedded in the plaque, and you may have more foreign body protruding into the lumen, increasing the risk of restenosis and thrombosis."

Dr. Colombo continued that using IVUS is critical, because after you expand the stent, you can very quickly check how well the stent is placed in relation to the artery wall and, if it is underexpanded, you can go back in with a larger balloon and expand the stent to a more perfect fit. Without this additional imaging tool, it would be difficult to judge.

While IVUS has been around for more than a decade, its use has suddenly increased in the past year -- most likely in reaction to the concerns about stent placement and its association with thrombosis. The two IVUS manufacturers, Volcano Corporation and Boston Scientific, report increased sales and, as Dr. William O'Neill of the University of Miami's Miller School of Medicine told the Wall Street Journal:

...patients who are candidates for stent procedures might ask their doctors how often they use the [IVUS] imaging technology. "If they say 'never,' shy away from them," he says. "Ultrasound is a surrogate for quality."

Read more about IVUS in Angioplasty.Org's special Intravascular Ultrasound Center, including our exclusive interview with Dr. Antonio Colombo.