How to Detect and Treat Coronary Fibroatheromas

Abstract

As you set out for Ithaka hope the voyage is a long one, full of adventure, full of discovery.-Constantine P. Cavafy, Ithaka (1) C oronary fibroatheromas can cause a wide spectrum of adverse events, such as sudden death, acute coronary syndromes, and procedural complications during percutaneous coronary interventions (PCI) (2). Accurate fibroatheroma detection could significantly enhance our ability to treat these lesions and prevent complications. FIBROATHEROMA DETECTION DURING CARDIAC CATHETERIZATION Fibroatheromas can be detected noninvasively with coronary computed tomography angiography. Three imaging modalities are currently available for fibroatheroma detection during cardiac catheterization: intravascular ultrasonography (IVUS), optical coherence tomography (OCT), and near-infrared spectroscopy (NIRS) (3) (Figure 1).Grayscale IVUS, which is the oldest and most widely available intravascular imaging modality, was not developed specifically for the detection of fibroatheroma. However, IVUS-attenuated plaque (attenuation of the ultrasound beam in the absence of calcification), especially when superficial (closer to the lumen than the media), is a specific (but not sensitive) fibroatheroma "signature" (4,5).Analysis of the backscattered radiofrequency IVUS signals (virtual histology IVUS and integrated backscatter IVUS) also allows plaque characterization, but it is challenging to perform in real time during the procedure because it requires accurate segmentation of the IVUS images, which is a time-consuming and labor-intensive process (3).OCT identifies fibroatheromas as signal-poor regions with ill-defined borders (6), but OCT image interpretation is subjective and highly dependent on operator experience (3). Moreover, deep fibroatheromas may be harder to detect due to poor penetration of the near-infrared light beam.NIRS was developed to specifically detect lipid core plaque in coronary arteries, on the basis of the specific chemical signature of the fibroatheroma (7).Near-infrared light is directed to the coronary artery wall, and the reflected light is collected and analyzed using algorithms developed based on histological analyses (7). NIRS is currently available as a combination catheter with IVUS (TVC, Infraredx, Burlington, Massachusetts)-the only such catheter currently in clinical use. In this issue of iJACC, Kang et al. (8) advance our understanding of fibroatheroma detection with IVUS and NIRS, compared with the gold standard, histology. In an autopsy study of 103 coronary arteries from 56 autopsied hearts, they compared superficial IVUS attenuation (for IVUS) and a yellow or tan block chemogram (for NIRS) with the histopathology obtained from 1,943 sections. Superficial IVUS attenuation had excellent specificity, yet low sensitivity for fibroatheroma detection, which was significantly improved by NIRS. The addition of NIRS significantly increased SEE PAGE 184 *Editorials published in JACC: Cardiovascular Imaging reflect the views of the authors and do not necessarily represent the views of JACC:...

Near-Infrared Spectroscopy (NIRS): A Novel Tool for Intravascular Coronary Imaging

“…However, as previously mentioned, the combined NIRS-IVUS-imaging catheter allows co-registration of both IVUS and NIRS data, which gives information on both plaque composition and morphology. NIRS-IVUS has shown to improve LCP detection, by comparison to IVUS, in calcified plaques as well as in lesions with small plaque burden [78]. The combined measures of plaque burden and LCBI improved the accuracy of fibroatheroma detection as compared with plaque burden alone by grayscale IVUS.…”

Coronary plaques with near‐infrared spectroscopy

“…One autopsy study showed that 52% of IVUS‐detected calcified plaques were actually fibroatheromas on histological analysis . NIRS/IVUS act synergistically to improve tissue characterization in calcified plaques as well as plaques with smaller plaque burden .…”