Two-Year COLOR Results Indicate PCI of NIRS-Defined Lipid-Rich Plaque is Safe

November 1, 2016—Two-year results from the COLOR trial found that percutaneous coronary intervention (PCI) on coronary artery lipid-rich plaque (LRP) detected by near-infrared spectroscopy (NIRS) was not associated with subsequent major adverse cardiac events (MACEs) compared to PCI of non-LRPs. The COLOR trial data were presented as a First Report Investigation at TCT 2016, the 28th annual Transcatheter Cardiovascular Therapeutics scientific symposium in Washington, DC. The COLOR trial was funded by InfraReDx, Inc.

The background of the study is that autopsy-based studies have suggested that LRP may be associated with increased PCI risk and subsequent events. Catheter-based NIRS can identify the presence and extent of LRP in the coronary artery. Previous case reports, as well as small studies, have suggested an association between LRP as assessed by NIRS and periprocedural outcomes after PCI.

As summarized in the TCT announcement, COLOR is the first large-scale, multicenter, prospective observational study of its kind. The registry was designed to determine whether LRP detected by NIRS is associated with subsequent MACEs. LRP was detected using an intracoronary NIRS imaging catheter that provides an assessment of coronary lipid distribution. Lipid core burden index (LCBI) was calculated as the fraction of yellow pixels within a scanned region multiplied by 1,000.

A total of 1,899 patients at 22 sites in the United States underwent NIRS during a clinically indicated catheterization procedure. The primary endpoint was MACEs (a composite of cardiac death, myocardial infarction, stent thrombosis, revascularization, and hospitalization) at 2 years. MACEs occurring within 2 years were adjudicated by an independent clinical events committee and further classified as to whether they arose from the originally treated coronary segments (culprit) or untreated segments (nonculprit). The relationship between baseline LCBI and MACEs at 2 years was also evaluated.

Preintervention NIRS of treated coronary segment(s) was available in 1,168 patients (1,265 lesions), and NIRS of untreated segment(s) was available in 927 patients (1,072 lesions). The overall rate of MACE at 2 years was 14.1% for all patients, 6% related to the culprit lesion, 8.3% related to the nonculprit lesion, and 2.4% indeterminate. Culprit lesion-related MACE at 2 years was 6.3% for maxLCBI_4mm < 304 (the median) and 5.4% for maxLCBI_4mm ≥ 304 (hazard ratio, 0.83; 0.52–1.3; P = .41). In multivariable analyses, MaxLCBI_4mm was not independently associated with culprit lesion-related MACE.

In the TCT press release, Giora Weisz, MD, commented, “In this large-scale registry, nonculprit lesion-related events were a little more common than culprit lesion post-PCI–related events during 2-year follow-up. The results also indicate that PCI of NIRS-defined lipid rich plaques was safe, and was not associated with increased periprocedural or long-term adverse outcomes compared to PCI of non-LRPs. Additional studies are needed to determine the clinical significance of NIRS-defined nonculprit LPRs.”