Aortic valve replacement with stentless and stented porcine valves: a case-match study

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.

Midterm Outcomes of Stented Versus Stentless Bioprosthetic Valves After Aortic Root Replacement

To determine the impact of aortic root replacement (ARR) with a stentless bioprosthetic valve on midterm outcomes compared to a stented bioprosthetic valve-graft conduit. This was an observational study of aortic root operations from 2010 to 2018. All patients with a complete ARR for nonendocarditis reasons were included, while patients undergoing valve-sparing root replacements or primary aortic valve replacement or repair were excluded. Of the patients with a complete ARR, bioprosthetic valve implants were included, while mechanical valve implants were excluded. Patients were dichotomized into the stented ARR group and the stentless ARR group. A total of 1:1 nearest neighbor propensity matching was employed to assess the association of stentless valves with short-term and midterm outcomes. A total of 455 patients underwent a complete ARR with a bioprosthetic valve implant for nonendocarditis reasons, of which 212 (46.6%) received a stented valve, while 243 (53.4%) received a stentless valve. After matching, postoperative outcomes were similar across each group (P > 0.05), including operative mortality and adverse neurologic events. Median follow-up for the entire cohort was 4.41 years (95% CI: 4.01, 4.95). At 1 year follow-up, aortic regurgitation ≥ 2+ and ejection fraction were similar across each group (P > 0.05); however, the stentless valve group had lower aortic valve velocity and transvalvular pressure gradient. Finally, reoperations and survival were similar for each group over the study's follow-up (P > 0.05). Stentless valves may provide hemodynamic benefits after ARR; however, the clinical impact of those benefits for survival and reoperation may not yet be evident in the midterm.

Treatment of aortic valve endocarditis with stented or stentless valve

OBJECTIVE

The study objective was to provide evidence for choosing a bioprosthesis in treating patients with active aortic valve endocarditis.

METHODS

From 1998 to 2017, 265 patients with active aortic valve endocarditis underwent aortic valve replacement with a stented valve (n = 97, 37%) or a stentless valve (n = 168, 63%) with further breakdown into inclusion technique (n = 142, 85%) or total root replacement (n = 26, 15%). Data were obtained from the Society of Thoracic Surgeons database aided with chart review, surveys, and National Death Index data.

RESULTS

The median age of patients was 53 years (43-56) in the stented group and 57 years (44-66) in the stentless group. The stented and stentless groups had high rates of heart failure (54% and 40%), liver disease (16% and 7.7%), prosthetic valve endocarditis (14% and 48%), root abscess (38% and 70%), and concomitant ascending aorta procedures (6.2% and 22%), respectively. The stentless group required permanent pacemakers in 11% of cases. Operative mortality was similar between groups (6.2% and 7.1%). The 5-year survival was 52% and 63% in the stented and stentless groups, respectively. Significant risk factors for long-term mortality included liver disease (hazard ratio, 2.38), previous myocardial infarction (hazard ratio, 1.64), congestive heart failure (hazard ratio, 1.63), and renal failure requiring dialysis (hazard ratio, 4.37). The 10-year cumulative incidence of reoperation was 12% and 3.4% for the stented and stentless groups, respectively. The 10-year freedom from reoccurrence of aortic valve endocarditis was 88% for the stented and 98% for the stentless groups.

CONCLUSIONS

Both stented and stentless aortic valves are appropriate conduits for replacement of active aortic valve endocarditis for select patients.

Midterm outcomes of subcoronary stentless porcine valve versus stented aortic valve replacement

INTRODUCTION

Stentless porcine xenografts are versatile bioprosthetic valves with the advantage of improved hemodynamics that mimic the function of the native aortic valve. However, these bioprostheses are challenging to implant in the subcoronary position.

METHODS

All consecutive patients who underwent a bioprosthetic aortic valve replacement (AVR) were included from our institutional database. Cox regression analysis was preformed to determine significant predictors for mid term mortality as well as all cause, cardiac, and heart failure readmission.

RESULTS

Patients in the subcoronary stentless group were older and more likely to be female and were likely to have a higher Society of Thoracic Surgery risk of mortality. Survival was superior in the stented AVR cohort at 30-days (96.4% vs 90.5%; P < .001), 1-year (90.5% vs 71.6%; P < .001), and 5-year (74.5% vs 56.9%; P < .001) follow up. Acute kidney injury (16.22% vs 5.22%; P < .001) and blood product transfusion (70.27% vs 44.0%; P < .001) were higher in the stentless group. Multivariable analysis revealed subcoronary stentless implantation as a significant independent risk factor for mortality (hazards ratio: 1.92 [1.35,2.72]; P < .001).

CONCLUSION

Stentless porcine xenograft implantation with the Freestyle bioprosthetic in the subcoronary position can be successfully performed in select patients, but its use is associated with increased perioperative morbidity and mortality affecting midterm outcomes. Individual patient selection and surgeon experience are important to ensure favorable outcomes.

Surgery for Young Adults With Aortic Valve Disease not Amenable to Repair

Aortic valve replacement is the gold standard for the management of patients with severe aortic stenosis or mixed pathology that is not amenable to repair according to currently available guidelines. Such a simplified approach may be suitable for many patients, but it is far from ideal for young adults considering emerging evidence demonstrating that conventional valve replacement in this cohort of patients is associated with inferior long-term survival when compared to the general population. Moreover; the utilisation of mechanical and bioprosthetic valves can significantly impact on quality and is linked to increased rates of morbidities. Other available options such as stentless valve, homografts, valve reconstruction and Ross operation can be an appealing alternative to conventional valve replacement. Young patients should be fully informed about all the options available - shared decision making is now part of modern informed consent. This can be achieved when referring physicians have a better understanding of the short and long term outcomes associated with every intervention, in terms of survival and quality of life. This review presents up to date evidence for available surgical options for young adults with aortic stenosis and mixed disease not amenable to repair.

Those who do not remember the past are condemned to repeat it

Transcatheter aortic valve replacement (TAVR) for aortic valve stenosis has rapidly progressed from its initial application in the inoperable or high-risk patients to those determined to be intermediate and low risk. It is our concern this has occurred without adequate knowledge or examination of the long-term durability of TAVR valves and the impact on subsequent aortic valve surgery, should it be required. In this editorial, we provide insight and reflect upon lessons learned from past surgical techniques and their subsequent abandonment.

Aortic Valve Replacement with the Medtronic Freestyle Stentless Bioprosthesis

During a five-year period from 1996 to 2000, the Medtronic Freestyle stentless bioprosthesis was implanted in 310 patients of advanced age. Age at operation ranged from 60 to 90 years (mean, 76 ± 4 years). 191 patients were female and 119 male. All implants were done by the modified subcoronary method using our own modification which enabled an improved adaptation of the porcine aortic root to the human anatomy. Two sinuses were scalloped and the third left intact. Additional coronary bypass grafts were necessary in 129 (39%) patients and mitral valve procedures in 23 (7%). Mean perfusion time was 109 ± 12 minutes and crossclamp time 87 ± 8 minutes. 16 (5%) patients died perioperatively. Another 17 (5.7%) patients died during a 1 to 5.6 year follow-up (mean, 2.9 years). There was only one valve related death due to infection of the valve. In spite of the advanced age, 95% of the survivors were free from cardiac symptoms and continued to live an active and fruitful life. The biological nature of the valve and the low gradients are perhaps reasons for the good results. The long-term results are expected to be good.

Aortic Valve Replacement with Toronto SPV in Elderly Patients: 10-Year Results

A retrospective assessment of clinical and echocardiographic variables was performed in 145 patients who received a Toronto SPV aortic valve replacement. The majority (90%) of these elderly patients (mean age, 75.5 ± 7.4 years) were preoperatively in New York Heart Association class III–IV. Operative mortality was 4.8%. Follow-up was complete up to 10 years and revealed few valve-related complications: thromboembolism (7), bleeding (4), and prosthesis dysfunction necessitating reoperation (3). Late mortality was cardiac-related in 11.7% and noncardiac-related in 17.2%. Actuarial survival was 83% at 5 years and 63% at 8 years. Echocardiography showed low transvalvular gradients (peak, 17.5 ± 7.5 mm Hg; mean, 9.2 ± 4.2 mm Hg) resulting in a significant reduction in left ventricular mass index during the first 3 years. Independent of the transprosthetic gradient, left ventricular mass index tended to increase again beyond the 5th year, which correlated positively with the presence of arterial hypertension in this older population. The Toronto SPV bioprosthesis offers an aortic valve substitute with excellent long-term hemodynamics, resulting in significant early left ventricular mass regression. Considering the limitations of this selected elderly population, the clinical outcome and survival up to 10 years are encouraging, with few observed valve-related events.

Aortic valve replacement and prosthesis-patient mismatch in the era of trans-catheter aortic valve implantation

Objective

The treatment strategy for aortic stenosis (AS) has been changing due to newly developed valvular prostheses and trans-catheter aortic valve implantation (TAVI). To determine the role of new modalities for AS with a small aortic root, papers using the concept of prosthesis-patient mismatch (PPM) were reviewed.

Methods

First, to determine the cut-off value of the indexed effective orifice area (IEOA) for defining PPM, the studies of surgical aortic valve replacement (SAVR) with a follow-up longer than 5 years and a patient number larger than 500 were reviewed. Second, the papers comparing TAVI and SAVR were reviewed. Furthermore, the prevalence of PPM was reviewed, with the addition of papers on aortic root enlargement, sutureless AVR, and aortic valve reconstruction with autologous pericardium.

Results and conclusion

The results of the long-term survival after aortic valve replacement (AVR) have indicated that an IEOA less than 0.65 cm²/m² should be avoided in all cases, whereas the indications for patients with an IEOA between 065 and 0.85 cm²/m² should be determined by considering multiple factors. A large body size and younger age have a significantly negative influence on the long-term survival. In Asian population, the prevalence of PPM was low, despite the fact that the size of the aortic annulus was small. The IEOA after TAVI was larger than after surgical AVR in population-matched studies. To evaluate the role of TAVI and other modalities for a small aortic root, studies with a longer follow-up and larger volume are thus warranted.

Prosthesis-patient mismatch causes a significantly increased risk of operative mortality in aortic valve replacement

BACKGROUND

Small aortic prosthesis can lead to prosthesis-patient mismatch (PPM). Implanting such small prosthesis remains a controversial issue. This study was done to investigate whether or not PPM causes an increased operative mortality in aortic valve replacement (AVR).

METHODS

Two-hundred-two consecutive patients undergoing primary AVR in a tertiary hospital were included. The sample was grouped according to the aortic valve prosthesis size: ≤21 mm (small) and >21 mm (standard). The effect of variables on outcomes was determined by univariate and multivariable regression analyses.

RESULTS

PPM was found significantly more among patients with AVR ≤ 21 mm (P < 0.0001). Moreover, the likelihood of mortality also was significantly higher in these patients (P < 0.0001). Univariate analysis demonstrated small prosthesis size, urgent operation, PPM, female gender, and NYHA Class IV as significant predictors of mortality. Multivariate regression identified female gender, PPM, and urgent operation as the key independent predictors of mortality.

CONCLUSION

PPM and female gender are significant predictors of mortality. Care should be taken to prevent PPM by implanting larger prosthesis especially in females.

Predictors of the size of prosthetic aortic valve and in-hospital mortality in aortic valve replacement

Purpose:

We hypothesized that gender, age, aortic root dimension, blood group and Left Ventricular End Diastolic and Systolic Diameters may have a significant correlation with the size of mechanical valve used.

Methods:

We included 48 patients retrospectively who had been operated at a single tertiary hospital. All patients with aortic stenosis or regurgitation were included in the study. Patients who had undergone previous cardiac surgery or concomitant surgical procedures, such as coronary artery bypass grafting, were excluded from the study.

Results:

The median size of the valves used in males (23mm) and females (21mm) were significantly different (P = 0.001). Size of the valve used was significantly associated with Left Ventricular End Systolic Diameter (LVESD) (r = 0.327, P = 0.007) and aortic root dimension (r = 0.526, P < 0.001). Moreover, significantly higher values of LVESD were observed in the expired patients (P = 0.023).

Conclusion:

This study shows that aortic root dimension and gender may be important predictors for the size of the prosthetic aortic valve used in aortic valve replacement. Our study also concludes that LVESD has significant relationship with in-hospital mortality. However, more long term clinical trials should be conducted to confirm these relationships.

Stentless aortic valve replacement: current status and future trends

Stentless aortic xenografts were introduced into clinical practice as aortic valve substitutes over a decade ago. Stentless prosthetic valves were expected to provide enhanced durability and more physiologic hemodynamic behavior when compared with stented bioprostheses. Whilst the former expectation has not been fulfilled, partly due to concomitantly improved durability of second-generation stented bioprostheses, the latter has consistently been satisfied in early and late clinical observation. Evidence is accumulating suggesting improved long-term survival due to more timely and thorough regression of ventricular hypertrophy. In addition, stentless xenografts have shown extreme versatility when adopted in a variety of complex clinical conditions associated with aortic valve disease, including small aortic anulus, ascending aortic aneurysm, endocarditis and left ventricular dysfunction. Future research in the form of prospective, multicenter, randomized trials must address the issues of very long-term durability and survival, while simplification in valve design is required to promote wider use of stentless valves.

Inclusion cylinder method for aortic valve replacement utilising the Ross operation in adults with predominant aortic stenosis - 99% freedom from re-operation on the aortic valve at 15 years

BACKGROUND

To report our experience with the Ross operation in patients with predominant aortic stenosis (AS) using an inclusion cylinder (IC) method.

METHODS

Out of 324 adults undergoing a Ross operation, 204 patients of mean age of 41.3 years (limits 16-62) underwent this procedure for either AS or mixed AS and regurgitation (AS/AR) between October, 1992 and February, 2012, implanting the PA with an IC method. Clinical follow up and serial echo data for this group is 97% complete with late mortality follow up 99% complete.

RESULTS

There has been zero (0%) early mortality, and late survival at 15 years is 98% (96%, 100%). Only one re-operation on the aortic valve for progressive aortic regurgitation (AR) has been required with freedom from re-operation on the aortic valve at 15 years being 99% (96%, 100%). The freedom from all re-operations on the aortic and pulmonary valves at 15 years is 97% (94%, 100%). Echo analysis at the most recent study shows that 98% have nil, trivial or mild AR. Aortic root size has remained stable, shown by long-term (15 year) echo follow up.

CONCLUSIONS

In an experience spanning 19 years, the Ross operation used for predominant AS using the IC method described, results in 99% freedom from re-operation on the aortic valve at 15 years, better than any other tissue or mechanical valve. For adults under 65 years without significant co-morbidities who present with predominant AS, the pulmonary autograft inserted with this technique gives excellent results.

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.

Animal models for the atherosclerosis research: a review

Atherosclerosis is a leading cause of death worldwide, and its mechanisms are still unclear. However, various animal models have significantly advanced our understanding of the mechanisms involved in atherosclerosis and have allowed the evaluation of therapeutic options. The aim of this paper is to review those animal models (i.e., rabbits, mice, rats, guinea pigs, hamsters, avian, carnivores, swine, and, non-human primates) that have been used to study atherosclerosis. Though there is no single perfect animal model that completely replicates the stages of human atherosclerosis, cholesterol feeding and mechanical endothelial injury are two common features shared by most models of atherosclerosis. Further, with the development of genetically modified animals, these models are significantly broadening our understanding of the pathogenesis of atherosclerosis.

Future of cardiac surgery: minimally invasive techniques in sutureless valve resection

Aortic valve replacement with mechanical or biological heart valves is the treatment of choice for aortic valve stenosis when it is symptomatic or with severe aortic stenosis (≤ 0.6 cm2/m2) or with left ventricular dysfunction. In an effort to improve the outcomes of patients with stented biological valves, stentless valves were introduced to clinical practices in the early 1990s. Theses valves were designed to be less obstructive, and thus result in a lower transvalvular gradient. Technically the implantations of these valves are more demanding resulting in longer cross clamp and bypass times. However, important comorbid conditions in elderly patients referred for aortic valve replacement require alternative treatment options with possible reductions of the extracorporeal bypass time and reliable hemodynamic features. In order to comply with these requirements, percutaneous valves and sutureless surgical valves have been developed. The percutaneous technique has the advantage of being performed without circulatory bypass but leaving the aortic calcifications in place, thereby resulting in a high degree of paravalvular insufficiency, atrioventricular block and strokes. The surgical approach has the advantage of removing all calcifications and the valves can be optimally implanted, resulting in minimal paravalvular leak with a low incidence of atrioventricular block and strokes; however, it requires cardiopulmonary bypass. In addition, it can be performed with a low mortality (<3% in isolated aortic replacement, even in older patients). This article reviews the various techniques, strength and limitations of these sutureless valves implanted in the aortic position.

Effect of surgeon on transprosthetic gradients after aortic valve replacement with Freestyle stentless bioprosthesis and its consequences: a follow-up study in 587 patients

Background

The implantation of stentless valves is technically demanding and the outcome may depend on the performance of surgeons. We studied systematically the role of surgeons and other possible determinants for mid-term survival, postoperative gradients and Quality of Life (QoL) after aortic valve replacement (AVR) with Freestyle^® stentless bioprostheses.

Methods

Between 1996 and 2003, 587 patients (mean 75 years) underwent AVR with stentless Medtronic Freestyle^® bioprostheses. Follow-up was 99% complete. Determinants of morbidity, mortality, survival time and QoL were evaluated by multiple, time-related, regression analysis. Risk models were built for all sections of the Nottingham Health Profile (NHP): energy, pain, emotional reaction, sleep, social isolation and physical mobility

Results

Actuarial freedom from aortic valve re-operation, structural valve deterioration, non-structural valve dysfunction, prosthetic valve endocarditis and thromboembolic events at 6 years were 95.9 ± 2.1%, 100%, 98.7 ± 0.5%, 97.0 ± 1.5%, 79.6 ± 4.3%, respectively. The actuarial freedom from bleeding events at 6 years was 93.1 ± 1.9%. Estimated survival at 6 years was similar to the age-matched German population (61.4 ± 3.8 %). Predictors of survival time were: diabetes mellitus, atrial fibrillation, peripheral vascular disease, renal dysfunction, female gender > 80 years and patients < 165 cm with BMI < 24. Predictive models showed characteristic profiles and good discriminative powers (c-indexes > 0.7) for each of the 6 QoL sections. Early transvalvular gradients were identified as independent risk factors for impaired physical mobility (c-index 0.77, p < 0.002). A saturated propensity score identified besides patient related factors (e.g. preoperative gradients, ejection fraction, haematological factors) indexed geometric orifice area, subcoronary implantation technique and individual surgeons as predictors of high gradients.

Conclusion

In addition to the valve size (in relation to body size), subcoronary technique (versus total root) and various patient-related factors the risk of elevated gradients after stentless valve implantation depends, considerably on the individual surgeon.

Although there was no effect on survival time and most aspects of QoL, higher postoperative transvalvular gradients affect physical mobility after AVR.

Inflammation and infection in nine surgically explanted Medtronic Freestyle® stentless aortic valves

BACKGROUND

The Medtronic Freestyle valve is fixed in glutaraldehyde at zero pressure on the cusps and treated with alpha-amino oleic acid. This valve reportedly has excellent clinical and hemodynamic results, but little has been reported about its long-term pathology.

METHODS AND RESULTS

Nine Freestyle valves explanted between 2003 and 2005 were reviewed to assess the reasons for bioprosthesis failure (six implanted at our institution). All valves were examined in detail, using histochemistry and immunohistochemistry to identify the cellular response. One Freestyle valve, explanted for mitral valve endocarditis on the fifth postoperative day, was excluded from analysis. Average implant duration was 52.8+/-35.5 months. Four valves were explanted for infective endocarditis, three for aortic insufficiency, two for aortic stenosis with cusp calcification seen in five valves, pannus and thrombus in all valves and a chronic inflammatory reaction involving the xenograft arterial wall seen in eight of nine valves. This was associated with significant damage to the porcine aortic wall in seven cases, and cusp myocardial shelf damage in six cases.

CONCLUSIONS

In this series of valves, we found (1) infective endocarditis; (2) pannus, thrombus, and calcification; and (3) unusual and significant inflammatory reaction and aortic tissue damage, which could by itself lead to aortic incompetence.

Association between indices of prosthesis internal orifice size and operative mortality after isolated aortic valve replacement

OBJECTIVES

The appropriate index of prosthesis internal orifice size and its effect on operative mortality after aortic valve replacement are controversial. We examined the association between several relevant indices and patient size on operative mortality. Indices examined included projected in vivo effective orifice area and geometric orifice area, with patient size defined as body surface area.

METHODS

A review of the Society of Thoracic Surgeons National Cardiac Database (2000-2004) yielded 48,722 patients who had isolated aortic valve replacement. This analysis is based on the cohort of 42,310 patients with the 8 most prevalent valve types with manufacturer's labeled sizes 19 mm through 29 mm. Multivariable logistic regression models were employed to determine the effects of body surface area, effective orifice area, geometric orifice area, and selected derived indices (eg, effective orifice area/body surface area) on risk-adjusted operative mortality.

RESULTS

In separate multivariable models, effective orifice area and geometric orifice area were both inversely correlated with operative mortality. However, an unanticipated finding was that with either effective orifice area or geometric orifice area held constant, body surface area was significantly and inversely correlated with operative mortality. When patients were stratified by effective orifice area, geometric orifice area, or manufacturer's labeled valve size and type, elevations in body surface area were associated with a decrease rather than an increase in operative mortality.

CONCLUSIONS

Prostheses with small geometric orifice area or small effective orifice area are associated with increased operative mortality after isolated aortic valve replacement. Even for valves with small effective orifice area, however, mortality decreases as body surface area increases. With respect to operative mortality, therefore, our results do not support using arbitrary cutoff values of effective orifice area/body surface area to determine the valve to utilize in a given patient.

Stentless valves for aortic valve replacement: where do we stand?

PURPOSE OF REVIEW

Following more than a decade's experience with stentless valves and the development of better profiled stented valves, the article discusses the advantages of stentless valves regarding hemodynamic performance, left ventricular mass regression, durability and survival.

RECENT FINDINGS

Recent studies show that stentless valves remain hemodynamically superior compared with modern porcine stented valves. This superiority is, however, rarely reported in comparison with modern pericardial stented valves. In general, patient-prosthesis mismatch is less frequent in stentless vs. stented valves. Recent randomized trials comparing stentless valves and modern stented valves show equivalent left ventricular mass regression at 1 year. At 10 years, stentless valve durability is excellent and comparable with that of stented valves. Recent comparative studies do not confirm the previously reported midterm survival advantages of stentless valves.

SUMMARY

Improvement of stented valves has significantly reduced the hemodynamic differences between them and their stentless counterpart. Patients with small aortic annulus, however, should benefit from a stentless valve due to the better expected gradients and lower risk of patient-prosthesis mismatch. Midterm results suggest equivalent durability and survival for both prosthesis types but additional and longer-term trials are necessary to confirm these results.

Long-term results after aortic valve replacement with the Bravo 400 stentless xenograft

BACKGROUND

This study was undertaken to evaluate the long-term clinical and echocardiographic outcome after aortic valve replacement with the Bravo Cardiovascular Model 400 stentless xenograft.

METHODS

Between February 1992 and January 1994, 67 patients underwent aortic valve replacement with the Bravo 400 bioprosthesis. The valvular pathology was aortic stenosis in 36 patients (53.7%), aortic insufficiency in 17 patients (25.4%), and mixed lesion in 14 patients (20.9%). Mean follow-up time was 9.8 +/- 2.73 years and median follow-up time was 11 years. Cumulative follow-up time was 659 patients-years and was 94% complete.

RESULTS

No early deaths were observed. Overall survival estimates at 11 years were 74.71% +/- 5.47%. The actuarial freedom from valve-related death at 11 years was 91.04% +/- 3.84%; from cardiac-related death at 11 years it was 87.95% +/- 4.29%; and from noncardiac death at 11 years it was 85.14% +/- 4.58%. Eleven-year Kaplan-Meier survival of patients younger than 65 years was 90.91% +/- 6.13% versus 66.08% +/- 7.38% for older patients (p = 0.0307, log-rank test). The actuarial freedom from all valve-related morbidity and mortality at 11 years was 80.3% +/- 5.4%. The mean transvalvular gradient decreased significantly after aortic valve replacement with a corresponding increase in effective orifice area. Left ventricular mass index at 10-year follow-up was 68.5% of the preoperative value.

CONCLUSIONS

The Bravo Cardiovascular Model 400 stentless xenograft has provided good clinical and hemodynamic results up until 11 years of follow-up.

Factors influencing the mean postoperative gradients across stentless porcine valves

BACKGROUND

To study the preoperative and intraoperative variables influencing the mean post-operative transvalvular gradient across stentless porcine valves.

METHODS

From 1995 to 2002, 84 patients underwent stentless valve insertion. The mean age was 73 years, and 63% were male. The valve pathology was aortic stenosis (AS) in 79%, aortic regurgitation (AR) in 12%, and mixed in 9%. Valve sizes ranged from 21 to 29 with size 27 being most frequent. 54% of patients had concomitant procedures. Patients had at least yearly clinical and echocardiographic follow-up.

RESULTS

There was no operative mortality. 9.5% of the patients had significant postoperative complications. The average echo interval was 18.6 months (range 1-88). The overall mean transvalvular gradient was 9.88+/-5.67 (SD) mmHg. Variables associated with significantly reduced gradients were: larger valve sizes (p=0.002), younger age (p=0.05), pre-op AR (p=0.008), and increasing post-operative interval (p=0.05). The mean gradients decreased by 0.28 mmHg for each post-operative year. The method of implantation did not significantly affect gradients (p=0.26).

CONCLUSIONS

Excellent mean transvalvular gradients were achieved with stentless valves studied, with a low operative risk. The gradients did not appear to be related to intra-operative factors, suggesting that insertion techniques can be tailored to suit patient conditions and surgeon preferences.

Carpentier-Edwards PERIMOUNT Magna bioprosthesis: A stented valve with stentless performance?

OBJECTIVE

We designed this study to evaluate the early hemodynamic performance of the recently introduced Carpentier-Edwards PERIMOUNT Magna bioprosthesis (Edwards Lifesciences, Irvine, Calif) and compare it with those of the conventional Carpentier-Edwards PERIMOUNT stented bioprosthesis (Edwards Lifesciences) and Edwards Prima Plus porcine stentless bioprosthesis (Edwards Lifesciences).

METHODS

Sixty-three patients (>70 years old) were enrolled in this prospective, randomized study. At operation, once the annulus had been measured, the best size suitable was assessed for each of the three valves before random assignment. Transthoracic echocardiography was performed before discharge to evaluate early postoperative hemodynamic performances of the different valves implanted.

RESULTS

The best size suitable of Edwards Prima Plus (24.3 +/- 1.7 mm) was significantly superior to those of both the Carpentier-Edwards PERIMOUNT Magna (23.4 +/- 2.1 mm) and Carpentier-Edwards PERIMOUNT (22.4 +/- 1.8 mm). The best size suitable of the Carpentier-Edwards PERIMOUNT Magna, however, was significantly superior to that of the Carpentier-Edwards PERIMOUNT. Furthermore the best size suitable of the Carpentier-Edwards PERIMOUNT Magna was equal to the measured annulus in 55% of patients, as opposed to 25% for the Carpentier-Edwards PERIMOUNT (P < .001). Mean implanted labeled size of the Edwards Prima Plus was significantly higher than those of both the Carpentier-Edwards PERIMOUNT Magna and the Carpentier-Edwards PERIMOUNT (24.6 +/- 1.9 mm, 23.1 +/- 1.9 mm, and 22.5 +/- 1.8 mm, respectively). Early postoperative hemodynamic performance of the Carpentier-Edwards PERIMOUNT Magna, however, was superior to those of both the Edwards Prima Plus and the Carpentier-Edwards PERIMOUNT in both effective orifice area index (1.07 +/- 0.4 cm2/m2, 0.87 +/- 0.3 cm2/m2, and 0.80 +/- 0.2 cm2/m2, respectively) and mean peak gradient (20 +/- 6 mm Hg, 27 +/- 8 mm Hg, and 28 +/- 12 mm Hg, respectively).

CONCLUSION

The improved design of the recently introduced third-generation stented bioprosthesis Carpentier-Edwards PERIMOUNT Magna allows implantation of a significantly bigger valve than with the old generation. Furthermore, the improved hemodynamic performance of the Carpentier-Edwards PERIMOUNT Magna compares favorably with both the Carpentier-Edwards PERIMOUNT and the Edwards Prima Plus.

Stentless Aortic Valves are Hemodynamically Superior to Stented Valves During Mid-Term Follow-Up: A Large Retrospective Study

BACKGROUND

Several studies have compared left venticular mass (LVM) regression and hemodynamic data for stentless versus stented aortic bioprostheses with conflicting results. The major limitations of these studies are their small sample size and short-term follow-up. We therefore compared midterm LVM regression, hemodynamic data, and survival in a large population of tissue aortic valve replacement (AVR) patients.

METHODS

All patients undergoing tissue AVR at our institution between 1998 and 2001 were included (n = 737). Patients were divided into two groups according to type of bioprosthetic implanted: stentless patients (total n = 310) (Toronto SPV [St Jude Medical, St Paul, MN], n = 146 and Freestyle [Medtronic, Minneapolis, MN], n = 164) and stented patients (total n = 427) (Perimount [Edwards Life Sciences Inc, Irvine, CA], n = 291 and Mosaic [Medtronic], n = 136).

RESULTS

The two groups of patients had similar preoperative transvalvular gradients and LVM index (130 +/- 47 vs 130 +/- 42 g/m2 for stentless versus stented valves, respectively). Predischarge echos revealed that stentless patients had significantly lower mean transvalvular gradients (11 +/- 5 vs 15 +/- 6 mm Hg, p < 0.001) and larger effective orifice areas (1.32 +/- 0.52 vs 1.22 +/- 0.48 cm2, p = 0.01). Follow-up echocardiograms were obtained in 99% of surviving patients 28 +/- 22 (range, 0-79) months postoperatively. Stentless patients had significantly lower LVM index during follow-up (100 +/- 32 vs 107 +/- 32 g/m2, p = 0.005) and stentless valves were an independent predictor of LVM regression. Furthermore, a higher proportion of stented patients had residual LV hypertrophy during follow-up (28% vs 18%, p = 0.001). Stentless valves were associated with improved midterm survival by univariate analysis, but not by multivariable analysis.

CONCLUSIONS

Midterm follow-up in a large number of patients reveals that stentless bioprostheses are hemodynamically superior to stented valves.

Mid term outcome and quality of life after aortic valve replacement in elderly people: mechanical versus stentless biological valves

OBJECTIVE

To assess the benefit for patients older than 65 years of aortic valve replacement with stentless biological heart valves in comparison with mechanical valves.

DESIGN

Multiple regression analysis of a retrospective follow up study.

SETTING

Single cardiothoracic centre.

PATIENTS

Between 1996 and 2001, 392 patients with a mean age of 74 years underwent aortic valve replacement with stentless Freestyle bioprostheses or mechanical St Jude Medical prostheses.

MAIN OUTCOME MEASURE

Operative mortality and morbidity, postoperative morbid events, mid term survival, and New York Heart Association (NYHA) class improvement, and quality of life.

RESULTS

No significant differences were found between patients receiving stentless biological valves and patients receiving mechanical prostheses. However, analysis of subgroups showed that patients older than 75 years with mechanical valves had an increased risk of major bleeding events (p = 0.007). Patients requiring anticoagulation by means of coumarin had a twofold increased risk of an impaired emotional reaction (p = 0.052). However, for patients who received a mechanical valve for severe combined aortic valve disease a survival advantage (p = 0.045) and a decreased risk of prolonged ventilation (p = 0.001) was observed. On the other hand, patients receiving a stentless bioprosthesis had an increased risk of a prolonged stay in intensive care (p = 0.04) and stroke (p = 0.01) if they had severely reduced cardiac function (NYHA class IV).

CONCLUSIONS

Elderly people receiving stentless bioprostheses benefit emotionally because of the avoidance of coumarin. However, in patients with severe hypertrophied ventricles and extraordinary calcifications, stentless bioprostheses should be chosen with caution.

Stentless vs. stented aortic valve replacement: left ventricular mass regression

The aim of this retrospective study was to evaluate the time-related regression of left ventricular hypertrophy after stentless vs. stented aortic valve replacement. From January 1992 to December 2002, 145 patients had a Toronto stentless porcine valve and 106 had a stented Carpentier-Edwards aortic valve replacement. Over a 10-year follow-up, survival was superior in the Toronto group vs. the Carpentier-Edwards group (84% vs. 74% at 4 years; 78% vs. 68% at 6 years; p < 0.001). A significant and constant reduction of peak and mean transvalvular gradients after valve replacement resulted in substantial regression of left ventricular mass index in both groups, which did not reach statistical significance. However, this phenomenon stopped at 3 years, and left ventricular mass index increased slowly after 5 years. Stentless and stented bioprostheses both showed good early and late clinical and hemodynamic outcomes, with the advantage of better midterm survival for stentless xenografts.

CryoLife-O'Brien Stentless Valve: 10-Year Results of 402 Implants

BACKGROUND

This truly stentless porcine valve is composite, without Dacron, and implanted supra-annularly. Ten-year analysis with magnetic resonance imaging is presented.

METHODS

From 1992 to 2002, 402 patients (mean 73.5 years) had aortic valve replacement. Associated procedures were required in 252 patients (63%). Serial echoes provided 1340 studies. Clinical follow-up was 100%. Magnetic resonance imaging focused on aortic annulus extensibility.

RESULTS

The 30-day mortality was 0.99% (4 deaths). Morbidity comprised thromboembolism (40 patients including 18 patients with permanent strokes); endocarditis (9 patients); and reoperation (9 patients [periprosthetic leak, 2; endocarditis, 5; technical needle damage, 1; and structural degeneration, 1]). Of 402 valves more than 10 years, five valves were explanted, one only for structural failure. Except for endocarditis (2 patients), no late deaths (69 patients, 1.5 months to 5.7 years) were valve related. Echocardiography demonstrated low gradients with good orifice areas, excellent ventricular regression (p = 0.0001 preoperative and postoperative comparisons) and late incompetence (mild in 45 patients and moderate in 9 patients). No living patient has severe incompetence. Magnetic resonance imaging demonstrated the annulus 'expanding and relaxing' throughout the cardiac cycle, the mean increase in cross-sectional area being 37%, resembling normal aortic root dynamics.

CONCLUSIONS

Elderly patients received this hemodynamically acceptable valve with its simple, supra-annular implantation and satisfactory mid-term morbid-free lifestyle to 10 years maximum follow-up. With only one structural failure, restoration of valve annular extensibility may have a favorable influence on long-term durability.

St. Jude Medical Toronto biologic aortic root prosthesis: Early FDA phase II IDE study results

BACKGROUND

Several biological aortic root replacement techniques have distinct advantages over mechanical composite root replacement including better valvular hemodynamic characteristics and the lack of need for anticoagulation. Current biological root replacement options lack proven long-term durability or are limited by technical or practical concerns. We report the early results from a phase II multicenter clinical trial of the porcine St. Jude Toronto Bioprosthesis with BiLinx (Toronto root).

METHODS

176 Toronto roots were implanted as total aortic root replacement from August 2001 through August 2003. Concomitant cardiac procedures including coronary artery bypass grafting (31%) and ascending aortic replacement (55%) were performed in 74%. Patients were followed clinically and were examined with an echocardiogram at discharge, 6 months, 12 months, and yearly thereafter. Root sizes implanted included 29 mm in 38%, 27 mm in 30%, 25 mm in 20%, 23 mm in 10%, and 21 mm in 2.2%.

RESULTS

There are 205 patient years of follow-up through October 2003. Operative mortality was 3.9% (none were valve related) and late mortality was 4%. Operative stroke rate was 1.1% and late stroke rate was 0.6%. Endocarditis developed in 1 patient. Freedom from aortic regurgitation is to date 100% at discharge, 6 months, and 1 year postimplant. Reoperation of the aortic valve/root was not required in any patient. Six-month mean transvalvular gradients for 21-29 mm valves were 12.8, 8.8, 5.3, 4.9, and 4.7 mm Hg, respectively.

CONCLUSIONS

Aortic root replacement with the Toronto root is safe and provides superb transvalvular hemodynamics with freedom from anticoagulation. The Toronto root seems widely applicable for all types of aortic root pathology and these early data offer very encouraging results. Long-term follow-up is required.

Patient‐Prosthesis Mismatch After Small‐Size Stentless Aortic Valve Replacement

OBJECTIVE

The aim of this study was to determine the occurrence of patient-prosthesis mismatch (P-PM) after aortic valve replacement (AVR) with a small-size Cryolife O'Brien (CLOB) bioprosthesis and to evaluate its clinical and hemodynamic implications.

METHODS

Sixty-two patients (mean age 70.9 +/- 5.2 years, 77.8% females), receiving a labeled 21-23 mm CLOB between 1993 and 2000, were retrospectively studied. Effective orifice area (EOA) was calculated by the continuity equation and then indexed to the patient's body surface area (BSA) to obtain the indexed EOA (EOAI). Based on previous observations a mismatch was defined as EOAI <or= 0.85 cm2/m2.

RESULTS

Twelve patients (20%) at discharge, two (3.3%) at 6 months and none at late controls had an EOAI <or= 0.85 cm2/m2. At ANOVA determinants of mismatch were female sex (p < 0.001), age (p = 0.01), and patient's annulus index (PAI, p < 0.001). Patients with mismatch had higher mean gradients (MG, p = 0.01, and p < 0.001 at discharge and 6 months, respectively) and EOAI correlated with MG at discharge (r2= 0.72, p < 0.001) and 6-month (r2= 0.40, p = 0.001) studies. At 1 year no difference in MG was detected between patients with or without mismatch (p = ns) and EOAI did not correlate with MG (r2= 0.01, p = ns). Midwall fractional shortening did not differ in patients with or without mismatch (p = ns). Patients with an EOAI >or= 0.8 cm/m2 showed an earlier concentric remodeling up to 1 year; no difference was demonstrated at later studies between groups. Survival and clinical status results were not affected by an EOAI <or= 0.85 cm2/m2.

CONCLUSIONS

After AVR with CLOB mismatch occurred early postoperatively in a small number of patients without clinical repercussions. EOAI, significantly increasing over time, was adequate to BSA in all patients at late controls.

The next generation of prosthetic heart valves needs a proven track record of patient outcomes at > or =15 to 20 years

Currently, a selection of good, albeit not perfect, prosthetic heart valves (PHVs) with data on patient outcomes with follow-up times of 15 to 20 years or longer is available. The "next generation" of PHVs have some interesting features, but there are no data on patient outcomes at > or =15 to 20 years. The history of PHVs is that: 1) major advances have come in small increments, and 2) extrapolations made from early results were not correct at long term, and when this occurred, patients paid the price in terms of mortality and morbidity. Thus, great enthusiasm from early results and premature prediction may be inappropriate. The data on long-term outcomes are needed and in 2003 one should preferentially select a PHV with proven long-term results.

Choice of prosthetic heart valves:update for the next generation

Intervention for valvular heart disease poses unique clinical challenges in cardiology because the diseases are of relatively low prevalence, the interventions do not lend themselves to randomized comparative trials, and important clinical end points are assessed only after decades of follow-up. In addition, continuing advances in prosthetic heart valve technology make follow-up a moving target because long-term data by definition are available only for older prostheses. Newer tissue and mechanical prostheses afford superior hemodynamics compared with their older counterparts, and data suggest that durability and patient mortality are superior with newer compared with older bioprostheses. Arbitrary cutoffs dictating valve choice based predominantly on patient age may not give appropriate weight to individual patient perspectives. In educating and counseling patients regarding choices in heart valve prostheses, the clinician should help the patient weigh the relative merits for the individual patient of projected mortality, valve durability, and requirement for anticoagulation, with associated freedom from re-operation, hemorrhagic and thromboembolic risk, and impact on lifestyle.

Risk in elderly patients after stentless versus stented aortic valve surgery

Recent studies suggest that the hemodynamic advantage of stentless bioprostheses over the stented type improves long-term survival after aortic valve replacement, but the more complex and time-consuming implantation technique may increase the risks of operative death and postoperative complications. Between April 1996 and June 2001, 519 patients with a mean age of 76 +/- 5 years underwent aortic valve replacement using a stentless (Medtronic Freestyle, n = 277) or stented bioprosthesis (Medtronic Mosaic, n = 242). Multiple logistic regression analysis considering different patient populations revealed no increased risk of operative death, postoperative complications, or neurological impairment after implantation of a stentless bioprosthesis. Survival curves in respect of 367 patients who underwent aortic valve replacement up to September 2000 and were followed up for 3 years were not different (p = 0.98). As the patients were elderly, improved survival due to implantation of a stentless valve could not be demonstrated within this time span.

Current thinking in stentless valve surgery

Aortic valve replacement for aortic stenosis represents a tremendous achievement in the management of cardiac disease. However, despite 4 decades of use, the ideal substitute for the diseased aortic valve is still not agreed upon. Stentless aortic valves represent the optimum in hemodynamic performance. This article reviews the current thinking in stentless aortic valve surgery.

Quantification of haemodynamic performance of stented and stentless aortic bioprostheses and potential influence on survival

BACKGROUND

The goal of aortic valve replacement is relief of symptoms, optimisation of haemodynamics, regression of left ventricular mass and advancement of survival. The objective of this review article is to provide the evidence-to-date on the clinical performance of stented and stentless heterograft bioprostheses with regard to haemodynamics, durability and survival.

METHODS

The haemodynamic advantage of aortic valve replacement prostheses is judged on ability to minimise postoperative gradients and to optimise the normalisation of left ventricular mass and function. The most frequent cause of high postoperative gradients occurs when the effective prosthetic valve area is less than that of the normal human valve. The effective orifice area index (EOAI) of >/= 0.85 cm(2)/m(2) is considered optimal to prevent patient-prosthesis mismatch (PPM) at rest and exercise.

RESULTS

The stented bioprostheses contribute to obstructive non-physiological flow patterns whereas stentless bioprostheses provide laminar non-obstructive flow. The stentless bioprostheses have been shown to have larger effective orifice areas and lower gradients. Mismatch is decreased with stentless bioprostheses especially when prosthesis size is </=21 mm. Left ventricular mass (LVM) postoperatively has been shown to relate to baseline LVM index (LVMI) and PPM. The EOAI >0.8 cm(2)/m(2) provides the best long-term regression of LVM. It has been identified that a tendency for PPM in sizes 21 and 23 mm stented bioprostheses did not prevent adequate achievement of appropriate LVMI. Survival at 5 years favoured stentless over stented bioprostheses for patients <70 years, but not in patients >/= _70 years of age. The durability comparison of the stentless bioprostheses must wait until 10-15 years experience is achieved. There is preliminary evidence that uneven shear stress on the leaflet of a regurgitant stentless bioprosthesis can accelerate leaflet tears at the level of the commissures. Dilation of the aortic root and, particularly, the sinotubular junction, can cause progressive stentless valve insufficiency.

CONCLUSIONS

The long-term performance advantages or disadvantages of stentless bioprostheses compared to stented bioprostheses will require at least another 5-7 years of cumulative stentless bioprostheses experience. Surgeons can use an algorithm intraoperatively to prevent patient-prosthesis mismatch while choosing the optimal prosthesis.

Aortic valve disease with severe ventricular dysfunction: stentless valve for better recovery

BACKGROUND

Stentless bioprostheses and homografts show better hemodynamic profiles compared with conventional stented bioprostheses and mechanical valves. Few data are available on stentless aortic valve implantation for patients with severe left ventricular dysfunction. The aim of this retrospective study was to assess the potential benefits of stentless aortic valve implantation for patients undergoing isolated aortic valve replacement with left ventricular ejection fraction < or = 35%.

METHODS

From November 1988 through March 2000, 53 patients (45 men and 8 women, aged 64.2 +/- 15.2 years) with a LVEF < or = 35% (mean EF, 28.7 +/- 5.4%) underwent isolated, primary aortic valve replacement for chronic aortic valve disease. Twenty patients received stentless aortic valves and 33 patients received conventional stented bioprostheses and mechanical valves. Predictive factors for LVEF recovery at echocardiographic follow-up (36.2 +/- 32.1 months) were analyzed by simple and multiple regression analysis.

RESULTS

There were no significant differences between groups in early and late mortality. Stentless aortic valve implantation required a longer aortic cross-clamp time (p = 0.037). The stentless aortic valve group showed a better LVEF recovery (p = 0.016). Stentless aortic valves had a larger indexed effective orifice area compared with conventional stented bioprostheses and mechanical valves (p < 0.0001). A smaller indexed effective orifice area (p = 0.0008), chronic obstructive pulmonary disease (p = 0.015), and implantation of a conventional stented bioprosthesis or mechanical valve (p = 0.016) were related to reduced LVEF recovery by univariate analysis. A larger indexed effective orifice area (p = 0.024) was an independent predictive factor for a better LVEF recovery by multivariate analysis.

CONCLUSIONS

Stentless aortic valve implantation for patients with severe left ventricular dysfunction, even if technically more demanding, is a safe procedure that warrants a larger indexed effective orifice area leading to an enhanced LVEF recovery.