Right ventricular false tendons, a cadaveric approach

Anatomy of the Right and Left Ventricular Subvalvular Apparatus of the Horse (Equus caballus)

Due to the growing interest among veterinarians and the increasing market demands, the development of equine cardiology is necessary. Currently, veterinary medicine for companion animals needs to catch up to human medicine-equine medicine included. A common condition in older horses is aortic valve regurgitation resulting from fibrosis, while its more severe form occurs in younger horses or develops due to a bacterial infection. Mitral valve regurgitation, especially dangerous due to the possibility of sudden death, has a better prognosis if the horse has valve prolapse. Tricuspid valve regurgitation usually does not pose a clinical problem, although its severe cases may lead to heart failure. Some pathologies can be treated surgically, which requires excellent knowledge of anatomy. The object of this study consisted of twenty domestic horse hearts. The focus was on the normal and comparative anatomy of the left and right subvalvular apparatus. The number of muscular bellies of the papillary muscles and the type of connection of the muscles were analysed. Moreover, the height of muscle originating from the ventricle wall was determined, the morphological regularity of the papillary muscle was assessed, and the chordae tendineae originating from the papillary muscles were examined. The conducted research allowed for comparing domestic horses with different species through other studies, the authors of which described this particular aspect. Interspecies similarities which may be correlated with the evolutionary relatedness, as well as differences that could reflect adaptation to different lifestyles, environmental conditions, or metabolic requirements of the animals, have been found. This study expands the knowledge of animals' normal and comparative anatomy, and contributes to the development of veterinary surgery, internal medicine, and biology.

Current management of tricuspid regurgitation: a focus on the spiral suspension approach

The indication for surgery for tricuspid regurgitation (TR) has reached a major turning point. It has become clear that the presence of moderate or severe TR alone worsens the prognosis of life, and the previous guidelines of Japanese Circulation Society, in which the indication for surgery was recommended at the timing of "right heart failure difficult to treat medically," now recommends surgery with a trigger of "repeated right heart failure" in the 2020 edition. In addition, a new repair technique targeting at subvalvular structure has been developed for end-stage TR to overcome a high TR recurrence rate that is associated with severe right ventricular enlargement and leaflet tethering. This review focuses on the spiral suspension technique, in which the papillary muscles are spirally suspended towards the septal leaflet annulus to correct tethering and enhances the understanding of its application in the context of TR management.

Anatomy of the Ventricular Outflow Tracts: An Electrophysiology Perspective

Outflow tract ventricular arrhythmias are the most common type of idiopathic ventricular arrhythmia. A systematic understanding of the outflow tract anatomy improves procedural efficacy and enables electrophysiologists to anticipate and prevent complications. This review emphasizes the three-dimensional spatial relationships between the ventricular outflow tracts using seven anatomical principles. In turn, each principle is elaborated on from a clinical perspective relevant for the practicing electrophysiologist. The developmental anatomy of the outflow tracts is also discussed and reinforced with a clinical case.

Cardiac ventricular false tendons: A meta-analysis

Ventricular false tendons are fibromuscular structures that travel across the ventricular cavity. Left ventricular false tendons (LVFTs) have been examined through gross dissection and echocardiography. This study aimed to comprehensively evaluate the prevalence, morphology, and clinical importance of ventricular false tendons using a systematic review. In multiple studies, these structures have had a wide reported prevalence ranging from less than 1% to 100% of cases. This meta-analysis found the overall pooled prevalence of LVFTs to be 30.2%. Subgroup analysis indicated the prevalence to be 55.1% in cadaveric studies and 24.5% in living patients predominantly studied by echocardiography. Morphologically, left and right ventricular false tendons have been classified into several types based on their location and attachments. Studies have demonstrated false tendons have important clinical implications involving innocent murmurs, premature ventricular contractions, early repolarization, and impairment of systolic and diastolic function. Despite these potential complications, there is evidence demonstrating that the presence of false tendons can lead to positive clinical outcomes.

Atypical imaging presentation of a massive intracavitary cardiac thrombus: A case report and brief review of the literature

Intracavitary cardiac thrombi, uncommonly found in the right chambers, have been shown to form secondary to endocardial and myocardial diseases. The differential diagnosis for an intracavitary cardiac mass is broad, including primary cardiac tumors, cardiac metastases, anatomic variants, vegetations, and thrombi. Here we present a unique case with a large calcified intracavitary cardiac thrombus in a 26-year-old woman with obesity, immune thrombocytopenic purpura, and a new diagnosis of systemic lupus erythematosus. Initial imaging presentation in this case masqueraded as a tumor, delaying the true diagnosis. A combination of cardiac imaging techniques, including transthoracic and transesophageal echocardiograms, cardiac CT, and cardiac MRI were required to correctly diagnose this calcified bland thrombus.

Resembling Left Ventricular False Tendon in a Father and His Daughter

Left ventricular false tendons (LVFTs) are linear fibrous or fibromuscular bands stretching across left ventricular cavity. Although LVFTs have been associated with various heart pathologies and investigated embryologically and histologically, there is only one report in the literature connoting possible hereditary transmission of this entity. We reported a father and his daughter having similar types of LVFTs with regard to location and thickness. With this report, we will contribute in the literature in respect to potential genetic inherence of LVFTs.

Atypical Chordae Tendineae of the Canine (Canis familiaris) Right Atrioventricular Valve

The canine right atrioventricular valve cusps are anchored to papillary muscles by chordae tendineae. During ventricular systole, these tendineae keep the cusps from being pushed into the atrium. While this is the general description for chordae tendineae, several researchers have briefly documented chordae tendineae in animal and human hearts that do not attach to papillary muscles. In the 39 canine hearts examined, atypical chordae tendineae were observed in two hearts. In both dogs, a single stranded chordae tendineae extended from the free edge of the parietal cusp of the right atrioventricular valve to the ventricular free wall. While the discovery of these atypical tendineae provides additional information on canine cardiac anatomy, their presence may also be clinically significant. A review of the veterinary and biomedical literature showed entanglement in normal chordae tendineae can be a complication during cardiac catheterization or pacemaker lead placement. Given this issue with normal chordae tendineae, it seems logical to propose that these atypical tendineae could also cause catheter or pacemaker lead entanglement and therefore warrant further study and documentation.

Modeling our understanding of the His-Purkinje system

The His-Purkinje System (HPS) is responsible for the rapid electric conduction in the ventricles. It relays electrical impulses from the atrioventricular node to the muscle cells and, thus, coordinates the contraction of ventricles in order to ensure proper cardiac pump function. The HPS has been implicated in the genesis of ventricular tachycardia and fibrillation as a source of ectopic beats, as well as forming distinct portions of reentry circuitry. Despite its importance, it remains much less well characterized, structurally and functionally, than the myocardium. Notably, important differences exist with regard to cell structure and electrophysiology, including ion channels, intracellular calcium handling, and gap junctions. Very few computational models address the HPS, and the majority of organ level modeling studies omit it. This review will provide an overview of our current knowledge of structure and function (including electrophysiology) of the HPS. We will review the most recent advances in modeling of the system from the single cell to the organ level, with considerations for relevant interspecies distinctions.

Morphology of moderator bands (septomarginal trabecula) in porcine heart ventricles

The morphology of moderator bands in both heart ventricular cavities was examined on macro- and microscopic levels in 14 six-month-old Landrace pigs. One transverse moderator band, measuring 2.9 ± 0.6 mm in diameter, was located between the septum and the free wall of the right ventricular cavity. On cross-section, clumps of conductive cells were found at the periphery of the moderator band and in its central part around the blood vessels. Large amounts of muscle fibres were identified. The left ventricular cavity contained moderator bands in the form of thin cords, measuring 1.05 ± 0.09 mm in diameter and located mostly between the interventricular septum and the papillary muscles. Conductive tissue was represented by clumps of Purkinje cells, surrounded by myocardial fibres. The proportion of conductive cells and muscle fibres in the moderator bands was approximately the same. Owing to different amounts of conductive cells and muscle fibres in the bands, we assume that moderator bands in the right and left ventricles play different primary functional roles. Our results were compared with previous data on pigs and other ungulate animal species.

Morphometric Analysis of the Foramen Magnum

OBJECTIVE

To further elucidate the importance of anatomic variations in morphology of the foramen magnum and associated clinical implications, we conducted a morphometric study.

METHODS

Seventy-two dry skulls were used for this study. Digital images were obtained of the foramen magnum from an inferior view. These images were studied using a computer-assisted image analysis system. Next, an image processor was used to calculate pixel differences between 2 selected points, which allowed accurate translation of pixel differences into metric measurements.

RESULTS

We found that the mean surface area of the foramen magnum was 558 mm2, the mean anteroposterior diameter was 3.1 cm, and the mean horizontal diameter was 2.7 cm. For comparison, surface areas were classified into 3 types based on size. Type I foramina were identified in 20.8% of the dry skulls (15 skulls) and exhibited a surface area of less than 500 mm2. Type II (66.6%, 48 skulls) was applied to foramina of an intermediate size with surface areas ranging between 500 to 600 mm2. Type III (12.5%, 9 skulls) was applied to large foramina with surface areas of more than 600 mm2.

CONCLUSION

These data may be of use as a morphometric database for description of “normal” variants of foramen magnum morphology.

Left ventricular myocardial bands: MDCT and MR appearance

Left ventricular (LV) myocardial bands or false tendons, which span the LV cavity to connect distant sites on the endocardium, are commonly visualized on echocardiography and at autopsy. However, this entity has not been described in the radiologic literature. In this article, we describe 4 cases of LV bands imaged using echocardiography, multidetector computed tomography, and magnetic resonance. We will also discuss the embryologic basis, anatomic findings, differential diagnosis, and clinical implications of this condition.

An endoscopic and anatomical approach to the septal papillary muscle of the conus

Many authors have questioned the gross anatomy of the septal papillary muscle of the conus known as the papillary muscle complex (PMC) during the past century. An anatomical investigation was conducted to identify the morphology and the topography of the PMC. Our study involved 200 formalin fixed adult human hearts. The PMC was present in 82% of the hearts, while in the remaining 18% of specimens, it was replaced by tendinous chords. The PMC was connected with the septal (59.7%), anterior (20.7%), or both septal and anterior leaflets (19.5%) with single (29.8%) or multiple chordae tendinae (70.1%). The PMC was also found to be present as a single papilla (51.8%), double papilla (32.9%) or triple papilla (15.2%). In addition to the PMC, we observed accessory single septal papillary muscles 42 specimens, double septal papillary muscles 32 specimens and triple septal papillary muscles 26 specimens. In the right ventricular inflow tract, the location of the PMC was consistently found to be in a position below the junction of the anterior and septal leaflets of the tricuspid valve. In the right ventricular outflow tract, we were able to identify 73 specimens in which the PMC was located at the junction formed superiorly by the inferior border of the subpulmonary infundibulum and inferiorly by the superior-lateral border of the septal band, extending into the region of the subpulmonary infundibulum. In the remaining 27%, the PMC was located primarily at the area occupied by the superiolateral border of the septal band without extending to the subpulmonary infundibulum. The present study describes the topography of the PMC according to its surrounding anatomical structures such as the tricuspid valve, subpulmonary infundibulum and septal band of the right ventricle. This anatomical data could have important clinical significance for cardiac surgeons operating in this area.