Vol.:(0123456789) 1 3 Int J Cardiovasc Imaging DOI 10.1007/s10554-017-1177-0 ORIGINAL PAPER New insight to estimate under-expansion after stent implantation on bifurcation lesions using optical coherence tomography Daisuke Nakamura 1  · Guilherme F. Attizzani 1  · Setsu Nishino 1  · Kentaro Tanaka 1  · Mohamad Soud 1  · Gabriel T. Pereira 1  · Milana Leygerman 1  · Anas Fares 1  · Audrey Schnell 1  · Marco A. Costa 1  · Andrejs Erglis 2  · Hiram G. Bezerra 1   Received: 27 January 2017 / Accepted: 24 May 2017 © Springer Science+Business Media Dordrecht 2017 and MSA were diferent in 72.7% (32/44) of cases. Volu- metric assessment enables to more accurately assess stent under-expansion. Keywords Coronary bifurcation · Drug-eluting stents · Optical coherence tomography · Stent underexpansion Abbreviations DES Drug-eluting stents CM Conventional method MSA Minimal stent area MLA Minimal lumen area OCT Optical coherence tomography IVUS Intravascular ultrasound PCI Percutaneous coronary intervention EI Expansion index MEI Minimum expansion index Introduction Several randomized clinical trials have demonstrated that drug-eluting stents (DES) dramatically improve angio- graphic restenosis and the incidence for repeat revasculari- zation [1, 2]. Even though optimal stent deployment with adequate expansion is considered to be necessary to avoid in-stent restenosis as well as stent thrombosis [3–5], we still rely on mere single cross sectional narrowing or its index compared to the reference area to determine stent expansion [conventional method (CM)]. This approach does not take into account vessel tapering and side branches, ultimately neglecting the volumetric nature of the coronary vascula- ture, likely masking true lesion (i.e., under-expansion) sig- nifcance [6]. For example, in the CM, minimal stent area (MSA) or minimal lumen area (MLA) completely depends Abstract Optical coherence tomography (OCT) allows full volumetric segmentation of the lumen. However, for the estimation of stent under-expansion we still rely on the conventional method (CM) of single cross-sectional narrowing compared with reference vessel, likely mask- ing true lesion signifcance, especially for bifurcations and tapered vessels. We, therefore, suggest a novel concept of volumetric metrics that take into account vessel tapering and major side branches and is capable of obtaining ideal lumen area for every frame of the stent by OCT. Forty-four patients with bifurcation lesions were enrolled. In volu- metric metrics, expansion index was calculated as [(actual lumen area/ideal lumen area) × 100] in all frames. While minimum expansion index (MEI) was often located in the proximal segment to the major side branch, minimum stent area (MSA) by CM was frequently located in the dis- tal segment (p < 0.001). Furthermore, the frequency of the under-expansion was signifcantly greater in newly metrics compared with CM [21 (47.7%) and 11 (25.0%), p = 0.045]. New metrics changed the presence of the under-expansion in 40.9% (18/44) of patients and the locations of MEI Daisuke Nakamura and Guilherme Attizzani have contributed equally as frst authors for this manuscript. Electronic supplementary material The online version of this article (doi:10.1007/s10554-017-1177-0) contains supplementary material, which is available to authorized users. * Daisuke Nakamura daifromn0525@gmail.com 1 Cardiovascular Imaging Core Laboratory, Harrington Heart & Vascular Institute, University Hospitals Case Medical Center, 11100 Euclid Avenue, Cleveland, OH 44106, USA 2 Institute of Cardiology, University of Latvia, Pauls Stradins Clinical University Hospital, Riga, Latvia