Mitral Valve Chordae Tendineae Research Articles

Simulated Effects of Acute Left Ventricular Myocardial Infarction on Mitral Regurgitation in an Ovine Model.

Ischemic mitral regurgitation (IMR) occurs from incomplete coaptation of the mitral valve (MV) after myocardial infarction (MI), typically worsened by continued remodeling of the left ventricular (LV). The importance of LV remodeling is clear as IMR is induced by the post-MI dual mechanisms of mitral annular dilation and leaflet tethering from papillary muscle (PM) distension via the MV chordae tendineae (MVCT). However, the detailed etiology of IMR remains poorly understood, in large part due to the complex interactions of the MV and the post-MI LV remodeling processes. Given the patient-specific anatomical complexities of the IMR disease processes, simulation-based approaches represent an ideal approach to improve our understanding of this deadly disease. However, development of patient-specific models of left ventricle-mitral valve (LV-MV) interactions in IMR are complicated by the substantial variability and complexity of the MR etiology itself, making it difficult to extract underlying mechanisms from clinical data alone. To address these shortcomings, we developed a detailed ovine LV-MV finite element (FE) model based on extant comprehensive ovine experimental data. First, an extant ovine LV FE model (Sci. Rep. 2021 Jun 29;11(1):13466) was extended to incorporate the MV using a high fidelity ovine in vivo derived MV leaflet geometry. As it is not currently possible to image the MVCT in vivo, a functionally equivalent MVCT network was developed to create the final LV-MV model. Interestingly, in pilot studies, the MV leaflet strains did not agree well with known in vivo MV leaflet strain fields. We then incorporated previously reported MV leaflet prestrains (J. Biomech. Eng. 2023 Nov 1;145(11):111002) in the simulations. The resulting LV-MV model produced excellent agreement with the known in vivo ovine MV leaflet strains and deformed shapes in the normal state. We then simulated the effects of regional acute infarctions of varying sizes and anatomical locations by shutting down the local myocardial contractility. The remaining healthy (noninfarcted) myocardium mechanical behaviors were maintained, but allowed to adjust their active contractile patterns to maintain the prescribed pressure-volume loop behaviors in the acute post-MI state. For all cases studied, the LV-MV simulation demonstrated excellent agreement with known LV and MV in vivo strains and MV regurgitation orifice areas. Infarct location was shown to play a critical role in resultant MV leaflet strain fields. Specifically, extensional deformations of the posterior leaflets occurred in the posterobasal and laterobasal infarcts, while compressive deformations of the anterior leaflet were observed in the anterobasal infarct. Moreover, the simulated posterobasal infarct induced the largest MV regurgitation orifice area, consistent with experimental observations. The present study is the first detailed LV-MV simulation that reveals the important role of MV leaflet prestrain and functionally equivalent MVCT for accurate predictions of LV-MV interactions. Importantly, the current study further underscored simulation-based methods in understanding MV function as an integral part of the LV.

Differential Development of the Chordae Tendineae and Anterior Leaflet of the Bovine Mitral Valve.

There is increasing evidence that some adult mitral valve pathologies may have developmental origins involving errors in cell signaling and protein deposition during valvulogenesis. While early and late gestational stages are well-documented in zebrafish, chicks, and small mammalian models, longitudinal studies in large mammals with a similar gestational period to humans are lacking. Further, the mechanism of chordae tendineae formation and multiplication remains unclear. The current study presents a comprehensive examination of mitral anterior leaflet and chordae tendineae development in a bovine model (a large mammal with the same gestational period as humans). Remarkably distinct from small mammals, bovine development displayed early branched chordae, with increasing attachments only until birth, while the anterior leaflet grew both during gestation and postnatally. Chordae also exhibited accelerated collagen deposition, maturation, and crimp development during gestation. These findings suggest that the bovine anterior leaflet and chordae tendineae possess unique processes of development despite being a continuous collagenous structure and could provide greater insight into human valve development.

Mechanical and morphometric study of mitral valve chordae tendineae and related papillary muscle

The mitral valve (MV) apparatus is a complex mechanical structure including annulus, valve leaflets, papillary muscles (PMs) and connected chordae tendineae. Chordae anchor to the papillary muscles to help the valve open and close properly during one cardiac cycle. It is of paramount importance to understand the functional, mechanical, and microstructural properties of mitral valve chordae and connecting PMs. In particular, little is known about the biomechanical properties of the anterior and posterior papillary muscle and corresponding chords. In this work, we performed uniaxial and biaxial tensile tests on the anterolateral (APM) and posteromedial papillary muscle (PPM), and their respective corresponding chordae tendineae, chordaeAPM and chordaePPM, in porcine hearts. Histology was carried out to link the microstructure and macro-mechanical behavior of the chordae and PMs. Our results demonstrate that chordaePPM are less in number, but significantly longer and stiffer than chordaeAPM. These different biomechanical properties may be partially explained by the higher collagen core ratio and larger collagen fibril density of chordaePPM. No significant mechanical or microstructural differences were observed along the circumferential and longitudinal directions of APM and PPM samples. Data measured on chordae and PMs were further fitted with the Ogden and reduced Holzapfel - Ogden strain energy functions, respectively. This study presents the first comparative anatomical, mechanical, and structural dataset of porcine mitral valve chordae and related PMs. Results indicate that a PM based classification of chordae will need to be considered in the analysis of the MV function or planning a surgical treatment, which will also help developing more precise computational models of MV.

P1782Synchrotron-based 4D-X-ray Phase Tomography of fresh chordae tendineae of mitral valve

Abstract Background Mechanical properties of chordae tendineae of mitral valve (MV) are still not fully investigated. Synchrotron-based X-ray phase tomography (XPCT) is a powerful tool to measure biological soft tissues. Recently, we have developed dynamic X-ray phase tomography (4D-XPCT) to discuss the dynamic phenomena of biological samples quantitatively and applied to chordae tendineae of MV (MVCT). Purpose This study evaluated 4-dimensional changes of MVCT and clarified structural changes of MVCT during cardiac cycles. Methods The X-ray energy for 4D XPCT was set to 20keV. The effective pixel size was 7.8μm. Fresh MVCT extracted from a pig heart were measured in the specially designed container filled with normal cold saline. MVCT installed on the sample stage was stretched and released with a continuous oscillation of 0.5Hz during a phase tomographic measurement. The amount of stretch was 400μm where a mechanical load caused by stretching was approximately 1N. In this measurement, projection images were acquired with a frame rate of 20Hz during a single sawtooth wave. Therefore, apparent frame rate of 20Hz is expected in 4D phase tomography. Cross section was determined by simple thresholding based on the density. In this case, the threshold was set to 1.018g/cm3. Results X-ray phase tomographic images of MVCT at the released (A) and stretched (B) conditions are shown in Fig. 1a. The load applied to the sample and change of the cross section obtained from tomography during stretching and releasing are shown in Fig. 1b and 1c, respectively. The diameter of chordae tendinea were changed approximately 2.5% during stretching and returned to initial diameter during releasing. Figure 1 Conclusions This result demonstrated that the 4D-XPCT had a capability to trace the detail of deformation process in the biological soft tissues during continuous oscillation. Even chordae tendinea are mainly consisted of collagen fibers, diameter of the chordae was changed according to stretching and releasing.

Morphological study on mitral valve chordae tendineae in the hearts of human fetuses

BACKGROUND: Mitral valve chordae tendineae (CTs) are filaments of connective tissue that attach the mitral valves to the papillary muscles, which contract and cause tension on these chordae, so as not to allow separation of the valves during left ventricular systoles. The morphological particularities of CTs not only facilitate understanding of the genesis of mitral valve diseases, but also provide the basis for improvement of surgical techniques. OBJECTIVE: To evaluate some morphological aspects of mitral valve CTs and papillary muscles, including number, distribution, type and macroscopic texture. MATERIAL AND METHODS: An anatomical descriptive study on mitral valve CTs and papillary muscles was conducted on 27 hearts from human fetuses. The CTs were dissected via a longitudinal incision adjacent to the interventricular septum, and were viewed using a binocular stereoscopic microscope and documented via photographs. The following variables were analyzed: number and anatomical distribution of papillary muscles, number of heads per group of papillary muscles and number of CTs per muscle head. The CTs were classified in accordance with the methodology proposed by Lam (1970) and Gunnal et al. (2015). RESULT: In 27 mitral valves, a total of 827 CTs was found, and “true chorda” was the predominant type of chorda. Approximately 717 CTs originated from the 497 muscle heads. These chordae and muscle heads were shared approximately equally among the papillary muscle groups, with similar chorda/head proportions. The number of CTs per head in the papillary muscle groups ranged from 0 to 6 chordae/head. There were 663 chordae with tendinous macroscopic texture and 84 with simultaneously tendinous and membranous texture. CONCLUSION: Mitral valve CTs were predominantly of true type, with similar distributions among papillary muscle groups; and the false chordae that were found were more commonly fixed in the posterior papillary muscle group. The CTs generally originated in the apexes of the papillary muscle groups, with variations in the numbers of muscle heads and the numbers of chordae per head. The main macroscopic texture of the CTs was tendinous, complemented by occurrences of chordae with simultaneously tendinous and membranous texture.

Development of a Functionally Equivalent Model of the Mitral Valve Chordae Tendineae Through Topology Optimization.

Ischemic mitral regurgitation (IMR) is a currently prevalent disease in the US that is projected to become increasingly common as the aging population grows. In recent years, image-based simulations of mitral valve (MV) function have improved significantly, providing new tools to refine IMR treatment. However, clinical implementation of MV simulations has long been hindered as the in vivo MV chordae tendineae (MVCT) geometry cannot be captured with sufficient fidelity for computational modeling. In the current study, we addressed this challenge by developing a method to produce functionally equivalent MVCT models that can be built from the image-based MV leaflet geometry alone. We began our analysis using extant micron-resolution 3D imaging datasets to first build anatomically accurate MV models. We then systematically simplified the native MVCT structure to generate a series of synthetic models by consecutively removing key anatomic features, such as the thickness variations, branching patterns, and chordal origin distributions. In addition, through topology optimization, we identified the minimal structural complexity required to capture the native MVCT behavior. To assess the performance and predictive power of each synthetic model, we analyzed their performance by comparing the mismatch in simulated MV closed shape, as well as the strain and stress tensors, to ground-truth MV models. Interestingly, our results revealed a substantial redundancy in the anatomic structure of native chordal anatomy. We showed that the closing behavior of complete MV apparatus under normal, diseased, and surgically repaired scenarios can be faithfully replicated by a functionally equivalent MVCT model comprised of two representative papillary muscle heads, single strand chords, and a uniform insertion distribution with a density of 15 insertions/cm2. Hence, even though the complete sub-valvular structure is mostly missing in in vivo MV images, we believe our approach will allow for the development of patient-specific complete MV models for surgical repair planning.

The use of the three-dimensional reconstruction method in the morphological investigation of the left ventricle chordae tendineae of the human's heart

Objective — to determine the properties of chordae tendineae of the human’s heart left ventricle by a comlex of morphological methods of investigation using the method of three-dimensional reconstruction.Material and methods. The macroscopic method, methods of light microscopy and three-dimensional reconstruction were used for the study. The material for the study was the chordae tendineae of the left ventricles of 45 hearts of people of mature age.Results. By using the macroscopic method and method of light microscopy, a typical mitral valve chordae tendineae, that in the form of strands extend from the apex of papillary muscles and combined with valve’s cusps, and false chordae tendineae, that unlike typical ones, do not attach to the mitral valve cusps, but are ectopically fixed to the free walls of the left ventricle, interventricular septum or papillary muscles were studied. The light microscopy method showed that the typical chordae tendineae formed by one centrally located collagen core, surrounded by the peripherally located collagen-elastic layer and lined by the endothelium outside. Based on the studies, the false chordae tendineae by histological structure of their core have been divided into the fibrous, fibro-muscular and muscular types. The reproduced models of the spatial organization of the typical and false chordae tendineae of the left ventricle of the human heart reproduced the outlines and character of the surface of the chords, and showed the spatial interaction of the structural components of their inner contents with the calculation of the parameters of their relative area.

Mitral Valve Chordae Tendineae: Topological and Geometrical Characterization.

Mitral valve (MV) closure depends upon the proper function of each component of the valve apparatus, which includes the annulus, leaflets, and chordae tendineae (CT). Geometry plays a major role in MV mechanics and thus highly impacts the accuracy of computational models simulating MV function and repair. While the physiological geometry of the leaflets and annulus have been previously investigated, little effort has been made to quantitatively and objectively describe CT geometry. The CT constitute a fibrous tendon-like structure projecting from the papillary muscles (PMs) to the leaflets, thereby evenly distributing the loads placed on the MV during closure. Because CT play a major role in determining the shape and stress state of the MV as a whole, their geometry must be well characterized. In the present work, a novel and comprehensive investigation of MV CT geometry was performed to more fully quantify CT anatomy. In vitro micro-tomography 3D images of ovine MVs were acquired, segmented, then analyzed using a curve-skeleton transform. The resulting data was used to construct B-spline geometric representations of the CT structures, enriched with a continuous field of cross-sectional area (CSA) data. Next, Reeb graph models were developed to analyze overall topological patterns, along with dimensional attributes such as segment lengths, 3D orientations, and CSA. Reeb graph results revealed that the topology of ovine MV CT followed a full binary tree structure. Moreover, individual chords are mostly planar geometries that together form a 3D load-bearing support for the MV leaflets. We further demonstrated that, unlike flow-based branching patterns, while individual CT branches became thinner as they propagated further away from the PM heads towards the leaflets, the total CSA almost doubled. Overall, our findings indicate a certain level of regularity in structure, and suggest that population-based MV CT geometric models can be generated to improve current MV repair procedures.

The effects of decellularization and cross-linking techniques on the fatigue life and calcification of mitral valve chordae tendineae

In cases of severely diseased mitral valves (MV), the required treatment is often valve replacement. Bioprosthetic and stentless replacement valves are usually either fully or partially composed of animal derived tissue treated with a decellularization process, a cross-linking process, or both. In this study, we analysed the effects of these treatments on the fatigue properties of porcine MV chordae tendineae (CT), as well as on the calcification of the CT using an in vitro technique. CT were tested in 4 groups; (1) native, (2) decellularized (DC), (3) decellularized and cross-linked with glutaraldehyde (DC-GTH), and (4) decellularized and cross-linked with 1-ehtyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)(DC-EDC). CT were tested in both uniaxial tension, and in fatigue at 10MPa peak stress (1Hz). The cycles to failure (mean±SD) for the four groups are as follows; Native- 53,397±55,798, DC- 28,013±30,634, DC-GTH- 97,665±133,556, DC-EDC- 318,601±322,358. DC-EDC CT were found to have a slightly longer fatigue life than the native and DC groups. The DC-EDC group also had a marginally lower dynamic creep rate, meaning those CT elongate more slowly. After in vitro calcification, X-ray microtomography was used to determine relative levels of calcification. The DC-EDC and DC-GTH groups had the lowest volume of calcific deposits. Under uniaxial testing, the ultimate tensile strength (UTS) of the DC-GTH CT was statistically significantly reduced after calcification, while the UTS was relatively unchanged for the DC-EDC group. Overall, these results indicate that a treatment of decellularization plus cross-linking with EDC may improve the fatigue life of porcine CT, reduce the rate of elongation, and help the CT resist the negative effects of calcification. This may be a preferable treatment in the preparation of porcine MVs for the replacement of diseased MVs.

Tissue-engineered mitral valve chordae tendineae: Biomechanical and biological characterization of decellularized porcine chordae

Chordae tendineae are essential for maintaining mitral valve function. Chordae replacement is one of the valve repair procedures commonly used to treat mitral valve regurgitation. But current chordae alternatives (polytetrafluoroethylene, ePTFE) do not have the elastic and self-regenerative properties. Moreover, the ePTFE sutures sometimes fail due to degeneration, calcification and rupture. Tissue-engineered chordae tendineae may overcome these problems. The utility of xenogeneic chordae for tissue-engineered chordae tendineae has not yet been adequately explored. In this study, polyelectrolyte multilayers (PEM) film modified decellularized porcine mitral valve chordae (PEM-DPC) were developed to explore tissue-engineered chordae tendineae as neochordae substitutes. Fresh porcine mitral chordae were decellularized and reserved the major elastic fiber and collagen components. Decellularized chordae with a PEM film were produced with chitosan–heparin by a lay-by-lay technique. Mesenchymal stem cells and vascular endothelial cells could grow well on the surface of the PEM-DPC. The superior biomechanical properties of PEM-DPC were proved with good flexibility and strength both in vitro and in vivo. PEM-DPC can be developed for potential alternative mitral valve chordae graft.

Structural organization of normally located mitral valve chordae tendineae of the human heart.

Background. The mitral valve complex of the human heart consists of: the fibrous annulus, valve leaflets, chordae tendineae and papillary muscles. Deficiency or degeneration one of these structures may result in the dysfunction of the valvular apparatus. Topography and structure of the chordae tendineae effect to the normal functioning of heart valve complex and its hemodynamics, due to the aim of our research was to examine the peculiarities of the structural organization normally located mitral valve chordae tendineae of the human heart. Methods. The investigation was made on sectional material. We used light microscopy and immunohistochemistry methods. Results. The chordae tendineae are cord-like tendons that connect the papillary muscles to the valve leaflets in the heart. The chordeae tendineae were covered by endocardium which contained superficial layer of endothelium. Subendocardial layer includes loosely located collagen and elastic fibers which were interwoven with each other. Cor of the chordae are composed of bundles of densely packed collagen fibrils with few elastic fibers. Conclusion. The investigations allowed to receive a new objective data on some structural peculiarities of chordae tendineae of the human mitral valve that later can become the basis for the differential diagnosis of disease, including valvular heart pathology.

Quantitative Evaluation of Annuloplasty on Mitral Valve Chordae Tendineae Forces to Supplement Surgical Planning Model Development

Computational models of the heart's mitral valve (MV) exhibit potential for preoperative surgical planning in ischemic mitral regurgitation (IMR). However challenges exist in defining boundary conditions to accurately model the function and response of the chordae tendineae to both IMR and surgical annuloplasty repair. Towards this goal, a ground-truth data set was generated by quantifying the isolated effects of IMR and mitral annuloplasty on leaflet coaptation, regurgitation, and tethering forces of the anterior strut and posterior intermediary chordae tendineae. MVs were excised from ovine hearts (N=15) and mounted in a pulsatile heart simulator which has been demonstrated to mimic the systolic MV geometry and coaptation of healthy and chronic IMR sheep. Strut and intermediary chordae from both MV leaflets (N=4) were instrumented with force transducers. Tested conditions included a healthy control, IMR, oversized annuloplasty, true-sized annuloplasty, and undersized mitral annuloplasty. A2-P2 leaflet coaptation length, regurgitation, and chordal tethering were quantified and statistically compared across experimental conditions. IMR was successfully simulated with significant increases in MR, tethering forces for each of the chordae, and decrease in leaflet coaptation (p<.05). Compared to the IMR condition, increasing levels of downsized annuloplasty significantly reduced regurgitation, increased coaptation, reduced posteromedial papillary muscle strut chordal forces, and reduced intermediary chordal forces from the anterolateral papillary muscle (p<.05). These results provide for the first time a novel comprehensive data set for refining the ability of computational MV models to simulate IMR and varying sizes of complete rigid ring annuloplasty.

Mitral chordae myxoma—chordae replacement with a premeasured gore-tex loop using a minimally invasive video-assisted approach

Cardiac myxomas are one of the most common types of primary cardiac tumors and are associated with embolization, angina, and sudden death. Most cardiac myxomas arise from the fossa ovalis, while those that arise from the mitral valve are exceedingly rare and those that arise from the chordae are even rarer. We report the case of a 28-year-old Caucasian woman who suffered from a brain infarction. A duplex ultrasound showed no cerebrovascular stenosis or occlusion, but an echocardiogram revealed a left ventricle pedunculated mobile mass (5 mm in diameter) that was attached to the mitral valve chordae tendineae. We elected cardiac surgery to resect the cardiac tumor and to avoid further embolic events. The traditional surgical strategy—mitral valve replacement through full sternotomy—has many disadvantages, particularly for young women. Therefore we desided to use the Premeasured Gore-Tex chordal loop method followed by annuloplasty using a minimally invasive video-assisted approach. Exploration of the mitral valve showed a globular tumor involving the anterior mitral leaflet chordae tendineae, which was removed along with the involved chordae tendineae. Histopathological examination of the tissue revealed a benign polypoid myxoma. The patient had an uneventful recovery and has remained symptom-free.Echocardiography one week after surgery showed satisfactory valve function. We believe our surgical treatment was the most appropriate option for this case and it resulted in an excellent medical outcome and improved the quality of life, including only a small lateral scar without the need for teratogenic anticoagulants.

Morphometry of chordae tendineae of mitral valves and annulopapillary distance for mitral allografts

Background: Mitral valve is the complex variable structure with 2 cusps and 2 papillary muscles which are connected by collagenous structure chordae tendineae supporting the entire free edge of the valvular cusps. Aims & Objective: To study the morphological and morphometric analysis of chordae tendineae and to compare the morphometric measurements among cadaveric and autopsied heart specimens of south Indians and the effect of formalin in causing shrinkage of chordae tendineae. The annulopapillary distances were measured for mitral allografts. Material and Methods: The prospective study was done on 45 cadaveric and 15 autopsied heart specimens. The left atrium and left ventricle were cut open and the measurements of the Mitral valve chordae tendineae were taken using Vernier calliper and recorded. The chordae tendineae was measured from tip of papillary muscles to the edges of the cusp. The annulopapillary distance was measured from tip of papillary muscles in 2 o\', 4 o\', 8 o\', 10 o\' clock positions to that of mitral annulus. The data’s were analyzed using student’s t test to compare between the cadaveric and autopsied heart specimens. Results: Aortic cusp chordae tendineae of both specimens were approximately same 1.6 to 1.8cm, whereas in mural and commissural cusp mild difference of 2-3mm was observed 1.5 to 1.7 cm. The annulopapillary distance was equal in both the specimens 2cm. Two heart specimens showed complete absence of commissural chordae and 6 hearts showed absence of basal chordae. Conclusion: Many studies were done on morphometry of mitral valve but the present study on morphometry of chordae tendineae of mitral valve did not show any significant changes among cadaveric and autopsied heart specimens. The data will be of great use to cardiac surgeons for surgical reconstruction of mitral valves and annulopapillary distance for mitral allografts.

Anatomic, histologic, and two-dimensional–echocardiographic evaluation of mitral valve anatomy in dogs

To compare echocardiographic variables of dogs with postmortem anatomic measurements and histologic characteristics of the mitral valve (MV). 21 cardiologically normal dogs. The MV was measured echocardiographically by use of the right parasternal 5-chamber long-axis view. Dogs were euthanized, and anatomic measurements of the MV annulus (MVa) were performed at the level of the left circumflex coronary artery. Mitral valve leaflets (MVLs) and chordae tendineae were measured. Structure of the MVLs was histologically evaluated in 3 segments (proximal, middle, and distal). Echocardiographic measurements of MVL length did not differ significantly from anatomic measurements. A positive correlation was detected between body weight and MVa area. There was a negative correlation between MVa area and the percentage by which the MVL area exceeded the MVa area. Anterior MVLs had a significantly higher number of chordae tendineae than did posterior MVLs. Histologically, layering of MVLs was less preserved in the distal segment, whereas the muscular component and adipose tissue were significantly more diffuse in the proximal and middle segments. The MV in cardiologically normal dogs had wide anatomic variability. Anatomic measurements of MVL length were correlated with echocardiographic measurements.

Understanding Left Ventricular Outflow Obstruction: Anatomoechocardiographic Correlation

Echocardiography is a valuable noninvasive technique for identifying the site and type of obstruction in the left ventricular outflow tract. Knowledge of the morphological details of each type of obstruction is the basis for correct interpretation of the diagnostic images and clinical decisions. This study was undertaken to provide improved understanding of the anatomy of left ventricular outflow obstruction with corresponding side-by-side echocardiographic images. Specimens were part of the collection of the Department of Embryology of the Instituto Nacional de Cardiología "Ignacio Chávez," Mexico City, Mexico. Twenty-eight patients were studied by echocardiography, and 22 specimens with different types of left ventricular outflow tract obstruction were analyzed. Echocardiographic characteristics: Eighteen (64.3%) patients were women and 10 (35.7%) men. Three had fibrous rings, 19 with obstructive asymmetric septal hypertrophic cardiomyopathy, 1 with posterior displacement of the infundibular septum, 2 with accessory mitral valve tissue, 2 with anomalous insertion of mitral valve chordae tendineae, and 1 with malposition of the mitral valve and papillary muscles. Anatomic characteristics: Twelve had fibrous ring, 2 asymmetric septal hypertrophic cardiomyopathy, 2 posterior displacement of the infundibular septum, 1 ectopic mitral tissue, 1 anomalous insertion of mitral valve chordae tendineae in the ventricular septum, 3 malposition of the mitral valve and papillary muscles, and 1 subaortic infundibulum. The anatomoechocardiographic correlation clearly demonstrates the mechanism of subaortic obstruction. The comparison with corresponding echocardiographic images of different subaortic obstruction types is potentially quite valuable in enhancing the echocardiographer's understanding especially of complex subaortic obstruction.

Papillary Muscle Rupture After Blunt Chest Trauma

We report a case of anterolateral papillary muscle rupture in a 22-year-old man who had blunt chest trauma caused by a car accident. Transesophageal echocardiography revealed severe mitral regurgitation caused by the rupture. He successfully underwent emergency mitral valve replacement and was discharged 9 days after the surgical correction.

STUDY OF THE TRACTION RESISTANCE OF MITRAL VALVE CHORDAE TENDINEAE

To determinate the extension and the resistance of the primary mitral valve chordae tendineae when submitted to traction. The importance of keeping the integrity of papillary muscle, chordae tendineae, and mitral valve cuspid when the replacement of this valve occurs is clear, but the knowledge of the maximum resistance that a primary tendinea chorda can withstand is not known. Eight hearts were dissected, and one hundred and thirty two primary human chordae tendineae were measured (length and thickness) and submitted to traction under controlled conditions so that the absolute resistance, resistance relative to thickness (relative resistance), and elongation could be measured. The correlation between the elongation at the moment of rupture and the thickness was equal to 1.54 + 17.02 x thickness (P = 0.026); and to absolute resistance was equal to 0.95 + 1.42 x resistance (P < 0.001); and to the resistance relative to thickness (relative resistance) was equal to 1.95 + 0.08 x relative resistance (P = 0.009). The correlation between the absolute resistance and the thickness was equal to 0.26 + 14.53 x thickness (P < 0.001). The resistance of primary mitral valve chordae tendineae is associated with its thickness and elongation at the moment of rupture, but is not associated with the length. The elongation at the moment of rupture shows a relationship with the resistance relative to thickness (relative resistance) and with the thickness of the primary chordae tendineae, but not with the length of the chordae tendineae.

Structural Characterization of the Chordae Tendineae in Native Porcine Mitral Valves

This study was aimed to characterize the different mitral valve chordae tendineae to provide additional understanding of their function. Mitral valve chordae tendineae from fresh porcine hearts were stained for collagen and elastin using either a Verhoeff and van Gieson stain or Verhoeff light green stain. Cellular distribution was determined using a hematoxylin and eosin stain. Immunohistochemistry was used to verify the findings of vasculature. Biochemical assays were performed to quantify DNA, collagen, and elastin content of each of the six different types of chordae tendineae. Blood vessels were observed in the longitudinal and circumferential directions of the chordae. The strut chordae on the anterior leaflet of the mitral valve showed an increased degree of vascularization compared with the other chordae. All chordae had an inner layer characterized by a high concentration of collagen and an outer layer that was mostly elastin with interwoven collagen fibers. The collagen microstructure was characterized by directional crimping. Hematoxylin and eosin staining showed fibroblasts evenly distributed throughout the inner and outer layer of the chordae tendineae. Quantitative analysis showed significantly higher levels of DNA and collagen content in the anterior and posterior marginal chordae compared with the other chordae. The chordae tendineae were seen to have different microstructures according to chordal type. The presence of vessels characterized the chordae tendineae as complex living components that work in coordination with the papillary muscles and mitral valve leaflets to prevent mitral valve prolapse and regurgitation. They may also function to supply nutrients to the valve leaflets.

Successful release of entrapped circumferential mapping catheters in patients undergoing pulmonary vein isolation for atrial fibrillation

The purpose of this study was to demonstrate a method for successful and safe release of an entrapped circular catheter. Segmental pulmonary vein (PV) isolation is widely practiced for patients with symptomatic drug-refractory atrial fibrillation. A circular mapping catheter is sometimes used with this technique to map the electrical connection between the left atrium (LA) and the PVs. This catheter reportedly can become entrapped in the mitral valve apparatus. Attempts to free the entrapped catheter can result in serious complications, including damage to the mitral valve chordae tendineae or fracture of the catheter itself. Three patients were referred for PV isolation for atrial fibrillation. A circular mapping catheter was used to map the sites of LA-PV electrical connections. During the procedure, the circular mapping catheter became entrapped in the mitral valve apparatus in two patients and in the PV in one patient. A series of maneuvers, which included use of another catheter and guiding sheaths as well as pushing forward rather than pulling back on the entrapped catheter, allowed safe and successful release of the entrapped catheter in all patients. Entrapment of the circular mapping in the mitral valve apparatus or the PVs during PV isolation is a rare complication associated with use this catheter. We describe a series of maneuvers that may allow safe and successful release of the entrapped catheter.