Cardiopulmonary bypass reduces atrial Na+-K+-ATPase expression in children

Cardiopulmonary bypass (CPB) may induce serious side effects, potentially leading to myocardial failure. The Na+-K+-ATPase is a key component for myocardial function. Due to its developmental regulation, results from adult studies cannot be adopted to the situation in childhood. Right atrial myocardium from patients with left-to-right shunts at atrial level (VO, n = 8) and those without (NO, n = 8) was excised during heart surgery before and after CPB. Na+-K+-ATPase isoforms ATP1A1 (p = 0.008) and ATP1A3 (p = 0.038) decreased during CPB, which decrease was restricted to the VO group. This study highlights the importance of the underlying heart defect for susceptibility to the effects of CPB, showing a reduced Na+-K+-ATPase mRNA expression only in patients with left-to-right shunts on the atrial level. This seemed to be an early molecular event, as apart from one, none of the patients showed heart failure before or after surgery.