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A glimpse into the coronary applications of optical coherence tomography

Principles and safety of optical coherence tomography

Optical coherence tomography (OCT) is an optical analogue of intravascular ultrasound (IVUS), measuring the back-reflection of infrared light from biological micro-structures (fig. 1). The axial OCT resolution is 10-20 mm what is approximately 10 times higher than that offered by IVUS. The imaging depth of only 1.0-1.5 mm within the coronary artery wall is mainly limited by the tissue attenuation of the infrared light. Near microscopic OCT resolution allows a very accurate visualization of superficial vessel wall structures and provides insight into the interaction between vessel wall and implanted stents [1].
Safety and feasibility of both IVUS and OCT (using exclusively occlusive technique in the latter) was addressed in the study of 76 patients by Yamaguchi et al. Although, transient chest pain and ischemic ECG changes during OCT image acquisition were not part of the study, they did not report any significant adverse events including vessel dissection or fatal arrhythmia [2]. Still, a number of potentially dangerous risks needs to be considered. Kim et al. reported thrombus formation during OCT imaging which highlights the need for careful systemic anticoagulation with activated clotting time (ACT) control [3]. In the LEADERS trial OCT sub-study ventricular fibrillation (VF) in one patient was induced by contrast flushing [4]. Finally, a retrospective multicenter registry was carried out to assess OCT safety in 468 patients. Of note, only 43.5% of these cases were performed using a non-occlusive OCT acquisition technique. Transient chest pain and QRS complex widening/ST segment depression/elevation were observed in nearly half of all cases. Major complications included five (1.1%) cases of ventricular fibrillation due to balloon occlusion and/or deep guide catheter intubation, 3 (0.6%) cases of air embolism and one case of vessel dissection (0.2%) [5]. To minimize the possibility of VF during non-occlusive OCT imaging iso-osmolar contrast is recommended. Its main advantage over other contrast agents lies in its higher viscosity, which permits optimal blood clearance during OCT imaging at a given flush volumes [6].

Technique of image acquisition

Currently, OCT image acquisition is performed using commercially available systems: M2, M3 (time-domain) or C7 (optical frequency domain imaging- OFDI; synonym: swept source- SSOCT or M4) (LightLab Imaging Inc....


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