Original Studies Frequency-Domain Optical Coherence Tomography Assessment of Unprotected Left Main Coronary Artery Disease—A Comparison With Intravascular Ultrasound Yusuke Fujino, 1,2 MD, Hiram G. Bezerra, 1 * MD, PHD, Guilherme F. Attizzani, 1 MD, Wei Wang, 1 MS, Hirosada Yamamoto, 1 MD, Daniel Chami  e, 1 MD, Tomoaki Kanaya, 1 MD, Emile Mehanna, 1 MD, Satoko Tahara, 2 MD, PHD, Sunao Nakamura, 2 MD, PHD, and Marco A. Costa, 1 MD, PHD Objectives: To investigate safety and feasibility of imaging unprotected left main (ULM) using frequency-domain optical coherence tomography (FD-OCT) compared with intra- vascular ultrasound (IVUS). Background: IVUS has been used to assess and guide per- cutaneous coronary intervention (PCI) of ULM disease. FD-OCT offers 10-fold higher axial resolution than IVUS and its high-speed image acquisition obviates the need for proximal balloon occlusion. Methods: We prospectively enrolled 35 consecutive patients with ULM disease. FD-OCT and IVUS assessments were attempted pre- and post-PCI and compared in regards to safety, ability to image the region of interest (ROI), number of pullbacks, volume of contrast and ability to detect malapposition, dis- section, and thrombus. Results: Patients were followed for 1 year when FD-OCT imag- ing was repeated. FD-OCT required more repeated pullbacks to image the ROI compared to IVUS. Mean lumen and stent areas were similar between FD-OCT and IVUS (11.24 6 2.66 vs. 10.85 6 2.47 mm 2 , P 5 0.13 and 10.44 6 2.33 vs. 10.49 6 2.32 mm 2 , P 5 0.82, respectively), whereas imaged stent length was shorter with FD-OCT. Malap- position areas and volumes were larger and more edge dissections were detected by FD-OCT. There were no clinical adverse events and no complications associated with FD-OCT at baseline and 1-year follow-up. All dissections were healed, whereas stent malapposition was still detected at follow-up. Conclusions: FD-OCT assessment of ULM is feasible and safe. Direct comparisons with IVUS reveal that FD-OCT achieved imaging completeness less often, whereas it was more sensitive in detecting malappo- sition and edge dissections, and similar to IVUS in the assessment of lumen and stent dimensions. V C 2013 Wiley Periodicals, Inc. Key words: optical coherence tomography; intravascular ultrasound; left main coronary artery disease; percutaneous coronary intervention 1 Harrington Heart and Vascular Institute, University Hospitals Case Medical Center, Case Western Reserve University, Cleveland, Ohio 2 Department of Cardiology, New Tokyo Hospital, Chiba, Japan Conflict of interest: Nothing to report. *Correspondence to: Hiram G. Bezerra, MD, PhD, Assistant Profes- sor of Medicine, Case Western Reserve University, Harrington Heart and Vascular Institute, University Hospitals Case Medical Center, Case Western Reserve University, 11100 Euclid Avenue, Cleveland, OH 44106, Tel.: (216) 983-5887, Fax: (216) 844-8318. E-mail: hiram.bezerra@uhhospitals.org Received 9 April 2012; Revision accepted 21 January 2013 DOI: 10.1002/ccd.24843 Published online in Wiley Online Library (wileyonlinelibrary.com). V C 2013 Wiley Periodicals, Inc. Catheterization and Cardiovascular Interventions 00:000–000 (2013)