Expectations and limitations of contemporary intravascular imaging: lessons learned from pathology

Abstract

Acute coronary syndrome is the leading cause of death worldwide and plaque rupture is the most common underlying mechanism of coronary thrombosis. During the last 2 decades the understanding of atherosclerotic plaque progression advanced dramatically and pathology studies provided fundamental insights of underlying plaque morphology, which paved the way for invasive imaging modalities, which bring a new area of atherosclerotic plaque characterization in vivo. The development of intravascular ultrasound (IVUS) allowed the field to evaluate the principles of vascular anatomy, which is often underestimated by coronary angiography. Furthermore, IVUS image technologies were developed to obtain improved characterization of plaque composition. However, since spatial resolution of IVUS is insufficient to distinguish details of plaque morphology, a broad adoption of this technology in clinical practice was missing. Optical coherence tomography is a light-based imaging modality with higher spatial resolution compared to IVUS, which enables the assessment of vascular anatomy with great detail.

Keywords::

• atherosclerosis
• fibroatheroma
• IVUS
• OCT
• pathologic intimal thickening
• pathology
• thin-cap fibroatheroma
• vulnerable plaque

Financial & competing interests disclosure

This work was in part supported by an educational research grant from CVPath Institute Inc. (Gaithersburg, MD), a private nonprofit research organization. O Sanchez has received speaking honorarium from Biosensors. K Sakakura has received speaking honorarium from Abbott Vascular, Boston Scientific and Medtronic CardioVascular. R Virmani receives research support from 480 Biomedical, Abbott Vascular, Atrium, Biosensors International, Biotronik, Boston Scientific, Cordis J&J, GSK, Kona, Medtronic, Microport Medical, OrbusNeich Medical, ReCore, SINO Medical Technology, Terumo Corporation, and W.L. Gore.; has speaking engagements with Merck; receives honoraria from 480 Biomedical, Abbott Vascular, Biosensors International, Boston Scientific, CeloNova, Claret Medical, Cordis J&J, Lutonix, Medtronic, Terumo Corporation and W.L.Gore; and is a consultant for 480 Biomedical, Abbott Vascular, Medtronic and W.L. Gore. M Joner is a consultant for Biotronik and Cardionovum, and has received speaking honorarium from Abbott Vascular, Biotronik, Medtronic and St. Jude. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.

Key issues

• Atherosclerotic coronary disease is a leading cause of death worldwide and atherosclerotic plaque progress up to rupture, which is believed to be the most common underlying mechanism of luminal thrombosis that leads to a sudden onset of acute coronary syndromes.

• The knowledge of basic pathology human progressive coronary artery disease, from intimal thickening to thin-cap fibroatheroma (The ‘Vulnerable Plaque’), is fundamental for understanding imaging findings.

• The development of IVUS let us evaluate ‘In vivo’ the arterial anatomy with really close relation to pathology findings. That early gray scale soon improved the image to virtual histology intravascular ultrasound (VH-IVUS) and integrated backscattered-IVUS (BS-IVUS) with better characterization of plaque composition.

• Since IVUS resolution was not good enough, even with the improvements, the technology developed the optical coherence tomography (OCT), which is based on infrared light emission that generates high-resolution cross-sectional images of tissue microstructures.

• FD-OCT systems, which are the most recent advance, are capable of obtaining A-lines (multiple axial scans) at much higher imaging speeds, facilitating rapid, 3D pullback imaging.

• The axial resolution of OCT is superior to the IVUS, ranges from 12 to 18 µm for OCT, compared with 150–200 µm for IVUS; on the other hand, the lateral resolution and depth of IVUS is superior than the OCT, range from 20 to 90 µm for OCT compared with 150–300 µm for IVUS.

• Current image tools give us the possibility to see, in vivo, almost the real vascular anatomy with a closer relationship to the pathological findings, helping us to make better treatment decisions.

Notes