Anatomical observations of the moderator band.

Apical ventricular septal defects are rare pathologies of the ventricular septum. The moderator band, or other large trabeculations, is the major obstacle for the repair of such defects. The aim of our study was to identify and describe variations in the size and anatomy of the moderator band. We studied the right ventricular apical trabeculations in 100 adult human cadavers. Overall, we identified the moderator band in 92% of hearts. In just over two-fifths (42%), the band was a short and thick trabeculation, whereas, in one-eighth (12%), it was long and thick. In just under one-quarter of the hearts (24%), the band was short and thin, whereas it was long and thin in 14% of the hearts. In the remaining eight hearts, we were unable to identify the moderator band. The mean thickness of the band was 4.5 +/-1.8 mm, and its mean length was 16.23 +/- 2.3 mm, ranging from 11.3 to 24.3 mm. According to these measurements, we were able to classify the band as originating less than 45% of the distance from the tricuspid valve to the apex (closer to tricuspid valve), seen in 12 hearts, between 45 and 55% of the distance from the valve to the apex, seen in 45 hearts, and greater than 55% of this distance (closer to the apex), seen in 39 specimens. We present these data that may prove useful in the setting of the surgical repair of apical ventricular septal defects through the right atrium. 2010 Wiley-Liss, Inc.