Infraredx imaging spots patients vulnerable to cardiac events

27 Sep 2018

Lipid-Rich Plaque Study indicates potential clinical value of the company's dual-modality system.

Results from a clinical trial using dual-modality infrared and ultrasound imaging to evaluate lipid-rich plaque (LRP) in blood vessels have indicated the potential clinical impact of the technique, as a means to identify patients at risk of major adverse cardiovascular events.

The Lipid-Rich Plaque Study, which employed an imaging platform from Massachusetts-based Infraredx, was discussed at the annual scientific symposium of the Cardiovascular Research Foundation, held this week in San Diego.

Accumulation of plaque in the wall of an artery is known to increase the chance of subsequent MACE (major adverse cardiac events) in patients, with those who may already have had a previous coronary intervention being particularly at risk.

However, established imaging techniques have proven to be limited in the information they can provide about potentially dangerous plaques, especially those which do not yet obstruct flow in the blood vessel.

The LRP Study, sponsored by Infraredx, enrolled 1563 individuals in the US and Europe, commencing in 2015. It investigated the use of a dual modality platform combining intravascular ultrasound and near-infrared spectroscopy (IVUS+NIRS) in a surgical catheter, to image LRP and identify any correlation between detection of LRP and the occurrence of a cardiac event within two years.

A multimodal approach should allow detection of a greater number of significant plaque characteristics than either imaging technique could provide on its own. In particular, IVUS can provide high-resolution structural images of the areas of interest and compositional information about the coronary arteries themselves, while NIRS accurately identifies the lipid-core plaque material of concern and yields additional morphological data, according to the company.

Infraredx currently markets the system as the Makoto intravascular imaging system and accompanying Dualpro intravascular ultrasound and near-infrared spectroscopy catheter.

"A previous model of the Makoto imaging system and Dualpro IVUS+NIRS catheter was the only imaging technology used in the LRP Study," the company confirmed to Optics.org. "This represents the largest ever study using near-infrared spectroscopy."

Patients at most risk

The dual-modality imaging data was used to calculate a single numerical diagnostic value for a patient, derived from the maximum lipid burden in a small four-millimeter segment of blood vessel. Subsequent tracking of patients confirmed an association between high values of this parameter and possible later lesions within the imaged segment, potentially leading to future MACE in the patient.

In addition, the data indicated an association between the LRP parameter and a patient's likelihood of MACE arising from other arteries, not just those specifically imaged by during the study - a "patient-level" risk assessment that could prove highly significant in clinical use.

"The role lipid rich plaques play in cardiovascular-related deaths has been studied for decades," commented Infraredx CEO Jason Bottiglieri at the announcement of the study's results. "Today’s findings validate that NIRS use in vivo can identify both vulnerable patients and vulnerable coronary plaque."

Infraredx announced in August 2018 that the platform had been launched in Japan, after approval from the country's regulatory agency the previous year. A launch in the US is now due to follow.

"The limited market release of the Makoto/Dualpro is planned for Q2 2019 in the US," the company told Optics.org. "There will be additional analyses of the LRP Study data in the future, but no additional studies are required before the US limited market release."