Blood Based Assessment of sST2, Taken During and After Surgery, for Pediatric Patients With Heart Defects to Predict Heart Failure.

This study is measuring a blood protein called sST2 in children who are having open-heart surgery to see if it can predict which patients might develop heart failure after surgery. **You may be eligible if:** - Your child is scheduled for open-heart surgery (cardiopulmonary bypass) for a heart condition - You and/or your child speak German well enough to provide written consent **You may NOT be eligible if:** - Your child has a known genetic condition that limits life expectancy - Your child has a syndrome that is likely to require surgery on more than one organ - Your child weighs less than 2.5 kg at the time of surgery - Your child is already enrolled in another interventional clinical study Talk to your doctor to see if this trial is right for you.