Hemodynamic Performance of Stentless Versus Stented Valves: A Systematic Review and Meta-Analysis

Adverse effects of left ventricular electrical dyssynchrony on cardiac reverse remodeling and prognosis after aortic valve surgery

BACKGROUND

Electrical dyssynchrony (ED) is one of the important contributing mechanisms in the progression of heart failure. We hypothesized that ED would interfere with cardiac reverse remodeling and affect prognosis after aortic valve surgery.

METHODS

A total of 411 consecutive patients (233 males, mean age 65±11 years) who underwent aortic valve surgery were retrospectively analyzed. The patients were divided into two groups according to the presence of ED [Group 1: no ED (n=382, 93%), Group 2: ED (n=29, 7%)]. ED was defined as either left ventricular bundle branch block, or electrical pacing rhythm. Cardiac reverse remodeling was assessed at 1 year after surgery by the changes in left ventricular ejection fraction (LVEF), LV end-systolic volume (LVESV), and left atrial volume index (LAVI). The primary endpoint was a composite of hospitalization for heart failure, and all-cause mortality.

RESULTS

At 1 year after surgery, group 2 showed lower LVEF (58±15% vs. 64±9%, p=0.044), and higher LAVI (42±18ml/m² vs. 33±13ml/m², p=0.018) than group 1. However, LVESV values (55±38ml vs. 42±24ml, p=0.076) were not significantly different. In particular, in patients with reduced preoperative LVEF, the LVEF was markedly increased in group 1 but not in group 2 after 1 year. During a median follow-up of 39 months, group 2 showed a worse clinical outcome than group 1 (20.7% vs. 7.6%, p=0.031). After adjusting for confounding factors in the multivariate analyses, age [hazard ratio (HR) 1.11, 95% confidence interval (CI) 1.06-1.16, p<0.001] and the presence of ED (HR 2.43, 95% CI 1.01-5.89, p=0.046) were found to be independent predictors of clinical outcomes.

CONCLUSIONS

ED after aortic valve surgery negatively affected cardiac remodeling and prognosis.

Four-dimensional flow MRI of stented versus stentless aortic valve bioprostheses

Objectives

To evaluate aortic velocity, wall shear stress (WSS) and viscous energy loss (EL) of stented and stentless bioprostheses using 4D flow MRI 1 year after surgical aortic valve replacement.

Methods

For this cross-sectional study 28 patients with stented (n = 14) or stentless (n = 14) bioprosthesis underwent non-contrast-enhanced 4D-flow MRI at 1.5 T. Analyses included a comparison of velocity, WSS and EL in the ascending aorta during peak systole for both spatially averaged values and a comparison of local differences using per-voxel analysis.

Results

No significant differences were found in peak and mean velocity (stented vs. stentless: 2.45 m/s vs. 2.11 m/s; p = 0.09 and 0.60 m/s vs. 0.62 m/s; p = 0.89), WSS (0.60 Pa vs. 0.59 Pa; p = 0.55) and EL (10.17 mW vs. 7.82 mW; p = 0.10). Per-voxel analysis revealed significantly higher central lumen velocity, and lower outer lumen velocity, WSS and EL for stentless versus stented prostheses.

Conclusion

One year after aortic valve implantation with stented and stentless bioprostheses, velocity, WSS and EL were comparable when assessed for averaged values in the ascending aorta. However, the flow profile described with local analysis for stentless prosthesis is potentially favourable with a significantly higher central velocity profile and lower values for outer lumen velocity, WSS and EL.

Key Points

• Stentless bioprostheses can be implanted instead of stented aortic valve bioprostheses.

• Haemodynamic performance of valve prosthesis can be assessed using 4D flow MRI.

• Averaged ascending aorta PSV, WSS and EL are comparable 1 year post-implantation.

• Centreline velocity is highest, WSS and EL is lowest for stentless prosthesis.

Biomechanical Behavior of Bioprosthetic Heart Valve Heterograft Tissues: Characterization, Simulation, and Performance

The use of replacement heart valves continues to grow due to the increased prevalence of valvular heart disease resulting from an ageing population. Since bioprosthetic heart valves (BHVs) continue to be the preferred replacement valve, there continues to be a strong need to develop better and more reliable BHVs through and improved the general understanding of BHV failure mechanisms. The major technological hurdle for the lifespan of the BHV implant continues to be the durability of the constituent leaflet biomaterials, which if improved can lead to substantial clinical impact. In order to develop improved solutions for BHV biomaterials, it is critical to have a better understanding of the inherent biomechanical behaviors of the leaflet biomaterials, including chemical treatment technologies, the impact of repetitive mechanical loading, and the inherent failure modes. This review seeks to provide a comprehensive overview of these issues, with a focus on developing insight on the mechanisms of BHV function and failure. Additionally, this review provides a detailed summary of the computational biomechanical simulations that have been used to inform and develop a higher level of understanding of BHV tissues and their failure modes. Collectively, this information should serve as a tool not only to infer reliable and dependable prosthesis function, but also to instigate and facilitate the design of future bioprosthetic valves and clinically impact cardiology.

Aortic valve and/or aortic root replacement using an aortic homograft

Aortic valve replacement using the homograft valve has a special place in the cardiac surgical practice although it has never been widely used, in part due to the lack of tissue donors but also due to the perceived difficulty of the procedure compared with aortic valve replacement using prosthetic devices and concerns regarding homograft valve failure. The principal indication for aortic valve replacement using a homograft aortic valve is for active aortic valve endocarditis (native or prosthetic) with or without perivalvular tissue destruction (abscess cavity, fistula, detachment of the anterior mitral valve leaflet from the aortic annulus). Since the homograft tissue is pliable and adaptable, it can be used to repair defects in complex cases with root destruction. A second interesting application of homograft aortic valve is in the treatment of small aortic root (in which replacement with a small prosthetic valve would produce an unacceptable orifice ratio and ultimately affect long-term outcome) and left ventricular outflow tract obstruction when the homograft aortic valve can be combined to the Konno procedure. Homograft aortic valve can be used in these cases without sacrifying the pulmonary valve to be used as aortic valve substitute (for instance in adolescents and young adults who do not want to undergo a 'two-valve' procedure like the Ross-Konno procedure). The most frequent operation technique is the cylindrical aortic root replacement, performed in a similar way than the classical Bentall procedure. This technique is the most easiest one and performed more frequently than the subcoronary implantation, which is substantially more demanding. Results from centres that have significant experience with homograft valve surgery report equivalent survival data. The University of Alabama had an 87% survival at 5 years in a 10-year period from 1981 to 1991. Of those who underwent isolated aortic valve replacement with a homograft, there was 99% survival at 30 days and 94% survival at 8 years. In the Mayo Clinic series, 82% were alive at 8 years. Like all tissue valves, homograft aortic valves may fail. An understanding of the mechanisms of homograft valve failure and the way in which these mechanisms interact has important surgical implications. Homograft aortic valves may develop progressive regurgitation as a result of a change in the mechanical properties of the leaflets over time.