European experience with the Mosaic bioprosthesis

Three-year outcomes of surgical valve replacement with Dafodil™ pericardial bioprosthesis: Dafodil™-1 trial

Background

The Dafodil™-1 trial was designed to evaluate the clinical safety and performance of Dafodil™ pericardial bioprosthesis for replacing diseased native or prosthetic aortic or mitral valves in patients with advanced valvular heart disease (VHD).

Methods

The Dafodil™-1 trial was a prospective, multicenter, first-in-human clinical trial. Patients were enrolled if they had advanced VHD requiring aortic valve replacement (AVR) or mitral valve replacement (MVR) with or without concomitant valve surgery and having surgical risk scores <4%. Major adverse cardiac events (MACE), including all-cause death, myocardial infarction (MI), and stroke; and hemodynamics were analyzed.

Results

A total of 136 patients (aortic: 67 and mitral: 69) were enrolled in the trial (with mean age-AVR group: 60.2 ± 8.3 years and MVR group: 49.7 ± 14.4 years). A total of 134 patients (aortic: 66 and mitral: 68) completed the 3-year follow-up (total 300 per 100 patient-years of follow-up). The AVR group demonstrated a significant reduction in the mean pressure gradients from 51.2 ± 24.1 mmHg at baseline to 11.1 ± 6.0 mmHg at the 3-year follow-up (p < 0.0001). The mean effective orifice area (EOA) improved from baseline (0.9 ± 0.6 cm2) to 3-year follow-up (1.8 ± 0.4 cm2) (p < 0.0001). In the MVR group, the mean indexed EOA (iEOA) increased significantly from baseline (0.7 ± 0.4 cm2/m2) to 3-year follow-up (1.1 ± 0.4 cm2/m2) (p < 0.001). There was significant improvement in New York Heart Association functional class and mean SF-12 scores in both groups. At 3-year follow-up, the MACE incidence was 2.3% per 100 patient-years (1.3% strokes per 100 patient-years and 1.3% deaths per 100 patient-years) for AVR group and 4.7% per 100 patient-years (0.6% strokes per 100 patient-years and 4.0% deaths per 100 patient-years) for MVR group. No cases of MI, structural valve deterioration and prosthetic valve endocarditis were reported. The AVR and MVR groups achieved 89.6% and 79.7% MACE-free survival, respectively at 3-year follow-up.

Conclusions

The Dafodil™-1 trial demonstrated satisfactory outcomes of clinical safety, hemodynamic performance, and quality-of-life metrics. Additionally, no incidence of structural valve deterioration and very low rates of valve thrombosis during the 3-year follow-up period of Dafodil™-1 first-in-human trial indicated acceptable valve durability up to three years and similar outcomes are warranted for longer follow-ups as a primary goal.

Clinical Trial Registration Number

https://www.ctri.nic.in/Clinicaltrials/showallp.php?mid1=18377&EncHid=&userName=CTRI/2017/07/009008, CTRI/2017/07/009008.

Systematic review of first-in-human and early phase clinical trials for surgically implantable biological mitral valve substitutes

BACKGROUND

The aim of this review was the creation of uniform protocols to carry out and disclose First-In-Human and preliminary clinical trials of biological mitral valve replacement. The need for consistent methodology in these early trials was highlighted by the observation of significant variability in the methods and protocols used across different research.

METHODS

An extensive search through six major databases was carried out to retrieve First-In-Human (FIH) clinical studies evaluating surgically implanted bio-prostheses in the mitral position.

RESULTS

Following the PRISMA guideline, a systematic search identified 2082 published articles until March 2023. After removing duplicates (189), 1862 citations were screened, resulting in 22 eligible studies with 3332 patients for analysis. The mitral valve prostheses in these studies ranged from 21 to 37 mm, with the 29 mm size being most prevalent. Patient numbers varied, with the FIH subgroup including 31 patients and the older subgroup including 163 patients. Average study durations differed: the older subgroup lasted 4.57 years, the FIH subgroup 2.85 years, and the early phase studies spanned 8.05 years on average.

CONCLUSION

FIH clinical report is essential to assess the significance of clinical data required for a "de novo" surgical implant. In addition, understanding the performance of the device, and recognizing the difficulties associated with the innovation constitute important lessons. These insights could be beneficial for the development of bioprosthetic heart valves and formulating a protocol for an FIH clinical trial.

Hemodynamic and clinical performance of the 25-mm Medtronic Mosaic porcine bioprosthesis in the mitral position

The 25-mm Medtronic Mosaic porcine bioprosthesis (MB25) is the smallest bioprosthesis that has been approved for use in the mitral position in Japan. Various studies have reported satisfactory hemodynamic performance and good long-term outcomes of the Medtronic Mosaic porcine bioprosthesis. However, the hemodynamic and clinical performances of the MB25 in the mitral position remain unknown. This study aimed to evaluate the hemodynamic and clinical performance of the MB25 in mitral valve replacement (MVR). Twenty patients who underwent MVR using the MB25 between February 2013 and April 2018 were studied. We evaluated the hemodynamic performance of the MB25, cardiac chamber size, cardiac function, and systolic pulmonary artery pressure (PAP) using echocardiography during follow-up. The study outcomes were major adverse cardiac events (MACEs) and all-cause mortality. Sixteen patients (80%) had a patient prosthesis mismatch defined as an index effective orifice area of ≤ 1.2 cm²/m². The left atrial dimension was significantly reduced after surgery (p = 0.0282). The mean pressure gradients (MPG) in the mitral position were 5.5 ± 1.7 mmHg at discharge and 4.2 ± 1.3 mmHg at 1 year postoperatively. The MPG in the mitral position significantly decreased during the follow-up period (p = 0.0489). Systolic PAP significantly improved postoperatively. The 1-, 3-, and 5-year survival rates were 87, 79, and 70%, respectively. No cardiac death occurred. There were no MACEs or reports of structural valve degeneration during the follow-up period. The hemodynamic and clinical performances of the MB25 in the mitral position were satisfactory as the smallest biological mitral valve. The MB25 is a reasonable option for MVR to reduce the surgical difficulty in high-risk patients with an advanced age, a small body size or MAC and when recurrent MVR or complex procedures are performed.

Late results after mitral valve replacement with Mosaic bioprosthesis in patients aged 65 years or younger

OBJECTIVES

Although in younger patients indications for biological prosthesis implantation in mitral valve replacement remain controversial, recently bioprostheses use increased considerably. We present late results obtained with the Medtronic Mosaic bioprosthesis in patients aged 65 years or younger.

METHODS

Between 2007 and 2017, 67 mitral Mosaic bioprostheses were implanted in patients aged 65 years or younger (58.5 ± 6.4 years). Follow-up extended up to 13 years. Survival, freedom from structural valve degeneration, endocarditis, thromboembolic events and reoperation were considered as main clinical end points evaluated at 1, 5 and 10 years.

RESULTS

The mean follow-up was 4.7 ± 2.8 years. Overall mortality rate was 12%. At 1, 5 and 10 years, survival was 94 ± 3%, 89 ± 4% and 77 ± 9%, respectively. Freedom from structural valve degeneration was 100%, 94 ± 4% and 71 ± 21%. Freedom from endocarditis was 95 ± 3%, 90 ± 6% and 84 ± 8%. Freedom from thromboembolic events was 94 ± 3%, 90 ± 5% and 90 ± 5%. Freedom from reoperation was 94 ± 3%, 87 ± 5% and 65 ± 19%.

CONCLUSIONS

Mosaic bioprosthesis appears a valid mitral valve substitute even when employed in ≤65-year-old patients.

Computational investigation of left ventricular hemodynamics following bioprosthetic aortic and mitral valve replacement

The left ventricle of the heart is a fundamental structure in the human cardiac system that pumps oxygenated blood into the systemic circulation. Several valvular conditions can cause the aortic and mitral valves associated with the left ventricle to become severely diseased and require replacement. However, the clinical outcomes of such operations, specifically the postoperative ventricular hemodynamics of replacing both valves, are not well understood. This work uses computational fluid-structure interaction (FSI) to develop an improved understanding of this effect by modeling a left ventricle with the aortic and mitral valves replaced with bioprostheses. We use a hybrid Arbitrary Lagrangian-Eulerian/immersogeometric framework to accommodate the analysis of cardiac hemodynamics and heart valve structural mechanics in a moving fluid domain. The motion of the endocardium is obtained from a cardiac biomechanics simulation and provided as an input to the proposed numerical framework. The results from the simulations in this work indicate that the replacement of the native mitral valve with a tri-radially symmetric bioprosthesis dramatically changes the ventricular hemodynamics. Most significantly, the vortical motion in the left ventricle is found to reverse direction after mitral valve replacement. This study demonstrates that the proposed computational FSI framework is capable of simulating complex multiphysics problems and can provide an in-depth understanding of the cardiac mechanics.

Durability of Mitral Valve Bioprostheses: A Meta-Analysis of Long-Term Follow-up Studies

BACKGROUND

Porcine and pericardial valves exhibited similar freedom from structural valve deterioration after aortic valve replacement. Limited data exist regarding their durability at long-term follow-up in the mitral position.

METHODS

A literature search was performed through online databases. Papers reporting freedom from tissue valve deterioration after mitral valve replacement with a follow-up longer than 5 years were retrieved. Four porcine valves (Carpentier-Edwards [Edwards Lifesciences, Irvine, CA] and Hancock, Hancock II, and Mosaic [Medtronic, Inc, Minneapolis, MN]) and 1 pericardial prosthesis (Carpentier-Edwards) were the objects of the study. The structural valve deterioration (SVD) rate per year was calculated for each type of prosthesis. Kaplan-Meier curves and log-rank test analysis were performed to compare the long-term durability of porcine and pericardial valves.

RESULTS

Forty full-text papers including more than 15,000 patients were considered for the meta-analysis. Porcine valves were generally implanted in younger patients in the first period after their introduction. The mean age of the patients receiving a mitral bioprosthesis increased from 50 to 70 years over the decades. In patients operated after 1980 who had similar mean age at the time of implant, freedom from SVD was higher in the group of porcine valves with Mosaic prosthesis, showing the lowest rate of SVD. Long-term survival was higher for Mosaic porcine and Carpentier pericardial valves.

CONCLUSIONS

In surgical populations that underwent mitral valve replacement after 1980 with new generation tissue valves and similar mean age at the implant time, we found, at long-term follow-up, a higher freedom from SVD in the group of porcine prostheses.

Hemodynamic Performance and Outcomes of Mosaic Valve for Aortic Stenosis with Decreased Left Ventricular Function: Results from J-MOVE Study

We evaluated impact of a small-sized Mosaic porcine bioprosthesis on hemodynamic performance and outcomes in patients with aortic stenosis (AS) and low left ventricular ejection fraction (LVEF) in a Japan multicenter cohort. Of 1,202 patients enrolled, 105 (8.7%) who had LVEF < 50% and AS underwent aortic valve replacement (AVR). Fifty-two patients received Mosaic porcine bioprosthesis ≤ 21 mm (S-AVR), and 53 received a bioprosthesis ≥ 23 mm (L-AVR). The median follow-up period was 3.1 [1.2, 5.1] years. At 5 years, LVEF significantly improved from median 41.2 [33.8, 45.9]% to 64.2 [49.8, 72.5]% in S-AVR (p < 0.001) and from median 43.2 [37.3, 46.8]% to 61.2 [47.2, 68.0]% in L-AVR (p < 0.001). The left ventricular mass index significantly decreased from median 158.4 [122.2, 194.9] to 110.0 [83.6, 129.4] gm/m in S-AVR (p < 0.001) and from median 169.8 [132.2, 203.6] to 109.6 [101.8, 132.4] gm/m in L-AVR (p < 0.001). There were no significant differences between S-AVR and L-AVR groups regarding freedom from cardiac death (93.1 ± 3.9% vs. 96.2 ± 3.8%; p = 0.119) and valve-related death (97.6 ± 2.4% vs. 100.0 ± 0.0%; p = 0.953). Clinical outcomes and improved hemodynamic performance were similar in both groups.

Antithrombotic Strategies After Bioprosthetic Aortic Valve Replacement: A Systematic Review

BACKGROUND

The optimal antithrombotic regimen after bioprosthetic aortic valve replacement (bAVR) is unclear. We conducted a systematic review of various anticoagulation strategies following surgical or transcatheter bAVR (TAVR).

METHODS

We searched Medline, PubMed, Embase, Evidence-Based Medicine Reviews, and gray literature through June 2017 for controlled clinical trials and cohort studies that directly compared different antithrombotic strategies in nonpregnant adults who had undergone bAVR. We assessed risk of bias and graded the strength of the evidence using established methods.

RESULTS

Of 4,554 titles reviewed, 6 clinical trials and 13 cohort studies met inclusion criteria. We found moderate-strength evidence that mortality, thromboembolic events, and bleeding rates are similar between aspirin and warfarin after surgical bAVR. Observational data suggest lower mortality and thromboembolic events with aspirin combined with warfarin compared with aspirin alone after surgical bAVR, but the effect size is small and the combination is associated with a substantial increase in bleeding risk. We found insufficient evidence for all other treatment comparisons in surgical bAVR. In TAVR patients, we found moderate-strength evidence that mortality, stroke, and major cardiac events are similar between dual antiplatelet therapy and aspirin alone, though a nonsignificantly lower rate of bleeding occurred with aspirin alone.

CONCLUSIONS

Treatment with warfarin or aspirin leads to similar outcomes after surgical bAVR. Combining aspirin with warfarin may lead to a small decrease in thromboembolism and mortality, but is accompanied by increased bleeding. For TAVR patients, aspirin is equivalent to dual antiplatelet therapy for reducing thromboembolism and mortality, with a possible decrease in bleeding.

Trifecta has lower gradient and less prosthesis-patient mismatch than Mosaic Ultra in the aortic position: A prospective randomized study

OBJECTIVE

When aortic valve replacement is needed, a biological valve is usually implanted in patients older than age 60 to 65 years. A large valvular opening area is important to avoid prosthesis-patient mismatch and facilitate reverse left ventricular remodeling. The Trifecta biological valve (St Jude Medical, St Paul, Minn) is, because of its design, believed to reduce transvalvular gradient compared with other biological valves, especially in smaller annuli. Several retrospective studies have compared transvalvular gradients of implanted valves prostheses using the respective manufacturers given size and not the actual annulus size measured by a metric sizer. This makes comparison of the hemodynamic properties of different valve brands and sizes difficult. We therefore performed a prospective randomized study, using the same metric sizer to measure annulus size, and compared hemodynamic profiles of the Trifecta to our standard Mosaic Ultra biological valve (Medtronic, Minneapolis, Minn).

METHODS

Ninety elective patients with small to medium annulus diameter undergoing aortic valve replacement were randomized to either Trifecta or Mosaic Ultra. After native valve removal and decalcification, a Hegar-sizer was used to measure true annulus size. Then the largest possible valve of either brand was implanted according to the randomization protocol. Echocardiography was performed 6 months postoperatively.

RESULTS

Baseline parameters of the 2 cohorts were comparable. There were lower transvalvular gradients in the Trifecta compared with the Mosaic Ultra group for the given annulus sizes. Severe prosthesis-patient mismatch was present in 28% of patients in the Mosaic group and 3% of patients in the Trifecta group.

CONCLUSIONS

Trifecta showed lower transvalvular gradients and less severe prosthesis-patient mismatch compared with Mosaic Ultra for the given annulus sizes. ClinicalTrials.gov Protocol ID: 2011/2596/REK.

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.

Late haemodynamic performance and survival after aortic valve replacement with the Mosaic bioprosthesis

OBJECTIVES

The objective was to evaluate the long-term haemodynamic performance of the Mosaic aortic bioprosthesis. Secondary objectives were to investigate the long-term survival, the rate of aortic valve reoperations, and the rate of prosthesis-patient mismatch and its effect on long-term survival.

METHODS

We included all patients who underwent aortic valve replacement with a Mosaic bioprosthesis at our institution between 2002 and 2008. Valve haemodynamics were assessed by transthoracic echocardiography as mean and peak pressure gradients. Patient characteristics and outcomes were collected from charts and national registers.

RESULTS

We included 355 patients and echocardiographic evaluation was performed at early follow-up in 340 patients (96%) and at late follow-up in 161 patients (45%). The mean follow-up time was 7.1 (maximum 11.7) years. The unadjusted survival at 1, 5 and 10 years was 92, 79 and 42%, respectively. At the early postoperative echocardiography, the peak pressure gradient was 39.9 mmHg (SD 14.4) and the mean pressure gradient was 21.1 mmHg (SD 7.7) and, on late echocardiography, the peak pressure gradient was 38.6 mmHg (SD 15.6) and the mean pressure gradient was 22.5 mmHg (SD 10.1). Moderate or severe prosthesis-patient mismatch was found in 250 (70%) and 49 patients (14%), respectively, but was not significantly associated with mortality in multivariable analyses.

CONCLUSIONS

We found that the Mosaic aortic bioprosthesis had acceptable clinical performance at late follow-up. However, a substantial proportion of patients had high transvalvular gradients or moderate or severe prosthesis-patient mismatch, although neither were significantly associated with long-term survival in our population.

Mitral bioprosthetic valve stenosis in a patient with antiphospholipid antibody syndrome and systemic lupus erythematosus

A 45-year-old woman with antiphospholipid antibody syndrome (APS) and systemic lupus erythematosus was admitted because of severe dyspnea. She had undergone mitral valve replacement (MVR) using a Mosaic bioprosthesis for infective endocarditis 9 years previously. She developed congestive heart failure secondary to mitral bioprosthetic valve stenosis resulting from relatively early structural valve deterioration. She underwent a second MVR using a mechanical valve prosthesis. The explanted bioprosthesis showed marked pannus formation and mineralization with fibrin thrombus formation, especially on the outflow surfaces of the leaflets. After the second operation, she was discharged without APS-related thromboembolic events under meticulous anticoagulant and antiplatelet therapies.

Long-term clinical evaluation of mitral valve replacement with porcine bioprosthetic valves in dogs

This study evaluated the long-term clinical performance of newly developed porcine bioprosthetic valves cross-linked with glutaraldehyde and polyepoxy compound for mitral valve replacement (MVR) in dogs. Five beagle dogs underwent MVR using the porcine bioprosthetic valves during cardiopulmonary bypass. Antithrombotic drugs were administered only for one month after MVR. Six months after MVR, transvalvular regurgitation was not observed in all dogs, paravalvular leakage was seen only in one dog. Twelve months after MVR, mild transvalvular regurgitations were observed in two dogs. Although diastolic atrioventricular pressure gradient was increased gradually, no significant differences were observed. Pressure half-time and valve area were within normal ranges as the bioprosthetic value. There was no clinical symptom of the thrombosis and the thrombogenesis was not observed in the porcine bioprosthetic valve and the annulus in all dogs for twelve months after MVR. The clinical findings suggest that antithrombogenicity of the valves were maintained, though the duability might not be enough in the long-term period.

Antithrombotic therapy following bioprosthetic aortic valve replacement

The life expectancy of the general population is increasing. This has meant that more elderly patients are requiring aortic valve replacement (AVR). The choice of valve replacement and its durability are important. Bioprosthetic (tissue) heart valves were introduced into clinical use in the 1960s and were developed primarily to reduce the complications associated with thromboembolism (TE) and the need for lifelong oral anticoagulation, due to their low thrombogenicity compared to mechanical prostheses. This makes them suitable for use in elderly patients (aged>65 years) and in others where the risks of anticoagulation are higher or anticoagulation is contraindicated. There is thought to be a higher risk of TE for up to 90 days following bioprosthetic AVR. Guidelines for the management of patients with valvular heart disease published by the American College of Cardiology (ACC)/American Heart Association (AHA), the American College of Chest Physicians (ACCP) and the European Society of Cardiology (ESC) all recommend the use of an anticoagulation regimen for the first 3 months following bioprosthetic AVR. However, there is division of opinion and practice, despite these recommendations, and more recent studies have not supported the evidence for these guidelines. In this article, we review the literature on the use of anticoagulation in the first 90 days following bioprosthetic AVR.

Impact of Prosthesis-Patient Mismatch on Survival After Mitral Valve Replacement

Background— We recently reported that valve prosthesis-patient mismatch (PPM) is associated with persisting pulmonary hypertension after mitral valve replacement. Thus, the objective of this study was to evaluate the impact of PPM on mortality in patients undergoing mitral valve replacement.

Methods and Results— The indexed valve effective orifice area was estimated for each type and size of prosthesis being implanted in 929 consecutive patients and used to define PPM as not clinically significant if >1.2 cm 2 /m 2 , as moderate if >0.9 and ≤1.2 cm 2 /m 2 , and as severe if ≤0.9 cm 2 /m 2 . Moderate PPM was present in 69% of patients; severe PPM was seen in 9%. For patients with severe PPM, 6-year survival (74±5%) and 12-year survival (63±7%) were significantly less than for patients with moderate PPM (84±1% and 76±2%; P =0.027) or nonsignificant PPM (90±2% and 82±4%; P =0.002). On multivariate analysis, severe PPM was associated with higher mortality (hazard ratio, 3.2; 95% confidence interval, 1.5 to 6.8; P =0.003).

Conclusions— Severe PPM is an independent predictor of mortality after mitral valve replacement. As opposed to other independent risk factors, PPM may be avoided or its severity may be reduced with the use of a prospective strategy at the time of operation. For patients identified as being at risk for severe PPM, every effort should be made to implant a prosthesis with a larger effective orifice area.

Short-Term Performance of Mitral Valve Replacement with Porcine Bioprosthetic Valves in Dogs

Porcine bioprosthetic valves cross-linked with glutaraldehyde and polyepoxy compound were newly developed for mitral valve replacement (MVR) in dogs. Five beagle dogs were performed a left thoracotomy and underwent MVR using the porcine bioprosthetic valves during cardiopulmonary bypass (CPB). A vein catheter inserted into right atrium and a vent catheter inserted into the right ventricle to drain. The hemodynamic conditions of CPB were excellent during surgery. The left atrial pressure was measured before and after MVR; there was no significant difference and it was normal. Thrombosis and the prosthetic valve regurgitation were not observed one week after MVR. Pressure half time (PHT) prolonged significantly (P<0.05) from 31.40 +/- 4.0 msec presurgery to 99.20 +/- 19.4 msec at seven days after MVR, although it indicated the normal range as the bioprosthetic valve. The symptom of the prosthetic valve failure was not observed. This study indicated that the MVR using porcine bioprosthetic valves under CPB might have been effective in dogs as a short-term evaluation.

New flexible polymeric heart valve prostheses for the mitral and aortic positions

OBJECTIVE

Current prosthetic heart valves necessitate permanent anticoagulation or have limited durability and impaired hemodynamic performance compared with natural valves. We report in vivo and in vitro results with new polymeric valve prostheses that have a special design for the mitral and aortic positions. The aims are improved durability and elimination of the need for permanent anticoagulation.

METHODS

The mitral and aortic prostheses (Adiam Life Science, Erkelenz, Germany) are made entirely of polycarbonate urethane (PCU). The bileaflet asymmetric mitral valve mimics natural, nonaxial inflow, which creates a left ventricular vortex, saving energy for systolic ejection of blood. The trileaflet aortic prosthesis has diminished pressure loss and reduced stress and strain peaks at the commissures. The valves were subjected to long-term in vitro testing and in vivo testing in a growing calf model (20 weeks; 7 mitral and 7 aortic valves) with comparison with 2 commercial bioprostheses (7 mitral, 2 aortic). Two-dimensional echocardiography was performed after implantation and prior to sacrifice with autopsy and valve examination.

RESULTS

In vitro durability of the PCU valves was proved up to 20 years. In vivo durability and hemodynamics were superior to those of all bioprostheses. Survival of PCU valves versus bioprostheses was 7 versus 2 mitral valves and 5 versus 0 aortic valves, respectively. Two animals with PCU aortic valves died of pannus overgrowth that caused severe left ventricular outflow tract obstruction without changes in the valves. Degeneration and calcification were mild (mitral) and moderate (aortic) in PCU valves but were severe in biological valves. There was no increased thrombogenicity of the PCU valves compared with bioprostheses.

CONCLUSION

The new flexible polymeric aortic and mitral valve prostheses were superior to current bioprostheses in animal testing.

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.

Clinical and hemodynamic implications of supra-annular implant of biological aortic valves

The use of stented bioprostheses in elderly patients with degenerative aortic stenosis, despite being desirable, raises concerns about the harmful effects of residual obstruction to left ventricular outflow. To overcome this limitation new stented and stentless bioprostheses have been designed for supra-annular implant. However, the actual hemodynamic advantage of supra-annular implant over the intra-annular one remains incompletely understood. This review focuses on the geometry of biological valve prostheses designed for supra-annular implant and its implications for the echocardiographic assessment of valve hemodynamics. Available data about the hemodynamic performance of these valves implanted in the supra-annular position in comparison with the usual intra-annular implant are also reviewed. Other issues related to biological heart valve performance, such as biomaterials, tissue mechanics, durability, and clinical outcome are not addressed in this review.

Rest and Exercise Performance of the Medtronic Advantage Bileaflet Valve in the Aortic Position

BACKGROUND

The aim of the study was to evaluate rest and exercise performance and left ventricular mass regression of the Medtronic Advantage (Medtronic, Inc, Minneapolis, MN) prosthesis in the aortic position at 1 year at a single center as part of a multicenter, prospective clinical trial.

METHODS

Between May 2002 and June 2003, 63 consecutive patients underwent aortic valve replacement with a Medtronic Advantage prosthesis (84.1% male; mean age, 56.0 +/- 9.7 years; ejection fraction, 56.5 +/- 15.8%). Valve lesions were stenosis (n = 20), mixed (n = 34), and insufficiency (n = 9). Concomitant procedures were performed in 34.9%. Follow-up was 100% complete. Echocardiographic data were obtained early postoperatively and at 1 year, combined with stress echocardiography by treadmill. Mean pressure gradients, stroke volume, and left ventricular mass were determined by echocardiography. Data are presented as mean +/- standard deviation.

RESULTS

Operative mortality was 0%. Valve-related complications were observed in 2 patients (endocarditis, n = 1; thromboembolic event, n = 1). There was no case of antithromboembolic hemorrhage, prosthesis-related explant, or reoperation. One patient showed moderate paravalvular regurgitation. Mean pressure gradients 1 year postoperatively ranged from 6.3 to 11.0 mm Hg across all valve sizes. Left ventricular mass regression at 1 year was 18.4% across all valve sizes (p < 0.001). No severe patient-prosthesis mismatch (effective orifice area index < or = 0.65 cm2/m2) could be observed.

CONCLUSIONS

After 1 year, the Medtronic Advantage valve shows comparable transvalvular mean pressure gradients across the valve sizes used during rest and exercise. This is accompanied by a significant left ventricular mass regression, an important indicator for long-term survival.

Exercise hemodynamics of bovine versus porcine bioprostheses: a prospective randomized comparison of the mosaic and perimount aortic valves

OBJECTIVE

This prospective randomized study compares a porcine with a bovine bioprosthesis in the aortic position with regard to hemodynamic performance during exercise.

METHODS

Between August of 2000 and December of 2002, 136 patients underwent aortic valve replacement with the porcine Medtronic Mosaic (n = 66) or the bovine Carpentier-Edwards Perimount (n = 70) bioprosthesis. Transthoracic echocardiography was performed to assess hemodynamic and dimensional data preoperatively and 10 months postoperatively; the latter follow-up included stress echocardiography with treadmill exercise.

RESULTS

At rest and during exercise (25 and 50 W), there was a significant difference in mean pressure gradient between the bovine and the porcine valves with labeled sizes 21 and 23, with superiority of the Perimount prosthesis. There was no difference in effective orifice area and incidence of patient-prosthesis mismatch among all sizes. The left ventricular mass index decreased significantly within 10 months postoperatively in the size 23 bovine group and the size 25 porcine group.

CONCLUSIONS

Our data show a significant superiority of pressure gradients for the bovine bioprosthesis, especially with small valve sizes, when compared with the porcine device, which is more distinctive during exercise.

Hemodynamic Comparison of Bioprostheses for Complete Supra-Annular Position in Patients With Small Aortic Annulus

OBJECTIVES

The present study evaluates complete supra-annular bioprostheses in patients with an aortic annulus of 18 to 23 mm in diameter.

BACKGROUND

Aortic valve replacement in patients with small aortic annulus using stented bioprostheses is often associated with unsatisfactory hemodynamic results and high incidence of patient-prosthesis mismatch.

METHODS

Between February 2000 and January 2004, 156 patients with aortic valve disease and an aortic annulus of 18 to 23 mm in diameter received the stented bovine Soprano (Sorin Biomedica Cardio, Saluggia, Italy) (n = 18), Perimount (Edwards Lifesciences, Irvine, California) (n = 52), Perimount Magna (Edwards Lifesciences) (n = 42), or the stented porcine Mosaic (Medtronic Inc., Minneapolis, Minnesota) (n = 44) bioprostheses. Intraoperatively, the surgeon measured the aortic annulus diameter by inserting a hegar dilator. Thus, postoperative hemodynamic results could be referred to the patient's aortic annulus diameter instead of referring the results to the labeled valve size. This allows for objective comparisons between different valve types.

RESULTS

There was no significant difference in hemodynamic results between the different valve types in patients with an aortic annulus 18 to 20 mm. In patients with an annulus 21 to 23 mm, the Magna was significantly superior to the other investigated devices in mean pressure gradient, effective orifice area, and incidence of patient-prosthesis mismatch. There was no significant difference between the complete supra-annular bioprostheses Mosaic and Soprano and the intra-supra-annular Perimount valve.

CONCLUSIONS

In patients with an aortic annulus of 18 to 20 mm in diameter, hemodynamic performance is independent of the implanted stented valve type and the annular position. Root enlargement or stentless valves may be beneficial alternatives. Patients with annulus diameter 21 to 23 mm benefit from the Magna in complete supra-annular position leading to superior hemodynamic results.

Introduction of a flexible polymeric heart valve prosthesis with special design for mitral position

BACKGROUND

Current heart valve prostheses are constructed mimicking the native aortic valve. Special hemodynamic characteristics of the mitral valve such as a nonaxial central inflow with creation of a left ventricular vortex have so far not been taken into account. A new polycarbonaturethane (PCU) bileaflet heart valve prosthesis with special design for the mitral position is introduced, and results of animal testing are presented.

METHODS AND RESULTS

After in vitro testing, 7 PCU-prostheses and 7 commercial bioprostheses (Perimount, n=4; Mosaic, n=3) were implanted in mitral position into growing Jersey calves (age 3-5 months, weight 60-97 kg) for 20 weeks. 2-Dimensional echocardiography was performed after implantation and before sacrification. Autopsy included histologic, radiographic, and electron microscopic examination of the valves. In vitro durability was proven for >15 years. After implantation 2-dimensional-echocardiography showed no relevant gradient or regurgitation of any prosthesis. Clinical course of the animals with PCU valves was excellent. In contrast, 5 of 7 calves with bioprostheses were sacrificed after 1-9 weeks because of congestive heart failure. 2-Dimensional echocardiography of the PCU valves after 20 weeks showed mild leaflet thickening with trivial regurgitation; mean gradient was 8.1+/-5.0 mm Hg (weight: 160-170 kg). The explanted PCU prostheses revealed mild calcification and no structural degeneration. All of the Perimount bioprostheses were severely calcified and degenerated after 11+/-7 weeks. One Mosaic bioprosthesis was thrombosed after 1 week, and 2 showed severe and mild-to-moderate degeneration after 4 and 22 weeks, respectively.

CONCLUSIONS

Polycarbonaturethane valve prostheses with special design for mitral position show excellent hemodynamic performance and durability in vivo. Calcification and structural changes are mild compared with bioprostheses. Controlled clinical studies are planned.