The role of optical coherence tomography in coronary intervention

Abstract

Optical coherence tomography (OCT) is an optical analog of intravascular ultrasound (IVUS) that can be used to examine the coronary arteries and has 10-fold higher resolution than IVUS. Based on polarization properties, OCT can differentiate tissue characteristics (fibrous, calcified, or lipid-rich plaque) and identify thin-cap fibroatheroma. Because of the strong attenuation of light by blood, OCT systems required the removal of blood during OCT examinations. A recently developed frequency-domain OCT system has a faster frame rate and pullback speed, making the OCT procedure more user-friendly and not requiring proximal balloon occlusion. During percutaneous coronary intervention (PCI), OCT can provide detailed information (dissection, tissue prolapse, thrombi, and incomplete stent apposition [ISA]). At follow-up examinations after stent implantation, stent strut coverage and ISA can be assessed. Several OCT studies have demonstrated delayed neointimal coverage following drug-eluting stent (DES) implantation vs. bare metal stent (BMS) placement. While newer DESs promote more favorable vascular healing, the clinical implications remain unknown. Recent OCT studies have provided insights into restenotic tissue characteristics; DES restenotic morphologies differ from those with BMSs. OCT is a novel, promising imaging modality; with more in-depth assessments of its use, it may impact clinical outcomes in patients with symptomatic coronary artery disease.

Keywords: Angioplasty; Coronary disease; Stents; Tomography, optical coherence; Ultrasonography, interventional.

Figure 1

(A) Time-domain optical coherence tomography system. (B) Fourier/frequency-domain optical coherence tomography system.

Figure 2

Optical coherence tomography-derived thin-cap fibroatheroma was defined as a lipid-rich plaque (lipid arc within a plaque in ≥ 2 quadrants) with a thin fibrous cap (thickness at the thinnest segment < 65 µm).

Figure 3

Optical coherence tomography image of ruptured plaque (arrows) with a thin fibrous cap at the site of an acute coronary syndrome culprit lesion.

Figure 4

A case with spontaneous dissection. Optical coherence tomography (C) visualized spontaneous dissection that could not be found with angiography (A) or intravascular ultrasound (B).

Figure 5

A case with cutting balloon angioplasty. Cutting balloon angioplasty was performed for stenosis in the right posterior descending artery (A, arrow). Multiple tears in the intima were observed after dilatation with a cutting balloon on the optical coherence tomographic image (D), which could not be detected by angiography (B, arrow) or intravascular ultrasound (C).

Figure 6

Identification of stent apposition. The stent is visualized as a linear structure with strong surface reflection and typical dorsal shadowing, and the posterior side of each strut near the vessel wall cannot be observed. Thus, it is necessary to determine whether the strut has made an indentation on the intimal surface of the vessel (A) or to measure the distance between the surface reflection of the strut and the adjacent visible vessel surface while taking the thickness of the strut into account (B).

Figure 7

Intravascular ultrasonic (IVUS) and optical coherence tomographic (OCT) images obtained at 7 months after implantation of a drug-eluting stent (Cypher; 3.0 × 18 mm). While no obvious intimal growth is observed on the IVUS image (A), the OCT image (B) shows that the stent strut is covered by a very thin neointima (-100 µm).

Figure 8

Classification of tissue coverage of stent struts. The left images (A, B) show uncovered struts and the right images (C, D) show covered struts. A strut with surrounding tissue beyond the strut surface is defined as covered. According to the shape of the tissue covering the struts, a covered strut is classified as convex (C) or embedded (D). The intimal thickness (NIT) was measured from the surface of the neointima covering the strut to the center line of the reflection.

Figure 9

Optical coherence tomographic patterns of restenotic tissue following bare metal stent implantation. Homogeneous (A) and heterogeneous (B, C) intima. Lipid accumulation is suggested in the low-signal area with a diffuse lumen border within the area of neointimal hyperplasia (* in B), and calcification in the low-signal area with a sharp lumen border (* in C).

Figure 10

Optical coherence tomographic patterns of restenotic tissue following drug-eluting stent implantation. Patchy (A), layered (B), and speckled (C) patterns.