Intracoronary optical coherence tomography—An introduction

Abstract

Optical coherence tomography (OCT) utilizes near infrared light with a wavelength of 1.30 μm and is generated from a rotating fibre-optic system.When compared to intravascular ultrasound (IVUS), the shorter wavelength of OCT (1.3 μm) confers excellent axial resolution but at the cost of lower depth penetration (1-2 mm vs. 5-6 mm). Red blood cells have a strong tendency to absorb and scatter light, which attenuates the image. Therefore, when assessing coronary arteries with OCT, it is important to clear blood from the field of examination and this is usually done with a contrast agent. This makes it prone to artefacts from residual blood, and limits its use in patients with advanced chronic kidney disease, ectatic vasculature and aorto-ostial lesions where IVUS tends to be preferred. However, OCT outperforms IVUS in the assessment of calcific lesions, identification of high-risk plaque features, and studying the mechanism of stent failure. In this article, we provide an up-todate review of the technology behind OCT, its limitations, and how the two intracoronary imaging modalities compare in various clinical scenarios.

Artificial Intelligence for the Interventional Cardiologist: Powering and Enabling OCT Image Interpretation

“…Conversely, vulnerable plaques tend to have a large lipid pool (necrotic core) and thin fibrous cap (thin-cap fibroatheroma; TCFA) that is soft in nature and prone to rupture. [ 4 ]…”

“…TCFA and plaque rupture have been strongly associated with acute coronary syndrome. [ 4 ] Lee et al developed an AI model that can automatically detect lipids and assess fibrous cap thickness on IVOCT. This model was able to accurately discriminate lipidic plaques (sensitivity of 85.8%) and clearly identify the fibrous caps in these lesions with minimal inter-observer variance.…”

“…[ 8 ] However, there remain problems with blood mixing, and the potential to provoke arrhythmias with non-contrast flushes. [ 4 ] To add to this, the development of an automated IVOCT algorithm based on poor-quality images can be challenging. Non-contrast flushes with similar biocompatibility need to be investigated to minimise these issues.…”

“…The short wavelength (1.3 μm) of the infrared light used in IVOCT confers superior axial resolution compared with other ICI modalities, such as intravascular ultrasound (IVUS), making it particularly useful for near-field plaque characterisation. [ 3 , 4 ]…”

“…The short wavelength (1.3 μm) of the infrared light used in IVOCT confers superior axial resolution compared with other ICI modalities, such as intravascular ultrasound (IVUS), making it particularly useful for near-field plaque characterisation. 3,4 At present, IVOCT is not routinely used in clinical practice, and data from the national audit of percutaneous coronary intervention (NAPCI) highlight that even in high-risk populations, such as in the case of left main PCI, ICI is used only in 66% of left main cases. 5 There is the perception that it prolongs the procedure and that the individual operators' experience with angiography alone is sufficient.…”