OXYGEN-PRESSURE DISTRIBUTION IN THE HEART IN-VIVO AND EVALUATION OF THE ISCHEMIC BORDER ZONE

Quantitation of the oxygen pressure distribution in the heart provides an accurate definition of metabolically viable cells adjacent to isch emic injury. By injection of a phosphorescent oxygen probe into the bl ood of newborn piglets and illumination of the heart with monochromati c light, a series of images of the heart were collected with use of a gated intensified CCD camera. These sets of images were used to calcul ate two-dimensional maps of the oxygen pressure in the epicardial micr ovasculature. Occlusion of a distal arterial vessel resulted in a hypo xic area containing a central focus of near-zero oxygen pressure borde red by tissue with diminished but nonzero oxygen pressures. These bord er zones extended for several millimeters from the hypoxic core, with the oxygen pressures progressively increasing from the focus to the no rmoxic region. The maps of oxygen distribution obtained by phosphoresc ence imaging provide rapid and quantitative measure of the oxygen pres sures in the beating heart in vivo. They accurately show the degree of oxygen deprivation and the extent of an ischemic border zone that may respond to treatment.