Neurodevelopmental Outcomes in Children With Fontan Repair of Functional Single Ventricle

DISCUSSION

Therapeutic advances that have resulted in improved survival and surgical outcomes for children with congenital heart disease during the past 3 decades may have also enhanced the neurodevelopmental outcomes in these children. In our study, the majority of children with Fontan correction of complex heart disease and functional single ventricle had intellectual function within the normal range. In early studies, developmental delay and lower IQ were more common in children with congenital heart disease.^{10 11} These lower scores were more evident in the first 3 years of life, especially in cyanotic children, when decreased physical capacity or symptoms would have negatively influenced gross motor function.¹² Age at cardiac repair was also older than current practice at most cardiac centers.

In contrast to early studies, our data revealed no significant correlation between IQ or visual motor integration ability and degree of hypoxemia or age at Fontan. Previous studies have reported lower intelligence for cyanotic than acyanotic children, attributed to the degree of hypoxemia.^{13 14} It is further suggested that these differences persist even when the effect of neurologic abnormalities and definitive surgery is removed and remain despite the severity of illness or the child's age at testing.¹³Newburger and colleagues¹⁴ also reported that postponing repair of a cyanotic congenital heart defect is associated with progressive impairment of cognitive function. The degree or duration of hypoxemia had no apparent effect on cognitive outcome in our patients. Consistent with our findings, Oates et al¹⁵ has recently reported no evidence of detrimental effect of older age at operation in children with cyanotic heart disease as assessed by neuropsychologic measures.

As previously mentioned, the likelihood of cerebral injury or poor neurodevelopmental outcome is also believed to be related to cardiopulmonary bypass, duration of hypothermic circulatory arrest, and patient age at time of surgery.^{5 16} Although longer cardiopulmonary bypass at Fontan had no apparent adverse effects on intelligence or visual motor integration ability, children who had prior deep hypothermic circulatory arrest with the Norwood procedure had a somewhat lower IQ. In a study of infants who underwent an arterial switch, surgery performed with circulatory arrest as the predominant support strategy has been associated with a higher risk of delayed motor development and neurologic abnormalities at 1 year of age.¹⁷ The score on the Psychomotor Development index¹⁷ was inversely related to the duration of circulatory arrest. In an earlier report, these investigators reported that the intraoperative variable most strongly associated with cognitive outcome was the duration of core cooling on cardiopulmonary bypass before deep hypothermic circulatory arrest.¹⁸ Our patients with prior circulatory arrest during Norwood procedures had intelligence quotients ranging from 70 to 100, in contrast to a recent report of major developmental disabilities (4 moderate and 3 severe-to-profound mental retardation) in 7 (64%) of 11 children who had prior Norwood procedures.¹⁹ Although the number and type of palliative or staged procedures before Fontan varied among our patients, the Fontan operation was the definitive surgical procedure. It is beyond the scope of our study to isolate the effects of these palliative procedures on intellectual functioning from the status after cardiac repair. The normal intellectual functioning in the majority of our patients after Fontan is encouraging, however, in view of the reported stability between preoperative child IQ and postoperative adult IQ in patients with cyanotic tetralogy of Fallot.²⁰

Our data suggested a mild weakness in visual motor integration in these children. Poor visual motor integration can result from slow maturation, inadequate educational experiences, socioeconomic disadvantage, and/or neurologic and chronic health problems.⁸ Three children with borderline to low VMI scores had significant behavior problems and 1 had below average academic performance. Significant improvements in VMI test scores and similar sensory-motor measures after various types of teaching programs have been reported.⁸ Recognition is important to help prevent learning and behavioral problems through early intervention.