Abstract 167: Growth Induction to Reverse Congenital Aortic Developmental Hypoplasia

Objectives: Congenital heart disease may include hypoplastic heart valves, ventricles or great arteries. Infants with coarctation of the aorta (CoA) often have a hypoplastic transverse aortic arch (TAA) which can greatly complicate surgical repairs. Although these defects are often considered to be genetic in origin, our hypothesis was that they are problems of development which are potentially reversible. We tested the corollary hypothesis that hypoplastic TAAs retain normal developmental potential and the increased aortic flow after CoA repair provides the biomechanical signal for catch-up growth. Methods: Infants (N = 19) with TAA hypoplasia who underwent surgical CoA repair were studied for TAA growth by echocardiography done prior to and at intervals up to 13 years later. The TAA diameters were indexed using nomograms and calculated as standard deviations from expected size (SDE). Normal range is ± 2 SDE and < −2 indicates hypoplasia. Results: 1) TAA growth was rapid and significant within 3 months. 2) The initial average TAA SDE = −3.7 (range: −7.6 to −2.1) (0/19 normal); 3 months = −1.5 (-4.1 to 0.9) (12/17); 1 year = −1.0 (-4.2 to 1.3) (15/19); 5 to 13 years = −0.6 (-2.1 to 0.9) (16/17 normal). Conclusions: 1) Hypoplastic aortic arches grew rapidly to normal size with increased flow following CoA repair. 2) The results suggest the cause of hypoplasia was underdevelopment from low flow and, when increased, flow provided the biomechanical signal to induce catch up growth. 3) Infants were a relevant model for demonstrating the aortic growth signal. 4) Growth induction by increased blood flow could be used to reverse aortic underdevelopment in other selected patients.