nitinol and Heart-Valve-Diseases

Mitral regurgitation is the most commonly occurring valvular heart disease in developed countries. Transcatheter mitral valve replacement (TMVR) has emerged as a novel potential therapy for patients with severe mitral valve disease who are unsuitable candidates for conventional surgery or transcatheter edge-to-edge mitral repair. TMVR with the Tendyne prosthesis has shown potential at short-term follow-up to be an effective and safe treatment alternative for high-risk patients with severe mitral valve disease.

Topics: Aged; Aged, 80 and over; Alloys; Cardiac Catheterization; Clinical Trials as Topic; Echocardiography, Transesophageal; Feasibility Studies; Heart Valve Diseases; Heart Valve Prosthesis Implantation; Humans; Mitral Valve; Mitral Valve Insufficiency; Multimodal Imaging; Non-Randomized Controlled Trials as Topic; Prospective Studies; Prosthesis Design; Quality of Life; Severity of Illness Index; Treatment Outcome; Ventricular Outflow Obstruction

We assessed the transventricular placement of porcine small intestinal submucosa (SIS) stent valves in a juvenile sheep model at the 3-month follow-up evaluation.. We constructed a pulmonary stent valve by suturing a porcine SIS bicuspid valve into a bell-shaped 'Z' nitinol stent and implanted 7 SIS stent valves transventricularly in the pulmonary position in 7 sheep. The function of the stent valves was assessed using a pulsatile flow simulation system in vitro. Haemodynamic, angiographic, echocardiographic, histologic and radiographic examinations were carried out before, immediately after implantation and 3 months after implantation.. All SIS stent valves were successfully implanted in the pulmonary position in 7 sheep. Angiographic, echocardiographic, haemodyamic and macroscopic studies confirmed firm anchoring and good positioning of the stents immediately after implantation and at 3-month follow-up. All stent valves had good function immediately after implantation and at the end of the protocol, with the exception of 1 stent valve with mild stenosis detected at the end of the protocol. All SIS valves were free of calcifications and thrombus formation, and all stents were intact with no fractures and migration based on postmortem examination and X-radiography.. We demonstrated successful implantation of porcine SIS stent valves in the pulmonary position in sheep with excellent valve function at the 3-month follow-up evaluation. Porcine SIS has potential superiority as a pulmonary stent bioprosthetic valve material, and the bell-shaped nitinol stent has potential superiority as a frame for pulmonary stent valves.

Topics: Alloys; Angiography; Animals; Bioprosthesis; Disease Models, Animal; Echocardiography; Heart Valve Diseases; Heart Valve Prosthesis; Heart Valve Prosthesis Implantation; Heart Ventricles; Hemodynamics; Intestinal Mucosa; Prosthesis Design; Pulmonary Valve; Sheep; Stents; Swine

The epidemiology of valvular heart disease has significantly changed in the past few decades with aging as one of the main contributing factors. The available options for replacement of diseased valves are currently limited to mechanical and bioprosthetic valves, while the tissue engineered ones that are under study are currently far from clinical approval. The main problem with the tissue engineered heart valves is their progressive deterioration that leads to regurgitation and/or leaflet thickening a few months after implantation. The use of bioresorbable scaffolds is speculated to be one factor affecting these valves' failure. We have previously developed a non-degradable superelastic nitinol mesh scaffold concept that can be used for heart valve tissue engineering applications. It is hypothesized that the use of a non-degradable superelastic nitinol mesh may increase the durability of tissue engineered heart valves, avoid their shrinkage, and accordingly prevent regurgitation. The current work aims to study the effects of the design features on mechanical characteristics of this valve scaffold to attain proper function prior to in vivo implantation.

Topics: Alloys; Heart Valve Diseases; Heart Valve Prosthesis; Humans; Models, Cardiovascular; Prosthesis Design; Surgical Mesh; Tissue Scaffolds

Transcatheter pulmonary valve replacement is currently performed in clinical trials, however limited by the use of glutaraldehyde treated bioprostheses. This feasibility study was performed to evaluate delivery-related tissue distortion during implantation of a tissue engineered (TE) heart valves.. The injectable TE heart valve was mounted on a self-expanding nitinol stent (n=7) and delivered into the pulmonary position of seven pigs, (weight 26 to 31 kg), performing a sternotomy or limited lateral thoracotomy. Prior to implantation, the injectable TE heart valve was crimped and inserted into an applicator. Positioning of the implants was guided by fluoroscopy and after carefully deployment angiographic examination was performed to evaluate the correct delivered position. Hemodynamic measurements were performed by epicardial echocardiography. Finally, the animals were sacrificed and the injectable TE heart valves were inspected by gross examination and histological examination.. Orthotopic delivery of the injectable TE heart valves were all successful performed, expect in one were the valve migrated due to a discrepancy of pulmonary and injectable TE valve size. Angiographic evaluation (n=6) showed normal valve function, supported by epicardial echocardiography in which no increase flow velocity was measured, neither trans- nor paravalvular regurgitation. Histological evaluation demonstrated absence of tissue damage due to the delivery process.. Transcatheter implantation of an injectable TE heart valve seems to be possible without tissue distortion due to the delivery system.

Topics: Alloys; Animals; Feasibility Studies; Fluoroscopy; Heart Valve Diseases; Heart Valve Prosthesis Implantation; Hemodynamics; Stents; Swine; Tissue Engineering

The study objective was to evaluate the safety and efficacy of sutureless self-expanding nitinol stent-frame aortic valve prostheses made of equine pericardium implanted in patients with symptomatic aortic valve disease.. We performed a retrospective analysis of 120 patients (mean age, 76.7 ± 5.9 years) who underwent isolated aortic valve replacement or in combination with other cardiovascular procedures. Preoperatively, Society of Thoracic Surgeons score was determined. Transthoracic echocardiography and clinical outcome evaluation were performed at the time of discharge and at 6, 12, and 18 months follow-up, respectively.. A total of 71 of 120 patients underwent isolated sutureless aortic valve replacement (mean aortic crossclamp time, 37 ± 11 minutes; mean bypass time, 62 ± 18 minutes). Coronary bypass grafting was performed in 30 patients. Overall mean Society of Thoracic Surgeons score was 14.8% ± 10%. Thirty-day mortality rate was 6.7% overall and 1.4% in stand-alone procedures. During a mean follow-up of 313 days, 3 more deaths occurred. The reoperation rate was 4.2%. Mean and peak transvalvular pressure gradients were 9 mm Hg (4-13 mm Hg) and 14 mm Hg (8-22 mm Hg) at discharge, respectively. In 8 patients (6.7%), permanent pacemaker implantation was necessary. No thromboembolic events or bleedings related to the bioprosthesis were observed.. In this large single-center experience with sutureless aortic valve replacement, the surgical procedure is shown to be safe and time-saving. In view of the excellent hemodynamic results and shortening of aortic crossclamp and bypass times, we notice advantages especially in high-risk patients. Minimally invasive access seems to be facilitated. The long-term durability of this prosthesis has yet to be determined.

Topics: Aged; Aged, 80 and over; Alloys; Animals; Aortic Valve; Bioprosthesis; Coronary Artery Bypass; Female; Heart Valve Diseases; Heart Valve Prosthesis; Heart Valve Prosthesis Implantation; Hemodynamics; Horses; Humans; Male; Middle Aged; Pericardium; Postoperative Complications; Prosthesis Design; Retrospective Studies; Risk Factors; Stents; Suture Techniques; Time Factors; Treatment Outcome; Ultrasonography

Topics: Alloys; Animals; Aortic Valve; Aortic Valve Insufficiency; Bicuspid Aortic Valve Disease; Cardiac Catheterization; Femoral Artery; Heart Defects, Congenital; Heart Valve Diseases; Heart Valve Prosthesis; Heart Valve Prosthesis Implantation; Incidence; Models, Animal; Prosthesis Design; Stents; Treatment Outcome

Topics: Alloys; Aortic Valve; Bicuspid Aortic Valve Disease; Bioprosthesis; Cardiac Catheterization; Heart Defects, Congenital; Heart Valve Diseases; Heart Valve Prosthesis; Heart Valve Prosthesis Implantation; Humans; Polyesters; Prosthesis Design; Stents; Treatment Outcome

The BioPhysio bioprosthesis (Edwards Lifesciences LLC, Irvine, CA, USA) was designed to further improve the hemodynamic performance currently achieved by stented valves. A flexible Nitinol stent that preserves aortic root dynamics, thus maximizing the effective orifice area (EOA), is a key innovation of this prosthesis. The study aim was to provide a clinical evaluation of this new device.. Between December 2004 and August 2005, a total of 50 patients (27 males, 23 females; mean age 75.8 +/- 5.1 years; range: 55-84 years) received a BioPhysio aortic bioprosthesis. Clinical outcomes, EOAs, mean gradients and regression of left ventricular hypertrophy were evaluated echocardiographically at discharge, and at six, 12, 24, 36, 48, and 60 months after surgery.. The 60-month follow up was complete for all patients. No patients died within 30 days of surgery, but the late mortality was 14% (n = 6). There was one sudden unexplained death. One patient developed endocarditis at two years after surgery and underwent reoperation. There were no cases of stroke or renal failure. The BioPhysio prosthesis showed a good hemodynamic performance, with a significant fall in mean gradient to 15.1 +/- 8.3 mmHg, a mean EOA of 1.5 +/- 0.7 cm2, and a mean ejection fraction of 61 +/- 7.2%. There were no cases of aortic regurgitation. The NYHA functional class was improved in all patients, and there was a significant reduction in the left ventricular mass index to 185.7 +/- 49.6 g/m2 at 24 months.. The clinical performance of the BioPhysio aortic bioprosthesis is comparable to that of regular stentless aortic valves. However, clinical approval for the widespread use of this bioprosthesis was not obtained.

Topics: Aged; Aged, 80 and over; Alloys; Aortic Valve; Bioprosthesis; Female; Follow-Up Studies; Heart Valve Diseases; Heart Valve Prosthesis; Heart Valve Prosthesis Implantation; Hemodynamics; Humans; Hypertrophy, Left Ventricular; Kaplan-Meier Estimate; Male; Middle Aged; Prospective Studies; Prosthesis Design; Time Factors; Treatment Outcome; Ultrasonography

Machining of shape memory alloys based on Nitinol (NiTi) creates difficulties due to its ductility and severe strain hardening. In this experiment, different cutting edges and grinding parameters were tested to optimize cutting results on NiTi-based blades intended for endovascular heart valve resection. The cutting procedure was performed using two counter-rotating circular NiTi blades of different diameter. A rotating/punching process should be performed. Different shapes (glazed, waved, and saw tooth), different grinding techniques (manual, manual grinder, and precise milling cutter) and additionally various velocities (50 and 200 rpm) were tested on specific test specimens. Cutting forces were measured and cutting quality was examined using digital microscopy. Preliminary tests with rotating blades showed superior results using cutting edges for the punching process (150 N vs. 200 N; n=7). In a second step special test specimens were tested. Maximum cutting-force was 265 N+/-20 N (mean+/-SD; n=7). Subsequently different shapes were tested at 50 and 200 rpm using the rotating/punching method regarding alternate grinding techniques. Cutting forces were 27 N+/-7.7 N for glazed blades (n=7) at 50 rpm and 18 N+/-4.7 N at 200 rpm, waved blades (n=7) required a maximum force of 18 N+/-5 N at 50 rpm and 11 N+/-3.3 N at 200 rpm, whereas saw tooth blades (n=7) needed 17 N+/-12.7 N at 50 rpm and 9 N+/-1.2 N at 200 rpm. Precise cutting quality was only seen when using glazed blades sharpened under accurate conditions with a high-speed milling cutter. Although shape memory alloys based on Nitinol are difficult to process, and well-defined grinding parameters do not exist, acceptable results can be reached using high-speed milling cutters. Best cutting quality can be observed by using glazed blades, performing a rotating/punching process at high velocities. Lower cutting forces can be observed by using other shape-types, however this leads to lower cutting quality. Therefore, further investigations on blade-machining and velocity-testing seem to be necessary to create optimal cutting results.

Topics: Alloys; Aortic Valve; Equipment Design; Heart Valve Diseases; Heart Valve Prosthesis Implantation; Humans; In Vitro Techniques; Microscopy; Minimally Invasive Surgical Procedures; Quality Control