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New imaging technique could improve outcome of popular heart procedure

Baltimore, MD (April 25, 2001) – Researchers at Harvard Medical School may have found a way to give patients, like Vice President Dick Cheney, peace of mind after undergoing stent angioplasty to open up a coronary artery partially blocked with plaque. Cheney underwent this procedure last December after having chest pains, and he had a follow up procedure this March when the stent became re-blocked, a problem known as restenosis. At a presentation May 8th at the annual meeting of Conference on Lasers and Electro Optics (CLEO) in Baltimore, Maryland, Dr. Brett Bouma and his colleagues will present research on a technique called optical coherence tomography (OCT), a technique that can be used on patients following a stent angioplasty procedure to monitor the stent deployment and how well the stent is keeping the artery open.

Stent angioplasty is one of the most popular ways doctors treat the life threatening condition called atherosclerosis, where coronary arteries become blocked with plaque. The procedure, which is performed on nearly 500,000 patients each year, uses a small metal mesh tube (stent) to reinforce an artery re-opened with balloon angioplasty. However, following the procedure, 20–30% of patients like Vice President Cheney, experience restenosis, or re-blockage in or around the stent. Until now, there has been little ability during, or following the procedure, to accurately monitor how the stents were deploying and working. "It is currently thought that stents with inadequate deployment are susceptible to restenosis," says Dr. Bouma. In addition, "over deployment, causing trauma to the vessel, is also a potential problem associated with restenosis."

Intravascular ultrasound (IVUS) is currently used in interventional cardiology to monitor stents, but because of the number of reflections of acoustic waves off the metal stent the technique doesn’t have high enough resolution to precisely determine if the stent deployed correctly, or if it has become partially re-blocked. Dr. Bouma says optical coherence tomography (OCT), which combines research in medicine, optics, and physics, operates much like ultrasound but uses infrared light rather than acoustic waves. He adds that OCT does a better job of imaging the stent because there is none of the reflected interference that’s a problem for IVUS. "Accurately monitoring stent deployment would allow for adequate stent dilation without injury," says Dr. Bouma, "this would potentially reduce restenosis rates."

In a study of 10 patients with 11 stents Dr. Bouma says the OCT technique was able to pick up some degree of plaque re-deposits in and around all 11 stents, with six having more significant plaque involvement. In contrast, the IVUS technique detected plaque re-deposit in only one stent. Dr. Bouma says that while this research is still in the early stages, "this is exciting technology that could change the way stents are deployed and the way patients are treated after stenting."

Conference on Lasers and Electro-Optics, Quantum Electronics and Laser Science Conference (CLEO/QELS) Baltimore Convention Center
May 6-10, 2001
www.osa.org/mtg_conf/CLEO/

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