Intrepid transcatheter mitral valve replacement system: technical and product description

The Current Landscape of Transcatheter Tricuspid Valve Intervention

Tricuspid regurgitation (TR) is common, and its prevalence increases with age. It was previously estimated that there are 1.6 million patients in the United States with moderate or worse TR, and more contemporary data suggest the age-adjusted prevalence of TR is 0.55%. Increasing TR severity is associated with an adverse prognosis independent of the pulmonary artery pressure and the degree of right heart failure. In heart failure with reduced ejection fraction, survival is significantly worsened when moderate or severe TR is present. The mainstay of therapy has traditionally been surgery, but outcomes are poor. There has been increasing attention on the potential role of transcatheter interventions for TR. Numerous platforms are in developmental evolution, which broadly fall into 3 categories: valve replacement, valve repair (subdivided into annular, leaflet, and chordal platforms), and caval valve implantation. In this review, we examine all these strategies and devices, including guidance on how to appropriately select patients who can benefit from intervention.

Transcatheter Mitral Valve Replacement Using Transcatheter Aortic Valve or Dedicated Devices: Current Evidence and Future Prospects

Transcatheter mitral valve replacement (TMVR) is a novel and evolving field dedicated to addressing the therapeutic challenges posed by patients at high surgical risk with mitral valve disease. TMVR can be categorized into two distinct fields based on the type of device and its specific indications: TMVR with transcatheter aortic valves (TAV) and TMVR with dedicated devices. Similar to aortic stenosis, TMVR with TAV requires a rigid support structure to secure the valve in place. As a result, it is indicated for patients with failing bioprothesis or surgical rings or mitral valve disease associated with severe mitral annular calcification (MAC), which furnishes the necessary foundation for valve anchoring. While TMVR with TAV has shown promising outcomes in valve-in-valve procedures, its effectiveness remains more contentious in valve-in-ring or valve-in-MAC procedures. Conversely, TMVR with dedicated devices seeks to address native mitral regurgitation, whether accompanied by MAC or not, providing an alternative to Transcatheter Edge-to-Edge Repair (TEER) when TEER is not feasible or expected to yield unsatisfactory results. This emerging field is gradually surmounting technical challenges, including anchoring a valve in a non-calcified annulus and transitioning from the transapical route to the transeptal approach. Numerous devices are presently undergoing clinical trials. This review aims to furnish an overview of the supporting evidence for TMVR using TAV in each specific indication (valve-in-valve, valve-in-ring, valve-in-MAC). Subsequently, we will discuss the anticipated benefits of TMVR with dedicated devices over TEER, summarize the characteristics and clinical results of TMVR systems currently under investigation, and outline future prospects in this field.

Multiphase Assessment of Mitral Annular Dynamics in Consecutive Patients With Significant Mitral Valve Disease

OBJECTIVES

The aim of this study was to clarify the dynamics of the mitral annulus throughout the cardiac cycle and its relevance to transcatheter mitral valve replacement (TMVR) sizing and case selection.

BACKGROUND

Limited data are available regarding the relevance of mitral annular (MA) and neo-left ventricular outflow tract (LVOT) dynamics in the overall population presenting with significant mitral valve disease.

METHODS

Patients attending a combined surgical-transcatheter heart valve clinic for severe symptomatic mitral valve disease were assessed using multiphase computed tomography. The relative influence of MA and neo-LVOT dynamics to TMVR case selection was studied.

RESULTS

A total of 476 patients with significant mitral valve disease were evaluated. In 99 consecutive patients with severe mitral regurgitation, a 10-phase assessment showed that the mitral annulus was on average largest in late systole. On comparing maximal MA dimension with late systolic dimension, TMVR size assignment changed in 24.2% of patients. If the average MA perimeter was used to determine sizing, 48.5% were excluded because of MA dimension being too large; in a multiphase assessment of the neo-LVOT, an additional 16.2% were excluded on the basis of neo-LVOT dimension. In an expanded series of 312 consecutive patients, selection protocol influenced anatomical exclusion: a manufacturer-proposed early systolic approach excluded 69.2% of patients, whereas a late systolic approach excluded 82.7% of patients, the vast majority because of large mitral annuli.

CONCLUSIONS

Contemporary TMVR can treat only a minority of patients with severe mitral regurgitation, principally because of limitations of large MA dimension.

Thirty-Day Outcomes Following Transfemoral Transseptal Transcatheter Mitral Valve Replacement: Intrepid TMVR Early Feasibility Study Results

OBJECTIVES

To evaluate outcomes of transcatheter mitral valve replacement (TMVR) with transfemoral access in patients at prohibitive or high surgical risk.

BACKGROUND

Prohibitive surgical risk may preclude MVR surgery in some patients. The investigational Intrepid TMVR system (Medtronic, Minneapolis, MN) has previously been evaluated using transapical access for delivery of a self-expanding bioprosthetic valve.

METHODS

This prospective, multi-center, non-randomized early feasibility study (EFS) evaluated safety and performance of the Intrepid valve using transfemoral/transseptal access in patients with moderate-severe/severe, symptomatic mitral regurgitation (MR) at high surgical risk. Candidacy was determined by heart teams with approval by a central screening committee. Echocardiographic data were evaluated by an independent core laboratory. Clinical events were adjudicated by a clinical events committee.

RESULTS

Fifteen patients were enrolled at 6 sites from Feb 2020-May 2021. Median age was 80 years and STS-PROM was 4.7%; 87% were male and 53% had prior sternotomy. Fourteen implants were successful. One patient converted to surgery during the index procedure. Patients stayed a median 5 days post-procedure. There were 6 (40%) access site bleeds and 11 (73%) iatrogenic ASD closures. At 30 days, there were no deaths, strokes, or reinterventions. All implanted patients had trace/no valvar or paravalvar MR and mean gradient was 4.7±1.8 mmHg.

CONCLUSIONS

Thirty-day results from the Intrepid transfemoral TMVR EFS demonstrate excellent valve function and no mortality or stroke. Additional patients and longer follow-up are needed to confirm these findings.

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.

Current Status and Future Prospects of Transcatheter Mitral Valve Replacement: JACC State-of-the-Art Review

Mitral regurgitation (MR) is the most prevalent valvular heart disease and, when left untreated, it confers a poorer prognosis. Catheter-based repair therapies face some limitations like their applicability on challenging anatomies and the potential recurrence of significant MR over time. Transcatheter mitral valve replacement (TMVR) has emerged as a less invasive approach potentially overcoming some of the current limitations associated with transcatheter mitral valve repair. Several devices are under clinical investigation, and a growing number of systems allow for a fully percutaneous transfemoral approach. In this review, the authors aimed to delineate the main challenges faced by the TMVR field, to highlight the key aspects for procedural planning, and to describe the clinical results of the TMVR systems under clinical investigation. Finally, they also discuss what the future perspectives are for this emerging field.

Transcatheter Mitral Valve Replacement: Current Evidence and Concepts

Over the past decade, several transcatheter devices have been developed to address the treatment of severe mitral regurgitation (MR) in patients at high surgical risk, mainly aimed at repairing the native mitral valve (MV). MV repair devices have recently been shown to have high efficacy and safety. However, to replicate promising trial results, specific anatomical and pathophysiological criteria have to be met and operators need a high level of experience. As yet, the longer-term durability of transcatheter MV repair remains unknown. Transcatheter MV replacement (TMVR) might be a treatment option able to target various anatomies, reliably abolish MR, and foster ease of use with a standardised implantation protocol. This review presents upcoming TMVR devices and available data and discusses how TMVR might further advance the field of transcatheter treatment of MR.

Multimodality Cardiac Imaging for Procedural Planning and Guidance of Transcatheter Mitral Valve Replacement and Mitral Paravalvular Leak Closure

Transcatheter mitral valve interventions are an evolving and growing field in which multimodality cardiac imaging is essential for diagnosis, procedural planning, and intraprocedural guidance. Currently, transcatheter mitral valve-in-valve with a balloon-expandable valve is the only form of transcatheter mitral valve replacement (TMVR) approved by the FDA, but valve-in-ring and valve-in-mitral annular calcification interventions are increasingly being performed. Additionally, there are several devices under investigation for implantation in a native annulus. Paravalvular leak (PVL) is a known complication of surgical or transcatheter valve implantation, where regurgitant flow occurs between the prosthetic sewing ring and the native mitral annulus. We sought to describe the role and applications of multimodality cardiac imaging for TMVR, and PVL closure, including the use of Cardiovascular Computed Tomography Angiography and 3-Dimensional Transesophageal Echocardiography for diagnosis, prosthetic valve evaluation, pre-procedural planning, and intraprocedural guidance, as well as evolving technologies such as fusion imaging and 3D printing.

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.

Causes and Clinical Outcomes of Patients Who Are Ineligible for Transcatheter Mitral Valve Replacement

OBJECTIVES

The aim of this study was to gain insight into the causes and outcomes of patients who do not qualify for transcatheter mitral valve replacement (TMVR).

BACKGROUND

Despite the increasing availability of TMVR, patients with severe mitral regurgitation may not be eligible. Thus far, no investigation has examined ineligible patients and their clinical outcomes.

METHODS

A total of 203 patients (mean age 79 ± 9 years, 48% men) who were ineligible for participation in early feasibility studies of TMVR were examined.

RESULTS

The ineligibility rate for TMVR was 89.0%. The most common reasons for TMVR exclusion were excessive frailty (15.3%), severe tricuspid regurgitation (15.3%), and prior aortic valve therapy (14.2%). Mitral anatomic exclusions were present in 15.8%, with severe annular calcification in 7.4%, and risk for left ventricular outflow tract obstruction was notably infrequent (4.4%). Overall, 76 patients (37.4%) did not undergo subsequent commercial surgical or transcatheter mitral therapy. Patients not eligible for TMVR and not treated commercially had high rates of cardiac death (11.8%) and death or heart failure hospitalization (22.4%) at 1 year. These rates were significantly higher than those who underwent surgery (2.4% for cardiac death; p < 0.001; 5.5% for heart failure hospitalization; p = 0.003) and remained worse after excluding patients with excessive frailty or medical futility and in multivariate modeling that adjusted for baseline differences.

CONCLUSIONS

Patients ineligible for TMVR and treated medically have poor outcomes. These data and the high rate of TMVR screen failure support the need for therapy iteration as well as development of alternative means of management, with the goal of improving the prognosis of these patients.

Early Experience With Transcatheter Mitral Valve Replacement: A Systematic Review

Background

Transcatheter mitral valve replacement (TMVR) has emerged as an alternative therapeutic option for the treatment of severe mitral regurgitation in patients with prohibitive or high surgical risk. The aim of this systematic review is to evaluate the clinical procedural characteristics and outcomes associated with the early TMVR experience.

Methods and Results

Published studies and international conference presentations reporting data on TMVR systems were identified. Only records including clinical characteristics, procedural results, and 30‐day and midterm outcomes were analyzed. A total of 16 publications describing 308 patients were analyzed. Most patients (65.9%) were men, with a mean age of 75 years (range: 69–81 years) and Society for Thoracic Surgery Predicted Risk of Mortality score of 7.7% (range: 6.1–8.6%). The etiology of mitral regurgitation was predominantly secondary or mixed (87.1%), and 81.5% of the patients were in New York Heart Association class III or IV. A transapical approach was used in 81.5% of patients, and overall technical success was high (91.7%). Postprocedural mean transmitral gradient was 3.5 mm Hg (range: 3–5.5 mm Hg), and only 4 cases (1.5%) presented residual moderate to severe mitral regurgitation. Procedural and all‐cause 30‐day mortality were 4.6% and 13.6%, respectively. Left ventricular outflow obstruction and conversion to open heart surgery were reported in 0.3% and 4% of patients, respectively. All‐cause and cardiovascular‐related mortality rates were 27.6% and 23.3%, respectively, after a mean follow‐up of 10 (range: 3 to 24) months.

Conclusions

TMVR was a feasible, less invasive alternative for treating severe mitral regurgitation in patients with high or prohibitive surgical risk. TMVR was associated with a high rate of successful valve implantation and excellent hemodynamic results. However, periprocedural complications and all‐cause mortality were relatively high.

Transcatheter Mitral Valve Replacement with Intrepid

Transcatheter mitral valve replacement with the Intrepid device is intended for patients who need mitral valve replacement and who are at an increased risk for conventional surgery. The early published results of the early feasibility trial are reviewed as well as device design and the implant procedure. The Apollo trial is reviewed: a randomized trial of the Intrepid device versus conventional surgery including a single arm study for inoperable patients. The mitral valve structure, pathophysiology, and postimplant physiology pose unique hurdles for any transcatheter implant.

Transcatheter Mitral Valve Implantation with the Medtronic Intrepid™ Transcatheter Mitral Valve Replacement System

Mitral regurgitation is the most prevalent yet undertreated valvulopathy despite its adverse prognosis. With the emergence of transcatheter mitral interventions, the potential for this huge unmet disease burden to be addressed may finally be realized. Medtronic Intrepid™ Transcatheter Mitral Valve Replacement System represents one of several novel solutions. Based on early data from the pilot study, its efficacy and clinical utility is currently being tested against the mainstay treatment of surgical mitral valve replacement in a randomized trial. While there remain significant challenges before transcatheter mitral intervention can become part of the routine treatment algorithm, the authors are optimistic that transcatheter mitral valve repair and intervention have the potential in revolutionizing the management of severe symptomatic mitral regurgitation.

Novel In Vitro Test Systems and Insights for Transcatheter Mitral Valve Design, Part II: Radial Expansion Forces

Transcatheter mitral valve (TMV) replacement technology has great clinical potential for surgically inoperable patients suffering from mitral regurgitation. An important goal for robust TMV design is maximizing the likelihood of achieving a geometry post-implant that facilitates optimal performance. To support this goal, improved understanding of the annular forces that oppose TMV radial expansion is necessary. In Part II of this study, novel circular and D-shaped Radial Expansion Force Transducers (C-REFT and D-REFT) were developed and employed in porcine hearts (N = 12), to detect the forces required to radially expand the mitral annulus to discrete oversizing levels. Forces on both the septal-lateral and inter-commissural axes (FSL and FIC) scaled with device size. The D-REFT experienced lower FSL than the C-REFT (19.8 ± 7.4 vs. 17.4 ± 10.8 N, p = 0.002) and greater FIC (31.5 ± 14.0 vs. 36.9 ± 16.2 N; p = 0.002), and was more sensitive to degree of oversizing. Across all tests, FIC/FSL was 2.21 ± 1.33, likely reflecting low resistance to radial expansion at the aorto-mitral curtain. In conclusion, the annular forces opposing TMV radial expansion are non-uniform, and depend on final TMV shape and size. Based on this two-part study, we propose that radial force applied at the commissural aspect of the annulus has the most potent effect on paravalvular sealing.

Transcatheter mitral valve replacement for mitral regurgitation-A meta-analysis

OBJECTIVES

We performed a meta-analysis to determine the outcomes in patients undergoing transcatheter mitral valve replacement (TMVR) for mitral regurgitation (MR).

METHODS

Databases including MEDLINE and EMBASE were searched through April 2018 using Web-based search engines (PubMed and OVID) to identify single-arm observational (case series) studies of TMVR enrolling ≥5 patients with MR. For each study, data regarding observed 30-day mortality and predicted operative mortality (Society of Thoracic Surgeons Predicted Risk of Mortality) were used to generate risk ratios (RRs) and 95% confidence intervals (CIs). Study-specific estimates were combined using the inverse variance-weighted average of logarithmic RRs in the random-effects model. One-group meta-analyses of 30-day and >30-day (including 30-day) mortality were also performed in the random-effects model.

RESULTS

Of 222 potentially relevant articles screened initially, nine eligible studies enrolling a total of 146 patients with MR undergoing TMVR were identified. In all but two studies, STS-PROM was available and varied from 3.3% to 15.4% (arithmetic mean, 7.6%). Pooled analyses demonstrated 30-day mortality of 20.4% (95%CI, 9.6-31.2%), >30-day mortality of 32.0% (95%CI, 19.8-44.2%), and non-significantly higher observed 30-day mortality than predicted operative mortality (RR, 1.70; 95%CI, 0.85-3.42; P = 0.14). There was no evidence of significant publication bias.

CONCLUSION

TMVR for patients with MR results in increased early and late mortality.

Early experience with the Intrepid system for transcatheter mitral valve replacement

Severe mitral regurgitation is common and results in a poor prognosis in patients with either symptoms or severe ventricular dilatation. While mitral regurgitation has traditionally necessitated surgical repair or replacement, new transcatheter methods, such as the IntrepidTM transcatheter mitral valve replacement, has recently emerged. The Intrepid system is a circular, self-expanding, tri-leaflet bovine pericardial prosthesis housed within a nitinol frame. In early feasibility studies, the Intrepid prosthesis has been found to be effective for relief of mitral regurgitation and associated with functional improvement in the majority of survivors.

Future Technology

Mitral regurgitation is the most common valvular disease and significant (moderate/severe) mitral regurgitation is found in 2.3% of the population older than 65 years. New transcatheter minimally invasive technologies are being developed to address mitral valve disease in patients deemed too high a risk for conventional open-heart surgery. There are several features of the mitral valve (saddle-shaped noncalcified annulus with irregular leaflet geometry) that make a transcatheter approach to repair or replacing the valve more challenging compared with the aortic valve. Several devices are under investigation for transcatheter mitral valve replacement, and also for mitral valve repair targeting the mitral valve leaflets, chordae tendinae, and mitral annulus. The MitraClip device is the only Food and Drug Administration-approved device to treat mitral regurgitation by targeting the mitral leaflets. There are eight minimally invasive devices being studied in humans that target the mitral annulus, and at least two devices being studied in animal models. There are 5 devices in clinical trials for minimally invasive approaches targeting the chordae tendinae. More than 10 different transcatheter mitral valves are in various stages of development and clinical trials. These transcatheter mitral valves can be delivered either through a transseptal, transapical, transaortic, or left atriotomy approach. It seems likely that transcatheter treatment approaches to mitral valve disease will become more common, at least in the sick and elderly patient population.

Early Experience With New Transcatheter Mitral Valve Replacement

BACKGROUND

Transcatheter mitral valve replacement (TMVR) is a potential therapy for patients with symptomatic, severe mitral regurgitation (MR). The feasibility of this therapy remains to be defined.

OBJECTIVES

The authors report their early experience with TMVR using a new valve system.

METHODS

The valve is a self-expanding, nitinol valve with bovine pericardial leaflets that is placed using a transapical delivery system. Patients with symptomatic MR who were deemed high or extreme risk by the local heart teams were enrolled in a global pilot study at 14 sites (United States, Australia, and Europe).

RESULTS

Fifty consecutively enrolled patients (mean age: 73 ± 9 years; 58.0% men; 84% secondary MR) underwent TMVR with the valve. The mean Society for Thoracic Surgery score was 6.4 ± 5.5%; 86% of patients were New York Heart Association functional class III or IV, and the mean left ventricular ejection fraction was 43 ± 12%. Device implant was successful in 48 patients with a median deployment time of 14 min (interquartile range: 12 to 17 min). The 30-day mortality was 14%, with no disabling strokes, or repeat interventions. Median follow-up was 173 days (interquartile range: 54 to 342 days). At latest follow-up, echocardiography confirmed mild or no residual MR in all patients who received implants. Improvements in symptom class (79% in New York Heart Association functional class I or II at follow-up; p < 0.0001 vs. baseline) and Minnesota Heart Failure Questionnaire scores (56.2 ± 26.8 vs. 31.7 ± 22.1; p = 0.011) were observed.

CONCLUSIONS

TMVR with the valve was feasible in a study group at high or extreme risk for conventional mitral valve replacement. These results inform trial design of TMVR in lower-risk patients with severe mitral valve regurgitation (Evaluation of the Safety and Performance of the Twelve Intrepid Transcatheter Mitral Valve Replacement System in High Risk Patients with Severe, Symptomatic Mitral Regurgitation - The Twelve Intrepid TMVR Pilot Study; NCT02322840).

Design, Analysis and Testing of a Novel Mitral Valve for Transcatheter Implantation

Mitral regurgitation is a common mitral valve dysfunction which may lead to heart failure. Because of the rapid aging of the population, conventional surgical repair and replacement of the pathological valve are often unsuitable for about half of symptomatic patients, who are judged high-risk. Transcatheter valve implantation could represent an effective solution. However, currently available aortic valve devices are inapt for the mitral position. This paper presents the design, development and hydrodynamic assessment of a novel bi-leaflet mitral valve suitable for transcatheter implantation. The device consists of two leaflets and a sealing component made from bovine pericardium, supported by a self-expanding wireframe made from superelastic NiTi alloy. A parametric design procedure based on numerical simulations was implemented to identify design parameters providing acceptable stress levels and maximum coaptation area for the leaflets. The wireframe was designed to host the leaflets and was optimised numerically to minimise the stresses for crimping in an 8 mm sheath for percutaneous delivery. Prototypes were built and their hydrodynamic performances were tested on a cardiac pulse duplicator, in compliance with the ISO5840-3:2013 standard. The numerical results and hydrodynamic tests show the feasibility of the device to be adopted as a transcatheter valve implant for treating mitral regurgitation.