Transcatheter Mitral Valve Replacement: State of the Art

Transcatheter mitral valve implantation versus conventional redo surgery for degenerated mitral valve prostheses and rings in a multicenter registry

OBJECTIVES

Degeneration of mitral prostheses/rings may be treated by redo surgery, and, recently, by transcatheter valve-in-valve/ring implantation. This multicenter registry presents results of transcatheter valve-in-valve and repeat surgery for prostheses/rings degeneration.

METHODS

Data provided by 10 German heart centers underwent propensity score-matched retrospective analysis. The primary endpoint was 30-day/midterm mortality. Perioperative outcome was assessed according to the Mitral Valve Academic Research Consortium criteria. Further, the influence of moderate or greater tricuspid regurgitation (TR) on 30-day/midterm mortality was analyzed.

RESULTS

Between 2014 and 2019, 273 patients (79 transcatheter mitral valve-in-valve [TM-ViV] and 194 redo mitral valve replacement [Re-MVR]) underwent repeat procedure for mitral prosthesis/ring degeneration. Propensity score matching distinguished 79 patient pairs. European System for Cardiac Operative Risk Evaluation (EuroSCORE) II-predicted risk was 15.7 ± 13.7% in the TM-ViV group and 15.0% ± 12.7% in the Re-MVR group (P = .5336). TM-ViV patients were older (74.73 vs 72.2 years; P = .0030) and had higher incidence of atrial fibrillation (54 vs 40 patients; P = .0233). Severe TR incidence was similar (17.95% in TM-ViV vs 14.10%; P = .1741). Sixty-eight TM-ViV patients previously underwent mitral valve replacement, whereas 41 Re-MVR patients underwent valve repair (P < .0001). Stenosis was the leading degeneration mechanism in 42 TM-ViV versus 22 Re-MVR patients (P < .0005). The 30-day/midterm mortality did not differ between groups. Moderate or greater TR was a predictor of total (odds ratio [OR], 4.36; P = .0011), 30-day (OR, 3.76; P = .0180), and midterm mortality (OR, 4.30; P = .0378), irrespective of group.

CONCLUSIONS

In both groups, observed mortality was less than predicted. Redo surgery enabled treatment of concomitant conditions, such as atrial fibrillation or TR. TR was shown to be a predictor of total, 30-day, and midterm mortality in both groups.

Polymeric Heart Valves Will Displace Mechanical and Tissue Heart Valves: A New Era for the Medical Devices

The development of a novel artificial heart valve with outstanding durability and safety has remained a challenge since the first mechanical heart valve entered the market 65 years ago. Recent progress in high-molecular compounds opened new horizons in overcoming major drawbacks of mechanical and tissue heart valves (dysfunction and failure, tissue degradation, calcification, high immunogenic potential, and high risk of thrombosis), providing new insights into the development of an ideal artificial heart valve. Polymeric heart valves can best mimic the tissue-level mechanical behavior of the native valves. This review summarizes the evolution of polymeric heart valves and the state-of-the-art approaches to their development, fabrication, and manufacturing. The review discusses the biocompatibility and durability testing of previously investigated polymeric materials and presents the most recent developments, including the first human clinical trials of LifePolymer. New promising functional polymers, nanocomposite biomaterials, and valve designs are discussed in terms of their potential application in the development of an ideal polymeric heart valve. The superiority and inferiority of nanocomposite and hybrid materials to non-modified polymers are reported. The review proposes several concepts potentially suitable to address the above-mentioned challenges arising in the R&D of polymeric heart valves from the properties, structure, and surface of polymeric materials. Additive manufacturing, nanotechnology, anisotropy control, machine learning, and advanced modeling tools have given the green light to set new directions for polymeric heart valves.

Gender-related differences on outcome following transcatheter mitral valve repair (TMVR): a systematic review and meta-analysis

BACKGROUND

The effect of gender on patients with mitral valve regurgitation (MR) undergoing transcatheter mitral valve repair (TMVR) remains to be defined. The aim of the present study is a comprehensive meta-analysis of studies that investigate differences between men and women after TMVR.

METHODS

A systematic literature search was carried out on eight databases to collect all relevant studies on gender-related outcomes of TMVR before March 1, 2021. The main outcomes of interest were mortality, cardiac function, MR class and other complications.

RESULTS

A total of eight literatures were included, all of which were retrospective observational studies. Compared to women patients, men had lower postoperative New York Heart Association (NYHA) class (OR = 1.53, 95%CI [1.23, 1.91], P = 0.0001) and higher incidence of postoperative acute kidney injury (AKI) (OR = 1.25, 95%CI [1.16, 1.34], P < 0.05). There were no significant difference on mortality in 30 days (OR = 0.95, 95%CI [0.81, 1.11], P = 0.53) and in 2 years (OR = 0.99, 95%CI [0.75, 1.30], P = 0.93), mitral valve regurgitation (MR) class (OR = 1.30, 95%CI [0.97, 1.75], P = 0.08) and incidence of myocardial infarction (MI) (OR = 0.88, 95%CI [0.65, 1.18], P = 0.38), stroke (OR = 0.80, 95%CI [0.63, 1.02], P = 0.08) and bleeding in hospital (OR = 0.84, 95%CI [0.59, 1.19], P = 0.32).

CONCLUSIONS

Our meta-analysis demonstrates that men undergoing TMVR have worse preoperative diseases (diabetes mellitus, coronary artery disease, renal failure and myocardial infarction) while they have superior postoperative NYHA class at one-year. There are no significantly difference in other indexes between men and women.

Valve interstitial cells under impact load, a mechanobiology study

Understanding the relationship between mechanobiology and the biosynthetic activities of the valve interstitial cells (VICs) in health and disease under severe dynamic loading conditions is of particular interest. The purpose of this study is to further understand the mechanobiology of heart valve leaflet tissue and the VICs under impact forces. Two novel computational and experimental platforms were developed to study the effect of impact load on the VICs to monitor for apoptosis. The first objective was to design and develop an apparatus to experimentally study viability (apoptosis) of the porcine heart valve leaflet tissue VICs in the aortic position under controlled impact forces. Apoptosis was assessed based on terminal transferase dUTP nick end-labelling (TUNEL) assay. The second objective was to develop a computational platform to estimate the stress and strain fields in the vicinity of VICs when the tissue experiences impact forces. A nonlinear finite element (FE) model with an anisotropic, hyperelastic and heterogeneous material model for the matrix and cells was developed. Preliminary results confirm that interstitial cells are successfully resistant to impact loads up to 30 times more than normal physiological conditions. Additionally, the structure and composition of heart valve leaflet tissue provides a mechanical shield for VICs protecting them from excessive mechanical forces such as impact loads. Although, the entire tissue may experience excessive stresses, which may lead to structural damage, the stresses around and near VICs remain consistency low. Results of this study may be used for heart valve leaflet tissue-engineering, as well as further understanding the mechanobiology of the VICs in health and disease.

Outcomes after Transcatheter Mitral Valve Implantation: A Literature Review

Mitral valve disease is the most common heart valve disease worldwide. Surgical mitral valve replacement or repair has been an established therapy in patients with severe mitral valve disease for many years. On the other hand, many patients with advanced mitral valve disease and severe comorbidities are treated conservatively and are excluded from the surgical procedure. Furthermore, in patients with severe comorbidities, transcatheter mitral valve repair by edge-to-edge technique with MitraClip or transcatheter mitral valve repair with a non-absorbable ring have been added as therapeutic options over the last few years. Alternative procedures for the treatment of patients with advanced prosthetic or native mitral valve diseases include transcatheter access for replacement or implantation of a new prosthetic valve in the diseased mitral valve. Promising results were published about short-term outcomes of patients who underwent the transcatheter mitral valve replacement. The current view and results of the transcatheter mitral valve implantation in patients with advanced native or prosthetic mitral valve disease are briefly discussed.

Splitting the anterior mitral leaflet impairs left ventricular function in an ovine model

OBJECTIVES

During mitral valve replacement, the anterior mitral leaflet is usually resected or modified. Anterior leaflet splitting seems the least disruptive modification. Reattachment of the modified leaflet to the annulus reduces the annulopapillary distance. The goal of this study was to quantify the acute effects on left ventricular function of splitting the anterior mitral leaflet and shortening the annulopapillary distance.

METHODS

In 6 adult sheep, a wire was placed around the anterior leaflet and exteriorized through the left ventricular wall to enable splitting the leaflet in the beating heart. Releasable snares to reduce annulopapillary distance were likewise positioned and exteriorized. A mechanical mitral prosthesis was inserted to prevent mitral incompetence during external manipulations of the native valve. Instantaneous changes in left ventricular function were recorded before and after shortening the annulopapillary distance, then before and after splitting the anterior leaflet.

RESULTS

After splitting the anterior leaflet, preload recruitable stroke work, stroke work, stroke volume, cardiac output, left ventricular end systolic pressure and mean pressure were significantly decreased by 26%, 23%, 12%, 9%, 15% and 11%, respectively. Shortening the annulopapillary distance was associated with significant decreases in the end systolic pressure volume relationship, preload recruitable stroke work, stroke work and left ventricular end systolic pressure by 67%, 33%, 15% and 13%, respectively. Shortening the annulopapillary distance after splitting the leaflet had no significant effect.

CONCLUSIONS

Splitting the anterior mitral leaflet acutely impaired left ventricular contractility and haemodynamics in an ovine model. Shortening the annulopapillary distance after leaflet splitting did not further impair left ventricular function.

Transcatheter mitral valve replacement: there is still work to be done

Transcatheter mitral valve replacement (TMVR) is a novel therapeutic option for patients with severe mitral regurgitation (MR) at high or prohibitive surgical risk. Most TMVR technologies under investigation use either a trans-apical or a trans-septal approach via dedicated multistep anchoring systems. Transcatheter mitral valve replacement offers several potential advantages over transcatheter repair, notably a greater and more sustained MR reduction. At the same time, significant engineering challenges and potential disadvantages must be acknowledged. Preclinical and clinical studies have shown promising results, demonstrating TMVR feasibility. Nevertheless, further development, testing, and trials are needed before considering TMVR as a definitive therapeutic option for MR in a wide range of anatomical scenarios.

In-Hospital Outcomes and Predictors of Mortality for Redo Surgical Mitral Valve Replacement Versus Transcatheter Mitral Valve-in-Valve Replacement

Durability is a major limitation with bioprosthetic heart valves. For mitral valve prosthesis dysfunction, redo surgical mitral valve replacement (rSMVR) has been the mainstay of treatment; however, transcatheter mitral valve-in-valve replacement (mViV) has emerged as a viable alternative. Data comparing these procedures remains limited; therefore, we sought to compare the real-world in-hospital mortality, likelihood of adverse peri-operative outcomes, and predictors of mortality between rSMVR versus mViV using the National Inpatient Sample. During the study period, a weighted total of 1,890 patients (78%) underwent rSMVR, and 520 (22%) underwent mViV. After propensity matching, there were 310 patients in each cohort. There was no statistically significant difference in mortality with these procedures (odds ratio 1.53; 95% confidence interval 0.67 to 3.45; p = 0.31). rSMVR was associated with increased length of hospitalization (13 vs 7.5 days; p <0.001), increased medical costs ($324,124 vs $241,147; p <0.001), and increased peri-operative complications compared with mViV. Predictors of mortality unique to rSMVR were age >75 years, cirrhosis, sleep apnea, malnourishment/low body mass index, and obesity, signalizing greater suitability for mViV in these populations.

Asymptomatic Stroke in the Setting of Percutaneous Non-Coronary Intervention Procedures

Advancements in clinical management, pharmacological therapy and interventional procedures have strongly improved the survival rate for cardiovascular diseases (CVDs). Nevertheless, the patients affected by CVDs are more often elderly and present several comorbidities such as atrial fibrillation, valvular heart disease, heart failure, and chronic coronary syndrome. Standard treatments are frequently not available for “frail patients”, in particular due to high surgical risk or drug interaction. In the past decades, novel less-invasive procedures such as transcatheter aortic valve implantation (TAVI), MitraClip or left atrial appendage occlusion have been proposed to treat CVD patients who are not candidates for standard procedures. These procedures have been confirmed to be effective and safe compared to conventional surgery, and symptomatic thromboembolic stroke represents a rare complication. However, while the peri-procedural risk of symptomatic stroke is low, several studies highlight the presence of a high number of silent ischemic brain lesions occurring mainly in areas with a low clinical impact. The silent brain damage could cause neuropsychological deficits or worse, a preexisting dementia, suggesting the need to systematically evaluate the impact of these procedures on neurological function.

Randomized Trials Are Needed for Transcatheter Mitral Valve Replacement

Transcatheter mitral valve replacement (TMVR) is a new therapy for treating symptomatic mitral regurgitation (MR) and stenosis. The proposed benefit of TMVR is the predictable, complete elimination of MR, which is less certain with transcatheter repair technologies such as TEER (transcatheter edge-to-edge repair). The potential benefit of MR elimination with TMVR needs to be rigorously evaluated against its risks which include relative procedural invasiveness, need for anticoagulation, and chronic structural valve deterioration. Randomized controlled trials (RCTs) are a powerful method for evaluating the safety and effectiveness of TMVR against current standard of care transcatheter therapies, such as TEER. RCTs not only help with the assessment of benefits and risks, but also with policies for determining operator or institutional requirements, resource utilization, and reimbursement. In this paper, the authors provide recommendations and considerations for designing pivotal RCTs for first-in-class TMVR devices.

Transcatheter mitral valve therapies: State of the art

Mitral regurgitation (MR) is one of the most prevalent valvular pathologies in the developed world. There continues to be a growing population of aging patients with MR who may be too high risk for surgical management. The rapid adoption and remarkable success of transcatheter aortic valve replacement (TAVR) generated enthusiasm for transcatheter mitral valve therapies; however, the complex anatomy and pathophysiology of the mitral valve confers several unique challenges for a fully percutaneous approach. Nevertheless, several devices are under development and in various phases of preclinical or clinical testing, both for transcatheter mitral valve replacement and repair. MitraClip (Abbott Vascular), which has received FDA approval, is the most established percutaneous repair strategy and has been performed in over 80,000 patients as of 2019. The following article serves as a review of the available and upcoming devices for the various etiologies of mitral valvular disease, as well as the unique challenges and potential complications of transcatheter mitral valve intervention.

Device Therapy in Chronic Heart Failure: JACC State-of-the-Art Review

The regulatory landscape for device-based heart failure (HF) therapies has seen a major shift in the last 7 years. In 2013, the U.S. Food and Drug Administration released guidance for early feasibility and first-in-human studies, thereby encouraging device innovation, and in 2016 the U.S. Congress authorized the Breakthrough Devices Program to expedite access for Americans to innovative devices indicated for diagnosis and treatment of serious illnesses, such as HF. Since December 2016, there has been an increase in the number of HF devices for which manufacturers are seeking approval through the breakthrough designation pathway. This has led to a rapid uptake in the development and evaluation of device-based HF therapies. This article reviews the current and future landscape of device therapies for chronic HF and associated comorbidities and the regulatory environment that is driving current and future innovation.

Transcatheter Heart Valves: A Biomaterials Perspective

Heart valve disease is prevalent throughout the world, and the number of heart valve replacements is expected to increase rapidly in the coming years. Transcatheter heart valve replacement (THVR) provides a safe and minimally invasive means for heart valve replacement in high-risk patients. The latest clinical data demonstrates that THVR is a practical solution for low-risk patients. Despite these promising results, there is no long-term (>20 years) durability data on transcatheter heart valves (THVs), raising concerns about material degeneration and long-term performance. This review presents a detailed account of the materials development for THVRs. It provides a brief overview of THVR, the native valve properties, the criteria for an ideal THV, and how these devices are tested. A comprehensive review of materials and their applications in THVR, including how these materials are fabricated, prepared, and assembled into THVs is presented, followed by a discussion of current and future THVR biomaterial trends. The field of THVR is proliferating, and this review serves as a guide for understanding the development of THVs from a materials science and engineering perspective.

Current Status of Catheter-based Mitral Valve Replacement

PURPOSE OF REVIEW

Transcatheter mitral valve replacement (TMVR) has been developed to address the need for an alternative therapeutic option to surgery in patients suffering from severe mitral regurgitation who are at high surgical risk. The present review illustrated the state-of-the-art of catheter-based mitral valve replacement evaluating technical characteristics and early clinical experience of different devices to outline prospects and challenges of TMVR.

RECENT FINDINGS

Several devices are currently under clinical assessment. Early experience has demonstrated high procedural success of TMVR. However, TMVR faces several possible hurdles such as left ventricular outflow tract obstruction (LVOTO) after prosthesis deployment, access site complications, and thrombotic risk requiring anticoagulatory therapy. Future studies should assess long-term prosthesis stability, optimal anticoagulation regime, and occurrence of paravalvular leakage. The development of smaller TMVR prostheses suitable for transseptal implantation could overcome bleeding complications. In perspective, TMVR may emerge to a clinically relevant therapeutic approach for patients with severe MR at high surgical risk.

A Single-opening&closing Valve Tester for Direct Measurement of Closing Volume of the Heart Valve

PURPOSE

The objective of this study was to develop a novel single opening&closing pulsatile flow in-vitro valve tester for direct measurement of closing volume of the heart valve.

METHODS

A single opening&closing valve tester was composed of a piston pump, valve mounting chamber, reservoir, measurement and control system. The piston pump was used to drive a valve to open and close with dictated flow which comprised three phases of accelerated, constant, and decelerated flow with six slopes. A high speed camera was used to record valve opening and closing images. Two pressure transducers across the tested valve were used to capture the ending time of valve closing which was verified by the high-speed photography. The closing time was measured and closing volume was calculated with a piston displacement volume during valve closing. A tilting disc valve and porcine mitral valve were tested.

RESULTS

There was a big difference in flowrate between the Transonic flowmeter and piston pump. The heart valve opened and closed under the dictated flow driven by the piston pump. The transvalvular pressure was minor during valve opening and then increased sharply during valve closing. The closing time varied approximately linearly with the slope of the decelerated flow and was comparable between the two methods by the transvalvular pressure and high-speed photography. The closing volumes did not change much with the slope of the decelerated flow and were 7.0 ± 1.0 and 14.0 ± 1.5 mL for the tilting disc valve and mitral valve, respectively.

CONCLUSION

Pulsatile flow is challenging to the flowmeter. A novel single opening&closing pulsatile flow in-vitro valve tester for the heart valve has successfully been developed and can be used to simulate and evaluate the opening and closing hemodynamics of the heart valve. The tester can be used to measure valve closing volume and time accurately with a standardized testing protocol free from effect of other components such as the resistance, compliance units and auxiliary valve in the continuous pulsatile flow valve tester.

Long-term outcomes of a totally thoracoscopic approach for reoperative mitral valve replacement: a propensity score matched analysis

BACKGROUND

This study aimed to summarize the perioperative and long-term outcomes of patients with previous mitral valve surgery (MVS) undergoing reoperative mitral valve replacement (MVR).

METHODS

Data for all reoperative mitral valve replacements (re-MVRs) with or without concomitant tricuspid surgery were analyzed from Guangdong Provincial People's Hospital between January 2013 and December 2019. Propensity score matching resulted in 30 matched pairs with improved balance after matching in baseline covariates. Perioperative data and long-term clinical outcomes were analyzed.

RESULTS

Results are based on the matched cohorts between the two groups. The in-hospital mortality was 3.3% (two deaths) in the entire cohort and was not significantly different between the median sternotomy (MS) group and the totally thoracoscopic (TT) group. Most patients in the TT group had their tracheal intubation removed within 24 hours of surgery. The TT group had a diminished requirement for blood transfusion and a reduced 4-day postoperative chest tube drainage amount. The incidence of early major complications, including all-cause death and reoperation due to bleeding, was lower in the TT group. No significant differences were observed in the 7-year survival probability between the two groups.

CONCLUSIONS

The encouraging results regarding the perioperative and long-term outcomes of patients who underwent a TT re-MVR show that this approach is particularly beneficial for patients requiring reoperation.

Transcatheter Mitral Valve Replacement: A Novel Anchor Technology

BACKGROUND

 Mitral valved stents tend to migrate or to develop paravalvular leakage due to high-left ventricular pressure in this cavity. Thus, this study describes a newly developed mitral valved stent anchoring technology.

METHODS

 Based on an existing mitral valved stent, four anchoring units with curved surgical needles were designed and fabricated using three-dimensional (3D) software and print technology. Mitral nitinol stents assembled with four anchoring units were successively fixed on 10 porcine annuli. Mechanical tests were performed with a tensile force test system and recorded the tension forces of the 10 nitinol stents on the annulus.

RESULTS

 The average maximum force was 28.3 ± 5.21 N, the lowest was 21.7 N, and the highest was 38.6 N until the stent lost contact with the annulus; for the break force (zero movement of stent from annulus), the average value was 18.5 ± 6.7 N with a maximum value of 26.9 N and a minimum value of 6.07 N. It was additionally observed that the puncture needles of the anchoring units passed into the mitral annulus in all 10 hearts and further penetrated the myocardium in only one additional heart. The anchoring units enhanced the tightness of the mitral valved stent and did not destroy the circumflex coronary artery, coronary sinus, right atrium, aortic root, or the left ventricular outflow tract.

CONCLUSION

 The new anchoring units for mitral nitinol stents were produced with 3D software and printing technology; with this new type of anchoring technology, the mitral valved stent can be tightly fixed toward the mitral annulus.

Cross-Linking Porcine Pericardium by 3,4-Dihydroxybenzaldehyde: A Novel Method to Improve the Biocompatibility of Bioprosthetic Valve

Heart valve replacement is an effective therapy for patients with moderate to severe valvular stenosis or regurgitation. Most bioprosthetic heart valves applied clinically are based on cross-linking with glutaraldehyde (GLUT), but they have some drawbacks like high cytotoxicity, severe calcification, and poor hemocompatibility. In this study, we focused on enhancing the properties of bioprosthetic heart valves by cross-linking with 3,4-dihydroxybenzaldehyde (DHBA). The experiment results revealed that compared with GLUT cross-linked porcine pericardium (PP), the relative amount of platelets absorbed on the surface of DHBA cross-linked PP decreased from 0.294 ± 0.034 to 0.176 ± 0.028, and the activated partial thromboplastin time (APTT) increased from 9.9 ± 0.1 to 15.2 ± 0.1 s, indicating improved hemocompatibility. Moreover, anticalcification performance and cytocompatibility were greatly enhanced by DHBA cross-linking. In conclusion, the properties of bioprosthetic valves could be effectively improved by processing valves with a DHBA-based cross-linking method.