Morphology of moderator bands (septomarginal trabecula) in porcine heart ventricles.

The morphology of moderator bands in both heart ventricular cavities was examined on macro- and microscopic levels in 14 six-month-old Landrace pigs. One transverse moderator band, measuring 2.9 ± 0.6 mm in diameter, was located between the septum and the free wall of the right ventricular cavity. On cross-section, clumps of conductive cells were found at the periphery of the moderator band and in its central part around the blood vessels. Large amounts of muscle fibres were identified. The left ventricular cavity contained moderator bands in the form of thin cords, measuring 1.05 ± 0.09 mm in diameter and located mostly between the interventricular septum and the papillary muscles. Conductive tissue was represented by clumps of Purkinje cells, surrounded by myocardial fibres. The proportion of conductive cells and muscle fibres in the moderator bands was approximately the same. Owing to different amounts of conductive cells and muscle fibres in the bands, we assume that moderator bands in the right and left ventricles play different primary functional roles. Our results were compared with previous data on pigs and other ungulate animal species.