The pathology of early failure in Mitroflow pericardial valve bioprosthesis (12A/LX).

BACKGROUND: Limited mid-term durability of 12A/LX Mitroflow bioprosthesis has been reported. Aim of the study was to ascertain the pathologic substrates and possible mechanisms of structural valve deterioration in explants from animals and humans. METHODS: Nine aortic 12A/LX Mitroflow bioprostheses preserved in hypotonic solution and three aortic 12A/LX bioprostheses, preserved in isotonic solution, were explanted from juvenile sheep, mean time from implant 95.66 ± 36.04 days and 132.33 ± 28.88 days from implant respectively. One stented unimplanted 12A/LX Mitroflow preserved in isotonic colution before glutaraldeyde fixation served as control. Ten aortic 12A/LX Mitroflow bioprostheses were explanted from humans because of severe dysfunction: five children, (3 females and 2 males, mean age 14.19 ± 4.77 years, range 11-21), 26 ± 8.24 months from implant and 5 adults (4 females and 1 male, mean age 57.4 ± 19.85 years, range 31-72), 64.4 ± 26.94 months from implant. X-ray, histology, and transmission electron microscopy were carried out as well as spectroscopy for calcium (Ca++) and phosphorus (P) content in human explants. RESULTS: Explants, from both animals and humans, showed cusp folding and stiffness, with coarse calcific deposits at gross examination and X-ray. Severe collagen denaturation, plasma insudation and massive calcification, involving both collagen and cell debris, were observed microscopically. Mean Ca++ content of 183.27 ± 62.48 and P content of 94.35 ±33.76 mg/g dry weight was found in children and Ca++ content of 205.49 ± 2.23 and P content of 99.75 ± 0.11 mg/g dry weight in adults. Obstructive fibrous tissue overgrowth was detected in 6 human cases. CONCLUSIONS: Collagen denaturation was observed in pericardial Mitroflow 12A/LX bioprosthesis with premature structural valve deterioration. Optimal collagen fixation and preservation as well as phospholipids reduction by removing cell debris, as employed in the novel CROWN PRT Mitroflow bioprosthesis, are expected to solve the flaw and achieve long-term durability.

Morphologic investigation on Perceval S, a sutureless pericardial valve prosthesis: collagen integrity after collapsing-ballooning and structural valve deterioration at distance.

Perceval S is a self-expandable, stent-mounted bioprosthetic valve (BPV), with glutaraldehyde treated bovine pericardium, processed with homocysteic acid as an anti-calcification treatment. The stent is crimpable but the valve insertion is done surgically via a shorter procedure which does not require sutures. OBJECTIVES: MATERIAL AND METHODS: RESULTS: CONCLUSIONS: Collapsing and ballooning do not alter cusp collagen periodicity. Structural valve deterioration with stenosis, due to dystrophic calcification and fibrous tissue overgrowth, seldom occurred in the mid-term. Glutaraldehyde fixed pericardium has the potential to undergo structural valve deterioration with time, similar to well-known BPV failure. This supports the recommendation to pursue improvement of tissue valve treatment with enhanced durability.

Structural valve deterioration and mode of failure of stentless bioprosthetic valves.

BACKGROUND: Aortic stentless bioprosthetic valve (SLBPV), either porcine or pericardial, minimizes transvalvular gradient and favors regression of left ventricular hypertrophy. The drawback consists of longer time for suturing. While structural valve deterioration (SVD) in stented porcine and pericardial BPVs has been extensively investigated, less information is available on SLBPVs. MATERIAL AND METHODS: We studied 82 SLBPVs explants, either porcine (Toronto SPV, [St. Jude Medical, MN, USA], CryolifeO'Brien Model 300 and CryoLife-O'Brien [Cryolife International, GA, USA], BioCor PVS [St. Jude Medical, MN, USA] Prima and Prima Plus [Edwards Lifesciences Corp. One Edwards Way, CA, formerly Baxter Inc, CA, USA]) or pericardial ([Pericarbon Freedom and Freedom Solo [Sorin-Biomedica, S.p.A., Saluggia, Italy]). RESULTS: By excluding cases with leak and endocarditis, we focused the investigation on 46 SLBPVs, which failed because of SVD. Gender was male in 29 (63%). Mean age of patients at time of implant was 59.8 years. Postoperative time of SVD was 115.0 months for porcine and 79.0 months for pericardial SLBPVs. Dysfunction requiring reoperation was mainly incompetence for porcine and stenosis for pericardial SLBPVs. Even pinpoint mineralization at the commissures resulted in sudden cusp tearing and incompetence. Cuspal atheromasia accounted for cusp tearing even in the absence of calcification. Mineralization showed progression with time in pericardial but not in porcine SLBPVs. CONCLUSIONS: Tissue mineralization remains the nightmare also of SLBPVs, with the peculiar features of pinpoint calcific deposits at commissures, tearing and abrupt incompetence in porcine SLBPVs and of massive cuspal mineralization and stenosis in pericardial SLBPVs.

Octanediol treatment of glutaraldehyde fixed bovine pericardium: evidence of anticalcification efficacy in the subcutaneous rat model.

OBJECTIVE: Anticalcification strategies of glutaraldehyde-fixed xenograft tissue aim to extract lipids or to neutralize toxic aldehyde residuals. The purpose of this study was to evaluate the efficacy of octanediol compared to standard treatments of glutaraldehyde-fixed bovine pericardium in the subdermal rat model. Octanediol treatment is an ethanolic solution (40%) containing a long chain aliphatic alcohol (5% 1,2-octanediol) that removes lipids without diminishing the stability of collagen. METHODS: Octanediol and standard glutaraldehyde fixed bovine pericardium were both implanted in 24 Sprague-Dawley rats, explanted after 30-75 days (12 animals each) and submitted to X-ray (score 0-4), histology, electron microscopy and elemental analysis by spectroscopy (Ca and P content). Unimplanted octanediol and standard glutaraldehyde fixed pericardium served as control. RESULTS: At 30 days octanediol-treated pericardium showed calcium content of 0.20+/-0.1 vs 20.07+/-36.79 mg/g dry weight for standard pericardium. The difference was also evident at 75 days: calcium content of 2.36+/-7.38 mg/g dry weight for octanediol vs 165.61+/-23.35 mg/g dry weight for standard (p<0.0001). Differences were also detected at X-ray (mean score 0.7+/-0.6 octanediol vs 3.8+/-0.4 standard at 75 days). Equally, mean P content was 11.69+/-21.33 mg/g dry weight for standard vs 0.60+/-1.45 mg/g dry weight for octanediol samples at 30 days, and 90.90+/-12.61 mg/g dry weight for standard vs 1.42+/-4.34 mg/g dry weight for octanediol at 75 days (p<0.0001). At electron microscopy collagen appeared well preserved regardless of the type of treatment; in octanediol treated pericardium cell membranes almost disappeared and only few profiles of endoplasmic reticulum and rare mitochondria were visible. CONCLUSIONS: Treatment with octanediol strongly prevents calcification of glutaraldehyde fixed bovine pericardium in rat subdermal model, even in the long-term. Evidence of octanediol efficacy may entail important implications for new generation bioprosthetic valves.

Relevance of apoptosis in influencing recovery of hibernating myocardium.

BACKGROUND: Hibernating myocardium (HM) is viable but dysfunctional myocardium which can recover following revascularization. Myocyte necrosis is virtually absent in HM; however, cellular loss may take place by apoptosis, although this is controversial. AIM: To assess the presence of apoptosis and its relevance in HM. METHODS: During coronary artery by-pass surgery (CABG), 21 patients underwent transmural biopsy in the dysfunctional left anterior descending artery tributary area of the left ventricle (LV), with kinetic recovery at follow-up, thus fulfilling the HM criteria. All patients underwent echocardiographic follow-up at 12 months. All biopsies were evaluated by light microscopy, electron microscopy (EM), and molecular analysis. RESULTS: All biopsies were structurally altered, showing increased fibrosis and myocytes with variable size. Myocyte dedifferentiation was not detected by immunohistochemistry or EM. On stepwise linear regression, 1 year LVEF was predicted by the apoptotic index (beta=-0.973, p=0.002), the normotrophic cell percentage (beta=0.449, p=0.038), and mean fibrosis (beta=-0.412, p=0.51). CONCLUSIONS: Our biopsy study detected a wide range of morphological substrate heterogeneity in HM with degenerative features. We have demonstrated for the first time in humans that myocyte apoptosis is an important phenomenon in HM, negatively influencing LV functional recovery after CABG.

Commissural dehiscence: a rare and peculiar cause of porcine valve structural deterioration.

OBJECTIVE: Calcification is the main cause of structural valve deterioration; however, other causes of failure have been identified, and among them, dehiscence of a commissure from the stent has been reported in several models of porcine valves. The aim of this study was to analyze the rate and mode of occurrence of this complication in first- and second-generation porcine bioprosthetic explants. METHODS: Among 586 porcine xenografts explanted and analyzed at the Institute of Pathological Anatomy of the University of Padua, 17 (2.9%) have been replaced for incompetence because of commissural dehiscence. All these explants were in the mitral position, with the exception of a Carpentier-Edwards supra-annular aortic valve prosthesis. RESULTS: Dehiscence was observed in 9 (1.9%) of 455 Hancock standard explants, in 1 (3.2%) of 31 Hancock II, in 3 (8.6%, 2 standard and 1 supra-annular) of 35 Carpentier-Edwards, in 1 (2.4%) of 42 Bioimplants, and in 3 (50%) of 6 Xenotech after a mean time function of 157 +/- 50, 156, 96 +/- 29, 143, and 130 +/- 8 months, respectively. Dehiscence was the sole cause of incompetence in 6 cases. An impending commissural dehiscence caused by blood creeping was observed in one case. This might be an explanation for the dehiscence other than excessive trimming of the aortic wall. CONCLUSIONS: Commissural dehiscence is an uncommon and peculiar mode of failure of porcine valves implanted in the mitral position and was observed earlier and more frequently with Carpentier-Edwards porcine explants (P < .05). We speculate that pericardial strip protection of the suture between the Dacron fabric and porcine aortic wall, as used in the Biocor porcine valve, might prevent this complication.

Evidence of mitigated calcification of the Mosaic versus Hancock Standard valve xenograft in the mitral position of young sheep.

OBJECTIVES: Durability remains the main problem of all bioprosthetic valves, and calcification is the major cause of failure. New tissue treatment processes are expected to reduce mineralization. A comparative animal study was undertaken to evaluate the behavior of a new-generation porcine bioprosthesis in contrast with a first-generation porcine bioprosthesis. The primary goal was to evaluate the efficacy of alpha-amino-oleic acid as an anticalcification treatment. METHODS: Seventeen Targhee sheep (aged 4.5-7 months) had a mitral valve replacement with a Mosaic or Hancock Standard. The animals were followed up to 20 weeks (144.1 +/- 4.0 days vs 144.3 +/- 8.2 days) and then euthanized as scheduled. After gross examination, the explants were radiographed for the presence of calcification. The central portions were preserved for histologic examination, and the remainder of the sample was analyzed for quantitative calcium content by atomic absorption spectroscopy. RESULTS: Four Mosaic sheep were excluded because of perioperative surgical mortality. The remaining 13 were enrolled in the study (9 Mosaic and 4 Hancock Standard). The mean calcium content was 1.97 +/- 2.21 microg/mg tissue weight for Mosaic versus 8.36 +/- 4.12 microg/mg for Hancock Standard valves (P < .01). Mild fibrous tissue overgrowth and fibrinous lining were observed regardless the xenograft type. CONCLUSIONS: The low level of calcification in the Mosaic versus Hancock Standard xenografts confirms the efficacy of alpha-amino-oleic acid treatment in mitigating mineralization. A longer durability is expected with the clinical use of the Mosaic porcine valve.

Sovering annuloplasty rings: experimental pathology in the sheep model.

INTRODUCTION: A new flexible annuloplasty ring (Sovering, Sorin Biomedica Cardio), both closed and open, has been designed and consists of radiopaque silicone core impregnated with barium sulfate and covered by a knitted polyester fabric coated with Carbofilm. The aim of the study was to test the biological compatibility of the new device in large animals in orthotopic position. METHODS: Ten Sovering rings were implanted in 10 female adult sheep, 7 mitral (3 open, 4 closed) and 3 tricuspid (all open). The size was 23-25 mm in the mitral and 28-30 mm in the tricuspid position, and the time in place varied from 63 to 110 days (mean = 89 +/- 14) and from 58 to 63 days (mean = 61 +/- 3), respectively. The morphological analysis consisted of gross, histological, immunohistochemical and ultrastructural investigations. RESULTS: The prosthetic ring appeared well implanted in the valve atrioventricular (AV) junction, encapsulated by a thin fibrous sheath without any evidence of thrombus deposition, fibrinous lining or exuberant fibrous tissue overgrowth. No adverse inflammatory reaction was observed, but rare lymphocytes, macrophages and foreign body giant cells. At electron microscopy, the fibrous tissue appeared to permeate deeply within the fabric network; reendothelization on the surface was noted and confirmed by immunohistochemistry. Sirius red staining at polarized light revealed a higher content of collagen type III in the mitral than in the tricuspid position. CONCLUSIONS: Sovering annuloplasty rings implanted in the AV valves of adult sheep showed excellent biocompatibility, fibrous encapsulation and reendothelization. The absence of thrombosis and exuberant fibrous tissue reaction supports the effective use of Carbofilm covering in annuloplasty devices.

BIOSA bileaflet pericardial valve: experimental study in sheep model.

BACKGROUND: BIOSA is a single sheet, two-cuspal-shaped ("bileaflet") glutaraldehyde fixed bovine pericardial valve prosthesis (BP), designed to minimize stress and prevent mechanical failure. We tested this device in the adult sheep model. METHODS: Seven BIOSA and two Baxter Carpentier-Edwards (Perimount) pericardial BPs, 25 mm in size, were implanted in the tricuspid position of adult sheep. A mid term BIOSA explant (81 days) died of infective endocarditis. The remaining BPs were divided in three early explants (0-3 days: two BIOSA and one Perimount) and five late explants (162-189 days: four BIOSA and one Perimount). Protocol of the study included gross examination, mammography X-ray (score 0-4), histology, scanning (SEM) and transmission (TEM) electron microscopy and atomic absorption spectroscopy. RESULTS: (a) Early explants: The mesothelium was detached, collagen-elastic fibers and pericardiocytes of the fibrosa showed optimal preservation. Calcium content in BIOSA BPs was 6.22 mg/g dry weight (mean) versus 7.75 mg/g of the Perimount BP. (b) Late explants: At naked eye all BPs showed regular cusp pliability and coaptation, without tears, perforations, fibrous pannus or calcific deposits. X-ray was either negative (three BPs) or exhibited score 1 (two BPs). Microscopic features were excellent both in terms of collagen-elastic fibers preservation and absence of inflammation. The calcium content was 4.95 mg/g dry weight (mean) in BIOSA BPs versus 5.29 mg/g in the Perimount BP. CONCLUSIONS: Tissue characteristics of BIOSA BPs were optimal, without difference with Perimount BPs and in this animal model no case of structural valve deterioration occurred in the long term.

Parenchymal transforming growth factor beta-1: its type II receptor and Smad signaling pathway correlate with inflammation and fibrosis in chronic liver disease of viral etiology.

BACKGROUND AND AIMS: Transforming growth factor-beta (TGF-beta) system is involved in the control of cell growth and extracellular matrix formation. Previous studies in patients with chronic liver disease have shown that increased TGF-beta expression significantly correlates with the degree of hepatic fibrosis. The aim of our study was to define TGF-beta system expression in hepatic parenchymal cells and its significance in patients with differing extents of chronic liver disease of viral etiology. METHODS: Expression of TGF-beta 1, TGF-beta 1 type II receptor (TGF-beta RII) and the Smad signaling pathway was evaluated in consecutive liver sections of 77 patients with chronic liver disease (65 HCV positive and 12 HBV positive). Results were correlated with histological scores and apoptotic activity. RESULTS: TGF-beta 1 was demonstrated in the liver of 30/56 (53.6%) patients with chronic hepatitis and 20/21 (95%) patients with cirrhosis, but in none of the 20 normal livers. Positive cytokine reaction was seen both in stromal cells and hepatocytes. Expression of TGF-beta RII and Smad proteins showed a distribution pattern similar to that of TGF-beta, with a direct correlation in terms of immunoreactivity extent. A significant correlation was found between parenchymal expression of TGF-beta system and inflammatory and fibrosis scores. No correlation was found with apoptotic index and other morphological, clinical or virological parameters. CONCLUSIONS: The TGF-beta system is up-regulated at the ligand, receptor and signaling level in the liver of patients with more active disease. The strong expression of TGF-beta and the Smad pathway in parenchymal cells suggests that hepatocytes, in addition to mesenchymal cells, may play an important role in the progression of liver disease.

Hancock II bioprosthesis: a glance at the microscope in mid-long-term explants.

BACKGROUND AND OBJECTIVES: The Hancock II bioprosthesis is a second-generation porcine valve xenograft treated with the detergent sodium dodecyl sulphate (T6) to retard calcification. The aim of this investigation was to study the gross and microscopic features in Hancock II explants to assess the structural changes occurring with time. METHODS: Among 1382 Hancock II bioprostheses (701 isolated aortic, 421 isolated mitral, 130 double) implanted from 1983 to 1997 in 1252 patients, 22 (16 mitral, 6 aortic) were removed at reoperation until 1999 and were available for pathological investigation: infective endocarditis occurred in 5 and structural deterioration in 8, whereas in the remaining 9 xenografts reoperation was performed for nonstructural valve deterioration (paravalvular leak in 4 and prophylactic replacement in 5). Morphological investigation consisted of gross examination and x-ray, histologic, immunohistochemistry, electron microscopic, and atomic absorption spectroscopic examination. RESULTS: The cause of structural valve deterioration was dystrophic calcification in 4 cases (1 aortic, 3 mitral; range of time graft was in place, 101 to 144 months), non-calcium-related tears in 3 cases (all mitral, range 121 to 163 months), and commissural dehiscence in 1 (aortic, range 156 months). Five of the nonstructural valve deterioration explants (range 42 to 122 months) showed only pinpoint mineralization at the commissures. Mean calcium content in nonstructural deterioration explants was 14.70 +/- 22.33 versus 99.11 +/- 81.52 mg/g in explants with structural valve deterioration. Electron microscopic examination showed early nuclei of mineralization mostly consisting of calcospherulae upon cell debris. Local or diffuse lipid insudation was observed in all but 2 explants and consisted of cholesterol clefts, lipid droplets, and lipid-laden macrophages featuring foam cells. The lipid insudation was the most plausible cause of tearing in 2 explants. CONCLUSIONS: These pathologic findings support the clinical results of a delayed occurrence of structural failure of Hancock II bioprostheses and a mitigation of mineralization by the anti-calcification treatment. However, other factors such as lipid insudation may come into play in the long term.