In vivo characterization of coronary atherosclerotic plaque by use of optical coherence tomography

Abstract

Background: The current understanding of the pathophysiology of coronary artery disease is based largely on postmortem studies. Optical coherence tomography (OCT) is a high-resolution ( approximately 10 microm), catheter-based imaging modality capable of investigating detailed coronary plaque morphology in vivo.

Methods and results: Patients undergoing cardiac catheterization were enrolled and categorized according to their clinical presentation: recent acute myocardial infarction (AMI), acute coronary syndromes (ACS) constituting non-ST-segment elevation AMI and unstable angina, or stable angina pectoris (SAP). OCT imaging was performed with a 3.2F catheter. Two observers independently analyzed the images using the previously validated criteria for plaque characterization. Of 69 patients enrolled, 57 patients (20 with AMI, 20 with ACS, and 17 with SAP) had analyzable images. In the AMI, ACS, and SAP groups, lipid-rich plaque (defined by lipid occupying > or =2 quadrants of the cross-sectional area) was observed in 90%, 75%, and 59%, respectively (P=0.09). The median value of the minimum thickness of the fibrous cap was 47.0, 53.8, and 102.6 microm, respectively (P=0.034). The frequency of thin-cap fibroatheroma (defined by lipid-rich plaque with cap thickness < or =65 microm) was 72% in the AMI group, 50% in the ACS group, and 20% in the SAP group (P=0.012). No procedure-related complications occurred.

Conclusions: OCT is a safe and effective modality for characterizing coronary atherosclerotic plaques in vivo. Thin-cap fibroatheroma was more frequently observed in patients with AMI or ACS than SAP. This is the first study to compare detailed in vivo plaque morphology in patients with different clinical presentations.

FIGURE 1

OCT images of 3 different types of atherosclerotic plaques. A, Lipid-rich plaque (L) covered by thin fibrous cap (arrow, magnified inset). B, Another type of lipid-rich plaque, but with thick fibrous cap. C, Dense, eccentric fibrous plaque (F) with no lipid component. A signal-rich, homogeneous reflective pattern is typical for fibrous tissue. In regions with no plaque (between 7 and 10 o’clock positions), intima, media, and adventitia are clearly visualized.

Figure 2

Examples of plaque disruption in patients with recent myocardial infarction. A, Large lipid-rich plaque (L) with localized rupture of a fibrous cap with a flap protruding into lumen (arrow). B, Severe disruption of plaque (arrows) with a large mural thrombus (T). Lipid is present in whole circumference (L). G indicates guidewire artifact.

Figure 3

Frequency of TCFA defined by lipid-rich plaque (≥2 quadrants) and fibrous cap thickness ≤65 µm. TCFA was observed in 72% of patients with AMI, in 50% of patients with ACS, and in 20% of patients with SAP (P = 0.012).