Myocardial Adenosine Triphosphate Content as a Measure of Metabolic and Functional Myocardial Protection in Children Undergoing Cardiac Operation

Abstract

In an effort to quantitate the metabolic and functional response to global myocardial ischemia as a prelude to specific interventions to improve myocardial protection in children, the following data were collected. Twenty children (age, 1.16 ± 0.3 years) underwent repair of congenital intracardiac malformations using aortic cross-clamping and cold potassium cardioplegia (ischemic time, 56.1 ± 4.5 minutes). Metabolic protection was assessed by measuring the myocardial adenosine triphosphate (ATP) content by microbioluminescence. Before and after ischemia 10-mg myocardial samples were obtained from the left ventricular apex using a Tru-cut biopsy needle. In 15 patients, postoperative ventricular function was measured by radionuclide ventriculography at 72 to 96 hours following operation. Five of 6 patients with a postischemic ATP level less than 40% of control (26.3 ± 2.8) had a left ventricular ejection fraction (EF) lower than 55% (50.3 ± 2.3). Seven of 9 patients with an ATP level greater than 40% of the preischemic level (98.0 ± 14.4) had a normal EF (61.8 ± 2.9; p < 0.04). Two other patients with postischemic ATP levels lower than 40% of control died of low cardiac output and had no postoperative ventricular function studies. Thus, of 7 patients with postischemic ATP levels lower than 40% of preischemic levels, 2 died and 5 had depressed left ventricular function. These data support the concept that low postischemic ATP levels correlate with death or poor postoperative ventricular function, and indicate that this variable will be useful to assess future improvements in myocardial protection during pediatric cardiac operations.