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PubMed1995

New bioactivation mode for vascular prostheses made of Dacron polyester.

The performance of vascular prostheses, especially those of small calibre, still presents several problems. The use of polyesters such as the well-known poly(ethylene terephthalate) (Dacron) and, more recently, poly(tetrafluoroethylene) and polyurethanes provides a marked improvement. We have developed a process to increase the efficiency of such prostheses, using the ability of the Dacron polyester to be covalently modified by proteins under mild chemical conditions. The biomaterial is obtained from the particular interaction of elastin-solubilized peptides with type I + III collagens under very precise conditions. We have obtained an irreversible covalent bonding on Dacron. These biological conditions and the addition of connective proteins and glycosaminoglycans conferred on the resulting material a composition and a three-dimensional structure equivalent to the subendothelium, providing bioactive properties suitable for the development of a vascular prosthesis.

Biocompatible Materials↗

PubMed1983

The suprasternal approach to recording aortic valve prostheses: a comparison with the precordial and subxiphoid approaches.

We evaluated 56 consecutive patients echocardiographically 9 days to 104 months after aortic valve replacement by the precordial, subxiphoid and suprasternal approach. In 11 patients, the mitral valve had also been replaced. For comparison, a subjective grading system (score 1 up to 3) was applied to the records obtained from each approach. Disc valves (n = 41) were equally scored from the precordial and suprasternal approach (score 2.6). Ball prostheses (n = 6) were best imaged from the suprasternal approach (score 3.0), whereas bioprostheses (n = 9) were best visualized from the precordial (1.8). Simultaneous imaging of both valves was possible in 6 out of 11 patients with a double prosthesis using the suprasternal approach but not from precordial and subxiphoid approaches. Six patients presented prosthetic valve dysfunction. Five patients had paravalvular insufficiency; 4 of these patients had a Björk-Shiley valve and one patient a Lillehei-Kaster valve. The echograms of 4 out of 5 patients with a paravalvular leak were normal from each approach. In another patient an obstructed Björk-Shiley prosthesis was found. The pre- and postoperative echograms demonstrated that the suprasternal approach was best to visualize the obstructed valve. The study shows that the suprasternal technique is superior for evaluation of most patients with aortic valve prostheses.

Adult↗

PubMed1988

Doppler ultrasound of normally functioning mechanical mitral and aortic valve prostheses.

Doppler ultrasound flow velocities across clinically normally functioning mitral (Bjork-Shiley, Medtronic Hall, Lillehei-Kaster, Duromedic and Starr-Edwards) and aortic (Bjork-Shiley, Medtronic Hall, Lillehei-Kaster and Duromedic) valve prostheses are described. To enable ease of reference for the echocardiographer and to avoid the need for time-consuming calculations of pressure drops and effective valve orifice areas, peak flow velocities and, where relevant, pressure half times across valves of different types and sizes are tabulated. In the mitral position, there was significant negative correlation between peak velocity and valve size and between pressure half time and valve size only when a large number and a wide range of sizes of a given type of mitral prosthesis was studied. Similarly, there was significant negative correlation between peak velocity and aortic valve size for Bjork-Shiley and Duromedic valves. Regurgitant jets were detected across 18.4% of mitral and 42% of aortic prostheses.

Adolescent↗

PubMed1992

The Hatle orifice area formula tested in normal bileaflet mechanical mitral prostheses.

The Hatle formula was derived empirically in native mitral stenosis and may not be valid for normal prosthetic valves. Bileaflet mechanical prostheses open fully at low flows and have minimal interindividual variation in orifice area. In these valves effective area and measured manufacturer's area should be similar. We studied 60 patients aged 58 +/- 12 yr at a mean of 5 months after implantation with a CarboMedics prosthesis. There was a coexistent aortic prosthesis in 21. All diastolic measurements were averaged over 5 beats and stroke volume was calculated from the integral of the subaortic velocity trace and the cross-sectional area of the left ventricular outflow tract. For the whole group, area by the Hatle formula was 3.1 +/- 0.7 cm2 and measured area was 2.8 +/- 0.4 cm2. There was no significant correlation between these values (p = 0.329). Pressure half-time was more closely correlated with peak transmitral velocity (p = 0.012), RR interval (p = 0.015), diastolic time interval (p = 0.062) and stroke volume (p = 0.074). We conclude that the Hatle formula should not be applied to normal bileaflet mitral prostheses where pressure half-time reflects nonprosthetic factors more closely than orifice area.

Aged↗

PubMed1994

Myoelectric prostheses in the management of Poland's syndrome. A report of 2 cases.

Two cases of Poland's syndrome are reported in whom myoelectric prostheses have been used. The rare congenital sporadic disorder of Poland's syndrome characterized by absence of pectoralis major and varying degrees of ipsilateral upper limb deficiency has been reported by various authors (Rasjad and Sutiaksa, 1991, Gausewitz et al, 1984; David, 1982; Ireland et al, 1976). Management of the upper limb deficiency depends on the degree of functional and cosmetic disability. We report two cases of Poland's syndrome where myoelectric prostheses have been successfully used. We have been unable to find any published report of the use of a myoelectric prosthesis in Poland's syndrome.

Adult↗

PubMed1996

An experimental study of damage accumulation in cemented hip prostheses.

OBJECTIVE: To develop a methodology to characterize the pattern of crack initiation and damage accumulation in intramedullary fixated cemented prostheses. DESIGN: An experimental physical model of intramedullary fixation was developed which both represents the implant structure and permits monitoring of fatigue crack growth. BACKGROUND: Many joint replacement prostheses are fixed into the medullary cavity of bones using a poly(methylmethacrylate) 'bone cement', which forms a mantle around the prosthesis and locks it to the bone. The endurance of the replacement is, to a great extent, determined by the mechanical durability of the cement and the implant interfaces under cyclic stresses generated by dynamic loading. The cement mantle is subjected to complex multiaxial stresses which vary in particular distribution depending on the prosthesis design. METHODS: Damage accumulation is reported in terms of the number of cracks, the location of cracks, and the rate of crack growth. RESULTS: The results clearly show the nature of damage accumulation in the cement mantle, and that many of the cracks which propagate within the cement mantle are related to cement porosity. CONCLUSION: This study gives experimental evidence to support the hypothesis of a damage accumulation failure scenario in cemented hip reconstructions. RELEVANCE: Cementing is the most popular technique for the fixation of joint replacement prosthesis. However, the sequence of events leading to the failure of cemented fixation is not fully understood. In this paper it is shown that damage accumulation can be directly monitored in an experimental model of cemented intramedullary fixation.

Journal Article↗

PubMed1991

Patterns of normal transvalvular regurgitation in mechanical valve prostheses.

The magnitude and spatial distribution of normal leakage through mechanical prosthetic valves were studied in an in vitro model of mitral regurgitation. The effective regurgitant orifice was calculated from regurgitant rate at different transvalvular pressure differences and flow velocities. This effective orifice area was 0.6 to 2 mm2 for three tilting disc prostheses (Medtronic-Hall sizes 21, 25 and 29) and 0.2 to 1.1 mm2 for three bileaflet valves (St. Jude Medical sizes 21, 25 and 33). In the single disc valves, Doppler color flow examination disclosed a prominent central regurgitant jet around the central hole for the strut, accompanied by minor leakage along the rim of the disc (central to peripheral jet area ratio 3.3 +/- 1.2). The bileaflet prostheses showed a peculiar complex pattern: in planes parallel to the two disc axes, convergent peripherally arising jets were visualized, whereas in orthogonal planes several diverging jets were seen. Mounting the disc and bileaflet valves on a water-filled tube allowed reproduction and interpretation of this pattern: for the bileaflet valve, the jets originated predominantly from valve ring protrusions that contained the axis hinge points and created a converging V pattern in planes parallel to the leaflets and a diverging V pattern in orthogonal planes. Similar patterns were observed during transesophageal echocardiography in 20 patients with a normally functioning St. Jude prosthesis. In 10 patients with a Medtronic-Hall valve, a dominant central jet was observed with one or more smaller peripheral jets. The median central to peripheral jet area ratio was 5 to 1.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗

PubMed1996

'In vivo' size of knitted Dacron prostheses (Gelseal) used in the thoracic aorta: a computed tomography study.

When replacing the thoracic aorta, gelatin-sealed triaxial knitted Dacron prostheses are used as they have zero porosity and are easy to handle. It is known that knitted prostheses (not triaxially constructed), when implanted in the abdominal aorta or in the peripheral vessels, show a dilatation of 10-20%. The initial in vivo expansion of this prosthesis in the thoracic aorta was assessed using computed tomography scanning in 18 patients. The graft sizes used were 18mm (n = 4). 20mm (n = 5). 22mm (n = 4), 26mm (n = 1), 28mm (n = 2) and 30mm (n = 2). All patients were kept normotensive postoperatively. Computed tomography scan measurement was performed within 4 weeks of operation. using standard computed tomography equipment and no contrast. Two radiologists checked and agreed upon the slice levels and measurements compared with the manufacturer's stated size referring to internal diameter of the crimped prosthesis. The mean(s.d.) 'in vivo' size was 16.2(6)% larger. This 'true size' should be taken as the reference measurement when considering further dilatation over the period of follow-up.

Adult↗

PubMed1988

Thrombosis of two St. Jude Medical prostheses in one patient after triple valve replacement. Case report and review of the literature.

Reports of experience with the St. Jude Medical (SJM) valve state that thrombosis of the prosthesis is a rare complication. In a 57-year-old woman, reoperation was necessary 12 months after triple valve replacement using SJM prostheses because of thrombosis of the valves in the tricuspid and aortic positions. Dysfunction of both mechanical valves was detected clinically by changing heart sounds and the appearance of murmurs. Echocardiography and cinefluoroscopy confirmed at least one fixed leaflet of the tricuspid prosthesis, but abnormalities of the aortic prosthesis could not be detected. At reoperation, the SJM prosthesis in the tricuspid position was almost completely thrombosed and was replaced by an Ionescu-Shiley bioprosthesis. A thrombotic formation at the hinge point of the SJM aortic prosthesis was removed. To our knowledge, this is the first report of a thrombotic complication of two SJM prostheses after triple valve replacement in one patient.

Aortic Valve↗

PubMed1996

Conduit-mounted cardiac valve prostheses: a review of their uses, design and in vivo performance.

Although providing an historical overview of the development and clinical applications of conduit-mounted prosthetic heart valves, with elementary explanations of operative techniques, this review concentrates on the impact of design and surgical considerations on their in vivo performance. Areas showing potential for design improvement of mechanical prostheses are highlighted, both in terms of haemodynamic efficiency and haemocompatibility. Comparisons are drawn throughout the paper with conventional valve prostheses, and the key features where they differ significantly are pointed out. It is concluded that there is considerable scope for further worthwhile development.

Animals↗

PubMed2005

Osteointegration of femoral stem prostheses with a bilayered calcium phosphate coating.

Our purpose was to evaluate the osteointegration of bilayered calcium phosphate (CaP)-coated femoral hip stems in a canine model. A first layer of hydroxyapatite (HA) 20 microm thick and a superficial layer of Biphasic Calcium Phosphate (BCP) 30 microm thick were plasma-sprayed on to the proximal region of sandblasted Ti6Al4V prostheses. Bilayered CaP-coated and non-coated canine femoral stems were implanted bilaterally under general anesthesia in 6 adult female Beagle dogs. After 6 and 12 months, a significant degradation of the bilayered coating occurred with a remainder of 33.1+/-12.4 and 23.6+/-9.2 microm in thickness, respectively. Lamellar bone apposition was observed on bilayered coated implants while fibrous tissue encapsulation was observed on non-coated femoral stems. The bone-implant contacts (BIC) were 91+/-3% and 81+/-8% for coated and 7+/-8% and 8+/-12% for non-coated implants, at 6 and 12 months, respectively. Our study supports the concept of a direct relationship between the biodegradation of CaP coating and the enhanced osteointegration of titanium prostheses. A bilayered CaP coating might therefore enhance bone apposition in the early stages because of the superior bioactivity of the BCP layer while the more stable HA layer might sustain bone bonding over long periods.

Animals↗

PubMed2004

Fiber-reinforced composite prostheses.

Metal-free prosthetic dentistry continues to gain interest. Although the metal alloys contribute great strength and stiffness to restorations and prostheses, they do so at a considerable esthetic liability. Two somewhat divergent metal-free approaches to fixed tooth replacement continue to be developed for a variety of clinical applications. These are all-ceramic and all-polymeric systems. The polymeric prostheses are the subject of this article.

Composite Resins↗

PubMed2006

Predicting the performance of mitral prostheses implanted in children under 5 years of age.

BACKGROUND: Mitral valve replacement (MVR) is occasionally indicated in infants and young children, necessitating the use of small prostheses. The performance of these small valves during somatic growth of the patient can lead to patient-prosthesis mismatch. This study examines performance of these valves over time to establish predicted performance and timing of replacement. METHODS: Records were reviewed of all patients under 5 years of who underwent small mechanical MVR between 1988 and 2004 (n=24). Valve sizes were between 17 and 23 mm (Bileaflet 91.6%, Tilting Disc 8.3%) with a median size of 19 mm. Mean age of patients was 1.4+/-1.3 years with a mean weight of 7.8+/-3.4 kg. RESULTS: Early deaths (n=5, 20.8%) were excluded. There were two late deaths and five patients required redo-MVR: four for outgrowth and one for acute thrombosis at 3 months. Age at redo for outgrowth was 8.6+/-6.6 years with mean body weight of 22.5+/-17.5 kg. Mean time between original operation and redo was 8.6+/-6.1 years in these four patients. Follow-up was a median of 7.5 years (range 0.1-15.7 years). Overall freedom from death or valve replacement was 82.6+/-9.1% at 5 years and 75.7+/-10.6% at 10 years. The performance of the original prostheses showed a peak blood flow velocity across the valves of 1.5+/-0.6 m/s at 5 years and 2.2+/-0.5 m/s at 10 years. Seventy-five percent of the survivors still have their original valve at a mean of 8.1+/-4.4 years postoperative with New York Heart Association status of I or II. Actuarial curves suggest that gradients across the valves reach a peak of >10 mmHg at a mean between 6.5 and 7 years postoperative. CONCLUSION: MVR in children under 5 years carries a high mortality. Nevertheless, small mechanical MVR perform remarkably well in young children with durable haemodynamics despite growth of the patients well beyond more than double the initial bodyweight. Valves can be expected to last over 8 years before requiring re-replacement.

Age Factors↗

PubMed2005

The value of contrast and subtraction arthrography in the assessment of aseptic loosening of total hip prostheses: a meta-analysis.

OBJECTIVE: To summarize and compare the diagnostic accuracy of contrast and subtraction arthrography in the assessment of aseptic loosening of total hip arthroplasties. DESIGN: This meta-analysis was performed using methods described by the Cochrane Methods Group on Systematic Reviews of Screening and Diagnostic Tests. We included original, English-language papers published between January 1975 to October 2004 that examined contrast-enhanced arthrography with or without subtraction for diagnosis of loosening of total hip prostheses. A qualitative and quantitative analysis was performed by two investigators. RESULTS: With regard to the acetabular component, pooled sensitivity and specificity for contrast arthrography was 70% (95% confidence interval, 52-84) and 74% (95% CI, 53-87), respectively. Subtraction arthrography had a significantly higher sensitivity of 89% (95% CI, 84-93) (p=0.01), with a similar specificity of 76% (95% CI, 68-82). For the femoral component, pooled sensitivity and specificity for contrast arthrography were 63% (95% CI, 53-72) and 78% (95% CI, 68-86). Pooled estimates for subtraction arthrography revealed a significantly higher sensitivity of 86% (95% CI, 74-93) (p=0.003). Specificity was 85% (95% CI, 77-91) and was similar to the data of contrast arthrography (p=0.23). CONCLUSION: Using the present data we found that the subtraction arthrography is a sensitive technique for detection of loosening of total hip prostheses, offering added value over contrast arthrography, especially for evaluation of the femoral component.

Adult↗

PubMed2005

Transcatheter radiofrequency ablation of atrial fibrillation in patients with mitral valve prostheses and enlarged atria: safety, feasibility, and efficacy.

OBJECTIVES: Few data have been published on transcatheter ablation of atrial fibrillation (AF) in patients with mitral valve prostheses. Thus, we sought to report our experience. BACKGROUND: Ablation is an effective treatment for AF. Patients with prosthetic mitral valves represent a special group because of an increased risk from the ablation procedure due to the possibility of damage to the prosthetic valve. METHODS: Between July 2001 and July 2003, 26 patients with mitral valve prostheses (MVP) underwent circumferential pulmonary vein ablation for AF. A matched group of 52 ablated patients without MVP acted as control subjects. After a blanking period of three months, a follow-up of 12 months was considered for MVP patients and controls. Holter recordings were performed in all subjects at 3, 6, and 12 months. RESULTS: Radiation exposure was higher in the MVP group, with fluoroscopy times of 35.3 +/- 21 min versus 20.9 +/- 15 min in controls. At the end of follow-up, 73% of MVP patients were in sinus rhythm, compared with 75% of controls. Atrial tachycardia occurred in six (23%) MVP patients, requiring repeat ablation in three, and one (2%) control subject, which settled without treatment. One transient ischemic attack and one femoral pseudoaneurysm occurred in the MVP group. No complications occurred in the control group. CONCLUSIONS: Ablation of AF in patients with MVP is feasible, with outcomes similar to those of standard patients. Complications were higher among MVP patients with a greater radiation exposure and a higher incidence of post-ablation atrial tachycardia.

Aged↗

PubMed2005

Comparison of the ovine and porcine animal models for biocompatibility testing of vascular prostheses.

OBJECTIVE: Evaluation of the pig and sheep models for biocompatibility investigations of vascular prostheses (VP). DESIGN: Comparative analysis of animal experimental investigations involving two different animal models. MATERIALS AND METHODS: Commercially available polyester vascular prostheses (PET-VP) were implanted into two different animal models (infrarenal porcine aorta and ovine carotid artery). The costs, surgical handling, patency rate, and healing on the basis of macroscopic, microscopic, and immunohistochemical criteria were analyzed over a period of 3 months. RESULTS: Handling and operating times (63 +/- 10 versus 76 +/- 16 min; P = 0.125) did not differ significantly. The cost of the two animal models was comparable. Integration of the VP was complete in the sheep model, but varied in the pig model (two complete, four incomplete). Complete endothelialization of all VPs was observed in the pig, which contrasted with the sheep with complete (circular) endothelialization only in the region of the anastomosis. The thickness of neointima in the region of the anastomosis differed insignificantly; immunohistochemically, only periprosthetic Ki67 was significantly reduced (28.7 +/- 9.9 versus 6 +/- 0.9%; P = 0.002) in the sheep. CONCLUSIONS: In the porcine model, extremely good endothelialization of the VP was observed, with formation of a rapid neointimal hyperplasia. The ovine model was characterized by the fact that postoperative follow-up investigations were easy to perform. Complete endothelialization was not observed.

Animals↗

PubMed2005

Left ventricular mass regression after aortic valve replacement with 17-mm St Jude Medical mechanical prostheses in isolated aortic stenosis.

OBJECTIVE: The present study investigated the outcomes of aortic valve replacement with 17-mm mechanical prostheses in patients with isolated aortic stenosis. METHODS: Between January 1997 and January 2003, 35 patients (mean age, 63.4 +/- 17 years; median age, 70 years; age range, 16-84 years) underwent isolated aortic valve replacement with a 17-mm St Jude Medical Hemodynamic Plus (16 [45.7%] patients) or a St Jude Medical Regent prosthesis (19 [54.3%] patients). The paired Student t test or the paired Wilcoxon rank sum test were used to compare preoperative with follow-up echocardiographic measurements. RESULTS: Thirty-two (91.4%) patients were female, mean height was 154.4 +/- 8.3 cm, mean weight was 62.2 +/- 9.2 kg, and mean body surface area was 1.59 +/- 0.13 m 2 . The preoperative average New York Heart Association class was 2.8 +/- 0.8. The mean preoperative left ventricular mass index was 135.2 +/- 31 g/m 2 . Preoperative echocardiography showed an average gradient of 65.7 +/- 19.2 mm Hg (mean) and 103.6 +/- 30.7 mm Hg (peak) and a mean indexed effective orifice area of 0.40 +/- 0.1 cm 2 /m 2 . Echocardiographic follow-up time averaged 28.2 +/- 22.7 months (range, 13-72 months). Follow-up was 100% complete (1131.7 patient-months). Hospital mortality was 8.6% (3 patients). Actuarial 5-year survival was 94.7%. The mean postoperative New York Heart Association class was 1.13 +/- 0.34 ( P < .001), with 27 (87.1%) patients in class I and 4 patients in class II. A significant regression of the indexed left ventricular mass was found (postoperative mean value, 107.8 +/- 22.8 g/m 2 ; P < .0001), despite a mean indexed effective orifice area of 0.67 +/- 0.14 cm 2 /m 2 (median, 0.66 cm 2 /m 2 ). CONCLUSIONS: Selected patients with aortic stenosis can experience satisfactory clinical improvement and significant indexed left ventricular mass regression after aortic valve replacement with modern small-diameter bileaflet prostheses.

Adolescent↗

PubMed2006

Are allografts the biologic valve of choice for aortic valve replacement in nonelderly patients? Comparison of explantation for structural valve deterioration of allograft and pericardial prostheses.

OBJECTIVE: To compare explantation for structural valve deterioration in nonelderly patients after aortic valve replacement with stented bovine pericardial and cryopreserved allograft valves. METHODS: From 1981 to 1985, 478 patients received pericardial prostheses during premarket approval; from 1987 to 2000, 744 patients received cryopreserved allografts. Mean age of patients receiving allografts was 49 +/- 12 years, and that of those receiving pericardial prostheses was 65 +/- 11 years; pericardial valves were used in 138 patients younger than age 60. Mean follow-up was 15 +/- 5.1 years for pericardial valves (4674 patient-years of follow-up) and 5.6 +/- 3.1 years for allografts (3892 patient years of follow-up). Multivariable hazard function methodology, age-group stratification, and propensity matching were used to compare age-specific explantation for structural valve deterioration. RESULTS: Ninety-five pericardial valves and 46 allografts were explanted, and structural valve deterioration was the mechanism of failure in 74% and 59%, respectively. The risk of structural valve deterioration increased with younger age at implantation for both allografts (P = .07) and pericardial valves (P < .0001), with a similar magnitude of effect in patients age 50 years or younger (P = .5), 50 to 60 years (P = .7), and greater than 60 years (P = .9) and in propensity-matched pairs (P = .2). Thus, pericardial valves were as durable as allografts at all adult ages. CONCLUSIONS: Structural valve deterioration is the most frequent cause of valve-related reoperation after both pericardial and allograft aortic valve replacement and is similarly age dependent, suggesting that pericardial valves may be appropriate for nonelderly as well as older persons.

Adult↗