Mitral Valve Prosthesis Insertion with Preservation of the Sub-Valvar Apparatus

Abstract

The atrio-ventricular valves (tricuspid and mitral) are characterized by their connections to their respective ventricles by tendinous chords that arise from muscular projections from within the ventricular walls, the papillary muscles. Within the left ventricle, there are two principal papillary muscles whose names are derived from their anatomical positions within the left ventricle. They are the antero-lateral and postero-medial papillary muscles. These muscle projections are composed of muscle fibers that descend from the base of the ventricle and then turn inward and upward to extend as vertical fibers, which form the papillary muscles.¹ Each papillary muscle gives rise to tendinous chords that insert into both aortic and mural leaflets, which are fan-shaped at the commissures. They, with the mitral valve leaflets, form a ventricular inflow tract for the blood leaving the left atrium (Fig. 6.1). There are three tiers of tendinous chords extending from the papillary muscles and are referred to as the primary, secondary, and tertiary chords. The primary chords insert into the leading edge of the leaflets, guiding them into early apposition; the secondary chords are responsible for load transference into the body of the leaflets; the tertiary chords are found in relation to the mural leaflet. They usually arise from the ventricular wall or toward the base of the papillary muscles and insert into the base of the leaflet at its origin from the atrio-ventricular junction.² They are loaded throughout the cardiac cycle, acting rather like “tie-rods” in an engineering sense.