Anat Cell Biol.  2019 Mar;52(1):38-42. 10.5115/acb.2019.52.1.38.

Morphological classification of the moderator band and its relationship with the anterior papillary muscle

• Lee JY
• Hur MS

• KMID: 2442327
• DOI: http://doi.org/10.5115/acb.2019.52.1.38

Abstract

This study investigated and classified the various types of moderator band (MB) in relation to the anterior papillary muscle, with the aim of providing anatomical reference information and fundamental knowledge for use when repairing the congenital defects and understanding the conduction system. The study investigated 38 formalin-fixed human hearts of both sexes obtained from donors aged 38-90 years. The MB was evident in 36 of the 38 specimens (94.7%). The morphology of the MB and its connection with the APM took various forms. The MBs that had a distinct shape were classified into three types according to their shape: cylindrical column, long and thin column, and wide and flat column. Types 2 and 3 were the most common, appearing in 15 (41.7%) and 14 (38.9%) of the 36 specimens, respectively, while type 1 was observed in seven specimens (19.4%). Type 3 was divided into subtypes based on their length. The MB usually originated from a single root (91.7%), with the remainder exhibiting double roots. The pairs of roots in the latter cases had different shapes. The originating point of the MB ranged from the supraventricular crest to the apex of the ventricle. The most-common originating point was in the middle (25 of 36 specimens, 69.4%), followed by the upper third (13.9%), the lower third (11.1%), and the top fifth (5.6%) of the interventricular septum. This study has produced fundamental anatomical and clinical information that will be useful when designing cardiac surgical procedures.

Keyword

Moderator band; Right ventricle; Anterior papillary muscle; Conduction system

MeSH Terms

Cardiac Surgical Procedures
Classification*
Congenital Abnormalities
Heart
Heart Ventricles
Humans
Papillary Muscles*
Tissue Donors

Figure

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  Fig. 1 Morphological classification of the moderator band (arrowheads). (A) Cylindrical column type. (B) Long and thin column type. (C) Wide and flat column type.

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  Fig. 2 Two types of roots of the moderator band (MB). (A) The MB usually originated from a single root. (B) A specimen that originated from double roots (asterisks).

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  Fig. 3 Branches of the moderator band (MB). The MB sometimes divided into two branches (A) or three branches (B) before attaching to the anterior wall of the right ventricle as well as the anterior papillary muscle (APM).

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