Left ventricular (LV) false tendons are chordlike structures that traverse the LV cavity. They attach to the septum, to the papillary muscles, or to the free wall of the ventricle but not to the mitral valve. They are found in approximately half of human hearts examined at autopsy. Although it has been more than 100 years since their initial description, the functional significance of these structures remains largely unexplored. It has been suggested that they retard LV remodeling by tethering the walls to which they are attached, but there are few data to substantiate this. Some studies have suggested that false tendons reduce the severity of functional mitral regurgitation by stabilizing the position of the papillary muscles as the left ventricle enlarges. LV false tendons may also have deleterious effects and have been implicated in promoting membrane formation in discrete subaortic stenosis. This article reviews current understanding of the anatomy, echocardiographic characteristics, and pathophysiology of these structures.
Left ventricular (LV) false tendons were first described in 1893 by the British anatomist and surgeon Sir William Turner. Although more than 100 years have passed since that initial description, the functional significance of these structures remains largely unexplored. Turner proposed that they retard LV enlargement (remodeling) by tethering the walls to which they are attached, but there are few data to substantiate this. It has also been suggested that false tendons reduce the severity of functional mitral regurgitation (MR) by stabilizing the position of the papillary muscles as the left ventricle enlarges. LV false tendons may also have deleterious effects and have been implicated in promoting membrane formation in discrete subaortic stenosis (DSS). This article reviews current understanding of the anatomy, echocardiographic characteristics, and pathophysiology of these structures.
Anatomy of Left Ventricular False Tendons
During embryologic development of the heart, two distinct myocardial layers can be identified: an outer condensed layer and an inner, less compact layer. The latter is composed of trabeculations that produce irregular ridges that protrude into the LV cavity and are separated from one another by intertrabecular recesses. False tendons arise from the inner trabeculated myocardial layer, but unlike trabeculations, these chordlike structures traverse the LV cavity.
LV false tendons are found in about half of hearts examined at autopsy and occur with equal frequency in normal hearts and in those with congenital malformations. Autopsy and surgical series have demonstrated a slight male preponderance. False tendons give attachment to the LV free wall, to the interventricular septum, or to the papillary muscles. On the basis of their sites of attachment, five types have been delineated, as depicted in Figures 1 and 2 . False tendons range in thickness up to about 3 mm and contain varying amounts of fibrous and myocardial tissue as well as coronary vessels, which run the length of their shafts, and Purkinje fibers, which are in continuity with the left bundle branch of the conduction system ( Figure 3 ). False tendons containing conduction tissue have been identified as substrates of intracavitary ventricular tachycardia and have been successfully ablated. In one study, such false tendons consistently extended from the inferoposterior LV wall to the septum and were the focus of ventricular tachycardia characterized by right bundle branch block morphology and left-axis deviation. It is worth noting that the right ventricle harbors a solitary false tendon, commonly called the moderator band, which contains conduction tissue arising from the right bundle branch of the conduction system.
Echocardiographic Features of Left Ventricular False Tendons
According to a number of early studies, LV false tendons are found far less often echocardiographically than at autopsy, but detection rates appear to have improved with the advent of harmonic imaging. In one study using pathologic specimens explanted at the time of cardiac transplantation as a standard, the preoperative sensitivity and specificity of echocardiography in detecting false tendons were 82% and 85%, respectively. It should be emphasized, however, that conventional imaging planes are not well suited for detecting LV false tendons, and off-axis imaging is often required. In general, longitudinally oriented false tendons can best be seen in parasternal or apical long-axis views, whereas transversely oriented false tendons are more readily visualized in the apical four-chamber and short-axis views ( Figure 4 ). False tendons become more taut in diastole and more lax in systole ( Figure 5 ); LV enlargement may render them taut throughout the cardiac cycle. When sufficiently taut and oriented more or less perpendicularly to the axis of blood flow, false tendons vibrate in much the same way as the strings of an Aeolian harp ( Figure 6 ) when swept by the wind. These vibrations can be seen as fine fluttering on M-mode recordings ( Figure 7 ) and may be the cause of innocent (Still’s) murmurs. Identification of false tendons is enhanced in the dilated, thin-walled ventricle, which causes them to stand away from away from the endocardial surface of the heart. LV false tendons are sometimes mischaracterized. Those near the LV apex may be confused with the edge of a thrombus, and those closely applied to the septum may give the false impression that there is LV hypertrophy or hypertrophic cardiomyopathy. Features that help in differentiating false tendons from other structures include the presence of echo-free spaces on both sides of the tendon and systolic laxity. It is worth noting that LV false tendons frequently fan out, creating a broad base of attachment to the LV wall, as depicted in Figures 2 F and 4 B, which can be mistaken for a papillary muscle, thrombus, or trabeculation. Rupture of a false tendon, whether spontaneous or in the setting of myocardial infarction, produces highly mobile intracavitary echoes that must be distinguished from vegetations, thrombi, and ruptured chordae tendineae.
Epidemiologic data from the Framingham Heart Study revealed that individuals with echocardiographically identified LV false tendons are more likely to have lower body mass indexes, but, this finding may be a reflection of the superior image quality obtained in such individuals. The same study found that electrocardiographic criteria for LV hypertrophy were more common among individuals with LV false tendons. Finally, the Framingham study concluded that the presence of LV false tendons on echocardiographic examination failed to impart any increase in mortality risk.
Echocardiographic Features of Left Ventricular False Tendons
According to a number of early studies, LV false tendons are found far less often echocardiographically than at autopsy, but detection rates appear to have improved with the advent of harmonic imaging. In one study using pathologic specimens explanted at the time of cardiac transplantation as a standard, the preoperative sensitivity and specificity of echocardiography in detecting false tendons were 82% and 85%, respectively. It should be emphasized, however, that conventional imaging planes are not well suited for detecting LV false tendons, and off-axis imaging is often required. In general, longitudinally oriented false tendons can best be seen in parasternal or apical long-axis views, whereas transversely oriented false tendons are more readily visualized in the apical four-chamber and short-axis views ( Figure 4 ). False tendons become more taut in diastole and more lax in systole ( Figure 5 ); LV enlargement may render them taut throughout the cardiac cycle. When sufficiently taut and oriented more or less perpendicularly to the axis of blood flow, false tendons vibrate in much the same way as the strings of an Aeolian harp ( Figure 6 ) when swept by the wind. These vibrations can be seen as fine fluttering on M-mode recordings ( Figure 7 ) and may be the cause of innocent (Still’s) murmurs. Identification of false tendons is enhanced in the dilated, thin-walled ventricle, which causes them to stand away from away from the endocardial surface of the heart. LV false tendons are sometimes mischaracterized. Those near the LV apex may be confused with the edge of a thrombus, and those closely applied to the septum may give the false impression that there is LV hypertrophy or hypertrophic cardiomyopathy. Features that help in differentiating false tendons from other structures include the presence of echo-free spaces on both sides of the tendon and systolic laxity. It is worth noting that LV false tendons frequently fan out, creating a broad base of attachment to the LV wall, as depicted in Figures 2 F and 4 B, which can be mistaken for a papillary muscle, thrombus, or trabeculation. Rupture of a false tendon, whether spontaneous or in the setting of myocardial infarction, produces highly mobile intracavitary echoes that must be distinguished from vegetations, thrombi, and ruptured chordae tendineae.
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