Biomechanical and flow characteristics of stentless and stented aortic valve bioprostheses

A comparative investigation of biomechanical and hydrodynamic characteristics of stentless and stented bioprostheses was carried out. It was demonstrated that stentless bioprostheses are functionally superior to stented ones. The differences between biomechanics and hydrodynamics of the examined stentless bioprostheses "BioLab", "AB-Mono-Kemerovo" and DD2 and stented bioprostheses "Wessex", "KemCor" and "Bionox-2" were shown.     

Hemodynamic performance after stented vs stentless aortic valve replacement

BACKGROUND: Stentless bioprostheses are anticipated to cause improved hemodynamics and increased longevity over stented bioprosthesis. We have compared echocardiographic analysis of stented bioprosthesis "Freestyle" with stented "Mosaic" bioprosthesis. Because of similar technology (0 pressure fixation, anticalcification) any differences may relate to stent. METHODS: Twenty-eight patients undergoing AVR were randomly assigned to receive either stented or stentless. Echocardiograms, by means of M-mode and Doppler were performed early, 3-6 months and 1 year postoperatively. RESULTS: The peak flow velocity was significantly lower in the stentless group, especially 1 week and 6 months after surgery. Mean transvalvular gradient dropped significantly in stentless group and did not change in stented group. EOA did not change significantly in either of groups. AoV velocity time integral was increasing in stentless group. LV mass had fallen significantly in both groups but degree of mass reduction was comparable. CONCLUSIONS: There are marked improvements of stentless valves hemodynamics. However it is not necessary equal to higher degree of LV mass reduction during 1 year follow-up.     

Hemodynamic performance of stented and stentless aortic bioprostheses

BACKGROUND: Acute type A aortic dissection is a surgical emergency still associated with high postoperative complications. The aim of this study was to investigate factors for hospital mortality and neurologic deficit in patients undergoing emergency operation for acute type A aortic dissection. METHODS: Eighty-five consecutive patients (age range, 20 to 82 years) operated on for acute type A aortic dissection over a 6-year period were evaluated. Univariate and stepwise multiple logistic regression analyses were conducted among 32 perioperative variables. RESULTS: All patients underwent surgical procedures under deep hypothermic circulatory arrest. Antegrade or retrograde cerebral perfusion was used in 23 patients (27.1%) and 18 patients (21.2%), respectively. Forty-three patients underwent arch/hemiarch replacement and the ascending aorta was replaced in 42 patients. Overall mortality rate was 25.9% (22 of 85 patients). Multiple logistic regression analysis showed that lack of cerebral perfusion (p = 0.021) and postoperative renal failure (p = 0.006) were the best predictors for hospital death. Twenty-one patients (24.7%) experienced neurologic accidents. The risk factor for postoperative neurologic complication was lack of cerebral perfusion (p = 0.013). Hospital mortality was 13% (3 of 23 patients) and 16.7% (3 of 18 patients) in the antegrade and retrograde cerebral perfusion groups (p > 0.05) and neurologic deficit was 13% (3 of 23 patients) and 11.1% (2 of 18 patients), respectively (p > 0.05). CONCLUSIONS: Hospital mortality and neurologic complications in patients undergoing emergent operation for acute type A aortic dissection were reduced when cerebral perfusion was used with deep hypothermic circulatory arrest.     

有支架与无支架生物瓣膜行主动脉瓣置换临床对比研究

目的　探讨无支架Medtronic生物瓣行主动脉瓣置换的临床效果。方法　将 6 8例同期施行主动脉瓣置换术病人分为 2组 ,38例行无支架Medtronic生物瓣置换 ,30例对照组行有支架生物瓣置换。术前及术后 2个月随访行超声心动图检查。结果　无支架组和有支架组病人术后各项检测指标差异有显著性意义。无支架组跨瓣压差 (18 0± 3 7)mmHg(1mmHg =0 133kPa)明显低于有支架组(33 7± 8 3)mmHg;左室射血分数 0 6 5± 0 0 5 ,明显高于有支架组 0 5 6± 0 0 8;左室收缩末内径和左室舒张末内径分别为 (3 8± 0 8)cm和 (4 5± 0 4 )cm ,明显低于有支架组 (4 2± 1 4 )cm和 (5 1± 0 9)cm ;无支架组瓣环内径 (2 2 1± 1 8)mm大于有支架组 (19 5± 1 7)mm。结论　无支架Medtronic生物瓣较有支架生物瓣具有较低的跨瓣压差和良好的血流动力学 ,能促进左室功能的恢复。     

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.     

Retrospective clinical analysis of stented vs. stentless porcine aortic bioprostheses.

OBJECTIVE: The study was designed to compare hemodynamic performance, structural failure and survival of patients undergoing aortic valve replacement (AVR) with a composite aortic stented or stentless porcine bioprosthesis. METHODS: From January 1990 to June 1999, the clinical data of 725 patients undergoing AVR with stented porcine aortic bioprosthesis were reviewed. We defined two groups of patients with similar clinical characteristics: 202 patients receiving aortic stented and 205 patients stentless valves. The two patients groups were similar in age, sex, valve lesion, valve size, preoperative New York Heart Association (NYHA) class status and follow-up. RESULTS: The number of patients available for follow-up, excluding hospital and late mortality, reoperations and patients lost to follow-up, was 157 for the stented and 175 for the stentless group. There was a higher incidence of rheumatic heart disease in the stented (59%) vs. stentless group (44%), (P=0.003). Fewer patients had prior aortic bioprosthetic dysfunction in the stented (7.6%) compared to the stentless group (25%) (P<0.001). The mean intensive care unit stay, hospital mortality and late mortality were similar (P, NS). The total complication rate was higher in the stented (12%) than the stentless (3.4%)(P=0.005). Valve related death was higher in the stented (2.5%) than the stentless (0%) (P=0. 049). Postoperatively, the aortic effective orifice area (AEOA) was larger (P<0.001) and the transvalvular peak and mean gradients were lower in the stentless group (P<0.001). The leaflet tissue degeneration analysis was 8.0% in patients at risk for stented and 0. 6% for stentless (P=0.001). Actuarial analysis disclosed no statistical difference in patient survival between groups (P=0.18). Reoperations were less frequent in the stentless group (P=0.010). CONCLUSIONS: Hemodynamic benefits in the stentless group were evident and expressed by larger AEOA, lower gradients, better left ventricular remodeling with significant decrease of the left ventricular mass. Lower complication rates, lower reoperation rates, less leaflet tissue degeneration, and lower valve related mortality rates were seen in the stentless group. A controlled clinical comparison trial with longer follow-up will be required to confirm these clinical and hemodynamic benefits.     

Minimally invasive aortic valve replacement: short-term efficacy of sutureless compared with stented bioprostheses

OBJECTIVESSutureless aortic valve prostheses have been introduced to facilitate the implant process, speed up the operating time and improve haemodynamic performance. The goal of this study was to assess the potential advantages of using sutureless prostheses during minimally invasive aortic valve replacement in a large multicentre population.METHODSFrom 2011 to 2019, a total of 3402 patients in 11 hospitals underwent isolated aortic valve replacement with minimal access approaches using a bioprosthesis. A total of 475 patients received sutureless valves; 2927 received standard valves. The primary outcome was the incidence of 30-day deaths. Secondary outcomes were the occurrence of major complications following procedures performed with sutureless or standard bioprostheses. Propensity matched comparisons was performed based on a multivariable logistic regression model.RESULTSThe annual number of sutureless valve implants increased over the years. The matching procedure paired 430 sutureless with 860 standard aortic valve replacements. A total of 0.7% and 2.1% patients with sutureless and standard prostheses, respectively, died within 30 days (P = 0.076). Cross-clamp times [48 (40–62) vs 63 min (48–74); P = 0.001] and need for blood transfusions (27.4% vs 33.5%; P = 0.022) were lower in patients with sutureless valves. No difference in permanent pacemaker insertions was observed in the overall population (3.3% vs 4.4% in the standard and sutureless groups; P = 0.221) and in the matched groups (3.6% vs 4.7% in the standard and sutureless groups; P = 0.364).CONCLUSIONSThe use of sutureless prostheses is advantageous and facilitates the adoption of a minimally invasive approach, reducing cardiac arrest time and the number of blood transfusions. No increased risk of permanent pacemaker insertion was observed.Open in a separate window     

Performance of stentless versus stented aortic valve bioprostheses in the elderly patient: a prospective randomized trial.

OBJECTIVES: Although stentless aortic bioprostheses are believed to offer improved outcomes, benefits remain unsubstantiated. The aim of our study was to compare stentless with stented bioprostheses, with regard to postoperative changes in left ventricular mass and hemodynamic performance, in the elderly patient. METHODS: Forty patients with aortic stenoses, over the age of 75 years, were randomized to receive either the stented Perimount (n=20) or the stentless Prima Plus (n=20) bioprosthesis. Left ventricular mass regression, effective orifice area, ejection fraction and mean gradients were evaluated at discharge, 6 months and 1 year after surgery. RESULTS: Overall a significant decrease in left ventricular mass was found 1 year postoperatively. However, there was no significant difference in the rate of left ventricular mass regression between the groups. Furthermore, 1 year postoperatively, the hemodynamic performance of the valves and the change in the ejection fraction did not differ between the groups. CONCLUSIONS: Our study shows that in a randomized cohort of elderly patients with aortic stenosis, we were not able to detect significant differences, with regard to hemodynamic performance and regression of left ventricular mass, between the stentless and stented valve groups. To our surprise, previously reported findings of non-randomized trials that showed faster and more complete regression of left ventricular mass and hemodynamic benefits of stentless valves were not reproducible.     

Short-term results after aortic valve replacement with stentless xenografts in elderly patients

OBJECTIVE: Our aim was to chart the short-term results of the first 75 of our patients who had undergone first-time aortic valve replacement (AVR) with stentless xenografts. DESIGN: Our study included a complete follow-up (mean/max. 1.5/3.7 years) of the first 75 patients (42 males, 33 females; mean age 74, range 61-84 years) who underwent a first AVR with stentless xenografts. RESULTS: Forty-three percent of patients were in functional class II and 57% in classes III-IV preoperatively. Coronary artery bypass grafting (CABG) was performed in 33 patients. Early mortality (< or = 30 days) was 6.7%, with no significant relation to CABG or age. Crude survival was 81% (95% confidence interval, CI: 71-91 %) at 3 years. Using a multivariate analysis, we identified a low left ventricular ejection fraction as a predictor of early and late mortality. Late survival (early mortality excluded) was comparable with the survival of a matched Danish background population. There were six embolic events (all cerebral: 3 minor, 1 major, 2 fatal), while two patients underwent redo-AVR because of either endocarditis (fatal) or aortic regurgitation caused by malaligned commissures. There were no other valve-related complications. Cumulative freedom was 89% (95% CI: 79-99%) for embolism and 86% (95% CI: 76-96 %) for all complications at 3 years. At the end of the study, 64% of the survivors were in functional class I, 34% were in class II and 2% in class III. CONCLUSIONS: Considering the age composition of our patients, and compared with international results, our early mortality rates were acceptable. The absence of late excess mortality compared with the background population and the functional status at end-of-study may indicate the potential haemodynamic advantages of stentless aortic valves, at least in the short term.     

Survival after stentless and stented xenograft aortic valve replacement: a concurrent,controlled trial

BACKGROUND: To define the impact of stentless versus stented valve design on survival late after xenograft aortic valve replacement, a retrospective analysis of all consecutive patients operated on between January 1992 and April 2000 was undertaken. METHODS: Two hundred ninety-two patients had stented (group 1) and 376 stentless (group 2) xenograft aortic valve replacements. Age was older in group 1 (75 +/- 4 vs 70 +/- 7 years, p = 0.01), whereas male gender and aortic stenosis were equally prevalent. Advanced New York Heart Association class III-IV (85% vs 78%, p = 0.03) and associated procedures (53% vs 41%, p = 0.01) were more common in group 1. Aortic cross-clamp (80 +/- 28 vs 96 +/- 23 minutes, p = 0.01) and bypass (91 +/- 56 vs 129 +/- 34 minutes, p = 0.01) times were shorter in group 1. Logistic regression and Cox proportional hazard methods were used to define the role of demographic and operative variables on hospital and late survival, freedom from valve-related mortality, and reintervention. RESULTS: Early mortality was higher in group 1 (6.2% vs 2.6%, p = 0.02). Smaller aortic anulus (p = 0.008), aortic cross-clamp (p = 0.03), and coronary disease requiring bypass (p = 0.03) were associated with hospital mortality. During follow-up (37 +/- 30 vs 43 +/- 35 months, p = NS), 66 late deaths were recorded (12% vs 9%, p = NS). At 8 years, survival (70 +/- 5% vs 81 +/- 3%, p = 0.01), freedom from cardiac- (85 +/- 1% vs 92 +/- 3%, p = 0.02), and valve-related death (79 +/- 5% vs 95 +/- 2%, p = 0.004) were higher in group 2. Freedom from structural deterioration was similar (92 +/- 5% vs 93 +/- 3%, p = NS), but freedom from reoperation was lower in group 2 (99 +/- 1% vs 90 +/- 4%, p = 0.009). Multivariate analysis showed female gender (p = 0.02), age (p = 0.03), and smaller valve size (p = 0.05) to be associated with late mortality; age (p = 0.06) and diagnosis of aortic stenosis (p = 0.008) with cardiac mortality; longer intensive care unit stay (p = 0.001) and stented xenografts (p = 0.05) with valve-related mortality; and younger age (p = 0.01) and stentless xenograft (p = 0.05) with reoperation. CONCLUSIONS: Use of stentless xenografts correlates with better survival and freedom from cardiac- and valve-related mortality than stented valves. However, bias favoring stented valves in older and sicker patients exists. Selective survival advantage of stentless xenograft is confined to valve-related mortality. Stentless valves are more likely to be replaced for dysfunction.     

Left ventricular mass reduction after aortic valve replacement: homografts, stentless and stented valves.

BACKGROUND: We studied the effect of four different types of prosthetic aortic valves on time course and extent of regression of left ventricular hypertrophy after aortic valve replacement for aortic stenosis. METHODS: Four groups of 10 patients each were randomly assigned to receive: (1) aortic homograft preserved in antibiotic solution at 4 degrees C, (2) Toronto stentless porcine valve, (3) Medtronic Freestyle stentless valve, or (4) Medtronic Intact aortic valve. The left ventricular mass index, effective orifice area index, and peak and mean transaortic gradients were measured by Doppler echocardiography before the operation and 8 months postoperatively. RESULTS: The hemodynamic performance indices were much better for the homograft and stentless valves than for the stented one. The absolute left ventricular mass index reduction was greater in the homograft group compared with the Intact (p = 0.0004) and Toronto (p = 0.007) groups. The extent of percent left ventricular mass index reduction was greater only in the homograft group versus Intact group (p = 0.005). The multilinear regression analysis showed that the only predictors of a larger percentage of left ventricular mass index reduction were the homograft type, a higher valve size index, and a higher preoperative left ventricular mass index. CONCLUSIONS: When a stentless or homograft aortic valve was used instead of a stented valve to replace a stenotic aortic valve there was more complete or at least faster regression of left ventricular hypertrophy. The hemodynamic performance of stentless porcine valves was similar to that of aortic homografts, nevertheless the aortic homografts preserved in antibiotic solution offered a faster regression of left ventricular hypertrophy during the same period of time.     

Comparative rest and exercise hemodynamics of 23-mm stentless versus 23-mm stented aortic bioprostheses

BACKGROUND: The hemodynamic superiority of stentless valves at rest has been generally accepted, but there is a lack of studies on exercise hemodynamics. METHODS: We assessed aortic valve hemodynamics at rest and during exercise in 10 patients with a 23-mm stentless aortic bioprosthesis (Medtronic Freestyle; Medtronic Europe SA/NV, St. Stevens Woluwe, Belgium), in 10 patients with a 23-mm stented aortic bioprosthesis (Carpentier-Edwards, SAV, model 2650; Baxter Edwards AG, Horw, Switzerland), and in 10 healthy volunteers (control group) by means of Doppler echocardiography. RESULTS: Gradients at rest and gradients on comparable maximum exercise levels were significantly lower in patients with stentless valves compared to those with stented valves (rest: 6 +/- 2/11 +/- 4 mm Hg [mean/peak] versus 12 +/- 3/21 +/- 10 mm Hg; exercise: 9 +/- 3/18 +/- 6 mm Hg [mean/peak] versus 22 +/- 8/40 +/- 11 mm Hg). Patients with stentless valves revealed, in comparison to healthy young men, significantly higher gradients, but the small gradient difference of 3/7 mm Hg (mean/peak) at rest remained nearly unchanged throughout the exercise protocol (4/8 mm Hg [mean/peak] at 25 W, 4/9 mm Hg at 50 W and 4/9 mm Hg at 75 W). In contrast, the gradient difference between patients with stented and stentless valves increased significantly from one exercise level to the next (6/12 mm Hg [mean/peak] at rest, 8/14 mm Hg at 25 W, 12/17 mm Hg at 50 W, and 15/25 mm Hg at 75 W). CONCLUSIONS: A stentless aortic bioprosthesis seems to be an appropriate aortic valve substitute, especially in patients who perform regular physical exercise.     

Survival advantage of stentless aortic bioprostheses

BACKGROUND: Bioprostheses (BPs) are used to avoid anticoagulation after aortic valve replacement (AVR) in patients over 65 years of age. Stentless BPs offer established hemodynamic benefits. We sought to determine whether these advantages translate into improved survival. METHODS: Between 1993 and 1997, follow-up data (for Food and Drug Administration submission) were collected prospectively for 160 consecutive, unselected hospital survivors who received the Freestyle valve (FS). Equivalent data were collected for 247 Carpentier-Edwards (CE) porcine xenograft patients. Detailed comparative statistical analysis was used to compare events and survival between the groups. Follow-up was 100% complete for the FS (5.2 years maximum; mean 3.2+/-1.0 years) group and 98% (7.2 years maximum; mean 3.8+/-2.0 years) for CE. RESULTS: The groups were well matched in age (FS, 73+/-6 years; CE, 74+/-6 years), gender (FS, 58% male; CE, 62% male), ventricular function, and number of patients requiring coronary grafts (FS, 41%; CE, 37%). Actuarial survival at 5 years was 84% for FS versus 69% for CE (p = 0.023 Kaplan Meier, p = 0.009 Cox). Annual mortality rates were 3.6% for FS versus 7.1% for CE (p = 0.001). Thromboembolic rate was 0.8% per year for FS and 2.4% for CE (p = 0.024) without a difference in cardiac rhythm. Incidence of nonstructural dysfunction (paravalvular leak) was 0.2% for FS versus 1.3% for CE (p = 0.020). CONCLUSIONS: By 5 years, the stentless valve patients had improved survival and reduced adverse events. Though differences in durability are yet to be proved, our findings support the use of stentless bioprostheses in this age group.