Optical coherence tomography for guidance in bifurcation lesion treatment

Optical coherence tomography (OCT) has higher resolution than IVUS (approximately 10 times), with the potential to precisely measure lumen diameters in the variable geometry of a bifurcational lesion and to identify superficial lipid laden plaques and calcium, relevant to confirm the severity of the lumen obstruction before treatment and guide location and diameter of the stent. In addition, OCT produces fewer strut-induced artifacts and offers precise evaluation of strut apposition in a real-life clinical setting. The increase in the speed of image acquisition consequent to the introduction of frequency domain OCT allows rapid pull-back at a speed of 2 cm/sec, minimising the amount of contrast required to clear blood during image acquisition, with an average injection of 10-18 ml required for the maximal length currently available of 5.6 cm. This allows serial OCT acquisitions, typically before treatment if the lesion is not very severe and flow is expected to be present around the OCT catheter, after predilatation and to assess and guide stent expansion. Repeated OCT examinations at follow-up may help to detect presence and characteristics of strut coverage, a potential predictor of late stent thrombosis. These applications are of particular interest in the context of bifurcational lesion treatment because this condition is still associated with a higher number of malapposed stent struts and frequent impairment of stent expansion, explaining the higher incidence of stent thrombosis and restenosis. In this article, all potential applications of OCT for bifurcational lesion treatment are explored. The use of OCT to characterise plaque components, and to optimise stent expansion and strut apposition are first discussed in detail. The conclusion of the article highlights some future research and technological developments that promise to expand the role of OCT further still.