This study evaluates the effect of heart-lung bypass on babies undergoing cardiac surgery. The investigators want to learn more about the inflammation that exposure to bypass creates in the body by studying markers of inflammation and cell injury in the bloodstream. Additionally, the investigators want to examine if these markers can predict which babies develop post-surgical complications. The hypothesis is that babies who undergo bypass will have higher levels of these markers than babies not exposed to bypass and that these markers will correlate with how the baby does clinically after surgery.

This study will evaluate markers via blood sampling in babies with congenital heart disease who do not undergo cardiac surgery, those that undergo surgery without bypass, and those that undergo surgery with bypass. The overall goal is that this study will lead to useful biomarkers and lay the groundwork for future novel therapies aimed at improving outcomes for babies who require heart-lung bypass.

This is a minimal risk observational study looking at markers of inflammation and cell injury in the bloodstream of babies with congenital heart disease, with a particular emphasis on whether these markers can predict low cardiac output syndrome in infants who undergo heart-lung bypass. Low cardiac output syndrome is a common postoperative complication marked by poor blood flow to the body affecting nearly 1/3 of infants post-bypass and is associated with significant morbidity and mortality.

Babies not requiring surgery will serve as the control group. Infants in group 1 will have 0.5 ml of blood drawn prior to discharge. This will be scavenged from the laboratory when possible. Infants in groups 2 and 3 will require serial blood draws over peri-operative time points each in the volume of 0.5 ml.

Group 2:

T0 = Before surgery (in the OR) T1 = After chest closure or end of case (in the OR) T2 = On admission to the pediatric intensive care unit T3 = Timed 4-6 hours after the time of admission T4 = Timed 12 hours (+/- 1 hour) after the time of admission T5 = Timed 24 hours (+/-1 hour) after the time of admission

Group 3:

T0 =Pre-cardiopulmonary bypass to be obtained in the operating room just prior to surgery T1 = After going on bypass (but prior to modified ultrafiltration) T2 = After modified ultrafiltration T3 = On admission to the pediatric intensive care unit T4 = Timed 4-6 hours after the time of admission T5 = Timed 12 hours (+/- 1 hour) after the time of admission T6 = Timed 24 hours (+/-1 hour) after the time of admission

Inclusion Criteria:

• Infants < 6 months of age
• Born at ≥ 36 weeks gestational age
• Birth weight ≥ 2.5 kilograms
• Postnatally confirmed congenital heart disease by echocardiogram

Exclusion Criteria:

• Requiring ≥ 2 vasopressors prior to surgery
• Preoperative proven sepsis within one week of surgery
• Prior surgery within one week of cardiac repair (except PA banding which is not excluded)
• Cardiac catheterization within one week of surgery
• Significant extra-cardiac anomalies that may impair organ function

Infants <6 months of age with congenital heart disease at OU Children's Hospital