ABSTRACT
SYMMETRIC AND ASYMMETRIC TETHERING Symmetric Tethering The displacement of the papillary muscles can cause symmetric tethering as for example in some cases, global dilatation of the left ventricle due to dilated cardiomyopathy. Apical infarction can cause symmetric or asymmetric tethering (6). Symmetric tethering can displace the complete line of coaptation rather symmetrically into the ventricle. In a normal heart, the anterolateral and posteromedial papillary muscles or groups of papillary muscles are situated more or less under the adjacent commissure. In severe dilatation of the left ventricle they may not only be displaced toward the apex but also be situated more eccentric (lateral or medial) in relation to the adjacent commissure (Fig. 16.1). Even severe left ventricular (LV)
dilatation not always induces relevant outward displacement of the papillary muscles (1). The extent and effect of the eccentric displacement may be dependent on the shape of the papillary muscles as well as on the extent and pattern of annulus dilatation. As a fi nal consequence, the mobility of the anterior mitral leafl et (AML) and posterior mitral leafl et (PML) may be restricted, and the free margin of the posterior and anterior leafl et may be displaced apically (7). As the PML is rather short, the echocardiographic appearance of apical displacement might be a posteriorly retracted PML. In some patients with severe LV dilatation the P1 segment of the leafl ets may be retracted laterally and the P3 segment medially. This lateral and medial retraction can lead to incomplete closing along the indentations on both sides of the P2 segment with two major jets originating from line of coaptation on the lateral and medial side of the P2. However, in most patients with symmetric tethering the major jet originates from the central part of the line of coaptation and may extend to the medial and lateral sides in various degrees.
