False chordae tendineae in the right ventricle of a human heart have been studied very cursorily so far. In the available literature there are no case studies referring to the build, localization and frequency of occurrence of the structures. They have rarely been described in the heart during additional examinations, for example echocardiography or when performing a routine autopsy.
The presence of FChT was observed in all examined hearts. The variety of frequency of their occurrence within individual types is very wide. In the right ventricle, mostly represented were FChT of type V, whose attachments are located below the bases of papillary muscles (except chordae reaching the septomarginal trabecula). Due to changeable localization of papillary muscles in the right ventricle, the area of occurrence of FChT of type V varies within the examined population and includes 1/3, even up to 1/2 of the bottom part of the ventricle. Topographically, chordae of that type occupy the largest area in the right ventricle. They also show the greatest morphological diversity. The remaining types of chordae occur in the examined population less frequently and show far less diversity of structure.
Very similar, average frequency of occurrence was observed within two other types of FChT – I and III (connection between papillary muscles and respectively outer wall of the ventricle and interventricular septum). No significant correlation between occurrence of the chordae was determined. However, they possess many common characteristics; usually they reach the posterior papillary muscle, are of medium length and thickness and most possess a simple attachment.
Similar to the two previous types, slightly lower average frequency of occurrence was observed in type VI. They are the chordae reaching the septomarginal trabecula. Each of the above types was observed in around a half of examined hearts.
The remaining kinds (type II and IV) occurred far less frequently, connecting segments of papillary muscle and papillary muscles with each other.
], in his first studies on FChT in the left ventricle of a human heart, used the term “moderator band”. This is an obvious analogy to the septomarginal trabecula present in the right ventricle. The expression “moderator band” is also commonly used in literature referring to animals (mammals, e.g. ungulates, carnivores), which do not possess a typical septomarginal trabecula, although multiple muscle bundles running through the lumen of the ventricles are present. Topographically they correspond with FChT occurring in primates; however, their microscopic build is different as they are mostly composed of Purkinje fibres.
The term “false chordae tendineae” is used in medical literature. Clearly, the expression became popular on the basis of macroscopic studies. False chordae tendineae, especially in preserved material, look identical to the chordae tendineae of valve apparatus, visibly different from neighbouring muscle structures. Also, in non-preserved material, differences between chordae are not serious. They are similar, filiform structures, differing only, and often very relatively, in colour. This results from filming muscle tissue through the endocardium, which lends false chordae a beige-rose hue. In preserved material, where the muscular tissue changes colour to light brown, the hue differences disappear.
False chordae tendineae in the human heart were described as a clinical problem in reference to the left ventricle. Already in the first publications, they were mentioned as a cause of abnormal acoustic phenomena occurring in the heart. Browicz, paying attention to FChT located in the outflow tract from the left ventricle, noted that by causing the vibrations of flowing blood stream, they may be the reason for unusual sounds [10
]. This quite cautious statement draws attention to the connection between turbulent flow and occurring murmurs. At present it is known that in adult humans, FChT without organic disease should not cause flow disorder resulting in occurrence of murmurs.
Along with improving non-invasive cardiac examination, especially echocardiography, there appeared a possibility of precise evaluation of inner heart structure in a living human. In the nineteen seventies and eighties, case studies describing FChT in the left ventricle appeared. These authors paid attention to those structures as a potential source of misdiagnosis when evaluating, for example, a clot located at the wall of the ventricle. The chordae were also discussed as a source of cardiac arrhythmia [3
], their role was taken into account in preventing the ventricle from dilatating [1
] or they were not connected with any pathology [11
False chordae tendineae were mentioned among the causes of functional murmurs observed in children and young adults. Attempts to explain the phenomenon have been present in the literature for many years [4
]. Due to the lack of direct correlation between occurrence of FChT and, according to many authors, observing changeable functional murmurs, connecting both phenomena seems to be very doubtful [13
]. The chordae located in the right ventricle are not a very probable substrate of additional acoustic phenomena, due to the haemodynamic conditions present in its lumen.
In the context of the human cardiac conduction system, the subject of FChT is rarely described in the literature. The right branch of the His bundle runs subendocardially in the front part of the septa and, according to many authors, it invades the septomarginal trabecula, going towards the base of anterior papillary muscle [15
]. Histological examinations of the septomarginal trabecula confirm the presence of the right branch only in a proportion of examined hearts [17
The significance of FChT was also noticed in the aspect of pulmonary thromboembolic problems. The conducted studies pay attention to the possibility of more frequent occurrence of thromboembolic incidents in the central nervous system in people who were diagnosed with FChT in the left ventricle during echocardiography [6
]. Due to haemodynamic conditions, forming new thromboembolic material in the right ventricle seems to be easier than in the left one. Recurring incidents of pulmonary thromboembolism are known from the literature in spite of such radical methods of treatment as using a filter in the inferior vena cava [19
]. With no other risk factors, formation of thromboembolic material in the right ventricle “cut” with FChT seems to be very probable.
Another problem deserving a more thorough discussion is the influence of FChT on introducing and final location of the electrode for heart stimulation. A number of factors seem to determine the process, as well as further intensification of morphological changes [7
]. Passing the electrode through the right atrioventricular orifice without a contact with the structures of the valve apparatus gives a greater chance for placing the tip in the apex of the right ventricle. In the examined material it is apparent that quite a clear influence may arise from the shape of anatomical structures located in the bottom part of the right ventricle. Apart from the obstacle caused by the septomarginal trabecula, one should also expect a significant proportion of FChT. Numerous structures around the apex of the ventricle (type V) and those reaching the septomarginal trabecula (type VI) may intensely hamper introduction of the electrode.
False chordae tendineae have also been described in animals [20
]. The internal structure of the human right ventricle and many primates is similar. The differences refer mostly to the development of the trabeculae carneae and the shape of the papillary muscles. Still, the structures are variable also within the above-mentioned groups [25
In other mammals, for example in carnivores, a typical septomarginal trabecula does not exist. However, there occur numerous and well-developed FChT. They are very visible while sectioning the heart, especially at almost smooth walls of the right ventricle, since trabeculae carneae of those animals are poorly diversified. Some ungulates, in which the septomarginal trabecula appears, also have a developed system of FChT.
Thorough discussion of FChT in the right ventricle of a human heart, taking into account anatomy, histology and functions, seems to be right and justified. Conducted analyses showed that they constitute permanent elements, creating, along with other structures of the right ventricle, a morphologically uniform build. The presented studies show that the still fragmentary knowledge needs to be deepened during further observations. It seems probable that in the future they will allow a firm definition of the role of FChT in the right ventricle and their presumptive connection with heart pathology.
The present work is the first of a scheduled series devoted to the problem of FChT. Further analyses will cover the subject of morphological aspects from a microscopic perspective.