Specifically, 12 of 14 (86%) neonates with the most severe scores—advanced AV block and/or at least one extranodal manifestation—have the highest serum levels of S100A4 (>86 ng/mL); the lowest of the 14 being a milder case (endocardial fibroelastosis with no block) (Figure 7). This evidence concerns the gene S100A4 and endocardial fibroelastosis.