Coronary flow and myocardial oxygen metabolism in the newborn lamb.

Analysis of factors which may influence oxygen metabolism of the heart has received much attention since the early part of this century (1). Quantitative measurements of coronary blood flow and myocardial oxygen consumption (MVO,) have been accumulated from both human and animal studies (2, 3). These studies were uniformily concerned with adults, however, and virtually no information is available from newborn or young mammals. This may, in part, be related to difficulties in measuring coronary flow by conventional techniques and to problems in collecting representative coronary venous samples from hearts of newborns. Recently an approach has been developed in our laboratory using the newborn lamb which has yielded consistent and reproducible data. It is based on the particular anatomical arrangement in this species in which the hemiazygous vein drains into the coronary sinus (4). It has permitted us to design a system involving cannulation of the sinus through this tributary. Blood flow measurements and collection of coronary sinus samples for study of oxygen consumption and substrate metabolism could be readily achieved by this approach. The purpose of the present study was to investigate the relative influence of individual hemodynamic factors on those measurements. A preliminary report on these findings has appeared (5).