Pericardial heterografts: why do these valves fail?

Eighteen explanted pericardial heterografts were studied (16 standard Ionescu-Shiley, one Hancock, and one Mitroflow). Regurgitation was the reason given for explantation of all the Ionescu-Shiley valves. The other two valves were removed for technical reasons. All the Ionescu-Shiley valves had commissural tears and there was concomitant gross calcification in 10 of the 16 valves. In addition, an apparent increase in cusp area had caused "leaflet sagging". The explanted leaflets were thicker and stiffer than leaflets from an unimplanted valve. These features were confirmed directly with an animal model of subcutaneous implantation. Examination with an electron microscope revealed that these changes in mechanical properties seemed to be linked to fiber separation and infiltration by an amorphous proteinlike matrix. The durability of the glutaraldehyde-fixed pericardium depended on a number of factors. Early and midterm failure appeared to be stress induced. Predisposition to high mechanical stresses near the stent was exacerbated by the changes induced by the host environment. This problem was aggravated further in the Ionescu-Shiley valves by stress concentrations around the hole associated with the holding suture. In the long term, collagen disruption associated with leaflet flexure was followed by secondary calcification at the boundary between the intact and disrupted material.     

An improved pericardial bioprosthetic heart valve : Design and laboratory evaluation

The design and development of a new three-leaflet pericardial valve are described and its function and durability evaluated in the laboratory. The unique design allows the leaflets to be located on small radially projecting pins on a pericardial covered frame. Leaflets are easily interchanged on the frame to allow each set of leaflets to be matched during a function test prior to final assembly. The valve has similar hydrodynamic function to other pericardial valves and accelerated fatigue tests have shown improved durability with the elimination of leaflet tears caused by abrasion at the edge of the frame.     

A morphologic study of Carpentier-Edwards pericardial xenografts in the mitral position exhibiting primary tissue failure in adults in comparison with Ionescu-Shiley pericardial xenografts

OBJECTIVE: We sought to investigate the durability and mechanism of the Carpentier-Edwards pericardial xenograft in the mitral position in comparison with that of the Ionescu-Shiley pericardial xenograft. METHODS: A total of 284 patients who received the Ionescu-Shiley pericardial xenograft in the mitral position between 1980 and 1984 and 84 patients who received the Carpentier-Edwards pericardial xenograft in the mitral position between 1984 and 1999 were included in the study. The freedom from reoperation rates for both graft types were determined. For morphologic study, the pathologic findings of 23 valves of 123 explanted Ionescu-Shiley pericardial xenografts with structural valve deterioration, nonstructural valve deterioration, or both were determined and compared with those of 20 explanted Carpentier-Edwards pericardial xenografts with structural valve deterioration, nonstructural valve deterioration, or both. Each pathologic finding was graded and assigned a score. Both types were matched for age at reoperation (50-75 years) and duration of valve function (8-11 years). RESULTS: Freedom from reoperation caused by structural valve deterioration, nonstructural valve deterioration, or both was significantly better for Carpentier-Edwards pericardial xenografts than for Ionescu-Shiley pericardial xenografts at 8 years after the operation (Carpentier-Edwards pericardial xenografts: 91.3% vs Ionescu-Shiley pericardial xenografts: 71.9%, P =.0061), but it was similar for both types at 12 years (Carpentier-Edwards pericardial xenografts: 43.6% vs Ionescu-Shiley pericardial xenografts: 43.6%, P =.2865). No severe leaflet tears were seen among Carpentier-Edwards pericardial xenografts. The mean area percentage of tissue overgrowth was 15.3% in Carpentier-Edwards pericardial xenografts and 3.4% in Ionescu-Shiley pericardial xenografts (P =.0001). The mean calcification area percentage was 13.6% in Carpentier-Edwards pericardial xenografts and 31.5% in Ionescu-Shiley pericardial xenografts (P =.0001). CONCLUSIONS: Tissue overgrowth on the atrial surface, ventricular surface, or both was the cause of structural valve deterioration, nonstructural valve deterioration, or both of Carpentier-Edwards pericardial xenografts in adults. This was different from Ionescu-Shiley pericardial xenograft failure, which resulted from severe calcification and leaflet tears. Organized thrombi on cusps, in addition to valve design, may have contributed to such tissue overgrowth on Carpentier-Edwards pericardial xenografts.     

Patterns of failure in Hancock pericardial bioprostheses

A series of Hancock pericardial valve bioprostheses was reviewed for cases of primary valve failure. Thirteen mitral and 10 aortic valve explants were recovered from 21 adult patients. Mitral valves had been in place for a mean of 56.4 months, and aortic valves for 53.8 months. All valves failed with cusp tears from stents (with a mean of 1.7 for mitral valves and 2.6 for aortic valves) in a predictable pattern, suggesting that wear and stress at cusp stitch sites are important in their pathogenesis. The topography of these tears is illustrated as are the less common associates of primary failure, such as calcification, fibrosis, and thrombosis. Similarities and differences of this valve's failure compared with that of the Ionescu-Shiley pericardial valve are discussed.     

Steady and pulsatile flow studies on a trileaflet heart valve prosthesis

The need for better and longer lasting trileaflet valves has led to the design and development of the ABIOMED polymeric trileaflet valve prosthesis. In vitro fluid dynamic studies in the aortic position indicate that overall it has improved leaflet motion characteristics and pressure drop characteristics compared to the Carpentier-Edwards porcine and Ionescu-Shiley pericardial tissue valves in current clinical use. The ABIOMED valve is, however, more stenotic compared to the St. Jude and Medtronic-Hall low profile mechanical valves, at normal cardiac outputs. Steady and pulsatile flow velocity measurements with a laser-Doppler anemometer system indicate that the flow field downstream of the ABIOMED valve is jet-like and leads to elevated shear stresses. These shear stresses are, however, lower than those observed with the Ionescu-Shiley and Carpentier-Edwards tissue valves. The ABIOMED valves tested had been originally configured for use in valved conduits, and it is therefore our opinion that further improvements can be made to the valve and stent design which would enhance its fluid dynamic performance.     

Middle term follow-up and comparative study of valve replacement with four kinds of new model bovine pericardial xenografts

Our early clinical experience (up to 4 year's follow-up) with four new pericardial xenografts were reviewed. During the period July 1983 to December 1986, 148 Ionescu-Shiley Pericardial Xenografts (ISL) in 130 patients, 68 Carpentier-Edwards pericardial xenografts (CEP) in 65, 32 Mitroflow pericardial xenografts (MF) in 29 and 36 Hancock pericardial xenografts (HP) in 29 have been implanted. The actuarial survival rates at 3.3 years are 89.9 +/- 2.7% for ISL, 92.3 +/- 3.3% for CEP, 93.1 +/- 4.7% for MF and 93.1 +/- 4.7% for HP. Fifteen cases of primary tissue failure (PTF) were caused in all groups but CEP. The actuarial free rates from PTF at 3.3 years were 92.9 +/- 2.4% for ISL, 100% for CEP, 95.5 +/- 4.4% for MF, 82.6 +/- 7.9% for HP. All bioprostheses explanted because of PTF showed commissural tears occurred at the top of the stent posts or at the edge of the stent. In this respect, it is the reason why the cases with CEP were free from PTF that CEP has been achieved to be improved its frame design. The incidences of prosthetic valve endocarditis were not different among these kinds of bioprosthetic valves. The free rates from thromboembolism at 3.3 years were 97.5 +/- 1.5% for ISL, 98.3 +/- 1.7% for CEP, 96.0 +/- 3.9% for MF and 88.7 +/- 6.1% for HP. There was no patient with CEP and MF suffered from thromboembolism with sinus rhythm. In comparison of these 4 valves, we conclude that CEP is useful clinically because of its satisfactory durability and antithrombogenicity.     

In Vitro Fluid Dynamic Characteristics of Ionescu-Shiley and Carpentier-Edwards Tissue Bioprostheses

Abstract: In the study Reported here, the in vitro fluid dynamic characteristics of the Ionescu-Shiley (calf pericardial) and Carpentier-Edwards (porcine) aortic tissue valves were studied. The experiments conducted were pressure drop measurements, leaflet photography, flow visualization, and velocity measurements. The pressure drop studies indicated that both types of tissue valves created relatively large pressure drops. These pressure drops were larger than those observed with the corresponding sizes of Bjork-Shiley, Hall-Kaster, and St. Jude aortic prostheses. The photographs of the opening of the valve leaflets indicated that the tissue valves do not open as ideally as do the natural valves. It was also observed that the Ionescu-Shiley aortic valves opened more symmetrically and with reproducibility than the corresponding Carpentier-Edwards aortic valves. Velocity and shear stress measurements made with a laser-Doppler anemometer indicated that the flow that emerged from the leaflets for both types of tissue valves was like a jet and could lead to turbulent shear stress on the order of 1,000–3,000 dynes/cm². Such turbulent shear stresses could be harmful to blood components. The jet-type flow could also damage the endothelial lining of the wall of the ascending aorta. The velocity measurements also indicated an annular region of stagnant fluid between the outflow surfaces of the leaflets and the flow channel wall. Such a region could lead to the build-up of thrombotic, fibrotic, and/or calcific material on the outflow surfaces of the leaflets. Both types of valve designs, however, created relatively low wall shear stresses and regurgitant volumes.     

Dynamic behavior of prosthetic aortic tissue valves as viewed by high-speed cinematography.

Using a valve testing apparatus of our own design and with a high-speed (600 to 800 frames per second) 16 mm movie camera, films were made of Hancock porcine, Carpentier-Edwards porcine, and Ionescu-Shiley bovine pericardial valves mounted in the aortic position and cycled under physiological conditions at 72 to 100 beats per minute. Fresh and explanted valves were observed using saline or 36.5% glycerol as the pumping solution. When fresh valves were studied using saline solution as the pumpint fluid, the Hancock and Carpentier-Edwards porcine valves showed high-frequency leaflet vibration, which increased in frequency with higher cycling rates. Abnormal leaflet motion was decreased when glycerol was used as the blood analogue. The Ionescu-Shiley bovine pericardial valve did not show abnormal leaflet motion under these conditions. Conclusions drawn from tissue valve testing studies that use excessively high pulsing rates and pressures (accelerated testing) and saline or water as pumping solutions cannot be transposed to predict the fate of tissue valves in a clinical setting.     

Experimental in vitro endothelialization of cardiac valve leaflets.

This study reports our results with vitro endothelialization of fresh nonpreserved homograft valve leaflets compared with mild alternatively preserved valves and valves treated by preservation procedures commonly used for commercially available tissue valves. In vitro lining of biological heart valves with cultured autologous endothelial cells might help prevent the detrimental effects of degeneration on valve durability. To investigate the growth characteristics of endothelial cells on valve bioprostheses, three different methods of storage and preservation were compared. After precoating with fibronectin and seeding of 4.4 x 10(4) endothelial cells/cm2 onto the different leaflet surfaces, primary adherence, growth kinetics, morphology, and maintenance of monolayer integrity were studied over a period of 10 days. On valve leaflet surfaces of group 1 (fresh nonpreserved homograft valve leaflets) and group 2 (mild alternatively preserved valves), endothelial cells grew to persistent monolayers between days 6 and 10. In contrast, endothelial cell proliferation with monolayer growth could not be achieved on the group 3 leaflets (preserved like commercially available biological valve prostheses). In that group, no viable endothelial cells could be found on the valve surfaces 2 days after seeding. These results demonstrate the theoretical feasibility of endothelializing biological heart valve leaflets in vitro if they are not preserved and stored according to commonly used procedures. Provided such an endothelium can withstand the mechanical forces after implantation in vivo, in vitro endothelialization might contribute either to the development of new biological heart valves for modern cardiac surgery or to the improvement of clinical results with homograft valve transplants.     

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.     

Ionescu-Shiley valve failure. I: Experience with 125 standard-profile explants.

A group of standard-profile Ionescu-Shiley valve implants, 357 aortic and 190 mitral, was reviewed for cases of failure requiring surgical explantation. To date, 90 (25.2%) of the aortic and 35 (18.4%) of the mitral valves have failed, and are the subject of this analysis. Observations of these explants confirm previous suggestions about the clinical and pathologic patterns of the Ionescu-Shiley valve's failure, but are extended in this study to allow more confident statistical analyses. Cusp tear with insufficiency remains the most important reason for explantation, precipitating removal to date of 19.1% of the aortic and 10.0% of the mitral valves implanted. This difference, aortic versus mitral, is significant (p less than 0.006) and the reverse of observations made in other studies of pericardial valves. In this review there is no significant difference in the proportion of aortic and mitral valves that failed with calcification (2.2% and 3.1%, respectively). Aortic Ionescu-Shiley valves failing with tears had a mean of 3.1 tears per valve, whereas mitral valves had 1.2. Aortic valves also showed considerably more pretear wear than did mitral valves. Although the large number of these Ionescu-Shiley valve failures has been a profound clinical disappointment, it has provided an opportunity to observe and detail the pathology of their failure.     

Porcine versus pericardial bioprostheses: a comparison of late results in 1,593 patients

From 1976 to 1988, 1,593 patients underwent valve replacement with a porcine (878 patients) or a pericardial bioprosthesis (715 patients). There were 701 aortic, 678 mitral, and 214 multiple-valve replacements. Follow-up was obtained for 1,559 patients (98%). Early mortality was 9% (79 patients) in the porcine valve group and 5% (37 patients) among patients with a pericardial valve (p less than 0.01). Late survival after replacement with porcine valves was 80% +/- 1% and 62% +/- 3% at 5 and 10 years, respectively. With pericardial valves, 5-year survival was 79% +/- 2%. Among valve-related complications, rates of freedom from thromboembolism, endocarditis, and hemorrhage after 6 years were similar for both valve groups. Freedom from reoperation at 6 years was also similar after aortic (96% versus 91%) or multiple-valve replacement (95% versus 88%). However, for mitral valve replacement, freedom from reoperation was significantly better with porcine valves than with pericardial valves at 6 years (92% versus 68%; p less than 0.001). This difference was mainly due to the Ionescu-Shiley valve, which accounted for 83% of primary tissue failures among pericardial bioprostheses implanted in the mitral position (10/12 patients). After 6 years, freedom from primary tissue failure of mitral valves was 92% +/- 2% with porcine and 70% +/- 11% with pericardial bioprostheses (p less than 0.0001). The degree of clinical improvement among survivors was similar with both valve types. Thus, in the aortic position, pericardial valves compare with porcine valves up to 6 years, whereas in the mitral position, the durability of the former is significantly less, mainly because of the suboptimal performance of the Ionescu-Shiley pericardial bioprosthesis.     

Long-term results of bioprosthetic mitral valve replacement: the pericardial perspective

Pericardial valve bioprostheses were introduced in early 1970s and were widely used in the 1980s. The longterm results with the Ionescu-Shiley valve, the first commercially available pericardial valve, were disappointing because of high rate cusp tears during the first decade after implantation. The enthusiasm for this type of bioprosthetic valve was further hampered by the premature failure of the Hancock pericardial valve. The long-term results of aortic valve replacement with the Carpentier-Edwards pericardial valve, which was introduced in 1981, indicated that that valve was durable and the issue of cusp tears had been resolved by an appropriate design. This knowledge prompted surgeons to revisit the merits of pericardial valves for mitral valve replacement and several other pericardial valves are now commercially available. The largest data on long-term results are with the Carpentier-Edwards pericardial mitral valve. The reported freedom from structure valve failure ranged from 69% to 85% at 10 years in patient population with mean age of 60 to 70 years. Young age is a major determinant of valve failure, which is largely due to calcification. There are also long-term data, albeit more limited on the Sorin Pericarbon and Mitroflow valves used for mitral valve replacement. This paper review the published experience with various pericardial bioprosthetic valves used for mitral valve replacement during the past 3 decades.     

Degenerative pathologic findings after long-term implantation of bovine pericardial bioprosthetic heart valves

Degeneration of bioprosthetic heart valves constitutes the most important limitation to their long-term durability and the factor that avoids a wider clinical use of these devices. We studied 26 degenerated bovine pericardial valves that belong to a series of 55 prostheses explanted for various reasons. Age of the patients at implantation of the valve and other factors predisposing to primary tissue failure did not seem to significantly influence the results obtained. Mean implantation time was longer for aortic than for mitral valves (p less than 0.05). Also, the mode of failure was different for mitral and aortic prostheses. Tearing of one or more leaflets without mineralization was more frequent (p less than 0.0025) among mitral than among aortic specimens. Coverage of the valve cusps by a macroscopically visible host sheath was more extensive on the outflow than on the inflow aspect (p less than 0.0015 aortic valves; p less than 0.015 mitral valves). On radiological examination the majority of valves had diffuse and severe mineralized lesions. Collagen degeneration was the most frequent histologic lesion to be found in both mineralized and calcium-free valves. Calcification was also frequent and appeared as mineral deposits that extended between different collagen planes. Scanning electron microscopy revealed the almost complete lack of "endothelium-like" cover on any of the valves and exposure of the underlying fibrous components of the pericardial tissue in areas subjected to abrasion. Transmission electron microscopy confirmed the collagen degeneration and disclosed electron-dense microparticles (probably mineralized) both in the extracellular space and within degenerated host connective tissue cells.     

The Bj?rk-Shiley and Ionescu-Shiley heart valve prostheses. In vitro comparison of their hydrodynamic performance in the mitral position

Shiley Scientific Inc., are now manufacturing six types of prosthetic heart valves. There are four different models of the Bj?rk-Shiley and two versions of the Ionescu-Shiley pericardial heart valve. The Bj?rk-Shiley valves are those with a spherical disc, 60 degrees and 70 degrees opening convexo-concave discs, and the latest monostrut model. The Ionescu-Shiley valves are the original titanium stent model and the latest Delrin stent low profile model. The hydrodynamic performance of these valves in the mitral position all having a tissue annulus diameter of 29 mm, has been measured. Tests were performed in a pulse duplicator simulating sinus rhythm at heart rates of 60, 80 and 120 beats per minute (BPM) with a stroke volume (SV) between 69 and 73 ml and at a heart rate of 200 BPM with SV between 27 and 34 ml. The latter test condition simulates a situation of supraventricular tachycardia. Mean transmitral pressure, regurgitation, and transmitral energy loss for each valve under each set of conditions were compared. All the Bj?rk-Shiley valves were tested in two orientations with the major flow orifice oriented either anteriorly (A) or posteriorly (P). For all valves, it was found that the major contribution to the total transmitral energy loss, most apparent at 200 BPM, was caused by regurgitation and that at 60, 80 and 200 BPM, the forward flow phase contributed only a small amount to the total energy loss. The small intentional leakage across the Bj?rk-Shiley valves is minor compared to closing regurgitation but is a major contributor to transmitral energy loss.(ABSTRACT TRUNCATED AT 250 WORDS)     

Rest and exercise hemodynamics following aortic valve replacement. A comparison between 19 and 21 mm Ionescu-Shiley pericardial and Carpentier-Edwards porcine valves

When aortic valve replacement is performed in a patient with a small anulus, significant obstruction of the left ventricular outflow tract may remain. Most prostheses are obstructive in the smaller sizes, and enlargement of the aortic anulus may be required to allow placement of a larger valve. To evaluate the hemodynamic performance of two commonly used tissue prostheses, the Ionescu-Shiley pericardial and Carpentier-Edwards porcine valves, 22 patients with either the 19 or 21 mm size were electively studied at rest and after exercise at a mean of 15 months after operation. The resting mean transvalvular gradient for 19 mm Ionescu-Shiley pericardial valves (n = 7), 10.6 +/- 9.2 mm Hg, was significantly lower than that for 19 mm Carpentier-Edwards valves (n = 3), 33.3 +/- 2.1 mm Hg, p less than 0.01. Following exercise, the mean gradient for 19 mm Ionescu-Shiley pericardial valves rose only to 13.8 +/- 8.5 mm Hg. No exercise data were available for the 19 mm Carpentier-Edwards valve. Among patients with 21 mm Ionescu-Shiley pericardial valves (n = 7), the mean transvalvular gradient at rest was 5.6 +/- 9.5 mm Hg, not significantly different from that of patients with 21 mm Carpentier-Edwards valves (n = 5), 9.8 +/- 18.3 mm Hg. After exercise, the gradients rose to 16.0 +/- 10.0 mm Hg and 25.5 +/- 23.8 mm Hg for the Ionescu-Shiley pericardial and Carpentier-Edwards valves, respectively (no statistical significance). Cardiac index was not different between groups. Gradients were not significantly higher in patients with body surface areas greater than 1.5 m2. It is concluded that the 19 and 21 mm Ionescu-Shiley pericardial valves possess excellent hemodynamics, even after exercise. This valve appears hemodynamically superior to the Carpentier-Edwards valve, particularly in the 19 mm size. Procedures to enlarge the aortic anulus are usually unnecessary when small Ionescu-Shiley pericardial valves are used, even in patients who have large body surface areas.     

Ionescu-Shiley valve failure. II: Experience with 25 low-profile explants.

A group of patients who had low-profile Ionescu-Shiley valves implanted, 237 aortic and 130 mitral, was reviewed for cases of bioprosthetic failure requiring explantation. Fourteen such aortic and 11 mitral valves were recovered at operation. The most common reason for explantation was valvular insufficiency due to cusp tears, accounting for 50.0% of aortic and 82.0% of mitral explants. Morphologic examination of the valves suggested a common mode of failure with tears, and this is illustrated. The clinical and pathologic patterns of this valve's failure are compared with those of the standard-profile Ionescu-Shiley valve, and many similarities exist. A tendency for a larger proportion of mitral valve failures with tears is, however, in contrast to observations of the standard-profile valve, in which aortic failures are more common. Additionally, low-profile valves, in either the aortic or mitral positions, fail after a shorter time in situ than their standard-profile counterparts, at a mean of 45.1 months versus 78.0 in the aortic position (p less than 0.01) and at 52.2 months versus 73.8 in the mitral position (p less than 0.05). These differences in the performance of the Ionescu-Shiley valve models may have implications for the design of future bioprostheses.     

Stent and leaflet stresses in a 26-mm first-generation balloon-expandable transcatheter aortic valve

Objective

Transcatheter aortic valve replacement is established therapy for high-risk and inoperable patients with severe aortic stenosis, but questions remain regarding long-term durability. Valve design influences durability. Increased leaflet stresses in surgical bioprostheses have been correlated with degeneration; however, transcatheter valve leaflet stresses are unknown. From 2007 to 2014, a majority of US patients received first-generation balloon-expandable transcatheter valves. Our goal was to determine stent and leaflet stresses in this valve design using finite element analyses.

Incidence of primary tissue valve failure with the Ionescu-Shiley pericardial valve. Preliminary results

This report provides retrospective follow-up data on 88 patients who received an Ionescu-Shiley bovine pericardial valve in the aortic position between August, 1977, and June. 1980. Seven instances of primary tissue degeneration occurred in seven of the 65 patients followed up until June, 1984. Cumulative duration of follow-up was 335.5 patient-years. The linearized incidence of primary tissue failure was 2.08% per patient-year. The actuarial rate of freedom from valve failure for patients with an Ionescu-Shiley valve in aortic position was 79% +/- 8% at 7 years of follow-up. This series shows a higher incidence of primary tissue failure with this prosthesis than with the glutaraldehyde-preserved porcine xenograft in the aortic position at 7 years' follow-up.     

Graft detachment, a cause of incompetence in stent-mounted aortic valve allografts

The detachment of allograft tissue from supporting stent posts has been a common mode of failure of stent-mounted aortic allografts. In an effort to reduce the localized stress loading on the tissue at the top of the stent posts, two changes were introduced to the previous fabrication protocol followed by Green Lane Hospital. Specifically, they were the use of a flexible acetyl-copolymer stent and covering of the peripheral attachment sutures with a bias strip of Dacron cloth. This study showed that these changes did not reduce the incidence of allograft failure caused by graft detachment. Unexpectedly, covering antibiotic-treated allograft tissue with a bias strip actually increased the likelihood of failure of the valve, by accelerating the biological degradation of the underlying graft aortic wall. The weakened aortic wall tissue was consequently less able to resist the high stress loadings at the top of the stent posts where detachment first occurred.