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Table of Contents
EDITORIAL REVIEW
Year : 2018  |  Volume : 1  |  Issue : 2  |  Page : 63-70

Transcatheter mitral valve replacement for failed mitral bioprosthesis: The new frontier!


Department of Cardiology, Medanta – The Medicity, Gurugram, Haryana, India

Date of Web Publication13-Dec-2018

Correspondence Address:
Dr. Nagendra S Chouhan
Department of Cardiology, Medanta – The Medicity, Sector 38, Gurugram 122001, Haryana
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/IHJI.IHJI_34_18

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  Abstract 

Structural deterioration is a major and inevitable complication of bioprosthetic heart valves. So far, a repeat surgery has been the only practical treatment option available for patients with hemodynamically significant bioprosthetic valve dysfunction. However, the exceedingly successful emergence of transcatheter aortic valve replacement therapy for native aortic valve disease has paved way for its extension to failed bioprosthetic valves also. Initially adopted for aortic bioprosthesis, this technique has now been successfully used for failed mitral bioprosthetic valves as well. This review summarizes the technical aspects and current evidence related to transcatheter mitral valve-in-valve procedures for failed mitral bioprosthetic valves.

Keywords: Bioprosthetic valve degeneration, transcatheter aortic valve implantation, transcatheter aortic valve replacement, transcatheter valve therapy, valve-in-valve procedure


How to cite this article:
Chandra P, Goel R, Chouhan NS. Transcatheter mitral valve replacement for failed mitral bioprosthesis: The new frontier!. Indian Heart J Interv 2018;1:63-70

How to cite this URL:
Chandra P, Goel R, Chouhan NS. Transcatheter mitral valve replacement for failed mitral bioprosthesis: The new frontier!. Indian Heart J Interv [serial online] 2018 [cited 2019 Jan 21];1:63-70. Available from: http://www.ihji.org/text.asp?2018/1/2/63/247454




  Introduction Top


The incidence and prevalence of structural valve disease is increasing with advancing age and improved longevity. Surgical repair or replacement of valve is the standard of care for the treatment of significant valvular dysfunction, with bioprosthetic valves constituting more than 50% of approximately 300,000 valves implanted surgically worldwide.[1] Although bioprosthetic heart valves allow freedom from lifelong anticoagulation, they are unfortunately associated with the risk of structural degeneration. The incidence of this structural valve deterioration requiring reintervention is 20%–30% at 10 years and approximately 50% at 15 years.[2] Increasing life expectancy and shorter durability of tissue valves is likely to translate into increasing pool of patients with failing tissue valves requiring repeat intervention. At present, surgical replacement remains virtually the only available treatment for degenerated tissue valves. However, redo surgery for bioprosthetic valve failure carries a high mortality of around 3%–23%.[3] Advancing age, female sex, renal or pulmonary dysfunction, severity and urgency of disease, and number of previous redo surgeries are some of the factors associated with increased risk.[4]

Advancement in transcatheter therapies for structural heart disease has revolutionized in last decade with transcatheter aortic valve replacement (TAVR) becoming an established alternative to surgery for high- and intermediate-risk patients with aortic stenosis.[5] Riding on the success of TAVR, device manufacturers and interventional cardiologists are now focusing on the development of percutaneous mitral valve repair/replacement systems. Compared with the aortic valve, the mitral valve poses a greater challenge to percutaneous treatment because of its structure and dynamic relationship with the left ventricle.

The major challenges in the development of transcatheter mitral valve replacement (TMVR) are that the mitral valve is large and asymmetrical, lacks an anatomically well-defined annulus for anchoring the replacement valve, its geometry changes throughout the cardiac cycle, and placing a replacement valve in it entails the risk of left ventricular outflow tract (LVOT) obstruction. Most of these major limitations are overcome in patients with failed bioprosthesis as they have an already implanted frame of prosthetic valve, which works as a platform with well-defined annulus for anchoring the replacement valve. This has led to the rapid development of this technology, as the already evolved TAVR valve prosthesis can be used easily in these patients for replacing failing bioprosthetic valves.

The valve-in-valve (ViV) concept was first described by Walther et al.[6] in 2007. On the basis of this concept, transcatheter mitral valve-in-valve replacement (TMViVR) has emerged as a feasible alternative to redo surgical mitral valve replacement (SMVR) in high-risk patients. At present, most of the studies show feasibility and safety of TMViVR using a balloon-expandable valve. There is complete resolution of mitral regurgitation indicating complete expansion of stent valve into degenerated xenografts. It has been shown to have similar 30-day and 1-year mortality rates as redo SMVR in a retrospective study, despite the former being performed in older, sicker patients. Although the initial transapical approach was associated with higher morbidity, the newer transvenous transseptal technique has shortened the length of stay and achieved similar clinical and echocardiographic outcomes compared with those of SMVR. As a result, faster recovery with rapid resolution of symptoms is observed. The only limiting factor for this technology to become a new gold standard for failing mitral bioprosthesis and to be adopted widely in low-risk patients is the lack of evidence regarding long-term durability and hemodynamic performance of TMViVR prosthesis. This review summarizes technical aspects and current evidence regarding TMViVR.


  Technical Aspects of TMViVR Top


Patient and valve selection

Appropriate patient and percutaneous valve selection are critical for TMViVR. A multidisciplinary heart team is a must for selecting patients.

The technique is currently reserved for elderly, high surgical risk patients with failed mitral bioprosthesis. The patients are evaluated by two-dimensional and three-dimensional (3D) transesophageal echocardiography (TEE) and multiplanar computed tomography (CT) scan to ascertain the cause and severity of mitral prosthetic heart valve (PHV) dysfunction and to obtain accurate measurements of left ventricle, mitral annulus, interatrial septum, and LVOT. 3D TEE and multiplanar CT are the most important modalities for patient selection, deciding the size of replacement valve and predicting the risk of postprocedure LVOT obstruction.

For selecting the right size of the valve, it is essential to precisely determine the diameter of the failing valve, shape and position of the sewing ring, and the valve morphology (whether stented or stentless and whether leaflets mounted internally or externally).[7] Nonstandardized labeling of surgical bioprosthetic valves is a major cause of concern. Actual internal diameter of a particular valve is different for different valves with same label, although the actual diameters can be confirmed with the manufacturer. However, the true internal diameter may even be less than the internal diameter provided by the manufacturer as the tissue leaflets themselves, pannus and calcification further reduce the actual internal diameter. The implanted transcatheter valve often projects into the LVOT and can lead to neo-LVOT obstruction. Preprocedure CT is very useful in predicting the neo-LVOT obstruction after implantation and in deciding the depth of implant valve for prevention of this complication when it is anticipated [Figure 1]. A less obtuse (<110°) aortic–mitral angle and a neo-LVOT area of ≤2.0cm2 seem to be associated with increased risk of neo-LVOT obstruction.[8]
Figure 1: Electrocardiogram-gated computed tomographic measurements on dedicated software (3mensio Structural Heart, Pie Medical Imaging BV, Maastricht, The Netherlands). (A) Measurement of bioprosthetic valve frame for confirmation of valve size. (B) Aortic–mitral angle for assessing risk of LVOT obstruction. (C) and (D) Neo-LVOT dimensions after virtual 26-mm Edwards S3 valve implant

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A “Valve in Valve Mitral app” (http://www.ubqo.com/vivmitral) has been developed, spearheaded by Dr. Vinayak Bapat, a consultant cardiac surgeon at St. Thomas’ Hospital, London, UK, to guide interventionists in performing TMViVR procedures. The app is useful in valve selection as it included most of the available valves and rings and gives details about various diameters and which valve to choose for a particular patient.

As transcatheter valves are sutureless devices, ensuring transcatheter valve fixation and stability greatly depends on the principle of relative oversizing (minimum 10% and not more than 20%) of the transcatheter valve in relation to the true internal diameter of the failing bioprosthetic valve.[9] Edwards SAPIEN XT and SAPIEN 3 valves (Edwards Lifesciences, Irvine, California) designed for aortic position are preferred considering their smaller frame size and deflectable delivery system for easy access across angulated path through interatrial septum to mitral valve. The other valves that can be used are Melody valve (Medtronic, Minneapolis, Minnesota) and Direct Flow Medical transcatheter aortic valve system, but they are not available in India. Self-expanding valves with bigger metallic frame are not suitable for mitral ViV procedure. The SAPIEN 3 valve is now approved by the United States Food and Drug Administration (FDA) for both mitral and aortic ViV procedures.[9]

Implantation procedure

TMViVR cases can be performed either via transapical approach or through a less invasive transvenous transseptal approach. The procedure should be performed preferably in a hybrid operating room under general anesthesia with intraprocedural TEE guidance and adequate anticoagulation (activated clotting time, 250–350s).

Transapical approach

Transapical approach typically involves a left minithoracotomy with purse-string sutures for access site management [Figure 2]. The left ventricular (LV) apex is entered with a standard puncture needle, and a 6F sheath is introduced inside the left ventricle. A J-tip guidewire is then advanced across the failing heart valve and parked in the pulmonary vein. The wire is then exchanged for a stiff guidewire with the help of a pigtail or multipurpose catheter.
Figure 2: (A) Minithoracotomy for left ventricular apical access. (B) Valve positioned more atrially for implantation. (C) Valve implantation during rapid atrial pacing by balloon inflation

Click here to view


The access site is pre-dilated, and an 18F sheath is positioned in the LV cavity. An Edwards SAPIEN valve, mounted on device delivery system, is positioned across the mitral PHV and is deployed under fluoroscopic and TEE guidance during rapid ventricular pacing.

Transvenous transseptal approach

A jugular or femoral venous access is obtained, and a 14F eSheath is positioned in the inferior or superior vena cava. A TEE-guided mid-posterior transseptal puncture is performed in the thin part of fossa ovalis and a deflectable Agilis sheath (St. Jude Medical, St. Paul, Minnesota) is then positioned in left atrium in line with the trajectory of failing PHV [Figure 3]. Routinely, a pigtail catheter is used to cross the failing PHV and is positioned in the left ventricle for hemodynamic assessment and for atraumatic placement of stiffer guidewire in the LV cavity. Interatrial septal puncture site is dilated with a 10-mm balloon over a manually shaped extra-stiff Amplatz wire or a pre-shaped Confida (Medtronic) guidewire positioned in the LV cavity at apex. Pre-dilatation of failing PHV is usually avoided. An Edwards SAPIEN valve, crimped in reverse manner on device delivery system [Figure 4], is advanced across the mitral PHV supported by deflectable delivery system and positioned in a way that at least 3–5mm of the valve is on the atrial side of the sewing ring of the bioprosthetic valve. The valve is deployed using slow balloon dilatation technique under fluoroscopic and TEE guidance during rapid ventricular pacing. Valve is positioned more on the atrial side and flared on both ends to prevent migration and embolization. 3D echocardiography is used to confirm the optimal position and valve function [Figure 5]. The residual interatrial communication is closed with a 12-mm Amplatzer atrial septal defect closure device [Figure 4] and the femoral venous access is closed with fishermen’s knot.
Figure 3: Transcatheter mitral ViV procedure via transseptal approach. (A) TEE-guided mid-posterior transseptal puncture is performed in the thin part of fossa ovalis. (B) Interatrial septal puncture site is dilated with a 10-mm balloon. (C) New valve is deployed using slow balloon dilatation technique during rapid ventricular pacing. (D) Residual interatrial communication is closed with an Amplatzer atrial septal defect closure device

Click here to view
,
Figure 4: (A) SAPIEN XT valve. (B) SAPIEN 3 valve. (C) Reverse crimped SAPIEN 3 valve (red arrow) for implant at mitral position by transseptal access

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,
Figure 5: Transesophageal echocardiographic guidance for the procedure. (A) and (B) Markedly thickened, degenerated mitral bioprosthetic valve with very limited valve opening (red arrows). (C) X-plane imaging for guiding transseptal puncture (red arrows). (D) Delivery sheath with transcatheter valve positioned across the failed surgical bioprosthetic valve. (E) Postprocedure showing well-functioning newly implanted valve with good valve opening and no flow turbulence across the valve

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A few points that need considerations are as follows:

  • TEE-guided mid-posterior septal puncture is a must for ensuring right trajectory for negotiating the device delivery system across the failed PHV.[10]


  • The need for snaring and externalization of wire in the aorta to provide support for valve delivery can be avoided using dedicated sheaths, wires, and deflectable delivery system.


  • In transseptal approach, the Edwards SAPIEN valve should be crimped in reverse manner and double checked to ensure proper functioning.


  • Balloon dilation of failed PHV before implantation is generally avoided unless there is difficulty in negotiating the transcatheter valve across the PHV.


  • The valve is usually positioned 3–5mm atrially in relation to the sewing cuff of the surgical valve and is deployed with a slow balloon inflation technique under rapid ventricular pacing.


  • It is also important to achieve at least 10% oversizing of the transcatheter valve compared to the true internal diameter of the surgical device. However, extreme oversizing can result in an underexpanded valve with impaired leaflet coaptation, elevated transvalvular gradient, and possibly, limited durability.



  •   Evidence Base for TMViVR Top


    Data from three representative large-scale multicenter registries, each with more than 300 patients in ViV group, are now available and are discussed below.

    The multicenter Valve-in-Valve International Data (VIVID) registry[11] included 349 patients who underwent TMViVR. The data from this registry were presented recently; following were the key findings:

    1. The procedures were performed in elderly patients (mean age, 74 years) with significant comorbidities (Society of Thoracic Surgeons’ [STS] score of 12.9%).


    2. Most of the ViV or valve-in-ring (ViR) procedures were performed using transapical access, with transseptal and left atrial approaches used for only 20% of the patients. General anesthesia was used in almost all cases (98.9%). Most of the procedures were performed with a balloon-expandable device (Edwards SAPIEN, SAPIEN XT, and Melody).


    3. The mechanism of bioprosthetic surgical valve failure included pure regurgitation (45%), pure stenosis (23%), and combined stenosis and regurgitation (32%).


    4. Balloon pre-dilation was performed in 24% cases; valve malpositioning was reported in 6.6%.


    5. Postprocedure mean gradient was 6.3mm Hg and significant (moderate or more) paravalvular leak was reported in 3.5% cases. LVOT obstruction was noted in 7% cases with a significantly higher incidence in ViR cases (8%) than that in ViV (2.5%). A small valve size (<25mm) was a key predictor of significantly elevated gradient (>10mm Hg). Significant residual mitral regurgitation (more than moderate) was more likely in ViR than that in ViV cases.


    6. Overall 30-day mortality was 8.5% (7.7% and 11.4% in ViV and ViR procedures, respectively) and the occurrence of stroke was 2.5% (2.9% and 1.1% in ViV and ViR procedures, respectively). Late mortality (beyond 12 months) was 20.5%.


    Guerrero et al.[12] presented outcome data from STS/American College of Cardiology Transcatheter Valve Therapy (STS/ACC TVT) registry. Of the 494 patients (mean age, 76 years) who underwent TMViVR, 60.9% were females, median STS score was 10.5%, transseptal access was used in 35% of the patients, and procedural success was 74.4%. LVOT obstruction was reported in 5.4% patients and more than mild mitral regurgitation was reported in 4.3%. In-hospital mortality was 6.9% and 30-day mortality was 9%. At 30-day follow-up, 85.6% of ViV patients were in New York Heart Association (NYHA) class I or II. Thus, this registry reaffirmed safety and efficacy of TMViVR in elderly patients with failed bioprosthetic valve deemed surgically unfit or high risk.

    Another recently published registry data by Yoon et al.[13] from TMVR multicenter registry with 322 patients (mean age, 72.6 years) undergoing TMViVR also reported a technical success rate of 94.4%, and 30-day and 1-year mortality rates of 6.2% and 14.0%, respectively. After adjustment in a multivariable analysis, the factors associated with increased mortality were STS score and LV ejection fraction. In 93.8% of these patients, SAPIEN valve was used although transseptal access was used only in 38.8% of the patients. In this registry data, no significant differences were observed in procedural complications between transseptal and transapical approaches with the exceptions of higher rates of atrial septal defect closure and alcohol septal ablation and lower rate of life-threatening or fatal bleeding with transseptal access. Patients were divided into early-experience and late-experience groups according to the median number of TMVR procedures at each institution. Compared with the early-experience group, the late-experience group had lower rates of conversion to surgery, 30-day mortality, life-threatening or fatal bleeding, and stage 2 or 3 acute kidney injury, mainly driven by the improved outcomes of ViV with increased experience.

    The key outcomes of this registry data are as follows:

    1. TMViVR provided excellent outcomes for patients with degenerated bioprosthetic valves but TMVR for failed annuloplasty rings and mitral annular calcification (MAC) were associated with frequent procedural complications.


    2. Valve thrombosis was more frequently observed after TMVR in patients without anticoagulation compared with those with anticoagulation.


    The experience with TMViVR in India started in 2017 and is currently in early stages.[14],[15] At our center, we have performed TMViVR in seven patients (mean age, 70 years; five women) over the last 1 year. Mean duration since the initial valve surgery was 7.3 years. All the patients were having NYHA class III or IV dyspnea and were at high surgical risk with mean STS score of 18.6 and EuroSCORE of 22.2. A dedicated heart valve team including a cardiac surgeon, a cardiologist, and a cardiac anesthetist approved the decision to proceed with TMViVR in each of these cases. All the cases were performed in hybrid operating room under general anesthesia with intraprocedure TEE guidance. On-site surgical support and in-lab primed extracorporeal membrane oxygen circuit were available for backup. The failed surgical PHVs included Epic valves (St. Jude Medical) in four cases, PERIMOUNT valves (Edwards Lifesciences) in two cases, and Mosaic valve (Medtronic) in one case; five of them were regurgitant and two were stenotic. Mean diameter of the failing valves was 27mm. The balloon-expandable Edwards SAPIEN 3 valve was used as the transcatheter valve in all the cases. Two patients required pre-dilatation, but post-dilatation was not required in any of the cases as no or only trace valvular/paravalvular leak was reported post-valve implantation. Procedural success rate (considered as successful vascular access, successful delivery and retrieval of the transcatheter valve delivery system, deployment of single valve in correct position, achieved mitral valve area >1.5cm2, no residual mitral regurgitation of grade 2 or more, no additional surgery or reintervention, which includes drainage of pericardial effusion, and the patient leaving the cath lab/operative room alive) was 100%. One patient who had presented with severe heart failure, low cardiac output, metabolic acidosis, and acute renal shutdown with STS score of 52.6 died during index hospitalization, 48h after the procedure. The remaining six patients were alive at 30-day follow-up, with mean NYHA class 1.8 and significantly reduced diuretic requirement. The mean transmitral gradient was 3.2mm Hg and no patient had residual mitral regurgitation of grade 1 or more severity. None of the patients had required rehospitalization. This limited Indian experience reassures that transvenous transseptal TMViVR in failed surgical bioprostheses is a viable option for Indian patients and is performed with high technical and procedural success and low 30-day mortality.


      Challenges Top


    The available evidence suggests that TMViVR provides excellent outcomes for patients with degenerated bioprostheses despite high surgical risk and is now an FDA-approved indication with use of balloon-mounted SAPIEN valve. However, the procedure remains grossly underutilized in Indian subcontinent because of low awareness about this procedure, limited availability, and lack of technical expertise.

    Over the last 10 years, this procedure has evolved from more complicated and invasive transapical approach to less demanding transseptal approach with excellent outcomes. The initial obstacle of entering the valve through transseptal access after a sharp bend has been overcome by guided septal puncture, deflectable delivery system, and the use of dedicated hardware.

    Another minor issue of LVOT obstruction can now be well anticipated by evaluating the preprocedure CT scan and can be treated by alcohol septal ablation in patients with significant LVOT gradient after procedure.[16] In some patients, LVOT obstruction can occur because of the leftover mitral valve tissue from the initial surgery. In such cases, the “Lampoon procedure” described by Khan et al.[17] provides a reasonable solution. Valve thrombosis and unknown durability are some of the other unresolved issues linked with this procedure. In addition, both the best antithrombotic regimen and the specific anatomic and patient characteristics increasing the risk of a mitral transcatheter procedure are yet to be determined.

    A similar procedure can also be performed in patients with failed mitral annular ring and in patients with severe MAC. The major challenges are high rates of LVOT obstruction and significant paravalvular regurgitation in these groups of patients. Nonetheless, the ultimate goal is to expand this indication to much bigger group of patients with native mitral valvular heart disease with the use of dedicated valves.


      Future Directions Top


    TMViVR has opened a new horizon for treating high surgical risk patients with no hopes. With further advancement and overcoming the limitations, growth of this technology is inevitable. Failure of surgical bioprosthetic valve with time is unavoidable and more and more number of patients will become eligible for TMViVR in near future. Considering this, it is imperative that the selection of valve type and technique during surgical aortic valve replacement is planned with a foresightedness about the feasibility of a transcatheter ViV procedure at a later time, if required. Device manufacturers have already started investing heavily for developing surgical valves with improved hemodynamics and safety of future ViV procedures; both surgical and TAVR valves are now being designed in such a manner that they can expand if required later for a ViV procedure. The latest INSPIRIS RESILIA aortic bioprosthetic valve (Edwards Lifesciences) with VFit technology incorporates two novel features—fluoroscopically visible size markers and an expansion zone—which are designed specifically for potential future ViV procedures [Figure 6].[18]
    Figure 6: INSPIRIS RESILIA aortic bioprosthetic valve (Edwards Lifesciences, Irvine, California) with VFit technology

    Click here to view


    Financial support and sponsorship

    Nil.

    Conflicts of interest

    There are no conflicts of interest.



     
      References Top

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    Leontyev S, Borger MA, Davierwala P, Walther T, Lehmann S, Kempfert J, et al. Redo aortic valve surgery: Early and late outcomes. Ann Thorac Surg 2011;1:1120-6.  Back to cited text no. 3
        
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    Gurvitch R, Cheung A, Ye J, Wood DA, Willson AB, Toggweiler S, et al. Transcatheter valve-in-valve implantation for failed surgical bioprosthetic valves. J Am Coll Cardiol 2011;1:2196-209.  Back to cited text no. 4
        
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    Rodés-Cabau J. Transcatheter aortic valve implantation: Current and future approaches. Nat Rev Cardiol 2011;1:15-29.  Back to cited text no. 5
        
    6.
    Walther T, Falk V, Dewey T, Kempfert J, Emrich F, Pfannmüller B, et al. Valve-in-a-valve concept for transcatheter minimally invasive repeat xenograft implantation. J Am Coll Cardiol 2007;1:56-60.  Back to cited text no. 6
        
    7.
    Bapat VN, Attia R, Thomas M. Effect of valve design on the stent internal diameter of a bioprosthetic valve: A concept of true internal diameter and its implications for the valve-in-valve procedure. JACC Cardiovasc Interv 2014;1:115-27.  Back to cited text no. 7
        
    8.
    Kohli K, Wei ZA, Yoganathan AP, Oshinski JN, Leipsic J, Blanke P. Transcatheter mitral valve planning and the neo-LVOT: Utilization of virtual simulation models and 3D printing. Curr Treat Options Cardiovasc Med 2018;1:99.  Back to cited text no. 8
        
    9.
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    De Backer O, Piazza N, Banai S, Lutter G, Maisano F, Herrmann HC, et al. Percutaneous transcatheter mitral valve replacement: An overview of devices in preclinical and early clinical evaluation. Circ Cardiovasc Interv 2014;1:400-9.  Back to cited text no. 10
        
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    Krishnaswamy A, Mick S, Navia J, Gillinov AM, Tuzcu EM, Kapadia SR. Transcatheter mitral valve replacement: A frontier in cardiac intervention. Cleve Clin J Med 2016;1:S10-7.  Back to cited text no. 11
        
    12.
    Guerrero M, Wang Dee Dee D, Vemulapalli S, Xiang K, Salinger M, Eleid M, et al. Abstract 23079: Clinical outcomes of transcatheter mitral valve replacement for degenerated mitral bioprostheses (mitral valve-in-valve) and surgical rings (mitral valve-in-ring) in the United States: Data from the STS/ACC/TVT registry. Circulation 2017;1:A23079.  Back to cited text no. 12
        
    13.
    Yoon SH, Whisenant BK, Bleiziffer S, Delgado V, Dhoble A, Schofer N, et al. Outcomes of transcatheter mitral valve replacement for degenerated bioprostheses, failed annuloplasty rings, and mitral annular calcification. Eur Heart J 2018. doi: 10.1093/eurheartj/ehy590.  Back to cited text no. 13
        
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    Gopalamurugan AB, Reddy YVC, Abubacker RM, Karthikeyan D, Shankar SV. India’s first transcatheter mitral valve implantation: Mitral valve-in-valve via transapical approach. IHJ Cardiovascular Case Reports (CVCR) 2018;1:40-3.  Back to cited text no. 15
        
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    Honěk J, Zemánek D, Veselka J. Left ventricular outflow tract obstruction after mitral valve repair treated with alcohol septal ablation. Catheter Cardiovasc Interv 2013;1:E821-5.  Back to cited text no. 16
        
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        Figures

      [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]



     

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