Atherosclerotic plaque composition can be imaged using the optical attenuation coefficient derived from intravascular optical coherence tomography (OCT) data. The relation between optical properties and tissue type has been established on autopsy tissues. In this study, we validate an ex-vivo model for the effect of temperature and tissue fixation on optical parameters. We studied the optical attenuation of human coronary arteries at three temperatures, before and after formalin fixation. We developed an en-face longitudinal display of attenuation data of the OCT pullbacks. Using the unfixed, body-temperature condition image as a standard, and after extensive registration with other condition images, we quantify the differences in optical attenuation and the backscattered intensity. The results suggest that tissue fixation and temperature do not introduce systematic errors in studies of arterial optical properties.