At low magnification (panel A), a transverse section through the central fibrous body shows the characteristic arrowhead configuration of the atrioventricular bundle (AVB) astride the interventricular septum (IVS). The specialized muscle of the bundle, however, contains granulation tissue and fibrosis (arrows) denoting healing damage. High magnification (panel B) discloses the interface between the healing damage and the remaining viable specialized muscle. Gomori trichrome, panel A calibration bar=300µ, panel B calibration bar=50µ).