Effects of Cardiac Pacing on Left Atrial Function in Post Operative Pediatric Cardiac Patients

Rationale for study: infants and children with congenital heart disease who have undergone cardiac surgery are particularly susceptible to low cardiac output syndrome in the immediate postoperative period. neonates have a limited FrankxStarling mechanism and lack contractile reserve compared with their adult counterparts, so they depend more on heart rate to maintain cardiac output. This phenomenon may be further exacerbated by decreased ventricular compliance after cardiopulmonary bypass. Finally, sinus node dysfunction, commonly seen after pediatric cardiac surgery, is estimated to occur in 8x30% of patients. The unique physiology in pediatrics have led some to postulate that increasing the sinus rate with temporary atrial pacing may augment cardiac output. There is, however, conflicting data on whether pacing is beneficial in this patient population. no study to date has looked directly at the intra-cardiac mechanics as a result of pacing in children after cardiac surgery. overall objective: The goal of our study is to prospectively assess the effect of temporary atrial pacing on left atrial function immediately after cardiac surgery for congenital heart disease via 2D speckle tracking echocardiography (STe). Hypothesis: electrical cardiac pacing results in decreased left atrial function as measured by strain echocardiography. Primary outcome: Changes in global longitudinal strain ([?]) in the left atrium at baseline and during electrical pacing. Secondary outcomes: The secondary aim of the project is to assess markers of cardiac output with and without pacing. This includes blood pressure, near-infrared spectroscopy (niRS), aortic outflow Doppler and global longitudinal strain in the left ventricle at baseline and during electrical pacing.