Optical coherent reflectometry: A new technique to guide invasive procedures

The success rate of percutaneous transluminal coronary angioplasty for chro nic total arterial occlusions is still unsatisfactory. Inability to cross t he lesion with a guidewire is a major cause of failure. Optical coherent re flectometry (OCR) is a new method of using laser light to measure the depth of tissue from the end of an optic fiber. This study tests whether an OCR prototype guidewire provides a guidance system that might be useful to assi st reopening chronic total arterial occlusions. An OCR fiber optic within a 0.014 " hypotube was developed using the interference pattern of two refle cted light beams (wave length 1,300 nm). To determine if OCR can distinguis h different tissue types, plaques of human lower extremity arterial segment s were visually divided into three types (calcified, white, or yellow). The slope of the initial reflectance of the OCR curve was calculated and compa red between the three groups. In six other arteries, the OCR wire was advan ced longitudinally through occluded human artery segments in vitro. Guidewi re position was determined by OCR and compared to the position of the guide wire tip observed simultaneously by intravascular ultrasound (IVUS) imaging . In 16 arterial surface segments, calcified plaques had a significantly st eeper slope than white or yellow plaques (-227.2 +/- 82.2; -81.5 +/- 12.9; -103.6 +/- 19.6 dB/mm; P < 0.01). For the determination of the guidewire po sition, IVUS and OCR corresponded correctly in 82% of 28 measurements. Sens itivity and specificity of OCR for detection of plaque versus the media/adv entitia boundary were 79% and 89%, respectively (P < 0.001). OCR can distin guish calcified from noncalcified plaque and may distinguish plaque from th e media/adventitia boundary. This technology may be useful as a means to he lp navigate a guidewire safely through an occluded artery. (C) 2001 Wiley-L iss, Inc.