The morphometric study of the moderator band in Thais

A moderator band, also known as the septomarginal trabecula, is a group of muscle bundles located in the ventricle of almost all human hearts. The morphology of the moderator band has various forms and several studies have focused mostly on its structure. Thus, in the present study, we sought to study the morphology and morphometry of the moderator band and tried to rearrange the criteria based on the previous studies to classify the moderator band in Thais. The study investigated 67 formalin-fixed human hearts of both sexes obtained from Thai donors aged 24-101 years with mean age at death 69.92 years. The moderator band was evident in 66 of the 67 specimens (98.51%). The moderator band had the mean or median of overall length, thickness, distance to the base of the tricuspid valve, distance to the base of the pulmonary valve, distance to the apex of the right ventricle, the angle at the septal connection, and angle of the papillary, which were 18.9 ± 6.4 mm, 3.17 (2.04-4.55) mm, 33.0 ± 7.97 mm, 38.8 ± 9.62 mm, 56.4 ± 8.09 mm, 50 (30-105)°, 73.9 ± 30.1°, respectively. The mean distance originating point from the supraventricular crest to the anterior papillary muscle was 0.396 ± 0.07 of the distance from the base of the tricuspid valve to the apex of the right ventricle. Our present classification found that crest-like and thick moderator band with complex secondary branching at high origin (type IVc), and low origin (type IVd) were the most common subtypes. This study provided both anatomical and clinical information that should be useful in cardiac surgery, radiology, and cardiac electrophysiological interventions.