Hot film coronary artery velocity measurements in horses.

Coronary velocity measurements have been carried out in anaesthetized, open-chest horses using a constant-temperature, hot-film anemometer system. L-shaped needle probes inserted by direct vessel puncture have been used to measure velocity profiles in the left common, left anterior descending (LAD), and left circumflex coronary arteries. The flow conditions were characterized by peak Reynolds numbers from approximately 200 to 1500 and values of the unsteadiness parameter from 3 to 10. These measurements indicate that in the left common coronary artery the profile is in general skewed towards the outer wall as would be expected for fully viscous flow in a curved tube. In the left anterior descending and left circumflex coronary arteries just distal to the bifurcation, the skewing was found in general to be away from the flow divider. However, in regions of the LAD and left circumflex 5-6 diameters downstream of the bifurcation, the peak systolic and diastolic profiles were indicative of a more fully developed, Poiseuille type flow with only slight skewing observed. The results of this study indicate that the flow in the coronary system, though in general laminar and disturbance free, is extremely varied in character and may exhibit large amplitude, low frequency flow oscillations. Furthermore, for these vessels which all lie on the surface of the myocardium, large systolic flows were observed to be present, even though the major portion of the volume flow was reserved for the diastolic period.

Clinicopathologic correlation of a macular hole treated by cortical vitreous peeling and gas tamponade.

PURPOSE: To study the histopathology of a stage III macular hole that had been treated by vitrectomy with cortical vitreous and epicortical vitreous membrane peeling and gas tamponade. METHODS: The light and electron microscopic features of a treated macular hole were studied. RESULTS: A 16-microns-wide break was present in the external limiting membrane. This was sealed by Müller cell processes. Photoreceptors adjacent to the healed defect appeared normal. No cystoid macular edema was present. CONCLUSION: Cortical vitreous peeling and gas tamponade can allow the macular hole to settle and the edges to re-approximate. The residual defect can be sealed by Müller cells.