Optical coherence tomography monitors coronary stenting

There is a limit to what conventional imaging can do during coronary artery stenting, especially in assessing microscopic vessel structures. Optical coherence tomography (OCT) might step in to alleviate this deficit, according to U.S. and Japanese researchers.

The multicenter, multidisciplinary team compared OCT with intravascular ultrasound in 39 patients undergoing coronary artery stenting. They found that OCT outperformed intravascular ultrasound for most parameters being assessed. Results of the study were published in the March issue of Heart.

For 42 stents imaged by both modalities, researchers found that:

? OCT identified vessel dissection in eight stents, while ultrasound identified it in two.
? OCT identified tissue prolapse in 29 stents; ultrasound identified it in 12.
? Prolapse extent was 242 micrometers (standard deviation 156 micrometers) for OCT and 400 micrometers (SD 100 micrometers) for ultrasound.
? Incomplete stent apposition was observed in seven stents by OCT and three by ultrasound.
? Irregular strut separation was identified in 18 stents by both OCT and ultrasound.

Neither angiography nor intravascular ultrasound can evaluate dissection, tissue prolapse, and stent apposition on a size scale under 100 micrometers. But OCT not only provided much higher resolution than ultrasound, it also allowed for a detailed visualization of structural changes occurring during coronary stenting, said coauthor Dr. Ik-Kyung Jang, an associate professor of medicine at Massachusetts General Hospital.

OCT, however, is far from perfect. Physicians encountered significant problems with visualization through blood and penetration depth. It is still too early to predict the modality's overall clinical value and cost-effectiveness in this area, Jang said.

The technique, however, could have important implications for interventional radiologists, cardiologists, and other clinicians. The proximity to the vessel wall could be key for drug-coated stents' effectiveness. If this is the case, guidance will be important, particularly if the imaging system could be integrated into a guidewire, said Dr. Mark Brezinski, an associate professor of medicine at Harvard Medical School.

Although it was not the focus of the study, the technology shows considerable promise for the assessment of plaque, said Brezinski, who also conducts research on other clinical applications for OCT.

The study did not address further comparisons between OCT and other modalities, such as multidetector-row CT and MR. This trial, however, confirms OCT's superior resolution over intravascular ultrasound in vivo, which had been demonstrated only in vitro, Brezinski said.