Animal Evaluation of a New Pericardial Bioprosthetic Heart Valve

Implantation in animals is an essential step in the evaluation of any new prosthetic heart valve before commencing clinical trials. A new three-leaflet pericardial bioprosthesis developed in Glasgow has been implanted in the mitral position in ten sheep and eight dogs. Eleven animals were electively killed after 3 months of observation and explanted valves were in good condition. Hydrodynamic tests of the explanted valves showed small changes in function compared to tests prior to implantation. This was mainly due to host tissue ingrowth over the edge of the leaflets. Histological studies confirmed good preservation of the pericardial tissue in explanted valves.     

Bioprosthetic Pulmonary Valve Dysfunction in Congenital Heart Disease

BackgroundWe aim to identify the incidence and timing of dysfunction and failure of stented bioprosthetic valves in the pulmonary position in congenital heart disease patients.MethodsA total of 482 congenital heart disease patients underwent 484 stented bioprosthetic pulmonary valve implantations between 2008 and 2018. There were 164 porcine valves (Porcine) and 320 bovine pericardial valves (Pericardial) implanted. Primary endpoints were survival, valve dysfunction, and valve failure.ResultsPericardial valves were implanted in older patients (22.0, interquartile range [IQR] 14-33 vs 16.0, IQR 11-23 years, P < 0.001). Five-year survival (96.7% vs 97.9%) for the Pericardial and Porcine groups, respectively, were similar, P > 0.05. Forty-six (34%) Porcine and 75 (27%) Pericardial group patients met criteria for valve dysfunction at a median echocardiographic follow-up time of 7.43 years (IQR 4.1-9.5 years) and 3.26 years (IQR 1.7-4.7 years), respectively. More Pericardial group patients suffered from at least mild late PR while late median peak gradient was higher in the Porcine group, P < .001 for both. Risk factors for valve dysfunction included decreasing patient age for the entire cohort (hazard ratio [HR] 1.02, 95% confidence interval [CI] 1.00-1.04, P = .015) and lack of anticoagulation at discharge for the Porcine group (HR 3.06, 95% CI 1.03-9.10, P = .044) but not the Pericardial group. Five-year cumulative incidence of dysfunction was 39% for the Pericardial group and 17% for the Porcine group.ConclusionsPorcine stented and bovine pericardial stented valves can be implanted in the pulmonary position in all age groups safely. However, despite similar rates of valve failure, bovine pericardial stented valves have a higher incidence of valve dysfunction at mid-term follow-up.     

Endothelial Cell Lining of Bioprosthetic Heart Valve Material

In this in vitro study, the growth properties of cultured endothelial cells on conventionally treated pericardial valve material were measured. These data were compared to endothelial cell proliferation on an alternatively treated valve material. This alternative preservation procedure was developed in order to bind free, residual glutaraldehyde in the valve tissue by reaction with L-glutamic acid. In order to optimize endothelial cell attachment and proliferation, fibronectin and fibrillar collagen type I were tested as surface precoating substances. Cell viability of the seeded cells was evaluated by means of proliferation kinetics, antithrombotic activity, and morphological appearance. Endothelial cell death occurred within the first 2 days after seeding on conventionally treated valve tissue, independent of the type of precoating. On alternatively treated tissue, regular endothelial cell proliferation was observed. Precoating with fibrillar collagen markedly increased endothelial cell attachment and proliferation as compared to fibronectin. Maintenance of antithrombotic activity of the seeded cells was proven by regular release of prostacyclin.     

Stent Fracture in Wessex Porcine Heart Valve Bioprostheses

Abstract: By January 1994, a total of 40 Wessex porcine bioprostheses (21 mitral, 18 aortic, and 1 tricuspid) were explanted from 31 subjects. They belonged to a series of 150 patients who received 184 of such prostheses in our unit. Seventeen of these explanted prostheses were available for study, and 11 of them presented some sort of stent fracture or fissuring (mean of 3.6 ±1.6 fractures per prosthesis). The disruption occurred in all cases at the base of the commissural arch or at the commissural bar of the stent. The fractures were not detected clinically nor echo-cardiographically before reoperation, and most valves were explanted for reasons other than the stent rupture itself. Trie actuarial probability of freedom from stent fracture in our series is 66 ±12% at 9 years of follow-up. In our experience, fracture of the stent is an important mode of structural dysfunction of the Wessex porcine bioprostheses.     

Mechanical Valve Replacement Versus Bioprosthetic Valve Replacement in the Tricuspid Valve Position

Background

The purpose of this study was to evaluate the clinical outcomes and risk of tricuspid valve replacements and to compare bioprosthetic versus mechanical valves.

Methods

Between 1991 and 2009, 104 consecutive patients (71 women; mean age, 57 ± 10.8 years) with tricuspid valvular disease underwent mechanical TVR (mechanical group; n = 59) or bioprosthetic TVR (bioprosthesis group; n = 45). Follow‐up was complete in 97.1% (n = 101) with a median duration of 49.9 months (range 0–230 months).

Results

Hospital mortality after mechanical TVR and bioprosthetic TVR was not different on adjusted analysis by propensity score. Ten‐year actuarial survival after mechanical and bioprosthetic TVR was 83.9 ± 7.6% and 61.4 ± 9.1%, respectively (p = 0.004). However, there was also no significant difference in terms of adjusted analysis by propensity score (p = 0.084). No statistically significant difference was detected between mechanical and bioprosthetic valves in regard to event‐free survival.

Conclusions

Mechanical TVR is not inferior to bioprosthetic TVR in terms of occurrence of valve‐related events, especially anticoagulation‐related complications. doi: 10.1111/jocs.12093 (J Card Surg 2013;28:212–217)     

Improved Biocompatibility of Bioprosthetic Heart Valves by L-Glutamic Acid Treatment

Treatment of glutaraldehyde-fixed pericardium with L-glutamic acid and storage in bacteriostatic preservatives (paraben) stably antagonizes free, reactive aldehyde groups within the fixed bioprosthetic heart valve tissue. In 63-day subcutaneous implants in rats, the calcification rate of this treatment (13.3 +/- 2 mg calcium/g wt tissue) was markedly reduced as compared to conventionally treated tissue (169 +/- 24 mg/g; p less than 0.05). To test the influence of tissue-released toxic aldehydes on spontaneous endothelial cell ingrowth in vivo, vascular grafts (8-cm long, 6-mm diameter) from fixed pericardium treated with L-glutamic acid were interposed into the carotid arteries in ten sheep. They were compared to grafts from conventionally treated pericardium implanted at the contralateral side. Following 3 months of implantation, planimetry revealed 49% +/- 20% of the surface of conventionally preserved pericardium to be covered with red thrombus, but only 12% +/- 5% in L-glutamic acid treated pericardium (p less than 0.05). The ultrastructural findings of a closed endothelial cell layer on the graft surface reveals the new technique to be a promising approach towards increased biocompatibility of aldehyde-fixed bioprosthetic heart valves.     

Stresses of Natural versus Prosthetic Aortic Valve Leaflets in Vivo

During normal function of the aortic valve, the aortic leaflets undergo not only cyclic loading and unloading but also cyclic reversal of their curvature. The stresses induced in the leaflet due to these variations have been computed using a new concept based on the structure of the leaflet. Membrane stresses have been related to the pressure difference across the leaflet and bending stresses to the leaflet curvature. Total stresses were obtained by adding the two stresses. Total stresses in bioprosthetic and synthetic leaflets also were computed using the same approach. In systole, the natural leaflet is subjected to much lower total stress than a bioprosthetic or a synthetic leaflet. The natural leaflet is not subjected to compressive stresses during the cardiac cycle, whereas bioprosthetic and synthetic leaflets must sustain compressive stresses during systole. The differences in stress patterns of these leaflets indicate that there is a difference in their longevity.     

Results of a European Multicentre Iliac Stent Trial with a Flexible Balloon Expandable Stent

PURPOSE: to determine the 12 months success rate with a balloon expandable, flexible stainless steel stent in iliac artery obstructions. MATERIALS AND METHODS: one-hundred and twenty-six consecutive patients with iliac obstructive disease and who demonstrated an unsatisfactory angioplasty result with a post-dilatation gradient of at least 10 mmHg, or a primary occluded lesion were included in the study. Follow-up was by Doppler sonography, ankle pressures with and without exercise and clinical parameters. RESULTS: after stent placement, the mean percentage diameter stenosis decreased from 79 to 4%, with a mean intra-arterial pressure gradient of 3 mmHg. Primary stent patency was 94% at 6 months and 89% at 12 months. Primary clinical result at 6 months was 88% and at 12 months 81%. Primary assisted clinical result (after re-pta) at 6 and 12 months was 89 and 86%, respectively. The Ankle Brachial Index (ABI) after exercise at 1 month follow-up was reduced from 0.88 to 0.75, with minor deterioration at 6 months to 0.72, and at 12 months to 0.68. The 1, 6, and 12 months follow-up Piek Systolic Velocity (PSV) ratios across the stented lesions remained stable at a mean of 1.4, 1.6, and 1.6, respectively. However, respectively 44, 39 and 34% of the patients still experienced symptoms of claudication. CONCLUSIONS: the results presented here support the suggestion stenting to be an effective device in the treatment of iliac artery obstructive disease. This study also, confirms other study results concerning haemodynamic patency after iliac stenting on the indication of a 10 mmHg pressure gradient after pta and the discrepancy between good haemodynamic patency and clinical result.     

体外循环心瓣膜置换术中止血环酸的应用

目的　体外循环心瓣膜置换术中应用止血环酸（ｔｒａｎｅｘａｍ ｉｃ ａｃｉｄ）,观察其对血小板的保护作用。　方法５０ 例心瓣膜置换术的患者随机分为止血环酸组和对照组,用双盲法进行实验。止血环酸组术前静脉注射止血环酸１０ｍ ｇ／ｋｇ,预充液中加５ｍ ｇ／ｋｇ（总量累计超过１ｇ 者,按１ｇ 计算,２／３ ｇ 静脉注射,１／３ ｇ 加入预充液中）;对照组分别加等量生理盐水。测定两组转流前、后血小板粘附率、血小板聚集率、血小板计数,观察术后 ２４ 小时出血量和输血量。结果　转流后两组血小板功能均有下降,但对照组明显低于止血环酸组（ Ｐ＜ ００５）;转流后止血环酸组血小板计数无明显变化（ Ｐ＞ ００５）;转流后对照组血小板计数明显低于转流前（ Ｐ＜ ００１）,且明显低于止血环酸组（ Ｐ＜ ００５）;出血量和输血量止血环酸组均低于对照组（ Ｐ＜ ００５）。　结论　止血环酸能有效保护血小板,明显减少术后出血及输血量。     

二尖瓣置换术后生物瓣瓣膜毁损的定义及再手术时机探讨

目的探讨二尖瓣置换术后生物瓣毁损的定义及再手术时机。方法对５５例患者施行牦牛心包瓣膜置换二尖瓣手术。术后随访至１９９３年９月，累积随访３７９．４患者／年，平均６．９年。结果瓣膜毁损１６例，轻度病例１年后仅１６．７％（２／１２）转变为重度；再手术５例，术后４例康复，１例死于呼吸衰竭。结论瓣膜毁损可分为轻度和重度。轻度为瓣膜钙化；重度指瓣膜穿孔或撕裂，瓣膜中度以上狭窄或返流。轻度毁损宜观察，重度毁损则应及时手术。     

Management of the Patient with a Prosthetic Heart Valve

Approximately 20,000 heart valve prostheses are inserted yearly in the United States. Even after successful heart operations, the patients who receive them cannot be regarded as healthy individuals but are a special group with special problems who need close medical attention for the rest of their lives. They are susceptible to many unusual complications because of their implanted foreign body, and it is a challenge to all physicians in contact with them to be aware of their peculiar problems in order to prevent complications if possible and to treat them immediately if they occur.General therapy, surgical complications, infection, and mechanical problems are reviewed, with means for management outlined. These difficulties can be dealt with only by careful follow-up and well-coordinated teamwork between the family physician and the institution where the operation was performed.     

The Effects of Sterilization and Storage Treatments on the Stress-Strain Behavior of Aortic Valve Leaflets

An investigation was made of the feasibility of using tensile tests to detect alterations in the molecular structure of aortic valve tissue brought about by sterilizing or storage treatments. Stressstrain tests were carried out on fresh valve leaflets from pigs and repeated with the same specimens after specified sterilization or storage treatments. It was found that the stress at a given strain was increased by treatment with ethylene oxide, buffered formalin, and tissue culture solution and decreased by treatment with antibiotics. The least change was with tissue culture solution and antibiotics.It has been suggested that the best method of allograft sterilization should involve minimal structural alteration to the collagen and elastic components of the tissue. Thus, treatment with tissue culture solution and antibiotics seems appropriate.