Stentless versus Stented Bioprosthetic Aortic Valves: A Systematic Review and Meta-Analysis of Controlled Trials

Stentless Versus Stented Aortic Valve Replacement for Aortic Stenosis

BACKGROUND

The differences in long-term outcomes of aortic valve replacement for aortic stenosis between stentless and stented bioprostheses are controversial.

METHODS

Between 2007 and 2018, 1173 patients underwent aortic valve replacement for aortic stenosis, including 559 treated with a stentless valve and 614 with a stented valve. A propensity score matched cohort with 348 pairs was generated by matching for age, sex, body surface area, bicuspid aortic valve, chronic lung disease, previous cardiac surgery, coronary artery disease, renal failure on dialysis, valve size, concomitant procedures, and surgeon. The primary endpoints of the study were long-term survival and incidence of reoperation.

RESULTS

Immediate postoperative outcomes were similar between the stentless and stented groups with an overall operative mortality of 2.9% (P = .19). Kaplan-Meier estimation for long-term survival was comparable between the stentless and stented valves in both the whole cohort and the propensity score matched cohort (10-year survival 59% vs 55%, P = .20). The hazard ratio of stentless vs stented valve for risk of long-term mortality was 1.12 (P = .33). The 10-year cumulative incidence of reoperation due to valve degeneration was 5.5% in the stentless group and 4.7% in the stented group (P = .25). The transvalvular pressure gradient at 5-year follow-up was significantly lower in the stentless group (7 vs 11 mm Hg, P < .001).

CONCLUSIONS

Both stented and stentless valves could be used in aortic valve replacement for aortic stenosis. We recommend stented valves for aortic valve replacement in patients with aortic stenosis for their simplicity of implantation.

Percutaneous versus Surgical Intervention for Severe Aortic Valve Stenosis: A Systematic Review

Aortic stenosis is a disease that is increasing in prevalence and manifests as decreased cardiac output, which if left untreated can result in heart failure and ultimately death. It is primarily a disease of the elderly who often have multiple comorbidities. The advent of transcatheter aortic valve therapies has changed the way we treat these conditions. However, long-term results of these therapies remain uncertain. Recently, there has been an increasing number of studies examining the role of both surgical aortic valve replacement and transcatheter aortic valve replacement. We therefore performed a systematic review using Ovid MEDLINE, Ovid Embase, and the Cochrane Library. Two investigators searched papers published between January 1, 2007, and to date using the following terms: "aortic valve stenosis," "aortic valve operation," and "transcatheter aortic valve therapy." Both strategies in aortic stenosis treatment highlighted specific indications alongside the pitfalls such as structural valve degeneration and valve thrombosis which have a bearing on clinical outcomes. We propose some recommendations to help clinicians in the decision-making process as technological improvements make both surgical and transcatheter therapies viable options for patients with aortic stenosis. Finally, we assess the role of finite element analysis in patient selection for aortic valve replacement. THVT and AVR-S are both useful tools in the armamentarium against aortic stenosis. The decision between the two treatment strategies should be best guided by a strong robust evidence base, ideally with a long-term follow-up. This is best performed by the heart team with the patient as the center of the discussion.

Stentless Pericarbon Freedom Versus Stented Perimount Aortic Bioprosthesis: Propensity-Matched Long-Term Follow-Up

OBJECTIVE

Stentless aortic valves have shown superior hemodynamic performance and faster left ventricular mass regression compared to stented bioprostheses. Yet, controversies exist concerning the durability of stentless valves. This case-matched study compared short- and long-term clinical outcomes of stentless LivaNova-Sorin Pericarbon Freedom™ (SPF) and stented Carpentier-Edwards Perimount (CEP) aortic prostheses.

METHODS

From 2003 through 2006, 134 consecutive patients received aortic valve replacement with SPF at our institution. This cohort was matched, according to 20 preoperative clinical parameters, with a control group of 390 patients who received CEP prosthesis during the same time. The resulting 55 + 55 matched patients were analyzed for perioperative results and long-term clinical outcomes.

RESULTS

Early mortality was 0% for both groups. Lower transvalvular gradients were found in the SPF group (10.6 ± 2.9 versus 15.7 ± 3.1 mmHg, P < 0.001). Overall late mortality (mean follow-up: 10.03 years) was similar for both groups (50.1% versus 42.8%, P = 0.96). Freedom from structural valve degeneration (SVD) at 13 years was similar for both groups (SPF = 92.3%, CEP = 73.9%, P = 0.06). Freedom from aortic valve reinterventions did not differ (SPF = 92.3%, CEP = 93.5%, P = 0.55). Gradients at 13-year follow-up remained significantly lower in SPF group (10.0 ± 4.5 versus 16.2 ± 9.5 mmHg, P < 0.001). Incidence of acute bacterial endocarditis (ABE) and major adverse cardiovascular and cerebrovascular events (MACCE) was similar.

CONCLUSIONS

SPF and CEP demonstrated comparable long-term outcomes related to late mortality, SVD, aortic valve reinterventions, and incidence of ABE and MACCE. Superior hemodynamic performance of SPF over time can make this valve a suitable choice in patients with small aortic root and large body surface area.

Stented versus Stentless Aortic Valve Replacement in Patients with Small Aortic Root

Objective

The aim of the study was to compare hemodynamic and perioperative outcomes of stented against stentless aortic valve replacement in patients with small aortic root (21 mm or less).

Methods

A comprehensive search was undertaken among the four major databases (PubMed, Embase, Scopus, and Ovid) to identify all randomized and nonrandomized controlled trials comparing stentless to stented bioprosthetic valves in small aortic root patients. Odds ratios, weighted mean differences, or standardized mean differences and their 95% confidence intervals were analyzed.

Results

A total of seven studies with a total of 965 patients fulfilled the inclusion criteria. There was no significant difference in preoperative baselines including mean age between both groups ( P = 0.08), peak aortic valve gradient ( P = 0.06), and effective orifice area ( P = 0.28), whereas higher mean aortic valve gradient in the stented group ( P = 0.007). No difference in cardiopulmonary bypass time ( P = 0.74), aortic cross-clamp times ( P = 0.88), intensive care unit stay ( P = 0.13), and stroke rate ( P = 0.56) were noted. However, stented group of patients showed higher rate of patient prosthesis mismatch ( P = 0.0001) and longer total hospital stay ( P = 0.002). Postoperatively, stentless group showed lower peak and mean aortic valve gradient ( P = 0.003 and P = 0.008, respectively) with a better effective orifice area ( P < 0.00001) at 6 months of follow-up. Mortality rates while in-hospital and at 1 year were similar in both groups ( P = 0.94 and P = 0.86, respectively).

Conclusions

Stentless aortic valves offer superior short-term hemodynamic outcomes in patients with small aortic root when compared with stented aortic valves. Although both groups have similar perioperative complications rates, stentless valves bring about a shorter hospital stay. A further large multicenter randomized controlled trial should address the longer-term benefit of stentless aortic valve over stented valve.

Aortic Valve Reoperation After Stentless Bioprosthesis: Short- and Long-Term Outcomes

BACKGROUND

Limited data are available regarding outcomes for stentless aortic valve reoperation. The reported reoperative mortality has been unacceptably high.

METHODS

Between 1997 and 2017, a retrospective analysis was performed on 143 patients who underwent open aortic valve reoperations for failed stentless aortic valve bioprostheses. We evaluated both short-term and long-term outcomes on this cohort of patients.

RESULTS

Bicuspid aortic valve was present in 107 of 143 patients (75%) at the time of the initial Freestyle (Medtronic, Minneapolis, MN) procedure, and 120 of 143 patients (84%) underwent a modified inclusion aortic root replacement procedure. The interval from first operation to reoperation was 9 years (range, 5.4 to 11.8), which was significantly shorter for patients with infectious endocarditis (4.1 years; range, 1.8 to 7.1) compared with patients with structural valvular deterioration (10.4 years; range, 8.1 to 12.4, p < 0.001). The median age at the time of reoperation was 59 years (range, 50 to 67). Aortic valve reoperation was performed for structural valve deterioration in 68% cases compared with 32% for infectious prosthetic valve endocarditis. Concomitant surgery included coronary artery bypass (13%), mitral valve surgery (4%), and ascending aorta and arch replacement (42%). The 30-day and inhospital mortality was 1% and 2%, respectively. The composite outcome including myocardial infarction, stroke, new-onset renal failure on hemodialysis, and operative mortality was 4%. The 5-year and 10-year Kaplan-Meier survival after reoperation for failed stentless valve was 83% (95% confidence interval: 73% to 89%) and 57% (95% confidence interval: 36% to 74%).

CONCLUSIONS

Aortic valve reoperation after stentless valve implantation can be performed with low operative mortality and favorable long-term survival.

Early and mid-term haemodynamic performance and clinical outcomes of St. Jude Medical Trifecta™ valve

Background

New models of aortic bioprostheses have proven excellent early haemodynamic profile, but their mid and long-term performance warrants further systematic assessment. The aim of this study is to report clinical and haemodynamic performance of St. Jude Medical Trifecta bioprosthesis during 5 years of implantation.

Methods

We performed a single centre, retrospective, observational and descriptive study including all 556 individuals who underwent aortic valve replacement (AVR) with the Trifecta bioprosthesis (between July of 2011 and June of 2016). Survival and re-intervention were censored in February 2017. Postoperative ambulatory echocardiographic data was available for 490 patients. A complete clinical follow-up was available in 463 individuals (mean follow-up time, 27±17 months).

Results

In our sample the mean age was 73±9 years, 57.6% were male and median European System for Cardiac Operative Risk Evaluation (EuroSCORE) II was 2.9 (interquartile range, 1.6-5.8). There were 301 (54.1%) combined procedures, mostly coronary artery bypass grafting in 170 (30.6%). Overall 30-days mortality was 5.4% (n=30) and cumulative survival at 5-years was 72.3%. There were 23 (4.3%) permanent pacemaker implantations. During follow-up, 5 (0.9%) patients presented non-structural valve dysfunction (NSVD) and 4 (0.8%) underwent reoperation due to prosthesis endocarditis. At the first ambulatory evaluation transvalvular mean gradient and effective orifice area (EOA) were 10.9±4.1 mmHg and 2.0±0.5 cm², respectively. Severe patient-prosthesis mismatch (PPM) was observed in 5 (1.1%) individuals and moderate in 52 (11.3%).

Conclusions

In a "real-world" clinical setting, our findings support the good overall mid-term haemodynamic and safety profile of the Trifecta bioprosthesis.

Biological aortic valve replacement: advantages and optimal indications of stentless compared to stented valve substitutes. A review

Controversy still surrounds the optimal biological valve substitute for aortic valve replacement. In light of the current literature, we review advantages and optimal indications of stentless compared to stented aortic bio-prostheses. Recent meta-analyses, prospective randomized controlled trials and retrospective studies comparing the most frequently used stentless and stented aortic bio-prostheses were analyzed. In the present review, the types and implantation techniques of the bio-prosthesis that are seldom taken into account by most studies and reviews were integrated in the interpretation of the relevant reports. For stentless aortic root bio-prostheses, full-root vs. sub-coronary implantation offered better early transvalvular gradients, effective orifice area and left ventricular mass regression as well as late freedom from structural valve deterioration in retrospective studies. Early mortality and morbidity did not differ between the stentless and stented aortic bio-prostheses. Early transvalvular gradients, effective orifice area and regression of left ventricular hypertrophy were significantly better for stentless, especially as full-root, compared to stented bio-prostheses. The long-term valve-related survival for stentless aortic root and Toronto SPV bio-prosthesis was as good as that for stented pericardial aortic bio-prostheses. For full-root configuration this survival advantage was statistically significant. There seems to be not one but different ideal biological valve substitutes for different subgroups of patients. In patients with small aortic root or exposed to prosthesis-patient mismatch full-root implantation of stentless bio-prostheses may better meet functional needs of individual patients. Longer follow-ups on newer generation of stented bio-prostheses are needed for comparison of their hemodynamic performance with stentless counterparts especially in full-root configuration.

Current indications for stentless aortic bioprostheses

The best aortic prostheses have been debated for decades. The introduction of stentless aortic bioprostheses was aimed at improving hemodynamics and potentially the durability of aortic bioprostheses. Despite the good short- and long-term outcomes after implantation of stentless aortic bioprostheses, their use remains limited owing to the technically demanding implantation techniques. Nevertheless, stentless aortic bioprostheses might be of special benefit in certain indications, where they could be a valuable addition to the surgical armamentarium.

A propensity matched analysis of outcomes and long term survival in stented versus stentless valves

BACKGROUND

To compare the perioperative and long term survival after aortic valve replacement using stentless versus stented valves in a large cohort of patients grouped using propensity score matching.

METHODS

From 1991 to 2012, 4,563 patients underwent aortic valve replacement with stentless and stented valves at our institution. Propensity score matching identified 444 pairs using 13 independent variables: incidence of operation, smoking status, renal failure, hypertension, diabetes, peripheral vascular disease, cerebrovascular disease, chronic lung disease, ejection fraction, gender, age, valve status, and use of coronary artery bypass graft. Data were collected from our Society of Thoracic Surgeons database and the Social Security Death Index. Groups were compared using univariate and Kaplan-Meier analysis.

RESULTS

The two groups demonstrated no significant differences for the 13 matching variables and the majority of 30-day outcomes (p > 0.05). The stented valve group showed a higher incidence of postoperative bleeding (3.6% vs 1.1%, p = 0.015), but a lower incidence of stroke (0.9% vs. 2.9%, p = 0.028). One, five, and 10-year survival was 95.0, 80.7, and 52.8% for stented and 93.2, 80.5, and 51.3% for stentless valves. Overall survival did not differ significantly between the two groups (p = 0.641).

CONCLUSIONS

Stentless and stented valves had identical 30-day outcomes except for a higher postoperative incidence of bleeding and a lower incidence of stroke in the stented group. There was no significant difference in long term survival between valve types. Both valves may be used for aortic valve replacement with low morbidity and excellent long term survival.

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.

Hospital-Based HTA and Know4Go at MEDICI in London, Ontario, Canada

The majority of healthcare in Canada is universally provided and publicly funded through the provincial government.

Long Term Outcomes Following Freestyle Stentless Aortic Bioprosthesis Implantation: An Australian Experience

BACKGROUND

The Freestyle stentless bioprosthesis (FSB) has been demonstrated to be a durable prosthesis in the aortic position. We present data following Freestyle implantation for up to 10 years post-operatively and compare this with previously published results.

METHODS

A retrospective cohort analysis of 237 patients following FSB implantation occurred at five Australian hospitals. Follow-up data included clinical and echocardiographic outcomes.

RESULTS

The cohort was 81.4% male with age 63.2±13.0 years and was followed for a mean of 2.4±2.3 years (range 0-10.9 years, total 569 patient-years). The FSB was implanted as a full aortic root replacement in 87.8% patients. The 30-day all cause mortality was 4.2% (2.0% for elective surgery). Cumulative survival at one, five and 10 years was 91.7±1.9%, 82.8±3.8% and 56.5±10.5%, respectively. Freedom from re-intervention at one, five and 10 years was 99.5±0.5%, 91.6±3.7% and 72.3±10.5%, respectively. At latest echocardiographic review (mean 2.3±2.1 years post-operatively), 92.6% had trivial or no aortic regurgitation. Predictors of post-operative mortality included active endocarditis, acute aortic dissection and peripheral vascular disease.

CONCLUSIONS

We report acceptable short and long term outcomes following FSB implantation in a cohort of comparatively younger patients with thoracic aortic disease. The durability of this bioprosthesis in the younger population remains to be confirmed.

Hemodynamic behavior of stentless aortic valves in long term follow-up

OBJECTIVES

Stentless aortic valve replacements show improved hemodynamics due to larger orifice area and lower transvalvular gradients in short and mid-term follow-up. Hemodynamic long-term behavior and the adaptation of the left ventricle as well as valve-durability in patients aged ≤60 years remains unclear.

METHODS

7 to 16 years after aortic valve replacement, 54 patients (mean age at operation 53.1 ± years) received echocardiography and clinical examination. Mean follow-up time was 10.8 ± 2.2 years. Evaluated were NYHA class, transvalvular gradients, estimated aortic valve orifice area, degree of aortic valve insufficiency, left ventricular mass and function.

RESULTS

At follow-up only one patient presented with NYHA class III. All other patients were in NYHA class I or II. Maximum and mean pressure gradients of the prostheses were 16.3 ± 7.4 mmHg and 9.1 ± 4.2 mmHg, respectively. Compared to echocardiography at discharge the mean pressure gradients dropped 18.0% (2.0 ± 0.9 mmHg) and stayed stable until 14 years after the operation. Only 5 patients showed relevant regurgitation (at 13-16 years after valve replacement), 49 showed no or trivial regurgitation. Left ventricular mass had decreased 26.5% (107.9 ± 18.5 g). Left ventricular ejection fraction (LVEF) had increased in most patients and decreased in only one. For patients with preoperatively impaired left ventricular function an increase of LVEF of 13.1 ± 3.1% was seen.

CONCLUSION

Porcine stentless aortic valves provide excellent hemodynamic long-term results without significant rise of transvalvular pressure gradients or relevant insufficiencies until 14 years after implantation, leading to sustained decrease of left ventricular mass and improvement of left ventricular function.

The freestyle aortic bioprosthesis: a systematic review

BACKGROUND

The Medtronic Freestyle bioprosthesis (FSB) provides an alternative to other prostheses for both aortic valve and aortic root surgery. This paper is a systematic review of the post-operative outcomes in patients with aortic valve and/or aortic root disease following FSB implantation.

METHODS

Electronic databases were searched for primary analysis, prospective randomised studies comparing the FSB with an alternative aortic prosthesis were included. Additionally, case series that included data for at least 100 individual operated patients were used for secondary analysis.

RESULTS

Among three identified randomised studies, 199 FSB cases were compared with homografts, and stented and an alternative stentless bioprosthesis. The FSB showed comparable hospital mortality (4.5% vs. 5.3%) and eight-year actuarial survival (80±5.0% versus 77±6.0%) with the homograft (respectively) and comparable reduction in left ventricular mass index relative to other prosthesis types. Over 6000 individual patients were included in the selected 15 case series. Weighted mean operative mortality, neurological event rate and five-year actuarial survival was 5.2%, 5.5% and 77.8%, respectively.

CONCLUSION

The FSB performed comparably against alternative prostheses regarding in-hospital mortality, long-term survival and reduction in left ventricular mass index. Included case series demonstrated robust post-operative outcomes in both the short and long term.

Stentless aortic valve replacement in the young patient: long-term results

Background

Stentless aortic valve replacement (SAVR) became a common surgical procedure to treat aortic valve disease, as it offers larger orifice area and improved hemodynamics. The aim of our single-centre retrospective study was to assess long term results of first generation stentless aortic valves in young patients, where mechanical prostheses are considered first line therapy.

Methods

From 1993 to 2001, 188 (149 male and 39 female) patients (≤60 years) underwent SAVR. Indications were in 63.3% stenosis or mixed lesions and in 36.7% isolated regurgitation. Mean age of patients at surgery was 53.1 ± 7.1 years. Associated procedures were performed in 60 patients (31.9%). Follow-up data were acquired through telephone interviews. Follow-up was 90.4% complete at a mean of 8.8 ± 4.7 years. Total follow-up was 1657.6 patient-years with a maximum of 17 years.

Results

Overall hospital mortality was 3.2% (2.5% for isolated SAVR). Overall actuarial survival-rate at 10/15 years and freedom from reoperation at 10/14 years were 73.0% ± 3.5%/ 55.8% ± 5.4% and 81.0% ± 3.4%/ 58.0% ± 7.5%, respectively. For isolated SAVR, actuarial survival at 10/15 years and freedom from reoperation at 10/14 years were 70.1% ± 4.4%/ 64.1% ± 4.8% and 83.1% ± 4.0%/ 52.9% ± 9.0%, respectively. Reoperation was performed in 42 patients (22.3%) due to structural valve deterioration and endocarditis. Age (≤50 years) and associated procedures did not significantly lower survival and freedom from reoperation, however, small prosthesis sizes (≤25 mm) did.

Conclusion

In patients aged 60 and younger, SAVR provides reliable long-term results especially for larger aortic 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.

Stentless versus Stented Bioprosthetic Aortic Valves

Objective

The purpose of this consensus conference was to determine whether stentless bioprosthetic valves improve clinical and resource outcomes compared with stented valves in patients undergoing aortic valve replacement, and to outline evidence-based recommendations for the use of stentless and stented bioprosthetic valves in adult aortic valve replacement.

Methods

Before the consensus conference, the best available evidence was reviewed in that systematic reviews, randomized trials, and nonrandomized trials were considered in descending order of validity and importance. At the consensus conference, evidence-based statements were created, and consensus processes were used to determine the ensuing recommendations. The American Heart Association/American College of Cardiology system was used to label the level of evidence and class of recommendation.

Results and Recommendations

Seventeen randomized studies published in 23 articles involving 1317 patients, and 14 nonrandomized trial published in 18 articles involving 2485 patients were included in the meta-analysis and consensus conference. All randomized trials inserted the stentless bioprosthetic valves in the subcoronary configuration. The consensus panel agreed upon the following statements and recommendations in patients undergoing aortic valve replacement: 1. Stentless and stented valves both provide an excellent valve substitute for aortic valve disease (class I, level A). 2. In certain situations, the early superior hemodynamic performance of stentless bioprosthesis offers advantages over stented valves (class IIa, level A). Because there were no randomized control trial comparing subcoronary stentless prosthetic valve and root replacement, the following recommendations are derived from expert opinion: 1. In the absence of aortic root disease and with an annulus greater than or equal to 21 mm, either stentless or stented valves are acceptable alternatives for the majority of patients when a current (second or third) generation bioprosthesis is indicated (class I, level C). 2. In the presence of an aortic annulus <21 mm, the use of a freestanding bioprosthetic root can be considered as an alternative to enhanced diameter stented bioprosthesis or a root enlargement procedure (class I, level C).