This is a prospective study looking at the effects of dexmedetomidine on pacemaker function in patients who have surgery for congenital heart disease utilizing cardiopulmonary bypass (CBP). For the purpose of the study, no change in intraoperative care will be dictated. The use of dexmedetomidine will be left up to the discretion of the treating physicians. The study will involve only the collection of data regarding the amplitude required to capture and specific demographics and intraoperative features including cross clamp time, time on CPB, and vasoactive agents that were and are being administered. In addition to these data, it will be noted whether dexmedetomdine was used or not and whether it is being administered on arrival to the CTICU.