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Age related changes in coronary blood flow and resistance in chronically instrumented sheep

Abstract:

115-127 day fetuses, 4-14 day old lambs, 36-42 day old lambs, and young adult ranch cross-bred sheep were studied. The finding that coronary flow is increased in the newborn LV to match post natal increases in O2 demand is reassuring that myocardial O2 supply is appropriate in the resting state. However, to increase flow in the neonate, coronary resistance is decreased. The limits of flow reserve available for stress may be more closely approached in the newborn than at any other time in post natal life. Since many neonates come to the operating room with circulatory disturbances ranging from mild dehydration to shock, acidosis, and hypoxemia, coronary flow reserve may contribute to a reduced functional reserve seen at this time.