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

Outcomes of Surgical Bioprosthetic Aortic Valve Replacement in Patients Aged ≤65 and >65 Years

BACKGROUND

Implantation of a bioprosthetic valve is a reasonable choice for patients aged > 65 years. For middle-aged patients there is less certainty about whether a mechanical or bioprosthetic valve is best.

METHODS

The Pericardial Surgical Aortic Valve Replacement (PERIGON) Pivotal Trial is evaluating the safety and efficacy of the Avalus bioprosthesis (Medtronic). We evaluated clinical and echocardiographic outcomes through 5 years of follow-up, stratified by age ≤ 65 and >65 years.

RESULTS

Two hundred seventy-one patients (24.2%) were ≤65 years old and 847 (75.8%) >65 years old. Most patients in both groups were men (217 [80.1%] vs 623 [73.6%], respectively; P = .031). Younger patients had a lower Society of Thoracic Surgeons risk of mortality (1.1% ± 0.9% vs 2.2% ± 1.4%, P < .001), better baseline New York Heart Association class (P = .004), and fewer comorbidities than older patients. At 5 years mortality was lower among younger than older patients (5.3% vs 14.0%, P < .001) and no cases of structural valve deterioration occurred in either group. Effective orifice area was similar between age groups (P = .11), and mean gradient was 13.9 ± 5.4 vs 12.0 ± 4.1 mm Hg (P < .001). Multivariable linear regression identified several parameters associated with mean aortic gradient at 5 years, including baseline age and mean aortic gradient, discharge stroke volume index and EOA, and implanted valve size. Ninety-five percent of patients were in New York Heart Association class I/II through 5 years in both age groups (P = .85).

CONCLUSIONS

Findings from this analysis demonstrate satisfactory safety, hemodynamic performance, and durability of the Avalus bioprosthesis through a 5-year follow-up in patients aged ≤ 65 and >65 years.

Surgical aortic valve replacement with a stented pericardial bioprosthesis: 5-year outcomes

OBJECTIVES

This analysis evaluated the safety, durability, and haemodynamic performance of a stented bovine pericardial valve through 5 years of follow-up in patients with an indication for surgical aortic valve replacement (SAVR).

METHODS

Kaplan-Meier analysis was used to estimate the incidence of survival and valve-related thromboembolism, major paravalvular leak (PVL), endocarditis, structural valve deterioration (SVD), and reintervention. Mean aortic gradient and New York Heart Association (NYHA) class were also evaluated.

RESULTS

1118 patients have received the Avalus valve (Medtronic); 564 have completed 5-year follow-up. Median follow-up was 4.85 years (4810 patient-years total follow-up). At baseline, mean age was 70.2 ± 9.0 years; 75.1% of patients were male. STS predicted risk of mortality was 2.0 ± 1.4%. Most patients were in NYHA class II (46.8%) or III (40.3%). At 5 years follow-up, the overall Kaplan-Meier survival rate was 88.1% (85.9-90.0%). The Kaplan-Meier event rates were 5.6% (4.3-7.2%) for thromboembolism, 4.4% (3.2-6.0%) for endocarditis, 0.2% (0.0-0.7%) for major PVL, and 3.2% (2.3-4.6%) for reintervention. There were no cases of SVD. Mean gradient decreased from 42.1 ± 17.1 mmHg at baseline, to 13.1 ± 4.7 mmHg at discharge, and remained stable at 12.5 ± 4.6 mmHg at 5 years. More than 95% of patients were in NYHA class I/II 5 years after surgery.

CONCLUSIONS

The findings of a high survival rate, excellent safety, no SVD, and stable haemodynamic performance and functional status through 5 years of follow-up are encouraging. Additional follow-up is needed to assess the long-term durability of this contemporary surgical bioprosthesis.

Biological Equivalence of GGTA-1 Glycosyltransferase Knockout and Standard Porcine Pericardial Tissue Using 90-Day Mitral Valve Implantation in Adolescent Sheep

Objective

There is growing interest in the application of genetically engineered reduced antigenicity animal tissue for manufacture of bioprosthetic heart valves (BHVs) to reduce antibody induced tissue calcification and accelerated structural valve degeneration (SVD). This study tested biological equivalence of valves made from Gal-knockout (GalKO) and standard porcine pericardium after 90-day mitral valve implantation in sheep.

Methods

GalKO (n = 5) and standard (n = 5) porcine pericardial BHVs were implanted in a randomized and blind fashion into sheep for 90-days. Valve haemodynamic function was measured at 30-day intervals. After explantation, valves were examined for pannus, vegetation, inflammation, thrombus, and tissue calcification.

Results

Nine of 10 recipients completed the study. There was no difference between study groups for haemodynamic performance and no adverse valve-related events. Explanted BHVs showed mild pannus integration and minimal thrombus, with no difference between the groups. Limited focal mineral deposits were detected by x-ray. Atomic spectroscopy analysis detected tissue calcium levels of 1.0 µg/mg ± 0.2 for GalKO BHVs and 1.9 µg/mg ± 0.9 for standard tissue BHVs (p = 0.4), considered to be both low and equivalent.

Conclusions

This is the first demonstration of biological equivalence between GalKO and standard pig pericardium. The GalKO mutation causes neither intrinsic detrimental biological nor functional impact on BHV performance. Commercial adaptation of GalKO tissue for surgical or transcatheter BHVs would remove the clinical disparity between patients producing anti-Gal antibody and BHVs containing the Gal antigen. GalKO BHVs may reduce accelerated tissue calcification and SVD, enhancing patient choices, especially for younger patients.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s13239-021-00585-0.

Comparative analysis of structural valve deterioration and long-term clinical outcomes after bovine pericardial versus porcine bioprosthetic mitral valve replacement

Background

This study aimed to compare long-term outcomes, including durability, after bovine pericardial valve replacement with those after porcine mitral valve replacement (MVR).

Methods

We enrolled 309 patients who underwent MV replacement (mean age: 65.8±11.5 years; 68.9% females) with Carpentier-Edwards PERIMOUNT bovine pericardial valves (bovine MVR group, n=241) or Hancock II porcine bioprosthesis (porcine MVR group, n=68). The mean clinical and echocardiographic follow-up durations were 81.4±60.0 and 57.8±53.3 months, respectively. Structural valve deterioration (SVD) was defined as prosthetic mitral valve (MV) regurgitation or stenosis of greater than moderate degree combined with a motion limitation, tear, or perforation of prosthetic valve leaflet on follow-up echocardiography. Propensity score (PS)-adjusted multivariable analyses were performed.

Results

Thirty-day mortality rate was 6.4% (20/309 patients). SVD occurred in 50 patients (33 and 17 patients in the bovine and porcine MV replacement groups, respectively). Cumulative incidences of SVD at 5, 10, and 15 years were 3.2%, 15.9%, and 32.4%, respectively, in the bovine MVR group and 1.9%, 15.3%, and 41.7%, respectively, in the porcine MVR group. Cumulative incidences of SVD in the two groups were not different in competing risk analysis (P=0.23). Other clinical outcomes including overall survival and cumulative incidences of cardiac death and MV-related events were not statistically significantly different between the groups in PS-adjusted multivariable analyses.

Conclusions

Long-term clinical outcomes including SVD were not different between the bovine and porcine bioprosthesis MVR groups during average 7 years of clinical follow-up after MVR.

Bovine pericardial versus porcine stented replacement mitral valves: early hemodynamic performance and clinical results of a randomized comparison of the Perimount and the Mosaic valves

Background

To compare the hemodynamic and clinical outcomes following mitral valve replacement with the Perimount valve with those of the Mosaic valve.

Methods

A total of 145 consecutive patients with rheumatic heart valve disease who underwent single bioprosthetic mitral valve replacement were randomized to receive either the Perimount (n=72) valve or the Mosaic bioprosthesis (n=73). The mean age of patients was 72.1 years (range, 58-89 years) with a sex distribution of 55.2% female and 44.8% male. Patients underwent follow up transthoracic echocardiography at 3 months and 1 year postoperatively. We compared demographics, preoperative clinical data, operative data, hemodynamic profiles, and clinical outcomes.

Results

The cross-clamp time was similar, with 50.7±15.3 minutes for the Perimount and 50.7±21.8 minutes for the Mosaic bioprosthesis. The total bypass time was also similar, with 91.3±25.7 minutes for the Perimount and 87.8±25.6 minutes for the Mosaic valve. The peak and mean pressure gradients were lower in the Perimount group for all valve sizes and the difference was statistically significant at 1 year. The effective orifice area (EOA) was slightly larger in the Perimount valve (1.98±0.21 vs. 1.89±0.71 cm², P=0.538) postoperatively, but there was no significant difference at 1 year. There were no differences in preoperative or postoperative left atrium diameter (LAD), left ventricular diastolic diameter (LVDD), left ventricular systolic diameter (LVSD), left ventricular ejection fraction (LVEF), pulmonary artery pressure (PAP). The mortality and major complications rate were similar between the two groups.

Conclusions

The Perimount prostheses is superior to the Mosaic prostheses after mitral valve replacement, achieving statistically significant lower gradients and larger EOA when compared on the basis of manufacturer-labeled valve sizes. Both valves appear to provide satisfactory clinical results.

In vivo evaluation of Vivere bovine pericardium valvular bioprosthesis with a new anti-calcifying treatment

The objective of this study was to evaluate the effect of chemical treatment with glutamic acid to avoid calcification of biological cardiac valves. The bovine pericardium (BP) tissues were fixed with 0.5% glutaraldehyde (BP/GA), followed by treatment with glutamic acid (BP/GA + Glu) for neutralization of the free aldehyde groups. Microscopic analysis showed that the wavy structure of collagen fibrils was preserved, but changes in elastin's integrity occurred. However, the treatment did not promote undesirable changes in the thermal and mechanical properties of the modified BPs. These samples were systematically studied in rat subcutaneous tissue: control (BP/GA) and anticalcificant (BP/GA + Glu). After 60 days, both groups induced similar inflammatory reactions. In terms of calcification, BP/GA + Glu remained more stable with a lower index (3.1 ± 0.2 μg Ca²⁺ /mg dry tissue), whereas for BP/GA it was 5.7 ± 1.3 μg Ca²⁺ /mg dry tissue. Bioprostheses made from BP/GA + Glu were implanted in the pulmonary position in sheep, and in vivo echocardiographic analyses revealed maintenance of valvar function after 180 days, with low gradients and minimal valve insufficiency. The explanted tissues of the BP/GA + Glu group had a lower average calcium content 3.8 ± 3.0 μg Ca²⁺ /mg dry tissue. The results indicated high anticalcification efficiency of BP/GA + Glu in both subcutaneous implant in rats and in the experimental sheep model, which is an advantage that should encourage the industrial application of these materials for the manufacture of bioprostheses.

Physical equivalency of wild type and galactose α 1,3 galactose free porcine pericardium; a new source material for bioprosthetic heart valves

Humans make high levels of antibody to carbohydrates with terminal galactose α 1,3 galactose (Gal) modifications. This Gal antigen is widely expressed in other mammals and is present on an array of current animal derived biomedical devices including bioprosthetic heart valves. There is growing interest in using Gal-free animal tissues from Gal knockout pigs (GTKO) as these tissues would not be affected by anti-Gal antibody mediated injury. In this study we compare the composition and biophysical characteristics of glutaraldehyde fixed porcine pericardium from standard and GTKO pigs. We show that with the exception of the Gal antigen which is only present in standard pig tissue both GTKO and standard pig tissue have the same general morphology and collagen content. Moreover uniaxial stress testing and suture retention testing indicate the tissues are equivalent in tensile strength. These studies indicate that genetic disruption of the α-galactosyltransferase (GGTA-1) which blocks synthesis of the Gal antigen has no significant impact on the structural integrity of porcine pericardium and suggest that this tissue could be directly substituted for standard pig pericardium in biomedical devices such as bioprosthetic heart valves.

STATEMENT OF SIGNIFICANCE

Surgical heart valve replacement is a proven life saving therapy to treat heart valve dysfunction due to birth defects, infection and the effects of aging. Bioprosthetic heart valves (BHV) made from glutaraldehyde fixed animal tissues are an effective durable therapy in older patients (>60years) but exhibit age-dependent structural valve degeneration (SVD) in younger patients (<60years). SVD is principally caused by BHV calcification. Immune injury contributes to age-dependent SVD through the interaction of galactose α 1,3 galactose (Gal) a dominant xenogeneic antigen present on commercial BHVs and universally abundant human anti-Gal antibody. This study measures the tissue equivalency between standard pig pericardium and Gal-free pericardium from genetically modified pigs as a first step towards making Gal-free BHVs.

The Mosaic Mitral Valve Bioprosthesis: A Long-Term Clinical and Hemodynamic Follow-Up

We reviewed the cases of 100 patients (mean age, 73 ± 10 yr; 64 men) who had mitral valve replacement with a Medtronic Mosaic porcine bioprosthesis from 1995 through 2011. The mean New York Heart Association (NYHA) class was 3 ± 0.7, and 52 patients were in atrial fibrillation. Prosthetic sizes were chiefly 27 mm (50 patients) and 29 mm (40 patients). Follow-up ended in December 2012 and is 97% complete, with a cumulative duration of 611 patient-years (mean duration, 6 ± 4.6 yr; maximum, 17.7 yr). The early mortality rate was 10% (6% in elective patients); late deaths occurred in 31 patients (5 valve-related). Actuarial survival rates at 5, 10, and 15 years were 74% ± 5%, 50% ± 6%, and 37% ± 8%. The mean NYHA class in survivors was 1.4 ± 0.6 (P <0.0001). Thromboembolic episodes occurred in 4 patients, with an actuarial freedom at 15 years of 91% ± 5%. No cases of endocarditis were observed. Four patients needed reoperation, 2 for structural failure, and 1 each for perivalvular leakage and valve thrombosis. Actuarial freedom from structural failure and from reoperation, respectively, was 93% ± 5% and 91% ± 5% at 15 years. Echocardiographic follow-up in 24 patients with 27-mm prostheses showed a mean gradient of 5 ± 1.7 mmHg and an effective orifice area of 1.57 ± 0.3 cm(2); in 16 patients with 29-mm prostheses, the mean gradient was 4.5 ± 1.9 mmHg, and the effective orifice area, 1.63 ± 0.4 cm(2). During nearly 17 years of follow-up, the Mosaic bioprosthesis has shown good overall clinical and hemodynamic performance after mitral valve replacement.

Degenerative processes in bioprosthetic mitral valves in juvenile pigs

Background

Glutaraldehyde-treated bioprosthetic heart valves are commonly used for replacement of diseased heart valves. However, calcification and wear limit their durability, and the development of new and improved bioprosthetic valve designs is needed and must be evaluated in a reliable animal model. We studied glutaraldehyde-treated valves 6 months after implantation to evaluate bioprosthetic valve complications in the mitral position in juvenile pigs.

Materials

The study material comprised eight, 5-month old, 60-kg pigs. All pigs received a size 27, glutaraldehyde-treated, stented, Carpentier-Edwards S.A.V. mitral valve prosthesis. After six months, echocardiography was performed, and the valves explanted for gross examination, high resolution X-ray, and histological evaluation.

Results

Five pigs survived the follow-up period. Preexplant echocardiography revealed a median peak and mean velocity of 1.61 m/s (range: 1.17-2.00) and 1.20 (SD = ±0.25), respectively, and a median peak and mean pressure difference of 10.42 mmHg (range: 5.83-16.55) and 6.51 mmHg (SD = ±2.57), respectively. Gross examination showed minor thrombotic depositions at two commissures in two valves and at all three commissures in three valves. High resolution X-ray imaging revealed different degrees of calcification in all explanted valves, primarily in the commissural and belly areas. In all valves, histological evaluation demonstrated various degrees of fibrous sheath formation, limited immunological infiltration, and no overgrowth of host endothelium.

Conclusions

Bioprosthetic glutaraldehyde-treated mitral valves can be implanted into the mitral position in pigs and function after 6 months. Echocardiographic data, calcification, and histological examinations were comparable to results obtained in sheep models and human demonstrating the suitability of the porcine model.