Are stentless valves hemodynamically superior to stented valves? Long-term follow-up of a randomized trial comparing Carpentier–Edwards pericardial valve with the Toronto Stentless Porcine Valve

Two-Year Clinical Follow-Up Assessment of the Novel Cingular Surgical Bovine Pericardial Valve

Objectives: To evaluate the 2-year clinical safety and hemodynamic outcomes of the Cingular bovine pericardial bioprosthesis. Methods: A prospective, multicenter, single-arm trial was conducted in patients who required aortic or mitral valve replacement. From March 2016 to October 2017, 197 patients were implanted with the Cingular bovine pericardial valve at five sites in China. The clinical outcomes and hemodynamic performance were assessed through a 2-year follow-up. Clinical safety events were reviewed by an independent clinical events committee, and echocardiographic data were assessed by an independent core laboratory. Results: The mean age was 66.9 ± 4.9 years. The 2-year survival rate was 96.4%. A complete 2-year clinical follow-up was achieved in 189 of 190 survivors. No case of structural valve deterioration, major perivalvular leak, prosthetic valve endocarditis, or valve-related reoperation was seen. For the aortic valve, the mean pressure gradient observed was 12.5 ± 4.0 mm Hg, and the effective orifice area (EOA) was 2.0 ± 0.3 cm2. For the smaller size aortic valves, 19 mm and 21 mm, respective mean EOA values of 1.7 ± 0.2 cm2 and 1.8 ± 0.2 cm2 were found. The values for mean pressure gradient and mean EOA for mitral bioprostheses were 4.0 ± 1.4 mm Hg and 2.2 ± 0.3 cm2, respectively. There was no significant change between 1-year and 2-year hemodynamic performance. Conclusions: The Cingular bovine pericardial valve showed favorable clinical safety and hemodynamic outcomes over a 2-year follow-up. Further follow-up is required to validate the long-term durability.

Geometric changes in aortic root replacement using Freestyle prosthesis

Background

The Medtronic Freestyle prosthesis has proven to be a promising recourse for aortic root replacement in various indications. The present study aims to evaluate clinical outcomes and geometric changes of the aorta after Freestyle implantation.

Methods

Between October 2005 and November 2020, the computed tomography angiography (CTA) data of 32 patients were analyzed in a cohort of 68 patients that underwent aortic root replacement using Freestyle prosthesis. The minimum and maximum diameters and areas of the aortic annulus, aortic root, ascending aorta, and the proximal aortic arch were measured at a plane perpendicular to the long axis of the aorta using 3D multiplanar reconstruction in both the preoperative (n = 32) and postoperative (n = 10) CTAs. Moreover, volumetric changes of the aortic root and ascending aorta were quantified.

Results

Mean age was 64.6 ± 10.6 years. Indications for surgery using Freestyle prosthesis were combined aortic valve pathologies, aortic aneurysm or dissection, and endocarditis, with concomitant surgery occurring in 28 out of 32 patients. In-hospital mortality was 18.6%.

Preoperative diameter and area measurements of the aortic annulus strongly correlated with the implanted valve size (p < 0.001). Bicuspid valve was present in 28.1% of the patients. Diameter and areas of the aortic root decreased after freestyle implantation, resulting in a reduction of the aortic root volume (45.6 ± 26.3 cm³ to 18.7 ± 4.5 cm³, p = 0.029). Volume of the aortic root and the ascending aorta decreased from 137.3 ± 65.2 cm³ to 54.5 ± 21.1 cm³ after Freestyle implantation (p = 0.023).

Conclusion

Implantation of the Freestyle prosthesis presents excellent results in restoring the aortic geometry. Preoperative CTA measurements are beneficial to the surgical procedure and valve selection and therefore, if available, should be considered in pre-operative planning.

Increased utilization of bioprosthetic aortic valve technology:Trends, drivers, controversies and future directions

Introduction: Bioprosthetic valves (BPV) implanted surgically or by transcatheter valve implantation (TAVI) comprise an overwhelming majority of substitute aortic valves implanted worldwide.Areas Covered: Prominent drivers of this trend are: 1) BPV patients have generally better outcomes than those with a mechanical valve, and remain largely free of anticoagulation and its consequences; 2) BPV durability has improved over the years; and 3) the expanding use of TAVI and valve-in-valve (VIV) procedures permitting interventional management of structural valve degeneration (SVD). Nevertheless, key controversies exist: 1) optimal anticoagulation regimens for surgical and TAVI BPVs; 2) the incidence, mechanisms and mitigation strategies for SVD; 3) the use of VIV for treatment of SVD, and 4) valve selection recommendations for difficult cohorts, (e.g. patients 50-70 years, patients <50, childbearing age women). This communication reviews trends in and drivers of BPV utilization, current controversies, and future directions affecting BPV use.Expert Opinion: Long-term data are needed in several areas related to aortic BPV use, including anticoagulation/antiplatelet therapy, especially following TAVI. TAVI and especially VIV durability and optimal use warrant will benefit greatly from long-term data. Certain populations may benefit from such high-quality data on multi-year outcomes, particularly younger patients.

One-year outcome with a bovine pericardial valve

Objectives

To evaluate the safety and effectiveness of a novel surgical bovine pericardial valve for aortic and mitral valve replacements.

Methods

Between March 2016 and October 2017, 197 patients (mean age, 66.9 ± 4.9 years; 40.6% were women) underwent aortic valve replacement and mitral valve replacement and were implanted with the Cingular bovine pericardial valve (Shanghai Cingular Biotech Corporation, Shanghai, China) in a prospective, multicenter, single-arm trial in China. A total of 161 aortic and 49 mitral prostheses were implanted. Patients were followed up to 1 year. The primary end point was the 1-year overall rate of valve-related complications, including thromboembolic event, valve thrombosis, major hemorrhage event, major perivalvular leak, and prosthetic valve endocarditis.

Results

The 1-year overall rate of valve-related complications was 0.5% (95% confidence interval, 0.1%-3.7%). The 1-year survival was 96.4%. The mean gradient and effective orifice area for aortic prostheses at 1 year postoperatively were 12.8 ± 4.4 mm Hg and 1.9 ± 0.3 cm², respectively. Particularly, the mean gradients and effective orifice area for 19 mm and 21 mm sizes of aortic prostheses at 1 year were 17.0 ± 3.8 mm Hg and 1.6 ± 0.2 cm², 13.1 ± 4.0 mm Hg and 1.8 ± 0.1 cm², respectively. Patient–prosthesis mismatch occurred in only 1.3% patients for aortic valve implantation at 1 month. No structural valve deterioration and no endocarditis occurred.

Conclusions

The Cingular bovine pericardial valve was safe and effective for surgical aortic and mitral valve replacement. The 1-year rate of valve-related complications was very low. Early hemodynamic performance was excellent even for the small aortic root.

Transcatheter aortic valve replacement in failed surgical valves

Aortic valve-in-valve is a less invasive alternative to surgical redo in the treatment of failed bioprosthetic valves. While only inoperable patients underwent the procedure before, operators currently offer it to those at lower risk and worldwide experience is in the thousands. Early mortality has diminished in recent analyses and improvements in symptoms and quality of life have been documented. Main considerations with aortic valve-in-valve include elevated postprocedural gradients, coronary obstruction and leaflet thrombosis. Risk factors for each of these adverse events have been described at length. Aortic valve-in-valve offers a safe and effective option in the management of failed bioprosthetic valves.

Thromboembolic acute myocardial infarction after aortic valve replacement using the Freestyle stentless aortic bioprosthesis with subcoronary valve replacement

A 70-year-old woman with substernal chest pain lasting 2.5 h presented to the emergency department of our hospital. She had a history of aortic valve replacement with the Freestyle stentless aortic bioprosthesis for severe aortic regurgitation 7 years ago. The initial electrocardiogram showed sinus rhythm at a rate of 71 bpm with ST-segment slight elevation in leads II, III and aVF. She was diagnosed as having acute coronary syndrome and was referred for an urgent catheterization. Urgent coronary angiography revealed total occlusion in the distal segment of the right coronary artery. Furthermore, a cavity was revealed around the aortic annulus by the contrast leaked from the ostium of the right coronary artery during angiography. Contrast-enhanced computed tomography showed an enhanced cavity between the native aortic wall and the bioprosthesis and the defect in the cavity. We diagnosed the incompetence of the bioprosthesis and decided to perform repeat aortic valve replacement. During surgery, the presence of a thrombus was confirmed in the cavity. The finding indicated that this embolic event was due to the thrombus from the cavity.

Early hemodynamics and clinical outcomes of isolated aortic valve replacement with stentless or transcatheter valve in intermediate-risk patients

OBJECTIVE

Stentless aortic valves have been developed to overcome obstructive limitations associated with stented bioprostheses. The aim of the current multi-institutional study was to compare hemodynamics of transcatheter (TAVR) and the Freedom SOLO Stentless (FS) valve in an intermediate risk population undergoing surgical aortic valve replacement.

METHODS

From 2010 to 2014, 420 consecutive patients underwent isolated surgical aortic valve replacement with FS and 375 patients underwent TAVR. Only patients with intermediate operative risk (Society of Thoracic Surgeons score 4-10) and small aortic annulus (≤23 mm) were included. After a propensity matched analysis 142 patients in each group were selected. Thirty-day postoperative clinical and echocardiographic parameters were evaluated.

RESULTS

Mean prosthesis diameter was 22.2 ± 0.9 mm for FS and 22.4 ± 1.0 mm for TAVR. In-hospital mortality was 2.1% for FS and 6.3% for TAVR (P = .02). Postoperative FS peak gradients were 19.1 ± 9.6 mm Hg (mean 10.8 ± 5.9 mm Hg); TAVR peak gradients were 20.2 ± 9.5 mm Hg (mean 10.7 ± 6.9 mm Hg) P = .57 (P = .88). Postoperative effective orifice area was 1.93 ± 0.52 cm² for FS and 1.83 ± 0.3 cm² for TAVR (P = .65). There was no prostheses-patient mismatch in either group. Postoperative grade 2-3 paravalvular leak was present in 3.5% for TAVR and 0.7% for FS. Postoperative permanent pacemaker implant rate was 12% for TAVR and only 1 case (0.7%) in the FS group (P < .001).

CONCLUSIONS

In patients with small aortic annulus and intermediate risk, both FS and TAVR demonstrated similar excellent hemodynamic performance. TAVR demonstrated greater mortality and rates of pacemaker insertion. Further studies are warranted to validate TAVR indications in this subset of patients.

[Aortic valve replacement with stentless bioprosthesis]

AIM

To evaluate prospectively the hemodynamic performance of «BioLAB Mono» stentless bioprosthesis implanted into aortic position.

MATERIAL AND METHODS

Twenty seven patients (mean age 71 (67; 73); 17 women) with severe aortic stenosis underwent aortic valve replacement with «BioLAB Mono» stentless bioprosthesis from 2012 to 2014. The valves were implanted into supra-annular position using continuous polypropylene suture.

RESULTS

In the early postoperative period 1 patient (3.7%) died for acute heart failure. The mean aortic cross-clamping time was 81 (75; 90) min. Echocardiographic peak pressure gradient were 18 (16; 23) mmHg (postoperative). There were no cases of valve dysfunction in early postoperative period. Level of thrombocytes recovered after 10 days postoperatively.

CONCLUSION

«BioLAB Mono» aortic bioprosthesis implantation is easy and reproducible. The valve has excellent hemodynamic performance in early postoperative period.

EFFICACY OF CARPENTIER-EDWARDS PERICARDIAL PROSTHESES: A SYSTEMATIC REVIEW AND META-ANALYSIS

Objectives: The Carpentier-Edwards pericardial (CEP) prostheses are the type of bioprostheses most used worldwide. Although they were designed to minimize the rate of valve deterioration and reoperation, their clinical superiority over other prostheses models still lacks confirmation. The objective of this study was to evaluate its effectiveness.

Methods: We performed a systematic review and meta-analysis in the PubMed, Embase, Cochrane, and Lilacs databases. Operative mortality, overall mortality and reoperation rates after heart valve surgery were compared between the use of CEP and other cardiac prostheses. Two independent reviewers screened studies for inclusion and extracted the data. Disagreements were resolved by consensus. The GRADE criterion was used to assess the evidence quality.

Results: A total of twenty-eight studies were selected, including 19,615 individuals. The studies presented a high heterogeneity and low quality of evidence what limited the reliability of the results. The pooled data from the selected studies did not demonstrate significant differences between CEP and porcine, pericardial or stentless prostheses regarding operative mortality, overall mortality and reoperation rates. However, the pooled data from 3 observational trials pointed out a higher risk for reoperation after valve replacement using CEP prostheses against mechanical prostheses (OR 4.92 [95 percent confidence interval 2.43–9.96]).

Conclusions: The current data present in the literature still does not support a clinical advantage for the use of CEP prostheses over other bioprostheses. The quality of the studies in the literature is limited and further studies are needed to address if CEP prostheses will have a clinical advantage over other prostheses.

Failing stentless aortic valves: redo aortic root replacement or valve in a valve?

OBJECTIVES

Reoperation for failing stentless aortic valve replacement is a technically demanding procedure that has traditionally been tackled in one of two ways: either root replacement or the more conservative option of implanting a stented valve within the valve. We sought to determine the relative operative risks, follow-up status and medium to long-term survival of these two methods.

METHODS

We conducted a retrospective review of a single surgeon's experience of the two techniques over a 10-year period from 2000 to 2010. Excluding cases of active endocarditis, 110 patients were identified, of which 65 underwent 'valve-in-valve' procedures ('Group A') and 45 had redo root replacement ('Group B'). The most common bioprostheses reoperated were homografts (roots or subcoronary implants) and Toronto Stentless Porcine Valves. Aortic valve replacement alone was performed in 68% in Group A and 64% in Group B, with males comprising 75% of Group A and 82% of Group B. Average ages were 61.5 ± 14.2 years and 61.9 ± 12.1 years, respectively.

RESULTS

Operative and cardiopulmonary bypass durations were significantly greater for redo root procedures and correspondingly, postoperative complications were more common. Thirty-day mortality after valve-in-valve replacement was 3%, and after redo root replacement it was 11%. Despite significantly higher transvalvular gradients in Group B, the symptomatic status was equally good at 2 months, 1 year and last follow-up. At an average interval of 5.1 ± 2.7 years for Group A, survival was 83% vs 76% at 7.3 ± 2.9 years for Group B. There have been two reinterventions in Group A and 3 in Group B. Only one valve-in-valve patient has developed a paraprosthetic leak.

CONCLUSIONS

This retrospective review has confirmed our hypothesis that where both root diameter permits and satisfactory debridement can be performed, valve-in-valve replacement is the more conservative surgical strategy for stentless aortic valve replacement revision. Although transvalvular gradients on echocardiography are significantly higher with the introduction of a stented prosthesis, medium-term outcomes in terms of symptomatic status, late complications and reintervention rate were non-inferior. We await the medium-term results of transcatheter aortic valve implantation for the same indication with interest.

Comparing aortic root replacements: porcine bioroots versus pericardial versus mechanical composite roots: hemodynamic and ventricular remodeling at greater than one-year follow-up

BACKGROUND

Stentless porcine bioroots and pericardial composite roots were developed as prostheses that avoid the anticoagulation necessary for mechanical composite roots. Data on the hemodynamics of all root replacements are lacking and questions remain regarding comparative performance.

METHODS

This study evaluated patients receiving a stentless porcine bioroot, a pericardial, or a mechanical composite root at a single institution from January 2000 to December 2008. All patients underwent preoperative, postoperative and greater than 1-year echocardiograms. All root replacements were performed for aortic insufficiency or aneurysm. Median follow-up was 3.3 years (1 to 8 years).

RESULTS

There were no significant differences in preoperative left ventricular ejection fraction, aortic valve peak gradient, mean gradient, left ventricular end diastolic diameter, and left ventricular end systolic diameter. Postoperative peak and mean gradients in mechanical composite roots were significantly higher than stentless porcine bioroots. At greater than 1 year, stentless porcine bioroots had significantly lower peak and mean gradients than both mechanical composite roots and pericardial composite roots. The end diastolic diameter was also significantly smaller in stentless porcine bioroots at greater than 1 year than mechanical composite roots.

CONCLUSIONS

All prostheses resulted in favorable hemodynamic and ventricular remodeling. Stentless porcine bioroots had the lowest gradients at greater than 1 year of all root replacements, with significantly better ventricular remodeling when compared with mechanical composite roots. Pericardial roots also had favorable hemodynamics and ventricular remodeling, suggesting that they are a viable alternative.

Sutureless perceval aortic valve replacement: results of two European centers

BACKGROUND

The Perceval S bioprosthesis (Sorin Biomedica Cardio Srl, Sallugia, Italy) is a self-expanding valve designed to preserve aortic sinuses and sinotubular junction. We report the midterm results of a prospective, multicenter clinical study evaluating the safety and efficacy of this stented bioprosthesis in patients undergoing aortic valve replacement with or without concomitant procedures.

METHODS

From January 2007 to September 2011, a total of 208 high-risk patients (mean European system for cardiac operative risk evaluation: 8.7±5.3 years) received a Perceval bioprosthesis in 2 European centers. Median follow up was 10±20 months and 100% complete, and the total accumulated follow-up was 156 patient-years. Ten patients have reached a 4-year follow-up. Valve function was assessed in all patients.

RESULTS

Valve implantation resulted in significant improvement of patients' symptoms. Mean preoperative and postoperative gradients were 48.6±18.6 mm Hg and 10.4±4.3 mm Hg, respectively, and preoperative and postoperative mean effective orifice areas were 0.7±0.2 and 1.4±0.4 cm2. Survival at 12 months was 87.1%, success of implantation was 95%, and freedom from reoperation was 96%. In hospital mortality was 2.4%. During follow-up, 9 patients (4%) required reoperation for paravalvular regurgitation; 7 early and 2 late reoperations. Mean cross-clamp time (CCT) and extracorporeal circulation time (ECT) were, respectively, 33±14 minutes and 54±24 minutes, including 45 patients who underwent surgery through ministernotomy. Concomitant coronary bypass was done in 48 patients with mean CCT 43±13 and ECT 68±25 minutes.

CONCLUSIONS

Perceval sutureless is a safe bioprosthesis that can easily be implanted, including by a minimally invasive technique. It provides excellent hemodynamic with significant clinical improvement. Overall, these data confirm the safety and utility of the Perceval bioprosthesis aortic valve replacement for high-risk patients.

Transcatheter aortic valve implantation in patients with severe aortic stenosis and small aortic annulus

OBJECTIVES

Valve hemodynamics and clinical outcomes among patients with a small aortic annulus who underwent transcatheter aortic valve implantation (TAVI) were examined.

BACKGROUND

The presence of a small aortic annulus may complicate the surgical management of patients with severe aortic stenosis (AS). TAVI is an alternative to aortic valve replacement (AVR) in high-risk patients, but few data exist on the results of TAVI in patients with a small aortic annulus.

METHODS

Between 2007 and 2010, 35 patients (mean age 79.2 ± 9.4 years) with severe AS and an aortic annulus diameter <20 mm (mean 18.5 ± 0.9 mm) underwent TAVI with a 23-mm Edwards SAPIEN bioprosthesis (Edwards Lifesciences, Inc., Irvine, California). Echocardiographic parameters and clinical outcomes were assessed prior to discharge and at 6, 12, and 24 months.

RESULTS

Procedural success was achieved in 34 patients (97.1%). There was 1 in-hospital death. Peak and mean transaortic gradients decreased from 76.3 ± 33.0 mm Hg and 45.2 ± 20.6 mm Hg at baseline to 21.8 ± 8.4 mm Hg and 11.7 ± 4.8 mm Hg post-procedure, respectively, both p < 0.0001. Mean indexed effective orifice area (IEOA) increased from 0.35 ± 0.10 cm(2)/m(2) at baseline to 0.90 ± 0.18 cm(2)/m(2) post-procedure, p < 0.0001. Severe prosthesis-patient mismatch (IEOA <0.65 cm(2)/m(2)) occurred in 2 patients (5.9%). At a mean follow-up of 14 ± 11 months, gradients remained low and 30 of the 31 remaining survivors were in New York Heart Association functional class I or II.

CONCLUSIONS

In high-risk patients with severe AS and a small aortic annulus, TAVI is associated with good post-procedural valve hemodynamics and clinical outcomes. TAVI may provide a reasonable alternative to conventional AVR in elderly patients with a small aortic annulus.

Reoperation of Left Heart Valve Bioprostheses According to Age at Implantation

Background—

Evidence supporting the use of bioprostheses for heart valve replacement in young adults is accumulating. However, reoperation data, which may help guide clinical decision making in young patients, remains poorly defined in the literature.

Methods and Results—

We examined the need for reoperation in 3975 patients who underwent first-time bioprosthetic aortic valve replacement (AVR) (n=3152) or mitral valve replacement (MVR) (n=823). There were 895 patients below the age of 60 years at bioprosthesis implant (AVR, n=636; MVR, n=259). The median interval to reoperation of contemporary, stented aortic bioprostheses was 7.74 years (95% CI 7.28 to 9.97 years) in patients less than 40 years, and 12.93 years (95% CI 11.10 to 15.76 years) in patients between 40 and 60 years of age. Multivariable risk factors associated with reoperation following bioprosthetic AVR include age (hazard ratio [HR] 0.94 per year, 95% CI 0.91 to 0.96, P <0.001) and concomitant coronary artery bypass grafting (HR 0.34, 95% CI 0.11 to 0.99, P =0.04). The median interval to reoperation of contemporary mitral bioprostheses was 8.11 years (95% CI 5.79 to 16.50 years) in patients less than 40 years, and 10.14 years (95% CI 8.64 to 11.14 years) in patients between 40 and 60 years of age. As for AVR, age (HR 0.96 per year, 95% CI 0.95 to 0.98, P <0.001) and concomitant coronary artery bypass grafting (HR 0.55, 95% CI 0.32 to 0.93, P =0.03) were associated with decreased reoperation risk following bioprosthetic MVR.

Conclusions—

These data constitute clinically relevant age-specific prognostic information regarding reoperation in young patients, who may wish to select a bioprosthesis at initial left heart valve replacement.

Stentless aortic valve replacement: an update

Although porcine aortic valves or pericardial tissue mounted on a stent have made implantation techniques easier, these valves sacrifice orifice area and increase stress at the attachment of the stent, which causes primary tissue failure. Optimizing hemodynamics to prevent patient–prosthetic mismatch and improve durability, stentless bioprostheses use was revived in the early 1990s. The purpose of this review is to provide a current overview of stentless valves in the aortic position. Retrospective and prospective randomized controlled studies showed similar operative mortality and morbidity in stented and stentless aortic valve replacement (AVR), though stentless AVR required longer cross-clamp and cardiopulmonary bypass time. Several cohort studies showed improved survival after stentless AVR, probably due to better hemodynamic performance and earlier left ventricular (LV) mass regression compared with stented AVR. However, there was a bias of operation age and nonrandomization. A randomized trial supported an improved 8-year survival of patients with the Freestyle or Toronto valves compared with Carpentier–Edwards porcine valves. On the contrary, another randomized study did not show improved clinical outcomes up to 12 years. Freedom from reoperation at 12 years in Toronto stentless porcine valves ranged from 69% to 75%, which is much lower than for Carpentier–Edwards Perimount valves. Cusp tear with consequent aortic regurgitation was the most common cause of structural valve deterioration. Cryolife O’Brien valves also have shorter durability compared with stent valves. Actuarial freedom from reoperation was 44% at 10 years. Early prosthetic valve failure was also reported in patients who underwent root replacement with Shelhigh stentless composite grafts. There was no level I or IIa evidence of more effective orifice area, mean pressure gradient, LV mass regression, surgical risk, durability, and late outcomes in stentless bioprostheses. There is no general recommendation to prefer stentless bioprostheses in all patients. For new-generation pericardial stentless valves, follow-up over 15 years is necessary to compare the excellent results of stented valves such as the Carpentier–Edwards Perimount and Hancock II valves.

Does stentless aortic valve implantation increase perioperative risk? A critical appraisal of the literature and risk of bias analysis

Stentless aortic valve replacement has potential benefits in terms of valve hemodynamics and clinical outcomes, although these may be offset by greater technical complexity of implantation with longer cardiopulmonary bypass and cross-clamp times compared with stented valves. Meta-analyses of the small number of published randomized trials have been limited by their lack of critical synthesis of the literature, including evaluation of the Risk of Bias. Our objective was to determine whether stentless aortic valves increase perioperative risk of mortality. We also examined secondary clinical outcomes of neurological, renal and respiratory complications as well as hemodynamic changes reported by studies following implantation of the two types of aortic prosthesis. The methodology used to answer this question was a rigorous meta-analysis of randomized controlled trials, using bias-assessment techniques designed to address limitations of conventional meta-analysis. Our findings show that many of the existing randomized trials have a high or uncertain risk of bias. Analysis of studies with low risk of bias reveals that stentless valves do not increase perioperative risk in terms of 30-day mortality and morbidity though neither do they exhibit benefits in hemodynamics or clinical outcomes compared with stented valves. Larger, more stringent randomized studies would be required to identify any robust clinical difference.