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Photonics reveals cardiac threat

01 Dec 2006

Data from a near-infrared spectroscopy system could help to identify patients who are at greatest risk of a heart attack.

Most heart attacks occur when plaque deposits on the walls of coronary arteries break away and block vital blood flow to the heart's muscle. But not all arterial plaques behave in this way, so the furring up of coronary vessels does not necessarily indicate an imminent coronary event.

Evidence is mounting that plaques containing a high proportion of lipids are most likely to split from the vessel wall, but current diagnostic techniques are unable to distinguish lipid-rich from lipid-poor plaques. Enter InfraReDx, an early-stage medical-device company based in Burlington, Massachusetts, that has developed a near-infrared spectroscopic system for evaluating the make-up of coronary plaques.

InfraReDx's system includes a laser light source that is delivered into a patient's coronary artery through a fiber-optic catheter. Once the device is in place, light in the NIR region is directed at the vessel wall. The system then collects differential absorption data from reflected NIR light as the laser rotates through 360°.

This information is used to determine the molecular composition of any plaque deposits that may be present. An automated pull-back mechanism allows the source to scan the entire length of the artery, collating similar spectral data on all identifiable lesions.

The technique, known as NIR diffuse spectroscopy, is used commonly in fields such as drug development to evaluate the chemical make-up of unknown substances. But it has never before been applied to arterial plaques, according to Jay Kaplan, vice-president for R&D with InfraReDx. "There are other people trying to do the same thing we are doing - identification of the chemical composition of the vessel wall - but they are pursuing other technologies," he told medicalphysicsweb. Potential rival strategies for predicting plaque vulnerability include intravascular ultrasound elastography and intravascular MRI.

InfraReDx is pitching its technology for use in patients scheduled for coronary catheterization because of chest pain or an initial heart attack. "We are not looking at preventing the first set of symptoms that brings individuals into the cardiac cath lab but at preventing a secondary event," said Bob Imhof, InfraReDx vice-president for sales and marketing.

InfraReDx has completed the first step towards the commercialization of its device, having secured 510(k) clearance from the US Food and Drug Administration. The privately held company, founded in 1998, has also just closed a $22.3 m round of funding.

The NIR spectroscopy system is now being put through its paces in a multicentre trial of approximately 100 patients. Results from the trial, which are required for the company's next FDA submission, are due in spring 2007.

"We are also in the process of finalizing the design of the commercial product," Kaplan said. "We expect to be selling that in the middle of next year."

Iridian Spectral TechnologiesCeNing Optics Co LtdLaCroix Precision OpticsMad City Labs, Inc.TRIOPTICS GmbHBerkeley Nucleonics CorporationCHROMA TECHNOLOGY CORP.
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