Significant ventricular hypoplasia in infants with unbalanced atrioventricular (AV) canal often leads to a univentricular rather than the more desirable two-ventricle repair. Our hypothesis is that forward flow across the AV valve generates a ventricular growth signal and creates the possibility of a two-ventricle repair. The growth potential exists even for severely hypoplastic ventricles, however, time must be available for it to occur and the septal defects can not be closed if the dominant ventricle must still contribute to the systemic output. The components of the surgical approach were suggested by the hypothesis. Flow was maximized across the hypoplastic AV (mitral or tricuspid) valve by patch closure of the primum atrial septal defect and creation of a snared (restrictive) secundum atrial septal defect. The mitral and tricuspid valves were also repaired. The snared defect was narrowed off cardiopulmonary bypass until a 5-7-mmHg mean gradient across the atrial septum was reached. If the ventricular septal defect was required to augment the systemic output by right-to-left shunting, only partial closure was done and a pulmonary artery band was also necessary. This staged approach safely allowed time for ventricular growth if the small ventricle was not able to immediately deliver a satisfactory cardiac output. With this flexible approach, time was available for the ventricular imbalance to correct and the two-ventricle repair to be safely completed. The growth response of the hypoplastic ventricles has been relatively rapid. Within weeks, ventricles more than 4 S.D.s of the mean below predicted, achieved an essentially normal end diastolic volume. For less severe ventricular hypoplasia, a two-ventricle repair was completed. When necessary, a snared atrial septal defect was created to allow atrial decompression until the moderately hypoplastic ventricle grew. The benefits of a two-ventricle repair in comparison to the univentricular solution should be considerable and will increase with time.
- Unbalanced atrioventricular canal defect
- Ventricular growth