ntimal thickening is considered to be an early phase of atherosclerosis; [1][2][3][4][5] in the coronary artery it is related to coronary spasm and is of prognostic importance in patients after cardiac transplantation. 6,7 Evaluation of intimal thickening of the coronary artery is thought to be important clinically and recent advancements in intravascular ultrasound (IVUS) have enabled pathological evaluation of the wall structure of the coronary artery. [8][9][10][11][12][13][14][15] However, intimal thickening is indirectly evaluated as the intima -media thickness (IMT) by IVUS because the boundary of the intima and media cannot be distinguished completely by this method. 16 Optical coherence tomography (OCT) is a new imaging method [17][18][19][20][21][22] with a resolution of approximately 10-20 m, which is approximately 10-fold greater than that of IVUS. 23 OCT can easily identify the internal elastic laminae, which cannot be identified by IVUS. 18,19 We thus hypothesized that OCT could enable more accurate measurement of the IMT and the intimal thickness than IVUS, so the aim of the present study was to test these hypotheses.
MethodsWe examined 54 randomly selected segments from 54 coronary arteries from 18 consecutive cadavers (10 males, 8 females; mean age 72±6 years). The cause of death was leukemia (n=3), lung cancer (n=3), acute myocardial infarction (n=2), pulmonary embolism (n=2), intracranial hemorrhage (n=2), liver cirrhosis (n=2), pneumonia (n=2),
Circulation Journal Vol.69, August 2005and trauma (n=2). The study protocol was approved by the ethics committee of Kawasaki Medical School, and written informed consent was obtained from each family. An approximate 5-cm length of the proximal site of the 3 major coronary arteries, the left anterior descending coronary artery, left circumflex artery, and right coronary artery, were obtained from cadavers at autopsy within 3 h of death. The surrounding soft tissue was dissected from each specimen. Small arterial perforators and the branches were tied off with sutures, and the distal end of the artery was occluded with a large cork. A 7F sheath was sewn into the proximal end of the artery to complete the closed system. Phosphate-buffered saline (154 mmol/L NaCl, 10 mmol/L NaH2PO4, pH 7.4), which was kept at 37°C, was infused through the side arm of the sheath. The pressure inside the coronary artery was maintained at a physiological level (60-80 mmHg) with a sphygmomanometer connected to the infusion.
OCT and IVUS ImagesAn intravascular OCT catheter (ImageWire ® , LightLab Imaging, Westford, MA, USA) and IVUS catheter (Atlantis SR Pro ® 2.5F, 40-MHz, Boston Scientific, Natick, MA, USA) were inserted through the diaphragm of the sheath. Serial OCT and IVUS images were obtained using an automatic pullback device at a rate of 0.5 mm/s. The OCT images were processed and analyzed using proprietary software from LightLab Imaging, Inc and the IVUS images were exported to commercially available image processing software (Netra 3D IVUS system, ScImage) for off-lin...