Development of Novel Sutureless Balloon Expandable Fetal Heart Valve Device Using Absorbable Polycaprolactone Leaflets

Congenital heart disease (CHD) accounts for nearly one-third of all congenital defects, and patients often require repeated heart valve replacements throughout their lives, due to failed surgical repairs and lack of durability of bioprosthetic valve implants. This objective of this study is to develop and in vitro test a fetal transcatheter pulmonary valve replacement (FTPVR) using sutureless techniques to attach leaflets, as an option to correct congenital defects such as pulmonary atresia with intact ventricular septum (PA/IVS), in utero. A balloon expandable design was analyzed using computational simulations to identify areas of failure. Five manufactured valves were assembled using the unique sutureless approach and tested in the fetal right heart simulator (FRHS) to evaluate hemodynamic characteristics. Computational simulations showed that the commissural loads on the leaflet material were significantly reduced by changing the attachment techniques. Hemodynamic analysis showed an effective orifice area of 0.08 cm2, a mean transvalvular pressure gradient of 7.52 mmHg, and a regurgitation fraction of 8.42%, calculated over 100 consecutive cardiac cycles. In conclusion, the FTPVR exhibited good hemodynamic characteristics, and studies with biodegradable stent materials are underway.

Design consideration of a novel polymeric transcatheter heart valve through computational modeling

Transcatheter heart valve replacement is becoming a more routine procedure, and this is further supported by positive outcomes from studies involving low-risk patients. Nevertheless, the lack of long-term transcatheter heart valve (TAV) durability is still one of the primary concerns. As a result, more research has been focused on improving durability through various methods such as valve design, computational modeling, and material selection. Recent advancements in polymeric valve fabrication showed that linear low-density polyethylene (LLDPE) could be used as leaflet material for transcatheter heart valves. In this paper, a parametric study of computational simulations showed stress distribution on the leaflets of LLDPE-TAV under diastolic load, and the results were used to improve the stent design. The in silico experiment also tested the effect of shock absorbers in terms of valve durability. The results demonstrated that altering specific stent angles can significantly lower peak stress on the leaflets (13.8 vs. 6.07 MPa). Implementing two layers of shock absorbers further reduces the stress value to 4.28 MPa. The pinwheeling index was assessed, which seems to correlate with peak stress. Overall, the parametric study and the computational method can be used to analyze and improve valve durability.

Transcatheter Heart Valves: A Biomaterials Perspective

Heart valve disease is prevalent throughout the world, and the number of heart valve replacements is expected to increase rapidly in the coming years. Transcatheter heart valve replacement (THVR) provides a safe and minimally invasive means for heart valve replacement in high-risk patients. The latest clinical data demonstrates that THVR is a practical solution for low-risk patients. Despite these promising results, there is no long-term (>20 years) durability data on transcatheter heart valves (THVs), raising concerns about material degeneration and long-term performance. This review presents a detailed account of the materials development for THVRs. It provides a brief overview of THVR, the native valve properties, the criteria for an ideal THV, and how these devices are tested. A comprehensive review of materials and their applications in THVR, including how these materials are fabricated, prepared, and assembled into THVs is presented, followed by a discussion of current and future THVR biomaterial trends. The field of THVR is proliferating, and this review serves as a guide for understanding the development of THVs from a materials science and engineering perspective.

Development and Fabrication of Vapor Cross-Linked Hyaluronan-Polyethylene Interpenetrating Polymer Network as a Biomaterial

Flexible heart valve leaflets made from hyaluronan-enhanced linear low-density polyethylene interpenetrating polymeric network (HA-LLDPE IPN) films have been shown to provide good hemodynamics, but the resulting surfaces were not consistent; therefore, the present work tries to mitigate this problem by developing a vapor cross-linked HA-LLDPE IPN. Herein, the HA-LLDPE fabrication process is studied, and its parameters are varied to assess their effects on the IPN formation. Thermal analysis and gas chromatography-mass spectrometry were used to quantify the effects of different treatment conditions on material properties. Water contact angle goniometry, infrared spectroscopy, and toluidine blue O (TBO) staining were used to characterize the surface of the HA-LLDPE IPN. The results show that a hydrophilic surface is formed on HA-LLDPE, which is indicative of HA. HA surface density data from TBO staining show consistent HA distribution on the surface. The IPN fabrication process does not affect the tensile properties that make LLDPE an attractive material for use in flexible heart valve leaflets. The 28 day in vitro biological assays show HA-LLDPE to be noncytotoxic and resistant to enzymatic degradation. The HA-LLDPE showed less platelet adhesion and caused less platelet activation than the plain LLDPE or tissue culture polystyrene. All of the results indicate that vapor cross-linked HA-LLDPE IPN is a promising material for use as flexible leaflets for heart valve replacements.

Hyaluronan enhancement of expanded polytetrafluoroethylene cardiovascular grafts

Heart disease continues to be the leading cause of death in the United States. The demand for cardiovascular bypass procedures increases annually. Expanded polytetrafluoroethylene is a popular material for replacement implants, but it does have drawbacks such as high thrombogenicity and low patency, particularly in small diameter grafts. Hyaluronan, a naturally occurring polysaccharide in the human body, is known for its wound healing and anticoagulant properties. In this work, we demonstrate that treating the luminal surface of expanded polytetrafluoroethylene grafts with hyaluronan improves hemocompatibility without notably changing its mechanical properties and without significant cytotoxic effects. Surface characterization such as ATR-FTIR and contact angle goniometry demonstrates that hyaluronan treatment successfully changes the surface chemistry and increases hydrophilicity. Tensile properties such as elastic modulus, tensile strength, yield stress and ultimate strain are unchanged by hyaluronan enhancement. Durability data from flow loop studies demonstrate that hyaluronan is durable on the expanded polytetrafluoroethylene inner lumen. Hemocompatibility tests reveal that hyaluronan-treated expanded polytetrafluoroethylene reduces blood clotting and platelet activation. Together our results indicate that hyaluronan-enhanced expanded polytetrafluoroethylene is a promising candidate material for cardiovascular grafts.

[Coronary embolism due to an adherent right atrium thrombus through a patent foramen ovale]

This observation relates to the discovery of native coronary paradoxical embolism secondary to thrombus adherent to the right atrium through a patent foramen ovale (PFO). A patient of 64 years, with a history of mitral regurgitation not followed, was hospitalized for acute respiratory distress due to a mitral insufficiency (MI) with a ruptured chordae and pulmonary embolism. Coronary angiography was performed and revealed two typical images of coronary embolism associated to a non-atheromatous coronary tree. The patient underwent a mitral valve replacement. After the establishment of cardiopulmonary bypass, adherent fibrin and cruoric thrombus of the right atrium and a PFO were found. The analysis of the valves did not reveal any arguments for infective endocarditis. A CT scan, performed as the patient remained unconscious after surgery, showed several cerebral infarcts. Paradoxical embolism coronary was diagnosed in front of the combination of adherent thrombus in the right atrium, pulmonary embolism and systemic coronary and cerebral embolism with a PFO. Coronary embolism rarely happens. It is mainly due to three causes: iatrogenic origin in most cases, direct causes due to micro emboli, particularly from infectious endocarditis and paradoxical embolic origin. There are two types of right atrial thrombus; the most common is the mobile thrombus from the peripheral venous system. The other one, which is more rare, is the adherent thrombus, which occurs in situ. Coronary embolism of paradoxical origin represents a small proportion of the causes of coronary embolism. However, this diagnosis must be considered.

PEG-based hydrogels with tunable degradation characteristics to control delivery of marrow stromal cells for tendon overuse injuries

Marrow stromal cells (MSCs) have been suggested as a means to improve healing in tendon overuse injuries (tendinopathy), but optimal delivery methods for these cells have yet to be determined. In this study novel degradable hydrogels based on oligo(poly(ethylene glycol) fumarate) (OPF) and acrylated poly(ethylene glycol)-dithiothreitol (Ac PEG-DTT) with tunable degradation times ranging from a few days to >1 month were synthesized as MSC carriers for tendon overuse injuries. The addition of higher amounts of OPF or higher dithiothreitol (DTT) concentrations resulted in enhanced fold swelling and degradation. Three formulations, including non-degrading, slower degrading (degraded in ∼10 days) and faster degrading (degraded in ∼5 days) hydrogels were selected for studies with MSCs in tendon tissue explants that had been treated with collagenase as a reproducible model of tendinopathy. Quantitative analysis of the resulting histology images indicated that cell delivery from the hydrogels was dependent on the degradation rate, with cells present in the tissue only after hydrogel dissolution. In addition, significantly more cells were found in the tendon after 14 days with the fast degrading (53±19) vs. slow degrading (20±6) hydrogels. Based on these results, OPF/Ac PEG-DTT hydrogels provide a versatile biomaterial platform to control cell delivery and thus better identify dosing regimens required for MSC-based therapies for tendinopathy.

[Peripheral arterial disease with lower limb claudication: Medical treatment]

Whereas the complaint from a patient with intermittent arterial claudication is walking impairment, prognosis is linked to an increased risk of cardiovascular ischemic events due to the diffuse nature of the atherosclerosis. The objectives of the medical treatment therefore include improvement of walking limit, prevention of myocardial infarction, stroke and cardiovascular death, and preventive measures to avoid progression to critical lower limb ischemia. The key areas of treatment focus on smoking cessation, exercise rehabilitation, with supervised therapy if possible, cardiovascular risk prevention with antiplatelet drugs, statins and angiotensin converting enzymes, and correction of atherosclerotic risk factors with well-defined targets (LDL less than 1g/L, HDL greater than 0.4g/L, HbA(1c) less than 6.5%, brachial blood pressure less than 140/90 or 130/80mmHg in case of diabetes or renal insufficiency, body mass index less than 25kg/m(2)). Limitation or avoidance of progression to local critical ischemia requires control of atherosclerotic risk factors and proper foot care. The patient with arterial claudication needs to understand the local and general risks of arterial atherosclerotic disease, and to be involved in his/her own treatment. Obtaining patient compliance to medical care is fundamental: specific educational workshops are of great value for this.

Tympanic membrane reconstruction using formaldehyde-formed autogenous temporalis fascia: twenty years' experience

This study describes 20 years' experience with autogenous temporalis fascia that is formed and shaped by formaldehyde cross-linking with special Fasciaform (Hear America, Palo Alto, Calif.) molds in the repair of large tympanic membrane perforations. One hundred twenty operations in 113 patients were performed between 1973 and 1993 to close large perforations in patients with intact ossicular chains. All perforations were successfully closed by this technique. Audiometric studies indicated that the postoperative air-borne gap was closed to within 0 to 10 dB in 63% and to within 0 to 20 dB in 97%. One patient had a 15-dB sensorineural hearing impairment. Graft lateralization requiring revision occurred in three patients, two of whom had previous unsuccessful tympanoplasties. Comparisons of adult vs. pediatric groups and primary vs. revision groups were made. The technique ensures the removal of any ectopic epithelium on the medial surface of the tympanic membrane remnant and provides for easy graft placement and stability during healing without the use of middle ear Gelfoam (Upjohn Co., Kalamazoo, Mich.). The formaldehyde-formed fascia graft or Fasciaform graft technique provides an effective method of closing large perforations with excellent functional results and minimal complications.

An immunohistochemical study of the endolymphatic sac in patients with acoustic tumors

Intraosseous endolymphatic sacs obtained from patients with acoustic neuromas who had undergone total labyrinthectomy during tumor removal were examined for the presence of T helper/inducer and T suppressor/cytotoxic lymphocytes, B lymphocytes, plasma cells, and macrophages. Immunoperoxidase staining of cryostat sections revealed the presence of T helper/inducer lymphocytes, T suppressor/cytotoxic lymphocytes, and macrophages. The number of B lymphocytes and plasma cells was much smaller than the number of T lymphocytes. The number of T suppressor/cytotoxic lymphocytes was higher than the number of T helper/inducer lymphocytes. This study supports the notion of local immune responsiveness in the human inner ear. This is the first immunohistochemical study to analyze lymphocyte subpopulations; specifically, to provide insight into T-cell function in the endolymphatic sac.

Electron microscopy of hyalin bodies in the human intraosseous endolymphatic sac

Hyalin bodies are amorphous, eosinophilic masses protruding from the subepithelial connective tissue into the lumen of the intraosseous endolymphatic sac (ES). We studied hyalin bodies at the electron microscopic level. Celloidin- embedded temporal bone sections known to have hyalin bodies were re-embedded into plastic and cut into thin sections appropriate for electron microscopy. The results revealed that the hyalin bodies are composed predominantly of thick bundles of collagenous fibers arranged in various directions. Fibroblasts and disintegrated macrophages were occasionally observed among the collagen fibers. Concentric calcific structures found within the hyalin bodies were composed of multiple smaller, concentric, lamellar calcifications. The results of this study support the hypothesis that the hyalin bodies are a repository of membranous cellular debris phagocytized by the macrophages.

Histologic and statistical studies on hyalin bodies in the human endolymphatic sac

Hyalin bodies are amorphous, eosinophilic masses that protrude from the subepithelial connective tissue into the lumen of the endolymphatic sac. In this study, hyalin bodies were analyzed in two groups of temporal bones: normal bones and bones with cochlear otosclerosis. The results revealed that bones with cochlear otosclerosis had significantly more and larger hyalin bodies that did normal bones. In addition, the hyalin bodies in cochlear otosclerosis were denser and associated with more edema and loose connective tissue in the surrounding areas. Foamy macrophages, concentric calcific structures, and bony ingrowth were frequent features of the hyalin bodies in the cochlear otosclerosis. Our current hypothesis is that these hyalin bodies are repository of membranous cellular debris phagocytized by the macrophages. If this is true, the hyalin bodies may further support the proposed resorptive and phagocytic functions of the endolymphatic sac and the enzymatic concept in cochlear otosclerosis.

Human endolymphatic sac: morphologic evidence of immunologic function

The ultrastructure of ten normal human endolymphatic sacs (ES), fixed immediately after death and obtained at autopsy, was observed by transmission electron microscopy. The roles of the epithelium, subepithelial space, vasculature, and ES leukocytes were morphologically studied to evaluate possible immunologic functions of the human ES. In addition, five intraosseous ES biopsies from patients undergoing translabyrinthine acoustic neuroma resection were studied using the immunoperoxidase technique to identify specific leukocyte subpopulations. Evidence of phagocytic activity included the presence of phagocytic epithelial cells, monocytes, macrophages, and polymorphonuclear leukocytes. Immune surveillance was suggested by intraepithelial and subepithelial T-lymphocytes, numerous fenestrated blood vessels, and the presence of a homogeneously staining substance within the lumina of ES epithelial tubules. No B-lymphocytes were found. The findings support the existence of a local immune system of the normal human inner ear.

[Surgical procedure in complicated mitral stenosis]

The experience with the surgical treatment of complicated forms of mitral stenosis in 110 patients with the III and IV classes of the disease according to the classification of the New York Heart Association was analyzed. Closed mitral commissurotomy was performed in 36 patients, opened commissurotomy--in 33 patients, prosthetics of the mitral valve was made in 41 patients. Closed mitral commissurotomy is believed to be the simplest method of correction of the duct in mild calcinosis and deformity of the mitral valve, and fixed thrombosis of the left auricle. Opened mitral commissurotomy was justified in case of thrombosis of the left auricle and mild calcinosis and deformity of the valve. Substitution of the valve is indicated in cases of massive calcinosis and rough deformity of the valve and subvalvular structures when valve-preserving operations are impossible.