Between April 1990 and November 1993, 1,252 open heart operations were performed in infants and children with congenital heart defects. Prolonged open sternotomy was used in 113 patients (9%) in 10 surgical categories. Thirty-six of these children (32%) were infants and 43 (38%) were newborns. Twenty-four patients (21%) had undergone operation previously; 3 newborns had been treated with extracorporeal membrane oxygenation before the operation. The patients were grouped according to indications for prolonged open sternotomy as follows: group I, 31 patients with squeezed (large) heart syndrome (1 death); group II, 14 patients with hemodynamic instability after sternal approximation (2 deaths/14.2%); group III, 35 patients with low output state after bypass (17 deaths/48.5%); group IV, 21 patients with extracorporeal circulatory assist devices (15 deaths/71.4%); group V, 3 patients with severe arrhythmias (no deaths); and group VI, 9 patients with atypical tamponade that necessitated reopening the sternum in the intensive care unit (6 deaths/66.6%). Overall mortality was 36.2% (41 patients). Four group IV patients were weaned successfully from extracorporeal membrane oxygenation and heart transplantation was performed successfully on two others. All but one of the deaths occurred before delayed sternal closure. After hemodynamic stabilization was achieved, the sternum was closed in all 72 surviving patients with absorbable sutures (in 86% within the first 6 days after operation). In 50 patients (69% of survivors) pericardial substitution with a polytetrafluoroethylene membrane was performed. One newborn with mediastinal infection after extracorporeal membrane oxygenation was treated successfully with retrosternal drain and suction lavage.(ABSTRACT TRUNCATED AT 250 WORDS)