Early Regional Assessment of LV Mass Regression and Function after Stentless Valve Replacement: Comparative Randomized Study

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.

Stentless versus Stented Bioprosthetic Aortic Valves

Objective

This meta-analysis sought to determine whether stentless bioprosthetic valves improve clinical and resource outcomes compared with stented valves in patients undergoing aortic valve replacement.

Methods

A comprehensive search was undertaken to identify all randomized and nonrandomized controlled trials comparing stentless to stented bioprosthetic valves in patients undergoing aortic valve replacement available up to March 2008. The primary outcomes were clinical and resource outcomes in randomized controlled trial (RCT). Secondary outcomes clinical and resource outcomes in nonrandomized controlled trial (non-RCT). Odds ratios (OR), weighted mean differences (WMD), or standardized mean differences and their 95% confidence intervals (CI) were analyzed as appropriate.

Results

Seventeen RCTs published in 23 articles involving 1317 patients, and 14 non-RCTs published in 18 articles involving 2485 patients were included in the meta-analysis. For the primary analysis of randomized trials, mortality for stentless versus stented valve groups did not differ at 30 days (OR 1.36, 95% CI 0.68–2.72), 1 year (OR 1.01, 95% CI 0.55–1.85), or 2 to 10 years follow-up (OR 0.82, 95% CI 0.50–1.33). Aggregate event rates for all-cause mortality at 30 days were 3.7% versus 2.9%, at 1 year were 5.5% versus 5.9% and at 2 to 10 years were 17% versus 19% for stentless versus stented valve groups, respectively. Stroke or neurologic complications did not differ between stentless (3.6%) and stented (4.0%) valve groups. Risk of prosthesis-patient mismatch was numerically lower in the stentless group (11.0% vs. 31.3%, OR 0.30, 95% CI 0.05–1.66), but this parameter was reported in few trials and did not reach statistical significance. Effective orifice area index was significantly greater for stentless aortic valve compared with stented valves at 30 days (WMD 0.12 cm2/m2), at 2 to 6 months (WMD 0.15 cm2/m2), and at 1 year (WMD 0.26 cm2/m2). Mean gradient at 1 month was significantly lower in the stentless valve group (WMD −6 mm Hg), at 2 to 6 month follow-up (WMD −4 mm Hg,), at 1 year follow-up (WMD −3 mm Hg) and up to 3 year follow-up (WMD −3 mm Hg) compared with the stented valve group. Although the left ventricular mass index was generally lower in the stentless group versus the stented valve group, the aggregate estimates of mean difference did not reach significance during any time period of follow-up (1 month, 2–6 months, 1 year, and 8 years).

Conclusions

Evidence from randomized trials shows that subcoronary stentless aortic valves improve hemodynamic parameters of effective orifice area index, mean gradient, and peak gradient over the short and long term. These improvements have not led to proven impact on patient morbidity, mortality, and resource-related outcomes; however, few trials reported on clinical outcomes beyond 1 year and definitive conclusions are not possible until sufficient evidence addresses longer-term effects.

Meta-Analysis of Valve Hemodynamics and Left Ventricular Mass Regression for Stentless Versus Stented Aortic Valves

BACKGROUND

Stentless aortic bioprostheses have been advocated as being superior to conventional bioprosthetic valves, with benefits including superior left ventricular mass regression and larger effective orifice area. Several high-quality randomized studies now exist on this topic, and we sought to summarize them by meta-analysis.

METHODS

The literature was searched from 1995 to 2006, in MEDLINE, EMBASE, CRISP, metaRegister of Controlled Trials, and the Cochrane database. Experts were also contacted and reference lists searched. Studies were combined using the inverse variance fixed-effects model. Heterogeneity was assessed and a sensitivity analysis performed. Publication bias was also investigated.

RESULTS

Ten studies were identified that included 919 patients in which the Freedom (Sorin Biomedica Cardio, Via Crescentino, Italy), Freestyle (Medtronic, Minneapolis, MN), Prima Plus (Edwards Life Sciences, Irvine, CA) and the Toronto and Biocor (St Jude Medical, St. Paul, MN) valves were used. The mean aortic valve gradient was lower in the stentless groups, with a weighted mean difference (WMD) of -3.57 mm Hg (95% confidence interval [CI], -4.36 to -2.78; p < 0.01). The left ventricular mass index was significantly lower in the stentless groups at 6 months (WMD, -6.42; 95% CI, -11.63 to -1.21; p = 0.02), but this improvement disappeared after 12 months (WMD, 1.19; 95% CI, -4.15 to 6.53; p = 0.66). The weighted mean increase in cross-clamp time was 23 minutes, and the increase in bypass time was 29 minutes with a stentless valve.

CONCLUSIONS

This meta-analysis showed that stentless aortic valves provide an improved level of left ventricular mass regression at 6 months, reduced aortic gradients, and an improved effective orifice area index, at the expense of a 23-minute longer cross-clamp time and a 29-minute longer bypass time.

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.

Impact of Stentless Aortic Valves on Left Ventricular Function and Hypertrophy: Current Best Available Evidence

Past four decades have seen a gradual evolution in aortic valve replacement surgery. The ideal valve substitute should combine central flow, low transvalvular gradient, low thrombogenicity, durability, easy availability, resistance to infection, freedom from anticoagulation, and easy implantability. Although there are several types of valves available to replace the diseased aortic valve-autograft, allograft, xenograft, mechanical, and bioprosthetic valves-none is ideal. On one end of the spectrum is the pulmonary autograft, which comes closest to achieving these goals, but creates a double valve procedure for single valve disease, while on the other end are the mechanical valves and stented tissue valves, which allow easy "off the shelf" availability as well as easy implantability but are limited by the potential drawback of causing intrinsic obstruction to some extent because of the space occupied by the stent and sewing ring. Stentless xenograft aortic valves have been developed as a compromise between these ends of the valve spectrum. Stentless aortic valves have been reported to provide more physiologic hemodynamic behavior and cause more timely and thorough regression of ventricular hypertrophy. This review article attempts to evaluate current best available evidence from randomized controlled trials to assess the impact of stentless aortic valves on left ventricular function and hypertrophy.