Prosthetic heart valves: selection of the optimal prosthesis and long-term management

Durability of transcatheter aortic valve implantation: A translational review

Until recently, transcatheter aortic valve implantation was restricted to high-risk and inoperable patients. The updated 2017 European Society of Cardiology Guidelines has widened the indication to include intermediate-risk patients, based on two recently published trials (PARTNER 2 and SURTAVI). Moreover, two other recent trials (PARTNER 3 and EVOLUT LOW RISK) have demonstrated similar results with transcatheter aortic valve implantation in low-risk patients. Thus, extension of transcatheter aortic valve implantation to younger patients, who are currently treated by surgical aortic valve replacement, raises the crucial question of bioprosthesis durability. In this translational review, we propose to produce a state-of-the-art overview of the durability of transcatheter aortic valve implantation by integrating knowledge of the basic science of bioprosthesis degeneration (pathophysiology and biomarkers). After summarising the new definition of structural valve deterioration, we will present what is known about the pathophysiology of aortic stenosis and bioprosthesis degeneration. Next, we will consider how to identify a population at risk of early degeneration, and how basic science with the help of biomarkers could identify and predict structural valve deterioration. Finally, we will present data on the differences in durability of transcatheter aortic valve implantation compared with surgical aortic valve replacement.

Mitral valve prosthesis choice in patients <70 years: A systematic review and meta-analysis of 20 219 patients

BACKGROUND

The optimal mitral prosthesis in young patients is unclear. This systematic review and meta-analysis were performed to compare outcomes between bileaflet mechanical mitral valve replacement (mMVR) and bioprosthesis mitral valve replacement (bioMVR) for MVR patients aged less than 70 years.

METHODS

We searched MEDLINE and EMBASE databases from inception to July 2018 for studies comparing surgical outcomes of mMVR vs bioMVR.

RESULTS

There were 14 observational studies with 20 219 patients (n = 14 658 mMVR and n = 5561 bioMVR). Patients receiving an mMVR were younger with fewer comorbidities including renal failure, dialysis, and less-infective endocarditis (P < .001). The estimated 10-year mortality ranged from 19% to 49% for mMVR and 22% to 58% for bioMVR among studies. Comparing matched or adjusted data, mMVR was associated with lower operative (risk ratio [RR]: 0.61; 95% confidence interval [CI]: 0.39, 0.94; P = .03) and long-term (HR: 0.81; 95% CI: 0.71, 0.92; P = .002) mortality at a median follow-up of 8 years (IQR: 6-10 years). Estimated 10-year risk for mitral valve reoperation ranged from 0% to 8% for mMVR and 8% to 22% for bioMVR among matched/adjusted studies. mMVR was associated with lower matched/adjusted risk of reoperation (HR: 0.35; 95% CI: 0.19, 0.65; P = .001) but with greater risk of bleeding (HR: 1.59; 95% CI: 1.19, 2.13; P = .002) and a trend to greater risk of stroke and embolism (HR: 1.70; 95% CI: 0.92, 3.15; P = .09).

CONCLUSION

Mechanical MVR in patients aged less than 70 years is associated with a lower risk of operative mortality as well as a 20% lower risk of long-term death and 65% lower risk of mitral valve reoperation but 60% greater risk of bleeding compared with bioMVR in matched or adjusted data.

Comparison of patient-prothesis mismatch after surgical aortic valve replacement and transcatheter aortic valve implantation

Background

The aim of this study is to analyze the outcomes and incidence of postoperative patient-prothesis mismatch after surgical aortic valve replacement using supra-annular bioprosthesis and transcatheter aortic valve implantation.

Methods

Between January 2012 and June 2015, a total of 73 patients (37 males, 36 females; mean age 71.8±5.7 years; range, 65 to 82 years) who underwent either surgical aortic valve replacement using supraannular bioprosthesis (n=36) or transcatheter aortic valve implantation (n=37) were included. Postoperative patient-prothesis mismatch was defined as absent, mild-to-moderate, and severe, if the indexed effective orifice area was >0.85 cm²/m², >0.65 to <0.85 cm²/m², and <0.65 cm²/m², respectively. Both groups were compared in terms of patient-prothesis mismatch, postoperative outcomes, and mortality.

Results

The overall incidence of mild-to-moderate patient-prosthesis mismatch was 17.8% (13/73). No severe patient-prosthesis mismatch was observed. Mild-to-moderate patient-prosthesis mismatch was found in three patients (8.1%) in the transcatheter group and in 10 patients (27.8%) in the surgery group (p=0.035). Body surface area was the significant predictor of patient-prosthesis mismatch (p=0.007). Diameters of bioprosthetic valves in the surgery and transcatheter groups were 21.4±2 and 23.9±2.6 mm, respectively (p=0.002). Early mortality and pacemaker implantation rates were higher in the transcatheter group (p>0.05). Postoperative outcomes were similar between the groups. Mid-term mortality at a mean follow-up of 47.7±7.3 months was similar between the groups (p=0.158).

Conclusion

In high-risk patients with severe aortic stenosis, patientprosthesis mismatch is mild-to-moderate after surgical aortic valve replacement and transcatheter aortic valve implantation; however, this has no effect on early mortality. Based on our study results, we suggest that the use of surgical approach for aortic valve replacement may prevent potential complications of transcatheter aortic valve implantation.

4D Flow MRI hemodynamic benchmarking of surgical bioprosthetic valves

PURPOSE

We exploited 4-dimensional flow magnetic resonance imaging (4D Flow), combined with a standardized in vitro setting, to establish a comprehensive benchmark for the systematic hemodynamic comparison of surgical aortic bioprosthetic valves (BPVs).

MATERIALS AND METHODS

4D Flow analysis was performed on two small sizes of three commercialized pericardial BPVs (Trifecta™ GT, Carpentier-Edwards PERIMOUNT Magna and Crown PRT®). Each BPV was tested over a clinically pertinent range of continuous flow rates within an in vitro MRI-compatible system, equipped with pressure transducers. In-house 4D Flow post-processing of the post-valvular velocity field included the quantification of BPV effective orifice area (EOA), transvalvular pressure gradients (TPG), kinetic energy and viscous energy dissipation.

RESULTS

The 4D Flow technique effectively captured the 3-dimensional flow pattern of each device. Trifecta exhibited the lowest range of velocity and kinetic energy, maximized EOA (p < 0.0001) and minimized TPGs (p ≤ 0.015) if compared with Magna and Crown, these reporting minor EOA difference s (p ≥ 0.042) and similar TPGs (p ≥ 0.25). 4D Flow TPGs estimations strongly correlated against ground-truth data from pressure transducers; viscous energy dissipation proved to be inversely proportional to the fluid jet penetration.

CONCLUSION

The proposed 4D Flow analysis pinpointed consistent hemodynamic differences among BPVs, highlighting the not negligible effect of device size on the fluidynamic outcomes. The efficacy of non-invasive 4D Flow MRI protocol could shed light on how standardize the comparison among devices in relation to their actual hemodynamic performances and improve current criteria for their selection.

Failure of decellularized porcine small intestinal submucosa as a heart valved conduit

OBJECTIVE

Decellularized extracellular matrix made from porcine small intestinal submucosa, commercially available as CorMatrix (CorMatrix Cardiovascular, Inc, Roswell, Ga) is used off-label to reconstruct heart valves. Recently, surgeons experienced failures and words of caution were raised. The aim of this study was to evaluate decellularized porcine small intestinal submucosa as right-sided heart valved conduit in a xenogeneic animal model.

METHODS

A pulmonary valve replacement was performed with custom-made valved conduits in 10 lambs and 10 sheep (1 month [3 lambs and 3 sheep], 3 months [3 lambs and 3 sheep], 6 months [4 lambs and 4 sheep]). Valve function was assessed after implantation and before the animal was put to death. Explanted conduits were inspected macroscopically and analyzed using immunohistochemistry and scanning electron microscopy. They also underwent mechanical testing and testing for biochemical composition.

RESULTS

All valved conduits were successfully implanted. Five sheep and 2 lambs died due to congestive heart failure within 2 months after surgery. In the animals that died, the valve leaflets were thickened with signs of inflammation (endocarditis in 4). Five sheep and 8 lambs (1 month: 6 out of 6 animals, 3 months: 4 out of 6 animals, 6 months: 3 out of 8 animals) survived planned follow-up. At the time they were put to death, 5 lambs had significant pulmonary stenosis and 1 sheep showed severe regurgitation. A well-functioning valve was seen in 4 sheep and 3 lambs for up to 3 months. These leaflets showed limited signs of remodeling.

CONCLUSIONS

Fifty percent of sheep and 20% of lambs died due to valve failure before the planned follow-up period was complete. A well-functioning valve was seen in 35% of animals, albeit with limited signs of tissue remodeling at ≤3 months after implantation. Further analysis is needed to understand the disturbing dichotomous outcome before clinical application can be advised.

Early detection of transcatheter heart valve dysfunction

Introduction: Transcatheter aortic valve implantation therapy is spreading rapidly, representing the standard of care in inoperable and high-risk patients, and a valid alternative in intermediate- and low-risk patients with severe symptomatic aortic stenosis. In this subset, the development and validation of noninvasive, quantitative, in vivo imaging modality, to monitor possible valve dysfunction is mandatory, in order to plan timely therapeutic interventions before the onset of symptoms.Areas covered: The implantation of transcatheter heart valves (THV) is increasing rapidly. As a consequence, THV dysfunction will become a major cause of cardiovascular morbidity after TAVI. Emergency repeat aortic valve replacement surgery is associated with a high rate of mortality compared with elective repeat surgery. In this context, early detection of THV dysfunction is therefore highly desirable. The review aims to examine the different diagnostic method to early detect THV dysfunction.Expert opinion: Most promising innovations in the diagnosis of early detection of THV dysfunction are evaluated, and the future outlook is explored. Waiting for upcoming evidence about the utility of CT, CMR, and PET on early detection of THV dysfunction, tailoring echocardiogram follow-up based on patients' characteristics is the desirable approach.

A Deep Learning Framework for Design and Analysis of Surgical Bioprosthetic Heart Valves

Bioprosthetic heart valves (BHVs) are commonly used as heart valve replacements but they are prone to fatigue failure; estimating their remaining life directly from medical images is difficult. Analyzing the valve performance can provide better guidance for personalized valve design. However, such analyses are often computationally intensive. In this work, we introduce the concept of deep learning (DL) based finite element analysis (DLFEA) to learn the deformation biomechanics of bioprosthetic aortic valves directly from simulations. The proposed DL framework can eliminate the time-consuming biomechanics simulations, while predicting valve deformations with the same fidelity. We present statistical results that demonstrate the high performance of the DLFEA framework and the applicability of the framework to predict bioprosthetic aortic valve deformations. With further development, such a tool can provide fast decision support for designing surgical bioprosthetic aortic valves. Ultimately, this framework could be extended to other BHVs and improve patient care.

Emerging Technologies for Percutaneous Mitral Valve Repair

Mitral regurgitation (MR) is a common disease affecting more than 4 million people in the United States and the European Union. A significant number of percutaneous valves have been developed recently, specifically designed for the mitral anatomy, and with a promising evidence of good procedural and echocardiographic outcomes. However, even if transcatheter mitral valve replacement (TMVR) will have a role in the future of percutaneous treatment of both functional and degenerative mitral regurgitation, percutaneous mitral valve repair will always play a vital role in the treatment of MR because of the favorable safety profile and the fact that it respects the native anatomy. In this review, we will discuss the new emerging technologies under development to treat mitral regurgitation focusing on different devices that aim to target different components of the mitral anatomy.

Simulation of personalised haemodynamics by various mounting positions of a prosthetic valve using computational fluid dynamics

Diseases of the cardiovascular system account for nearly 42% of all deaths in the European Union. In Germany, approximately 12,000 patients receive surgical replacement of the aortic valve due to heart valve disease alone each year. A three-dimensional (3D) numerical model based on patient-specific anatomy derived from four-dimensional (4D) magnetic resonance imaging (MRI) data was developed to investigate preoperatively the flow-induced impact of mounting positions of aortic prosthetic valves to select the best orientation for individual patients. Systematic steady-state analysis of blood flow for different rotational mounting positions of the valve is only possible using a virtual patient model. A maximum velocity of 1 m/s was used as an inlet boundary condition, because the opening angle of the valve is at its largest at this velocity. For a comparative serial examination, it is important to define the standardised general requirements to avoid impacts other than the rotated implantation of the prosthetic aortic valve. In this study, a uniform velocity profile at the inlet for the inflow of the aortic valve and the real aortic anatomy were chosen for all simulations. An iterative process, with the weighted parameters flow resistance (1), shear stress (2) and velocity (3), was necessary to determine the best rotated orientation. Blood flow was optimal at a 45° rotation from the standard implantation orientation, which will offer a supply to the coronary arteries.

Durability and Clinical Outcomes of Transcatheter Aortic Valve Replacement for Failed Surgical Bioprostheses

Background:

Valve-in-valve transcatheter aortic valve replacement (TAVR) is an option when a surgical valve demonstrates deterioration and dysfunction. This study reports 3-year results following valve-in-valve with self-expanding TAVR.

Methods:

The CoreValve US Expanded Use Study is a prospective, nonrandomized, single-arm study that evaluates safety and effectiveness of TAVR in extreme risk patients with symptomatic failed surgical biologic aortic valves. Study end points include all-cause mortality, need for valve reintervention, hemodynamic changes over time, and quality of life through 3 years. Patients were stratified by presence of preexisting surgical valve prosthesis-patient mismatch.

Results:

From March 2013 to May 2015, 226 patients deemed extreme risk (STS-PROM [Society of Thoracic Surgeons Predicted Risk of Mortality] 9.0±7%) had attempted valve-in-valve TAVR. Preexisting surgical valve prosthesis-patient mismatch was present in 47.2% of the cohort. At 3 years, all-cause mortality or major stroke was 28.6%, and 93% of patients were in New York Heart Association I or II heart failure. Valve performance was maintained over 3 years with low valve reintervention rates (4.4%), an improvement in effective orifice area over time and a 2.7% rate of severe structural valve deterioration. Preexisting severe prosthesis-patient mismatch was not associated with 3-year mortality but was associated with significantly less improvement in quality of life at 3-year follow-up ( P =0.01).

Conclusions:

Self-expanding TAVR in patients with failed surgical bioprostheses at extreme risk for surgery was associated with durable hemodynamics and excellent clinical outcomes. Preexisting surgical valve prosthesis-patient mismatch was not associated with mortality but did limit patient improvement in quality of life over 3-year follow-up.

Clinical Trial Registration:

URL: http://www.clinicaltrials.gov . Unique identifier: NCT01675440.

High-Resolution Measurements of Leakage Flow Inside the Hinge of a Large-scale Bileaflet Mechanical Heart Valve Hinge Model

PURPOSE

It is believed that non-physiological leakage flow through hinge gaps during diastole contributes to thrombus formation in Bileaflet Mechanical Heart Valves (BMHVs). Because of the small scale and difficulty of experimental access, fluid dynamics inside the hinge cavity has not yet been characterised in detail. The objective is to investigate small-scale structure inside the hinge experimentally, and gain insight into its role in stimulating cellular responses.

METHODS

An optically accessible scaled-up model of a BMHV hinge was designed and built, preserving dynamic similarity to a clinical BMHV. Particle Image Velocimetry (PIV) was used to visualize and quantify the flow fields inside the hinge at physiological Reynolds number and dimensionless pressure drop. The flow was measured at in-plane and out-of-plane spatial resolution of 32 and 86 μm, respectively, and temporal resolution of [Formula: see text] RESULTS: Likely flow separation on the ventricular surface of the cavity has been observed for the first time, and is a source of unsteadiness and perhaps turbulence. The shear stress found in all planes exceeds the threshold of platelet activation, ranging up to 168 Pa.

CONCLUSIONS

The scale-up approach provided new insight into the nature of the hinge flow and enhanced understanding of its complexity. This study revealed flow features that may induce blood element damage.

Sudden cardiac death and valvular pathology

Sudden death due to valvular heart disease is reported to range from 1% to 5% in native valves and around 0.2%-0.9%/year in prosthesis. The nature of the diseases is varied, from heritable, congenital to acquired. It may affect both genders in multiple age groups. The authors show and comment examples of the major nosologic aetiologies underlying unexpected exitus letalis of valvular nature.

Prevalence and Evolution of Susceptibility-Weighted Imaging Lesions in Patients With Artificial Heart Valves

Background

In patients with mechanical heart valves, cerebral susceptibility‐weighted imaging (SWI) lesions on magnetic resonance imaging, postulated to be caused by degenerative metallic abrasion, are frequently referred to as valve abrasion. It remains unclear whether valve implantation not requiring cardiopulmonary bypass or biological heart valves also shows those lesions.

Methods and Results

Two blinded readers rated SWI lesions and cerebral amyloid angiopathy probability according to established criteria on brain magnetic resonance imaging pre‐ and postinterventionally. We assessed the association between valve type/cardiopulmonary bypass use and SWI lesion count on the first postinterventional scan using multivariable logistic regression. On postinterventional magnetic resonance imaging, 57/58 (98%) patients with mechanical heart valves had at least 1 and 46/58 (79%) 3 or more SWI lesions, while 92/97 (95%) patients with biological heart valves had at least 1 and 72/97 (74%) 3 or more SWI lesions. On multivariate analysis, duration of cardiopulmonary bypass during implantation significantly increased the odds of having SWI lesions on the first postinterventional magnetic resonance imaging (β per 10 minutes 0.498; 95% CI, 0.116–0.880; P=0.011), whereas valve type showed no significant association (P=0.338). Thirty‐seven of 155 (23.9%) patients fulfilled the criteria of possible/probable cerebral amyloid angiopathy.

Conclusions

SWI lesions in patients with artificial heart valves evolve around the time point of valve implantation and the majority of patients had multiple lesions. The missing association with the valve type weakens the hypothesis of degenerative metallic abrasion and highlights cardiopulmonary bypass as the main risk factor for SWI occurrence. SWI lesions associated with cardiac procedures can mimic cerebral amyloid angiopathy. Further research needs to clarify whether those lesions are associated with intracranial hemorrhage after intravenous thrombolysis or anticoagulation.

Bioprosthetic Valve Fracture for Valve-in-Valve Transcatheter Aortic Valve Replacement: Rationale, Patient Selection, Technique, and Outcomes

Patient-prosthesis mismatch (PPM) is common after surgical valve aortic replacement. A significant percentage of patients with a small annulus have moderate to severe PPM. The outcomes for patients with larger effective orifice areas and lower gradients are better than for patients with PPM. With the advent of valve-in-valve TAVR, a degenerated surgical bioprosthesis can be treated with a percutaneous approach. However, the issue of PPM cannot be overcome by simply implanting a new valve. The technique of bioprosthetic valve fracture was therefore developed. This allows for implantation of a fully expanded transcatheter valve and results in a large effective orifice.

Porcine versus bovine bioprosthetic valves in mitral position: does choice really matter?

Background

Bioprosthetic valves are increasingly used for surgical mitral valve replacement (MVR). The long-term outcomes of bovine (BoMVR) vs porcine (PoMVR) remain an enigma regarding the durability. This study aims to examine the outcomes of BoMVR vs PoMVR.

Methods

A retrospective analysis of all bioprosthetic MVRs, with concomitant procedures, at a single tertiary referral institution from January 2005 to December 2008 was conducted. Procedures were classified as BoMVR or PoMVR. The age group was from 40 to 70 years.

Results

We identified 154 BoMVR patients and 120 PoMVR patients after matching the two groups with respect to age, sex, valve size and concomitant procedures. Kaplan-Meier survival analysis model was used for corresponding statistical analysis. Freedom from reoperation (all cause), freedom from non-structural valve deterioration, freedom from structural valve deterioration, freedom from heart failure and freedom from infective endocarditis were 96.4 ± 0.08, 97.1 ± 0.07, 96.4 ± 0.08%, 98.2 ± 0.07, and 98.6 ± 0.06% in PoMVR, respectively, and 92.6 ± 0.09, 91.6 ± 0.08, 90.6 ± 0.09, 94 ± 0.08, and 92.8 ± 0.08% in BoMVR groups, respectively, at the end of 10-year follow-up (mean follow up of 6.2 ± 2.3 years). Overall, 20 (12.9%) patients were lost to follow-up in the BoMVR and 15(12.5%) patients in the PoMVR groups for a global follow-up of 87.1%.

Conclusions

For patients undergoing MVR with a bioprosthetic valve, the choice of PoMVR vs BoMVR favours more in favour of PoMVR as evidenced by the outcome results. Probably long-term follow-up with more patients might throw further light on the debatable topic.

Recent advances in aortic valve replacement

Aortic valve replacement has stood the test of time but is no longer an operation that is exclusively approached through a median sternotomy using only sutured prostheses. Currently, surgical aortic valve replacement can be performed through a number of minimally invasive approaches employing conventional mechanical or bioprostheses as well as sutureless valves. In either case, the direct surgical access allows inspection of the valve, complete excision of the diseased leaflets, and debridement of the annulus in a controlled and thorough manner under visual control. It can be employed to treat aortic valve pathologies of all natures and aetiologies. When compared with transcatheter valves in patients with a high or intermediate preoperative predictive risk, conventional surgery has not been shown to be inferior to transcatheter valve implants. As our understanding of sutureless valves and their applicability to minimally invasive surgery advances, the invasiveness and trauma of surgery can be reduced and outcomes can improve. This warrants further comparative trials comparing sutureless and transcatheter valves.

Multimodality Imaging of Complications of Cardiac Valve Surgeries

Replacement with a prosthetic heart valve (PHV) remains the definitive surgical procedure for management of severe cardiac valve disease. PHV dysfunction is uncommon but can be a life-threatening condition. The broad hemodynamic and pathophysiologic manifestations of PHV dysfunction are stenosis, regurgitation, and a stuck leaflet. Specific structural abnormalities that cause PHV dysfunction include prosthetic valve-patient mismatch, structural failure, valve calcification, dehiscence, paravalvular leak, infective endocarditis, abscess, pseudoaneurysm, abnormal connections, thrombus, hypoattenuating leaflet thickening, and pannus. Multiple imaging modalities are available for evaluating a PHV and its dysfunction. Transthoracic echocardiography is often the first-line imaging modality, with additional modalities such as transesophageal echocardiography, CT, MRI, cine fluoroscopy, and nuclear medicine used for further characterization and establishing a specific cause. The authors review PHVs and the role of imaging modalities in evaluation of PHV dysfunction and illustrate the imaging appearances of different complications. Online supplemental material is available for this article. ^©RSNA, 2019.

Evaluation of transcatheter heart valve biomaterials: Computational modeling using bovine and porcine pericardium

OBJECTIVE

The durability of bioprosthetic heart valve (BHV) devices, commonly made of bovine (BP) and porcine (PP) pericardium tissue, is partly limited by device calcification and tissue degeneration, which has been associated with pathological levels of mechanical stress. This study investigated the impacts of BP and PP tissues with different thicknesses and tissue mechanical properties in BHV applications.

METHODS

Second Harmonic Generation (SHG) imaging was employed to visualize the collagen fibers on each side of the pericardium. Structural constitutive modeling that incorporates collagen fiber distribution obtained from multiphoton microscopy for each tissue type were derived to characterize the corresponding biaxial mechanical testing data collected in a previous study. The models were verified through finite element (FE) simulations of the biaxial test and implemented in valve closing simulations.

RESULTS

Smooth side collagen fibers were found to correlate with the mechanical response. BHVs with adult (ABP) and calf (CBP) BP tissues had lower maximum principal stresses than those with PP and fetal (FBP) BP tissues. Collagen fiber orientation along the circumferential axis resulted in lower maximum principal stresses and more uniform and symmetric stress distributions throughout the valve.

CONCLUSIONS

The use of PP and FBP tissue resulted in higher peak stresses than ABP and CBP tissues in the given valve design. Additionally, ensuring collagen fiber orientation along the circumferential axis led to lower maximum stresses felt by the valve leaflets, which could also improve BHV durability.

Structural valve deterioration does not alter tissue valves' radiopaque landmarks: Implications for valve-in-valve therapy

BACKGROUND

Valve-in-valve is established as a safe and efficient alternative to redo surgery in the treatment of structural valve deterioration (SVD). In vitro models rely on the radiopaque landmarks of undeteriorated tissue valves to establish the optimal implantation level of the transcatheter heart valves inside the deteriorated valves. In computed assisted procedures, the radiopaque landmarks of the deteriorated valves may be used to guide valve implantation through image fusion. The purpose of this study is to determine whether SVD alters the radiopaque landmarks of stented tissue valves.

METHODS

Our approach was based on the computation of relevant anatomical measurements from CT images. Radiopaque landmarks of degenerated bioprostheses and the corresponding undeteriorated valves were extracted to create surface meshes and cloud points using grey-level thresholding. 3D registration using an iterative closest point algorithm was used to align the corresponding cloud points, while the modified Hausdorff Distance was applied to determine the differences between them.

RESULTS

The proposed evaluation was performed on 19 degenerated tissue valves. 15 valves were scanned from patients evaluated for valve-in-valve procedures, and 4 bioprostheses were scanned after surgical extraction during redo aortic valve replacement. All the degenerated valves were compared to the corresponding undeteriorated models. Overall, the mean difference between degenerated and undeteriorated valves was 0.33 ± 0.12 mm. The maximum observed registration error was 0.66 mm.

CONCLUSIONS

Our study demonstrates no significant difference between the radiopaque landmarks of deteriorated and undeteriorated bioprostheses after the occurrence of SVD. Our findings suggest therefore that SVD does not alter radiopaque landmarks of stented tissue valves. These results validate in-vitro studies of optimal transcatheter heart valves implantation inside deteriorated tissue valves based on their radiopaque landmarks, and allow the use of non-deteriorated valves' imaging features in computer assisted valve-in-valve procedures.

Impact of Valve Size on Prosthesis-Patient Mismatch and Aortic Valve Gradient After Transcatheter versus Surgical Aortic Valve Replacement

OBJECTIVE

Limited data is available about the effect of implanted valve size on prosthesis-patient mismatch (PPM) incidence and aortic gradient (AG) after transcatheter aortic valve replacement (TAVR) and surgical aortic valve replacement (SAVR). We compared PPM incidence and postprocedural AG between TAVR and SAVR patients considering the impact of implanted valve size.

METHODS

From March 20, 2012, to September 30, 2015, 563 consecutive patients underwent TAVR (n = 419) or isolated SAVR (n = 144). Postprocedural transthoracic echocardiography was obtained within 30 days; AG, effective orifice area (EOA), and EOA index were calculated.

RESULTS

A total of 381 patients in TAVR group and 82 patients in SAVR group were included. Mean preoperative AG and mean aortic valve area were not significantly different between the 2 groups. Postprocedural AG was significantly lower in TAVR than SAVR group, 7.74 ± 5.39 versus 14.27 ± 8.16 (P < 0.001). Between patients who had TAVR and SAVR with a valve size ≤23 mm, SAVR patients were 3 times more likely to have greater than mild AG after the procedure, OR: 3.1 (95% CI, 1.1 to 8.9) (P < 0.001). PPM incidence was significantly higher in SAVR group than TAVR group, 44 (53.7%) versus 112 (29.4%), OR = 2.8 (95% CI, 1.7 to 4.5) (P < 0.001). The PPM incidence was also higher in SAVR group than TAVR group among those who had the procedures with a valve size ≤23 mm, 35 (64.8%) versus 56 (47.9%), OR = 2 (95% CI, 1.1 to 3.9) (P = 0.048). Postprocedural outcomes were comparable between the 2 groups.

CONCLUSIONS

In comparison to SAVR, TAVR is associated with less PPM and lower AG, especially in patients receiving a valve size ≤23 mm.

Bioprosthetic Heart Valves: Upgrading a 50-Year Old Technology

Prosthetic heart valves have been commonly used to address the increasing prevalence of valvular heart disease. The ideal prosthetic heart valve substitute should closely mimic the characteristics of a normal native heart valve. Despite the development of various interventions, an exemplary valve replacement does not exist. This review provides an overview of the novel engineering valve designs and explores emergent immunologic insights into age-dependent structural valve degeneration (SVD).

Detection and Prediction of Bioprosthetic Aortic Valve Degeneration

BACKGROUND

Bioprosthetic aortic valve degeneration is increasingly common, often unheralded, and can have catastrophic consequences.

OBJECTIVES

The authors sought to assess whether 18F-fluoride positron emission tomography (PET)-computed tomography (CT) can detect bioprosthetic aortic valve degeneration and predict valve dysfunction.

METHODS

Explanted degenerate bioprosthetic valves were examined ex vivo. Patients with bioprosthetic aortic valves were recruited into 2 cohorts with and without prosthetic valve dysfunction and underwent in vivo contrast-enhanced CT angiography, 18F-fluoride PET, and serial echocardiography during 2 years of follow-up.

RESULTS

All ex vivo, degenerate bioprosthetic valves displayed 18F-fluoride PET uptake that colocalized with tissue degeneration on histology. In 71 patients without known bioprosthesis dysfunction, 14 had abnormal leaflet pathology on CT, and 24 demonstrated 18F-fluoride PET uptake (target-to-background ratio 1.55 [interquartile range (IQR): 1.44 to 1.88]). Patients with increased 18F-fluoride uptake exhibited more rapid deterioration in valve function compared with those without (annualized change in peak transvalvular velocity 0.30 [IQR: 0.13 to 0.61] vs. 0.01 [IQR: -0.05 to 0.16] ms-1/year; p < 0.001). Indeed 18F-fluoride uptake correlated with deterioration in all the conventional echocardiographic measures of valve function assessed (e.g., change in peak velocity, r = 0.72; p < 0.001). Each of the 10 patients who developed new overt bioprosthesis dysfunction during follow-up had evidence of 18F-fluoride uptake at baseline (target-to-background ratio 1.89 [IQR: 1.46 to 2.59]). On multivariable analysis, 18F-fluoride uptake was the only independent predictor of future bioprosthetic dysfunction.

CONCLUSIONS

18F-fluoride PET-CT identifies subclinical bioprosthetic valve degeneration, providing powerful prediction of subsequent valvular dysfunction and highlighting patients at risk of valve failure. This technique holds major promise in the diagnosis of valvular degeneration and the surveillance of patients with bioprosthetic valves. (18F-Fluoride Assessment of Aortic Bioprosthesis Durability and Outcome [18F-FAABULOUS]; NCT02304276).

In Search of the Ideal Valve: Optimizing Genetic Modifications to Prevent Bioprosthetic Degeneration

BACKGROUND

Bioprosthetic heart valves undergo structural degeneration and calcification. Similarities exist in the histopathologic features of explanted bioprosthetic valves and rejected pig tissues and organs after xenotransplantation into nonhuman primates. The development of more durable bioprosthetic valves, namely from genetically modified pigs, could negate the need for the insertion of mechanical prostheses in children and young adults with the requirement for life-long anticoagulation and might avoid the need for reoperation in elderly patients.

METHODS

We reviewed the literature (MedlinePlus, PubMed, Google Scholar) through September 1, 2018, under four key terms: (1) bioprosthetic heart valves, (2) xenograft antigens, (3) immunologic responses to bioprosthetic valves, and (4) genetic modification of xenografts.

RESULTS

Advances in tissue and organ xenotransplantation have elucidated important immunologic barriers that provide innovative approaches to prevent structural degeneration of bioprosthetic heart valves. The current evidence suggests that bioprosthetic valves derived from genetically modified pigs lacking xenogeneic antigens (namely Gal, Neu5Gc, and Sda), termed triple-knockout pigs, would function considerably longer than current wild-type (genetically unmodified) porcine valves in human recipients.

CONCLUSIONS

Preclinical and clinical studies to determine the safety and efficacy of triple-knockout porcine bioprosthetic valves will likely establish that they are more resistant to human immune responses and thus less susceptible to structural degeneration.

Comparison of Biological and Mechanical Prostheses for Heart Valve Surgery: A Systematic Review of Randomized Controlled Trials

Background

The choice of a mechanical (MP) or biological prosthesis (BP) for patients with valvular heart disease undergoing replacement is still not a consensus.

Objective

We aimed to determine the clinical outcomes of MP or BP placement in those patients.

Methods

We conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) that compared biological prostheses and mechanical prostheses in patients with valvular heart diseases and assessed the outcomes. RCTs were searched in the MEDLINE, EMBASE, LILACS, CENTRAL, SCOPUS and Web of Science (from inception to November 2014) databases. Meta-analyses were performed using inverse variance with random effects models. The GRADE system was used to rate the quality of the evidence. A P-value lower than 0.05 was considered significant.

Results

A total of four RCTs were included in the meta-analyses (1,528 patients) with follow up ranging from 2 to 20 years. Three used old generation mechanical and biological prostheses, and one used contemporary prostheses. No significant difference in mortality was found between BP and MP patients (risk ratio (RR = 1.07; 95% CI 0.99-1.15). The risk of bleeding was significantly lower in BP patients than MP patients (RR = 0.64; 95% CI 0.52-0.78); however, reoperations were significantly more frequent in BP patients (RR = 3.60; 95% CI 2.44-5.32). There were no statistically significant differences between BP and MP patients with respect to systemic arterial embolisms and infective endocarditis (RR = 0.93; 95% CI 0.66-1.31, RR = 1.21; CI95% 0.78-1.88, respectively). Results in the trials with modern and old prostheses were similar.

Conclusions

The mortality rate and the risk of thromboembolic events and endocarditis were similar between BP and MP patients. The risk of bleeding was approximately one third lower for BP patients than for MP patients, while the risk of reoperations was more than three times higher for BP patients.

Comparison of Incidence, Predictors, and Outcomes of Early Infective Endocarditis after Transcatheter Aortic Valve Implantation Versus Surgical Aortic Valve Replacement in the United States

Infective endocarditis (IE) of prosthetic or bioprosthetic heart valves is a serious complication associated with significant morbidity and mortality. Data on the incidence, risk factors, and outcomes of IE after transcatheter aortic valve implantation (TAVI) in the United States are limited. We used the 2013 to 2014 Nationwide Readmissions Databases to determine the incidence of early IE after TAVI and surgical aortic valve replacement (SAVR) in the US. Clinical characteristics, independent predictors, and outcomes of patients with IE post-TAVI were examined. In 29,306 TAVI and 66,077 SAVR patients, the incidence rates of early IE were 1.7% (95% confidence interval [CI] 1.5% to 1.9%) and 2.5% (95% CI 2.3% to 2.9%) per person-year, respectively. In a propensity-matched cohort of 15,138 TAVI and 15,030 SAVR patients (weighted), there were no significant differences in the incidence rates of IE (1.7% [95% CI 1.4% to 2.0%] vs 1.9% [95% CI 1.6% to 2.2%] per person-year, log-rank p = 0.29) or in the median (interquartile range) time to IE (91 [48 to 146] vs 92 [61 to 214] days, p = 0.13). Staphylococcus (30.4%), Streptococcus (29.9%), and Enterococcus (20.5%) were the most common causative organisms of IE post-TAVI. Younger age, history of heart failure, need for permanent pacemaker placement, cardiac arrest, major bleeding, and sepsis during the index TAVI hospitalization were independently associated with an increased risk of IE. In-hospital mortality rate during readmission for IE was 15.6%. In conclusion, in a nationally representative cohort of TAVI patients in the US, the incidence rate of early IE was 1.7% per person-year. Age, co-morbid conditions, invasive procedures, and complications during the index hospitalization were associated with incident IE post-TAVI.

Initial scaffold thickness affects the emergence of a geometrical and mechanical equilibrium in engineered cardiovascular tissues

In situ cardiovascular tissue-engineering can potentially address the shortcomings of the current replacement therapies, in particular, their inability to grow and remodel. In native tissues, it is widely accepted that physiological growth and remodelling occur to maintain a homeostatic mechanical state to conserve its function, regardless of changes in the mechanical environment. A similar homeostatic state should be reached for tissue-engineered (TE) prostheses to ensure proper functioning. For in situ tissue-engineering approaches obtaining such a state greatly relies on the initial scaffold design parameters. In this study, it is investigated if the simple scaffold design parameter initial thickness, influences the emergence of a mechanical and geometrical equilibrium state in in vitro TE constructs, which resemble thin cardiovascular tissues such as heart valves and arteries. Towards this end, two sample groups with different initial thicknesses of myofibroblast-seeded polycaprolactone-bisurea constructs were cultured for three weeks under dynamic loading conditions, while tracking geometrical and mechanical changes temporally using non-destructive ultrasound imaging. A mechanical equilibrium was reached in both groups, although at different magnitudes of the investigated mechanical quantities. Interestingly, a geometrically stable state was only established in the thicker constructs, while the thinner constructs' length continuously increased. This demonstrates that reaching geometrical and mechanical stability in TE constructs is highly dependent on functional scaffold design.

A Novel Sensorized Heart Valve Prosthesis: Preliminary In Vitro Evaluation

Background: Recent studies have shown that subclinical valve thrombosis in heart valve prosthesis (HVP) can be responsible for reduced leaflet motion detectable only by advanced imaging diagnostics. We conceived a novel sensorized HVP able to detect earlier any thrombus formation that may alter the leaflets motion using an electric impedance measurement, IntraValvular Impedance (IVI). Methods: For IVI measurement, dedicated electrodes are embedded in the structure of the HVP to generate a local electric field that is altered by the moving valve leaflets during their cyclic opening/closing. We present preliminary in vitro results using a first prototype of sensorized mechanical heart valve connected to an external impedance measurement system. The prototype was tested on a circulatory mock loop system and the IVI signals were recorded during both normal dynamics and experimentally induced altered working of the leaflets. Results: Recordings showed a very repetitive and stable IVI signal during the normal cyclic opening/closing of the HVP. The induced alterations in leaflet motion were reflected in the IVI signal. Conclusions: The novel sensorized HVP has great potential to give early warning of possible subclinical valve thrombosis altering the valve leaflet motion, and to help in tailoring the anticoagulation therapy.

Heart valve tissue-derived hydrogels: Preparation and characterization of mitral valve chordae, aortic valve, and mitral valve gels

Heart valve (HV) diseases are among the leading causes of death and continue to threaten public health worldwide. The current clinical options for HV replacement include mechanical and biological prostheses. However, an ongoing problem with current HV prostheses is their failure to integrate with the host tissue and their inability grow and remodel within the body. Tissue engineered heart valves (TEHVs) are a promising solution to these problems, as they are able to grow and remodel somatically with the rest of the body. Recently, decellularized HVs have demonstrated great potential as valve replacements because they are tissue specific, but recellularization is still a challenge due to the dense HV extracellular matrix (ECM) network. In this proof-of-concept work, we decellularized porcine mitral valve chordae, aortic valve leaflets, and mitral valve leaflets and processed them into injectable hydrogels that could accommodate any geometry. While the three valvular ECMs contained various amounts of collagen, they displayed similar glycosaminoglycan contents. The hydrogels had similar nanofibrous structures and gelation kinetics with various compressive strengths. When encapsulated with NIH 3 T3 fibroblasts, all the hydrogels supported cell survivals up to 7 days. Decellularized HV ECM hydrogels may show promising potential HV tissue engineering applications. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1732-1740, 2019.

Cell Sources for Tissue Engineering Strategies to Treat Calcific Valve Disease

Cardiovascular calcification is an independent risk factor and an established predictor of adverse cardiovascular events. Despite concomitant factors leading to atherosclerosis and heart valve disease (VHD), the latter has been identified as an independent pathological entity. Calcific aortic valve stenosis is the most common form of VDH resulting of either congenital malformations or senile “degeneration.” About 2% of the population over 65 years is affected by aortic valve stenosis which represents a major cause of morbidity and mortality in the elderly. A multifactorial, complex and active heterotopic bone-like formation process, including extracellular matrix remodeling, osteogenesis and angiogenesis, drives heart valve “degeneration” and calcification, finally causing left ventricle outflow obstruction. Surgical heart valve replacement is the current therapeutic option for those patients diagnosed with severe VHD representing more than 20% of all cardiac surgeries nowadays. Tissue Engineering of Heart Valves (TEHV) is emerging as a valuable alternative for definitive treatment of VHD and promises to overcome either the chronic oral anticoagulation or the time-dependent deterioration and reintervention of current mechanical or biological prosthesis, respectively. Among the plethora of approaches and stablished techniques for TEHV, utilization of different cell sources may confer of additional properties, desirable and not, which need to be considered before moving from the bench to the bedside. This review aims to provide a critical appraisal of current knowledge about calcific VHD and to discuss the pros and cons of the main cell sources tested in studies addressing in vitro TEHV.

Hemodynamic and clinical performance of Solo stentless bioprosthetic aortic valves

OBJECTIVE

To report the hemodynamic profile and short- and medium-term outcomes of Freedom Solo and Solo Smart stentless aortic valves implanted at our center.

METHODS

Between 2009 and 2015, all patients undergoing aortic valve replacement using Solo stentless valves at our center were enrolled. Clinical and echocardiographic follow-up was carried out six months postoperatively. Survival and major events, including structural valve deterioration and non-structural valve dysfunction, endocarditis, reoperation and stroke, were assessed through medical records or telephone interview with the referring cardiologist up to November 2015 (mean and maximum follow-up 39±22 and 78 months, respectively).

RESULTS

Patients' (n=345) mean age was 72±8 years, 52% were female and median euroSCORE II was 2.7 (1.5-4.7). There was no intraoperative mortality and in-hospital mortality was 2.6%. Postoperatively, mean transvalvular gradient was 11.9±4.5 mmHg and effective orifice area was 1.9±0.5 cm². Patient-prosthesis mismatch occurred in 14% but was severe in only one patient. Cumulative survival at six years was 72%. Six patients were reoperated: three due to endocarditis, two for structural prosthesis deterioration and one because of periprosthetic fistula. Five patients suffered stroke, three had medically-treated endocarditis and one had structural valve deterioration but was not considered suitable for reoperation. None of the remainder had structural valve deterioration or non-structural valve dysfunction.

CONCLUSIONS

Solo stentless aortic valves are safe to implant, with promising clinical outcomes in short- and medium-term assessment. Moreover, they show an excellent hemodynamic performance: low transvalvular gradients, large effective orifice areas and low incidence of patient-prosthesis mismatch.

Adverse Hemodynamic Conditions Associated with Mechanical Heart Valve Leaflet Immobility

Artificial heart valves may dysfunction, leading to thrombus and/or pannus formations. Computational fluid dynamics is a promising tool for improved understanding of heart valve hemodynamics that quantify detailed flow velocities and turbulent stresses to complement Doppler measurements. This combined information can assist in choosing optimal prosthesis for individual patients, aiding in the development of improved valve designs, and illuminating subtle changes to help guide more timely early intervention of valve dysfunction. In this computational study, flow characteristics around a bileaflet mechanical heart valve were investigated. The study focused on the hemodynamic effects of leaflet immobility, specifically, where one leaflet does not fully open. Results showed that leaflet immobility increased the principal turbulent stresses (up to 400%), and increased forces and moments on both leaflets (up to 600% and 4000%, respectively). These unfavorable conditions elevate the risk of blood cell damage and platelet activation, which are known to cascade to more severe leaflet dysfunction. Leaflet immobility appeared to cause maximal velocity within the lateral orifices. This points to the possible importance of measuring maximal velocity at the lateral orifices by Doppler ultrasound (in addition to the central orifice, which is current practice) to determine accurate pressure gradients as markers of valve dysfunction.