Biventricular Pacing in Children After Surgery for Congenital Heart Disease

"Randomization into one of 3 study arms for acute phase and for extended phase.~Measurement of baseline variables on arrival to CCU. Acute pacing protocol (order of pacing randomized):~1. Atrial sensing- right ventricular pacing 10 min.~2. 5 min no pacing (washout).~3. Atrial sensing - biventricular pacing 10 min.~4. 5 min no pacing (washout).~5. Intrinsic rhythm~6. 5 min no pacing (washout). Start extended phase pacing according to randomization. Measure hemodynamic variables 10 min after start of pacing.~Measure hemodynamic variables 30 min after start of pacing. Pacing hiatus for 60 minutes at 24 hours with measurement of hemodynamics without pacing and after reinitiating pacing.~Stop pacing at 72 hours or after extubation, whichever comes first. For those patients who are extubated before 72 hours: measurements will be taken before extubation and one hour after extubation. Pacing will then be stopped."