The clinical anatomy of the crista terminalis, pectinate muscles and the teniae sagittalis

The crista terminalis (CT) is an important anatomic landmark due its close association with the sinoatrial node artery and the origin of the pectinate muscles (PM). However, the gross anatomy of the PM in relation to the CT has not been well described. The aim of our study has been to investigate the location and the morphology of PM in relation to the CT. We examined 300 adult formalin-fixed human hearts. All PM originated from the CT and extended along the wall of the appendage toward the vestibule of the tricuspid valve. It was observed that the PM varied significantly with respect to arrangement and course of its fibers. We were able to classify the course of the PM, including the most prominent PM called the tenia sagittalis (TS), into 6 different patterns with 3 different TS types. In Type A (15%), the TS was absent. Type B (65%) demonstrated a single TS and Type C (20%) was characterized by the presence of multiple TS. Furthermore, the course of the PM was classified into 6 patterns: Type I (40%), the PM was oriented perpendicular to the CT with uniform spacing and lack of crossover (trabeculation); Type II (20%), non-uniform PM was organized in a haphazard, trabecular fashion with numerous crossovers; Type III (15%), the PM had uniform spacing with no trabeculation with fibers oriented parallel to the CT; Type IV (10%), had arborizing PM originating from a common muscular trunk (solitary trunk); Type V (10%), fibers were oriented both perpendicular and parallel to the CT, similar in architecture to Type III, but with more than one common muscular trunk; Type VI (5%), prominent muscular column with velamentous PM with potential implications in cardiac catheterization procedures. The exact morphology of PM and TS may be clinically important in right atrial catheterization procedures, as well as in the development of arrhythmias but further investigations are now necessary to prove this theory.