title: Age-related differences in the response to myocardial ischemic stress.
abstract: Clinical experience indicates that the risk of reparative cardiac operations is increased in the neonatal period relative to that in older infants and children. Age-related differences in the susceptibility to myocardial ischemic dysfunction were evaluated by comparison of left ventricular function and metabolism in neonatal (mean age = 7 days) and weanling (mean age = 96 days) piglets. Six animals in each group supported on cardiopulmonary bypass were subjected to (1) 120 minutes of hypothermic crystalloid cardioplegic arrest (CP-120) and (2) 15 minutes of normothermic ischemic arrest (NA-15) after a 60 minute interval of reperfusion. Left ventricular systolic and diastolic function was measured after each intervention via endocardially implanted ultrasonic dimension crystals in a septolateral minor-axis position. In both groups, systolic dysfunction was evidenced by an increase in the dimension-axis intercept (p = 0.001), but not the slope of the end-systolic pressure-dimension relation. Left ventricular end-diastolic stiffness, expressed as left ventricular end-diastolic pressure versus Lagrangian strain, increased to a similar degree in both groups (p = 0.001). Adenosine triphosphate levels declined significantly (p = 0.001) in both groups in response to the ischemic interventions with no evident intergroup differences. Lactate levels increased significantly during the course of the experiment (p = 0.04); however, the increases were greater (p = 0.009) at all intervals in the neonatal group. This study demonstrates age-related metabolic differences in response to ischemia consistent with a greater dependence on glycolysis in neonatal myocardia. However, the fact that discriminating age-related differences in left ventricular function were not evident suggests that factors other than young age per se account for the increased surgical mortality in the neonatal period.
authors: Department of Cardiovascular Surgery, Hospital for Sick Children, Toronto, Ontario, Canada.
authors: J G
authors: JG
authors: Coles
authors: T
authors: T
authors: Watanabe
authors: G J
authors: GJ
authors: Wilson
authors: L N
authors: LN
authors: Benson
authors: G M
authors: GM
authors: Kent
authors: D A
authors: DA
authors: Mickle
authors: A D
authors: AD
authors: Romaschin
authors: J
authors: J
authors: Villamater
authors: H
authors: H
authors: Ujc
authors: W G
authors: WG
authors: Williams
mesh_terms: D000255:Adenosine Triphosphate / Q000032:analysis; D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D001794:Blood Pressure; D002315:Cardiopulmonary Bypass; D003327:Coronary Disease / Q000378:metabolism / Q000503:physiopathology*; D004195:Disease Models, Animal; D007773:Lactates / Q000032:analysis; D009206:Myocardium / Q000032:analysis; D013552:Swine
chemical_list: D007773:Lactates; D000255:Adenosine Triphosphate