Article

Off-pump transapical mitral valve replacement: Evaluation after one month

Department of Cardiovascular Surgery, University Hospital Schleswig-Holstein, Campus Kiel, Kiel, Germany.
European journal of cardio-thoracic surgery: official journal of the European Association for Cardio-thoracic Surgery (Impact Factor: 3.3). 03/2012; 41(3):512-7. DOI: 10.1093/ejcts/ezr106
Source: PubMed

ABSTRACT

The present study investigates outcomes one month after implanting pigs with a novel mitral valved stent.
A novel nitinol stent custom designed for this study included a bovine pericardial valve. Six pigs received a valved stent into the mitral position by means of the transapical implantation technique. Afterwards, haemodynamic stability and valve function were assessed, immediately after implantation (n = 6), 4 weeks (n = 4) and 8 weeks (n = 1) thereafter using transoesophageal echocardiography (TEE), ventriculography and cardiac computed tomography (CT). Four of 6 surviving pigs were sacrificed at 4 weeks after implantation and one at 8 weeks thereafter.
Optimal deployment and positioning were obtained in all but one animal. This animal died of unrecognized imperfect valved stent positioning after 4 days. The average mean gradient across the new valves and the left ventricular outflow tract (LVOT) were small. Mild regurgitation developed after valved stent deployment in one of six animals just after 1 h, and in none thereafter. All animals exhibited normal haemodynamics after mitral valved stent implantation, and stability was maintained throughout the monitoring period. Migration, embolization and paravalvular leakage were not evident in the remaining animals after 4 and 8 weeks. Gross evaluation revealed that 50-70% of the atrial element was covered by tissue growth at 4 weeks/8 weeks.
This study demonstrates adequate deployment and anchorage of a unique, repositionable mitral valved stent. A good valve function was revealed in animals observed for 4 weeks and in one pig after 8 weeks.

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Available from: Rainer Petzina, Jan 04, 2016
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    • "In 2005, Boudjemline et al. [11] reported first progress on replacement of the TV using a transcatheter method under angiographic guidance noting difficulties of deploying and securing a stent in the tricuspid position. We have previously reported on the feasibility of replacing AV valves by transcatheter implanted valved stents under transoesophageal echocardiographic (TOE) guidance [12] [13] [14] and presented our first preliminary results of TV replacement via transventricular access in an acute study including seven animals [15]. "
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    ABSTRACT: Objectives: Off-pump transcatheter valved stent implantation could be a treatment option for patients suffering from symptomatic tricuspid regurgitation (TR) who are classified as inoperable. In this study, we present our recent short-term results of transventricular tricuspid valved stent implantation and compare different stent types for atrial anchorage. Methods: Fifteen pigs received a self-expandable valved stent implantation off-pump via a transventricular access. Successfully implanted pigs were observed over a period of 6 h (n = 9), 48 h (n = 1) and 4 weeks (n = 1). Haemodynamic and full transoesophageal echocardiographic (TOE) evaluations were done before, 1 h, 3 h (n = 11; all successfully implanted pigs), and 6 h (n = 9; acute group) after implantation. Nine days postimplantation, one pig received additional angiography, computed tomography (CT) and transthoracic echocardiography (TTE). Post-mortem, gross examination was conducted to analyse the stent position and deformation. In two pigs (48 h and 4 weeks survival) histological staining and immunohistochemistry of surrounding myocardium was performed. Results: The heart rate significantly increased in all pigs postimplantation from 66.8 ± 13.6 to 101.8 ± 24.6 bpm, whereas cardiac output and pressure levels remained unchanged. Orthotopic positioning was reproducibly achieved. TOE showed an efficient reduction of paravalvular leakages from a mean grade of 1.4 1 h postimplantation to a mean of 0.9 at 6 h postimplantation due to a special sealing pouch. The ratio early and late ventricular filling velocities remained constant and the valvular gradient across the valved stent stayed low during the observation period. Angiography, CT and TTE confirmed orthotopic positioning and mild grade of paravalvular leakage after 9 days (n = 1). Only mild TR was observed here. The ventricular part of the stent was deformed to an oval shape in 7 of 14 animals as shown via post-mortem examination. The surrounding tissue after 1 month (n = 1) showed normal morphology, without inflammation or calcification. Conclusion: This study shows the feasibility of catheter-based replacement of the tricuspid valve by a valved stent in an off-pump procedure. The successive enhancements in this tricuspid valved stent design lead to a prototype being ready for mid- to long-term evaluations.
    Preview · Article · Jan 2014 · European journal of cardio-thoracic surgery: official journal of the European Association for Cardio-thoracic Surgery
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    • "Studies investigating the biological responses of different intracardiac devices showed complete coverage with endothelial cells after three months [14, 15]. Therefore we assume that a similar healing process is achievable with our valved stent, since we have also observed good secondary stability up to now (Figure 4) [8]. "
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    ABSTRACT: The development of transcatheter techniques for treatment of severe mitral valve regurgitation in the beating heart is focus of recent research. An off-pump treatment technique poses great benefits, particularly for multimorbid patients, often being non-compliant to the gold standard treatment, being open heart surgery with use of a cardiopulmonary bypass. Thereto, two approaches are being followed: transcatheter valve repair and transcatheterimplantation of a valved stent into the native mitral valve annulus. A valved stent has to provide safe and secure fixation within the high pressure system of the left heart. One of the main challenges in the development of such a valved stent is the complex anatomy of the mitral valve, with no clearly defined structures for device anchorage. Our group has developed a self-expanding nitinolvalved stent for transapical implantation in the beating heart. During the development process of thevalved stent, different design iterations were conducted to decrease the risk of paravalvular leakages, to enhance the reproducibility and to improve the overall stent performance. This article reviews the major milestones passedin the development process of our mitral valved stent and advances achieved withinthe last years. Multiple design iterations lead to a prototype providing secure stent deployment, hig h reproducibility, low paravalvular leakages and only mild stent deformation in the beating heart. In future, further long-term in vivo trials have to be conducted before attempting the step towards clinical application of this novel device.
    Full-text · Article · Apr 2013
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    • "The cavity-to-pericardial (“leakage”) pressure gradient is lower for a RV free wall entry compared with LV free wall entry, and in this way our trajectory may enhance acute procedural safety of closed-chest direct cardiac access. Translated into patients, our approach would allow subxiphoid introduction of large appliances into the heart without surgery, for example transcatheter mitral valves having delivery systems 10 mm wide or more [17]. In this preclinical experience, we found that the entry tract across the interventricular septum recoiled completely, was associated with no early or late ventricular septal defect, was associated with no evident myocardial dysfunction or conduction abnormality, and left a small residual fibrotic scar with no evident bystander injury. "
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    ABSTRACT: Background We aim to deliver large appliances into the left ventricle through the right ventricle and across the interventricular septum. This transthoracic access route exploits immediate recoil of the septum, and lower transmyocardial pressure gradient across the right versus left ventricular free wall. The route may enhance safety and allow subxiphoid rather than intercostal traversal. Methods The entire procedure was performed under real-time CMR guidance. An “active” CMR needle crossed the chest, right ventricular free wall, and then the interventricular septum to deliver a guidewire then used to deliver an 18Fr introducer. Afterwards, the right ventricular free wall was closed with a nitinol occluder. Immediate closure and late healing of the unrepaired septum and free wall were assessed by oximetry, angiography, CMR, and necropsy up to four weeks afterwards. Results The procedure was successful in 9 of 11 pigs. One failed because of refractory ventricular fibrillation upon needle entry, and the other because of inadequate guidewire support. In all ten attempts, the right ventricular free wall was closed without hemopericardium. There was neither immediate nor late shunt on oximetry, X-ray angiography, or CMR. The interventricular septal tract fibrosed completely. Transventricular trajectories planned on human CT scans suggest comparable intracavitary working space and less acute entry angles than a conventional atrial transseptal approach. Conclusion Large closed-chest access ports can be introduced across the right ventricular free wall and interventricular septum into the left ventricle. The septum recoils immediately and heals completely without repair. A nitinol occluder immediately seals the right ventricular wall. The entry angle is more favorable to introduce, for example, prosthetic mitral valves than a conventional atrial transseptal approach.
    Full-text · Article · Jan 2013 · Journal of Cardiovascular Magnetic Resonance
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