Analysis of the aortic root in patients with tetralogy of Fallot undergoing early repair: Form follows function

Objective Aortic root dilatation remains of concern late after repair for tetralogy of Fallot (ToF). We have previously demonstrated that the aortic root size decreases progressively after early correction. To test whether the aortic wall changes are intrinsic or acquired, a histologic study was performed of infants at early repair. Methods From 24 of 31 infants undergoing ToF repair (mean age, 5.9 ± 4.9 months), ascending aortic biopsies were obtained. After conventional staining, the specimens were given a histologic score (0-3) for medionecrosis, ground substance accumulation, fibrosis, smooth muscle cell disarray, and apoptosis. The aortic root diameters were monitored using echocardiography for ≤2 years postoperatively. Results Nearly one half of the specimens showed signs of fibrosis (45%), with increased mucoid accumulation in 15% and elastin fragmentation in 5%. The aortic root was dilated in all infants at operation (mean indexed diameter—annulus, 38.1 ± 5.8; sinus, 47.8 ± 6; sinotubular junction, 38.7 ± 5.4 mm/m2 ) and had regressed significantly within 2 years (mean indexed diameter—annulus, 27.9 ± 4.7; sinus, 36.4 ± 5.1; sinotubular junction, 30.4 ± 6 mm/m2 ; P