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New Technology

Sutureless Aortic Valve Replacement With the 3f Enable Aortic Bioprosthesis

Department of Thoracic and Cardiovascular Surgery, JW Goethe University Hospital, Frankfurt, Germany

Accepted for publication January 21, 2009.

^_* Address correspondence to Dr Martens, Department of Thoracic and Cardiovascular Surgery, JW Goethe University Hospital, Thoedor Stern Kai 7, Frankfurt, D-60590, Germany (Email: martens.herz{at}gmx.de).

	Abstract

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Purpose: Important comorbid conditions in elderly patients referred for aortic valve replacement require alternative treatment options with possible reduction of the extracorporeal circuit time and reliable hemodynamic features. We report on clinical experiences with the sutureless, nitinol-stented 3f Enable (ATS Medical, Minneapolis, MN) aortic valve prosthesis in 32 patients.

Description: The procedure was performed using cardiopulmonary bypass with cardioplegic arrest. After resection of the stenotic aortic valve and debridement of the annulus, the valve was inserted and released. Mean age was 78 ± 3; mean logistic Euroscore was 13.7. Concomitant procedures were mitral valve and tricuspid valve repair (n = 1), coronary artery bypass graft (n = 9), and subvalvular myectomy (n = 3).

Evaluation: Implantation of the valve required 9 ± 5 minutes. Cardiopulmonary bypass and aortic cross-clamp time were 87 ± 16 and 55 ± 11 minutes for stand-alone procedures. Combined procedures required 126 ± 42 and 84 ± 28 minutes, respectively. Two patients were abandoned intraoperatively and converted to standard procedures due to misalignment of the valve. In the other 30 patients, no paravalvular leakage was detected. The transvalvular gradient at discharge was 9 ± 6 mm Hg (mean) and 18 ± 9 mm Hg (peak). Six months after surgery, gradients were 10 ± 4 mm Hg (mean) and 18 ± 6 mm Hg (peak).

Conclusions: Sutureless valve implantation is feasible and safe with the 3f Enable (ATS Medical) bioprosthesis. Reduction of cardiopulmonary bypass and aortic cross-clamp time seems to be possible with increasing experience. Hemodynamic data are promising with low gradients at discharge and after 6 months.

	Introduction

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Aortic valve replacement with mechanical or biological heart valves is the treatment of choice for aortic valve stenosis. With increasing patient comorbidity and age, there is a tendency toward biological valve implants avoiding long-term anticoagulation. In an effort to improve the outcome of patients with stented biological valves, stentless valves were introduced to clinical practice in the early 1990. These valves were designed to be less obstructive, and thus result in lower transvalvular gradients. However, the implantation technique of stentless valves is more complex and demanding, with prolonged cross-clamp and bypass times. In 2005, Cox and colleagues [1] presented in vitro data on the newly designed 3f aortic bioprosthesis, a stentless bioprosthesis, which consists of a tubular structure assembled from three equal sections of equine pericardial tissue. Our group presented clinical and hemodynamic data from 24 patients. Hemodynamic data were equivalent to commercially available stentless valves; however, implantation still required a cross-clamp time of 74 minutes [2]. To facilitate implantation, the 3f aortic bioprosthesis was modified with the addition of a self-expanding Nitinol external frame that imparts flexibility, which is designed for sutureless implant. We report our clinical experiences with the valve in 32 patients, representing a high-risk cohort of cardiosurgical patients.

	Technology

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The 3f Enable (ATS Medical, Minneapolis, MN) consists of a 3f Aortic Bioprosthesis Model 1000 (ATS Medical) mounted on a self-expanding nitinol frame (Fig 1). The nitinol frame contributes to the fixation of the device in the deployed location by virtue of outward radial forces inherent in the Nitinol material, thus reducing the number of sutures required to secure the bioprosthesis in the annulus. A polyester flange has been incorporated at the inflow aspect to minimize the potential of paravalvular leaks and migration.

View larger version (67K): [in this window] [in a new window]   Fig 1. ATS 3f Enable (ATS Medical, Minneapolis, MN).

	Technique

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After excision of the aortic valve and debridement of the aortic annulus, we accurately size the aortic annulus with especially designed sizers. These sizers reflect the real annulus size, the external diameter of the corresponding Enable prosthesis (ATS Medical) is larger to enhance fixation. Because the fixation of the valve in place is obtained through outward radial forces of the nitinol frame, care has to be taken for exact sizing. If the implant chosen is too small for the annulus, paravalvular leakage or migration might occur; if it is too large, complete deployment might become impossible. The prosthesis requires rinsing in saline solution three times for 2 minutes each time. While rinsing the valve, a single-guiding suture (2-0 polyethylene) is placed under the left-to-acoronary commissure or the annulus corresponding to the deepest point of the acoronary sinus. With increasing implant experience, we changed our technique toward positioning the guiding suture in the annulus (acoronary sinus), because two intraoperative conversions of clinical implants were caused by malpositioning in this region.

After the rinsing process is completed, the valve is placed in chilled physiological saline to make it pliable. It is carefully folded under water to avoid frame fracture (Fig 2). The valve is inserted in a deployment tool. The guiding suture is now attached to the superior portion of the flange, in a position corresponding to the placement in the annulus.

View larger version (122K): [in this window] [in a new window]   Fig 2. Folding of the valve in chilled water.

View larger version (138K): [in this window] [in a new window]   Fig 3. Deployment of the valve using warm saline solution.

	Clinical Experience

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From July 2007 through August 2008, 32 elective patients who presented for isolated aortic valve replacement or combined procedures were included in the study in our institution, as a part of a multicenter trial. Exclusion criteria were life expectancy of less than 24 months due to noncardiac disease, intravenous drug, and alcohol abuse, or both, and active infective endocarditis or other systemic infection, participation in concomitant research studies, chronic renal failure, and the presence of annulo-aortic ectasia, Marfan syndrome, aneurysmal dilatation of the ascending aorta, Ehlers-Danlos syndrome or other condition causing the ascending aorta, or the aortic annulus to be irregular in geometry or physiology. Mean age was 78 ± 3 years, mean logistic Euroscore was 13.7, The Society of Thoracic Surgeons score revealed a mean risk for mortality of 16.4 ± 6.4%; thus our patients represented a high-risk cohort of cardiosurgical patients with possible benefit from reduced implantation time of a sutureless bioprosthetic valve. All patients gave written informed consent. The consent form and the study protocol were approved by our local ethical committee. The study was sponsored by ATS Medical. None of the investigators or patients received payments for study participation.

	Results

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Concomitant procedures were mitral valve and tricuspid valve repair (n = 1), coronary artery bypass grafting (n = 9) and subvalvular myectomy (n = 3). Prosthetic valve sizes were 19 mm (n = 1), 21 mm (n = 9), 23 mm (n = 8), 25 mm (n = 13), and 27 mm (n = 1). After initial deployment of the valve, exact positioning was time consuming, especially in the first cases of our series. Implantation of the valve required 9 ± 5 minutes for all patients. With increasing experience with the sutureless valve implant, procedural times were reduced. Cardiopulmonary bypass and aortic cross-clamp time were 87 ± 16 and 55 ± 11 minutes for stand-alone procedures. Combined procedures required 126 ± 42 and 84 ± 28 minutes, respectively. Two cases were abandoned intraoperatively due to misalignment of the valve, which was a 25-mm size in both cases. Although we believe that the reason for failure might have been oversizing, we converted to standard procedures with a 23-mm, commercially available, bioprosthetic, stented valve to ensure patients safety.

In the other 30 patients, no paravalvular leakage was detected in the operating room or at discharge. In 1 patient, mild paravalvular leakage occurred at the 6-month follow-up; however, 12 months after surgery it could not be detected any more. Hemodynamic data is available for 18 patients at the 6-month follow-up, and we have only seen 5 patients for 12-month follow-ups.

The transvalvular gradient at discharge was 9 ± 6 mm Hg (mean) and 18 ± 9 mm Hg (peak). Six months after surgery, gradients were 10 ± 4 mm Hg (mean) and 18 ± 6 mm Hg (peak). Interestingly, the gradients did not correlate to the size of the valve prosthesis 6 months after surgery (see Table 1).

	Comment

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Although the concept of percutaneous transfemoral aortic valve implantation gains further acceptance, with transapical aortic valve implantation, a more surgical approach was developed. One of the advantages is a significantly reduced stroke rate as compared with the transfemoral approach. With both techniques, the calcified aortic valve is just pressed into the aortic wall without decalcification of the annulus. However, the rate of paravalvular leakage will always remain an important issue with this technology [3].

Implantation of a sutureless aortic valve prosthesis after resection of the native aortic valve, allowing for reduced cardiopulmonary bypass and aortic cross-clamp time, might be an alternative treatment option for patients at increased risk for morbidity and mortality after cardiac surgery. The transaortic approach adds the advantage of allowing for concomitant procedures as coronary artery bypass grafting or mitral and tricuspid valve surgery, as long as flexible implants are being used in the latter.

First clinical results with the 3f Enable sutureless valve were reported in 2008 by the group of Wendt and colleagues [4]. In their experience, 3 of 6 patients presented with paravalvular leakage at follow-up, 1 of them underwent successful reoperation after 8 months. The design of the valve implanted in this initial series showed small but possibly important differences regarding the polyester flange. The inferior aspect of the flange was enlarged in the model we implanted, allowing for broader coaptation with the annulus (Fig 1). The other difference regarded the implantation technique (ie, up to three stay sutures were placed in the annulus in this initial series, possibly causing distortion of the valve). In our series of 30 implants, only one stay suture was tied down, nine implants did not receive a stay suture at all. Mild paravalvular leakage occurred in only 1 patient of our series after 6 months, and after 12 months we could not detect it anymore.

Shrestha and colleagues [5] described their initial clinical experiences with the Perceval S sutureless valve (Sorin Biomedica, Saluggia, Italy). Its functional component is a bovine pericardial valve fixed in a metal cage. The elastic alloy of the cage allowed the device to be compressed and subsequently released in the annulus. Only two valve sizes were available (21 and 23 mm). However, the transvalvular gradients were higher as compared with our results obtained with the Enable valve (mean 18 mm Hg at 1 month with Perceval vs 9 mm Hg at discharge with Enable).

We have shown that sutureless aortic valve implantation is possible and safe with the ATS 3f Enable prosthesis. Paravalvular leakage is not an issue with the newly designed inferior flange of the valve, if it is adequately positioned. Exact positioning is still time consuming, but with increasing experience, reduction of aortic cross clamp and coronary pulmonary bypass time seems possible. Minimal invasive implantation of this prosthesis through partial upper sternotomy is feasible and was performed in all our patients without concomitant surgery. Hemodynamic features of the valve are very promising. The sutureless transaortic valve implantation offers the advantage of resection of the native calcified valve, reducing the risk of paravalvular leakage as compared with transcatheter approaches. In contrast with percutaneous procedures, concomitant cardiac surgical procedures as coronary artery bypass grafting are possible. Despite encouraging short-term results with this new aortic valve prosthesis, we need data documenting its long-term performance.

	Disclosures and Freedom of Investigation

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The institution received an unrestricted research grant from ATS Medical to conduct this study. The authors had full control of the design of the study, outcome measurements, analysis of data, and production of the written report.

	Footnotes

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^Disclaimer The Society of Thoracic Surgeons, the Southern Thoracic Surgical Association, and The Annals of Thoracic Surgery neither endorse nor discourage use of the new technology described in this article.

	References

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1. Cox JL, Ad N, Myers K, Gharib M, Quijano RC. Tubular heart valves: a new tissue prosthesis design—preclinical evaluation of the 3f aortic bioprosthesis J Thorac Cardiovasc Surg 2005;130:520-527.[Abstract/Free Full Text]
2. Doss M, Martens S, Wood JP, et al. Aortic leaflet replacement with the new 3F stentless aortic bioprosthesis Ann Thorac Surg 2005;79:682-685.[Abstract/Free Full Text]
3. Walther T, Simon P, Dewey T, et al. Transapical minimally invasive aortic valve implantation: multicenter experience Circulation 2007;116(Suppl 11):I240-I245.[Medline]
4. Wendt D, Thielmann M, Buck T, et al. First clinical experiences and 1-year follow-up with the sutureless 3F-Enable aortic valve prosthesis Eur J Cardiothorac Surg 2008;33:542-547.[Abstract/Free Full Text]
5. Shrestha M, Khaladj N, Bara C, Hoeffler K, Hagl C, Haverich A. A staged approach towards interventional aortic valve implantation with a sutureless valve: initial human implants Thorac Cardiovasc Surg 2008;56:398-400.[Medline]

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Sven Martens Anton Moritz Mirko Doss Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Martens, S. Articles by Doss, M. Search for Related Content PubMed PubMed Citation Articles by Martens, S. Articles by Doss, M. Related Collections Valve disease Related Article