Novel catheter combines FLIm, IVUS to assess plaque buildup in heart patients

A newly developed, single-catheter probe that combines intravascular ultrasounds with fluorescence lifetime imaging (FLIm) in one device could be the answer to physicians’ difficulties predicting plaque rupture, a study published in Scientific Reports suggests.

The catheter was developed by Laura Marcu, PhD, and colleagues at her UC Davis-based lab. The device was a response to the fact that plaque rupture—an often fatal event that spurs heart attacks—is the number one root problem leading to sudden cardiac deaths in the U.S.

Previous attempts to identify plaque buildup in arteries have been limited; many cardiologists order angiographies, but those screenings only identify stenosis in blood vessels, and not all plaque buildup results in the narrowing of arteries. Intravascular ultrasounds (IVUS) can identify plaque burden based on its penetration depth of up to 10 mm-squared, Marcu and co-authors explained, but don’t have the spatial ability to recognize smaller-scale, biochemical changes in vessels. Optical coherence tomography succeeds in spatial resolution, but lacks the penetration depth necessary to assess plaque buildup.

Marcu’s research led her to FLIm, which is based on UV-light induced tissue autofluorescence and could have a greater ability to retrieve both structural and biochemical information about a patient’s coronary arteries. By integrating FLIm and IVUS into one compact catheter, Marcu’s team was able to create a device that successfully co-registered structural and biochemical images of coronary arteries in vivo.

“New imaging techniques for evaluation of plaque pathophysiology are of great interest to both improve the understanding of mechanisms driving plaque formation as well as support the development of new pharmaceutical and interventional therapies,” Marcu and co-authors wrote in the paper. “By providing this information, the presented device could become a valuable addition to the field of cardiovascular imaging.”

The researchers tested the new catheter in swine samples, as well as a handful of human artery samples provided by the University of Pennsylvania heart transplant program. The system allowed for scans of 20-mm sections of vessels at a time, with each scan taking about 5 seconds to complete. With a rotation speed of 1,800 rpm, the catheter system used 25,000 independent multispectral fluorescence lifetime point measurements of the vessel surface to take its specifications.

Marcu and colleagues based the success of the device on four characteristics: the ability of the catheter to access tortuous anatomy; the ability of the device to flush blood from the field of view using Dextran 40 solution; its ability to image a range of vessel diameters; and its ability to discriminate targets based on lifetime and spectral information.

In the study cases, the catheter was able to collect bi-modality data—a first for the field. The device is also able to acquire co-registered structural and biochemical information without the use of other contrast agents, which are necessary in angiographies.

“This new approach may benefit both patients and researchers alike,” Marcu and co-authors wrote. “Enabling in vivo evaluation of plaque type may improve understanding of plaque physiopathology and mechanisms of disruption. In addition, the effect of therapeutic agents on biochemical and structural composition of plaque could be evaluated, leading to a non-invasive method to monitor efforts aimed at acute coronary syndromes prevention.”