10 Lesion characteristics such as lipid and calcium content can be defined prior to the intervention and these findings can be predictive of post-procedure myocardial infarction. OCT is potentially more accurate than IVUS at determining lesion severity although it is unlikely to replace FFR.
Prior to PCI, OCT can be utilized to measure the reference vessel diameter, minimal luminal diameter and the length of the target lesion.
In addition to its role in characterizing atherosclerotic plaques, OCT can in theory provide important information to guide coronary interventions. 8-9 The high resolution of OCT permits identifications of plaque characteristics that predispose to rupture including thin fibrous caps, large lipid cores and accumulation of macrophages. All three plaque types can be accurately identified by OCT. Based on histological analysis of autopsy specimens, there are three general plaque types: fibrous, fibro-calcific and lipid rich. Unlike with IVUS, OCT cannot measure total plaque burden because of its relatively shallow tissue penetration.Īmong intravascular imaging modalities, OCT provides uniquely detailed images of superficial coronary plaque components. 7 As result, far clearer images of the vessel lumen and wall, superficial coronary plaque components and endovascular stents are generated when compared to IVUS. 6 OCT provides an image resolution of 15 µm to a depth of 2-3mm. The procedures are performed via a 6F guiding catheter with low complication rates. Current OCT systems utilizing a rapid automated pull back system can image vessels at rate of 20mm/s minimizing the flush time required during image acquisition. Because blood scatters light, images are obtained from a vessel segment cleared of blood by either saline or contrast flush. 5 It uses near-infrared light and measures the magnitude and echo time delay of reflected light. OCT functions as an optical analog to IVUS detecting the back scatter of light to generate an image. In comparison to IVUS, optical coherence tomography (OCT) is a novel technology with the first in-human studies performed in 2008. 4 The clinical role for IVUS was established via both prospective and retrospective studies showing potential clinical benefit to patients. Post-intervention, PCI complications and inadequate stent expansion can be identified. Pre-intervention, IVUS can accurately determine the lesion length and reference lumen diameter. 4 As a clinical tool, the IVUS has an established role in guiding coronary interventions. 3 By the most recent guidelines, IVUS can also be utilized to assess allograft vasculopathy and the mechanism of stent restenosis or thrombosis. 2 Lesion severity can be assessed more accurately by IVUS than angiography but this role has been largely supplanted by fractional flow reserve (FFR) which allows for the more important functional assessment of lesion severity. 1 As a research tool, IVUS has allowed for better understanding of plaque morphology, vessel wall remodeling and the natural history of atherosclerotic disease. Via a 6-F and 5-F pull back system, IVUS uses high frequency ultrasound to visualize coronary arteries to a depth of 10mm with a resolution of 150µm. As result, there has been significant interest in the development of techniques that allow for more direct assessment of lesion severity and more accurate guidance during PCI.ĭeveloped in the 1980s, intravascular ultrasound (IVUS) is currently the most commonly utilized methods for endovascular imaging. During percutaneous coronary interventions (PCI), decisions on stent size and expansion are based on “eye-ball” estimates which can result in lesion-stent mismatch or malapposition of stent and vessel lumen.
This can result in unnecessary interventions on functionally insignificant lesions. As result, lesion severity and plaque burden can be difficult to assess. Most prominently, coronary angiography produces a two-dimensional representation of the vessel lumen only. Over this time, the limitations of angiography have also become clear. JACC Cardiovasc Imaging 2011 4(9):1047-9.ĭecades after its development, coronary angiography remains the standard technique for both the diagnosis of coronary artery disease and for guiding endovascular interventions. Editor's Note: The following is a related resource to this Hot Topic.įinn AV, Chandrashekhar Y, Narula J.
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