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Eur J Cardiothorac Surg 2008;33:542-547. doi:10.1016/j.ejcts.2007.12.045
Copyright © 2008, European Association for Cardio-thoracic Surgery. Published by Elsevier. All rights reserved.
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Right arrow Minimally invasive surgery
Right arrow Valve disease

First clinical experience and 1-year follow-up with the sutureless 3F-Enable aortic valve prosthesis

Daniel Wendta,*, Matthias Thielmanna, Thomas Buckb, Rolf-Alexander Jánosib, Torsten Bossertc, Nikolaus Pizanisa, Markus Kamlera, Heinz Jakoba

a Department of Thoracic and Cardiovascular Surgery, West-German Heart Center Essen, University Hospital Essen, Hufelandstraße 55, 45122 Essen, Germany
b Department of Cardiology, West-German Heart Center Essen, University Hospital Essen, Essen, Germany
c Department of Cardiac Surgery, Heart Center Leipzig, University Hospital Leipzig, Leipzig, Germany

Received 16 September 2007; received in revised form 23 December 2007; accepted 29 December 2007.

* Corresponding author. Tel.: +49 201 723 84912; fax: +49 201 723 5451. (Email: daniel.wendt{at}uk-essen.de).


   Abstract
Top
 Abstract
1. Introduction
 2. Methods
 3. Results
 4. Discussion
 Appendix A
 References
 
Background: Aortic valve replacement (AVR) with extracorporeal circulation (ECC) is currently the treatment of choice for symptomatic aortic stenosis. However, patients with multiple high-risk comorbid conditions may benefit from reduced ECC time and thus, reduced myocardial ischemia, by the use of sutureless AVR. We describe the initial experience and 1-year results of our first 3F-Enable AVR implants. Methods: Between 09/05 and 12/05, six patients (age 74 ± 1.8 years; three females) with symptomatic aortic stenosis (NYHA III) underwent AVR with an equine pericardial and nitinol-stented sutureless prosthesis. For additional safety up to three stay sutures were placed. Echocardiography was performed preoperatively, intraoperatively, at 6- and 12-month follow-up. Clinical data, adverse events and patient outcome were recorded prospectively. Results: Prosthesis sizes were 27 mm (n = 3), 25 mm (n = 1), 23 mm (n = 1) and 21 mm (n = 1). ECC time was 87 ± 32 min; aortic clamp time was 56 ± 24 min. Prosthesis deployment time was 148 ± 173 s. There were no intraoperative deaths or complications. At 12-month follow-up mean pressure gradients (MPG) were 6.8 ± 3.5 mmHg and aortic valve area (AVA) was 2.2 ± 0.5 cm2. One patient underwent successful redo AVR after 8 months due to severe paravalvular leakage (PVL), and one patient died due to lung cancer 10 months after surgery. At 12 months follow-up four out of six patients are alive and asymptotic (NYHA I) with the 3F-Enable aortic valve prosthesis, however, one patient showed mild paravalvular leakage. Conclusions: These first 1-year follow-up data suggest the feasibility of this new concept of sutureless aortic valve implantation. However, severe aortic insufficiency at 8 months and paravalvular leakage at 1-year follow-up should prompt further procedural and device enhancements.

Key Words: Sutureless • Aortic valve replacement • 3F-Enable


   1. Introduction
Top
 Abstract
 1. Introduction
2. Methods
 3. Results
 4. Discussion
 Appendix A
 References
 
Aortic valve replacement (AVR) is the treatment of choice in patients with severe and/or symptomatic aortic stenosis [1]. Due to an aging population and subsequent increasing comorbidities (e.g. chronic obstructive pulmonary disease, poor left ventricular function, renal insufficiency or in the case of reoperation) open-heart surgery using cardiopulmonary bypass may be associated with an unacceptable morbidity and mortality [2,3]. To date, percutaneous aortic valve replacement either via transfemoral or transapical access is of inexorable progress and has even been suggested as an alternative to heart valve surgery in selected cases [4–6]. However, using these techniques, the calcified valve-pathology remains in-situ and has to be dilated into the aortic wall prior to the implantation procedure. As a result, the prosthesis may be implanted in an inhomogeneous and non-circular layer, leading to warping and geometry-changing of the prosthesis; paravalvular leakage/insufficiency may then remain a major concern [5,7,8].

Although these highly sophisticated and rapidly emerging catheter-based technologies do allow a minimally invasive treatment option of high-risk patients on the one hand, on the other hand further additional developments and new surgical approaches are coming up in conventional aortic valve surgery. By the use of sutureless aortic heart valves, a new challenging field in aortic valve surgery with less radical invasiveness may save implantation time. However, the concept of heart valve implantation without the use of any suture goes back to the early sixties, but this method was ahead of time due to several disadvantages, such as frequent valve-related thromboembolic complications and severe paravalvular leakages [9,10].

To date, a new bio-prosthetic nitinol-based heart valve has been designed (3F-Enable, Model 6000, once 3F Therapeutics, now ATS Medical) for first clinical application [11]. The purpose of the present study was therefore to evaluate the feasibility of implantation and to analyze the short- and mid-term results in a prospective single-center study.


   2. Methods
Top
 Abstract
 1. Introduction
 2. Methods
3. Results
 4. Discussion
 Appendix A
 References
 
2.1 Study design
The present study was a prospective, non-randomized, single-center feasibility study including six consecutive patients, who underwent isolated AVR at the West-German Heart Center Essen between September and December 2005. Echocardiographic and clinical examinations (including NYHA-classification) were performed preoperatively, postoperatively, and at 6- and 12-month follow-up.

Patients were excluded from the study, if (1) age was <70 or >80 years, (2) life expectancy was less than 12 months, (3) had active endocarditis, (4) patients were addicted to IV drug abuse, (5) had previous cardiac surgery, (6) concomitant procedures or (7) any irregularities of the ascending aorta were present.

The study was approved by the local medical ethics committee and all patients gave written informed consent.

2.2 Surgical management
Surgical strategy was routinely performed in all patients using median sternotomy, standard cardiopulmonary bypass (CPB) technique with ascending aortic and two-stage venous cannulation, mild hypothermia and cold crystalloid cardioplegic arrest. Transversal aortotomy with subsequent conventional valve resection and debridement of the native annulus was performed. The prosthesis required rinsing in saline solution (room temperature) three times for 4 min each time and was then stored in ice-cold water to enable the valve folding prior to delivery. After sizing, the 3F-Enable valve was inserted and two or three alignment stitches were done to avoid valve torsion and to assure exact placement at the lowest point of the native annulus. These stay sutures were performed to get an additional level of safety. Valve function was assessed by intraoperative transesophageal echocardiography (TEE) after decannulation.

2.3 Technology of the sutureless prosthesis
The 3F-Enable sutureless valve (Model 6000, 3F Therapeutics, Lake Forest, CA, USA) was developed for aortic valve replacement. The valve was constructed from a self-expandable, nitinol-based stent with an attached equine pericardial trileaflet valve. The valve was stored in glutaraldehyde. The 3F-Enable valve may not require any anchoring sutures for deployment but for additional safety up to three stay sutures were placed. The self-expandable stent allowed the device to remain in position due to radial recall forces. A polyester cloth was attached at inflow aspect. Valves were supplied sterile in glutaraldehyde and were available from 19 up to 29 mm. Previous to delivery valves were crimped under ice-cold conditions (4 °C). Valve is illustrated in Fig. 1 .


Figure 1
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  		Fig. 1. Self-expandable 3F-Enable aortic valve prosthesis (Model 6000).

 
2.4 Statistics
Continuous and normally distributed data were reported as mean ± standard deviation. Student's t-test was used for paired data testing. A p value less than 0.05 was considered to indicate statistical significance. All statistical analyses were performed using the Sigma-Stat System®, version 2.0 (Systat Software Inc., San Jose, CA, USA).


   3. Results
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
4. Discussion
 Appendix A
 References
 
3.1 Patient population
Six consecutive patients (three females and three males) with severe aortic stenosis were enrolled in the study. Mean age was 73.8 ± 1.8 years (range 72–76 years). Baseline patient characteristics are listed in Table 1 . All patients had severe aortic stenosis with a preoperative mean pressure gradient (MPG) of 50 ± 11 mmHg (range, 38–65 mmHg). The preoperative mean calculated aortic valve area was 0.65 ± 0.1 cm2. One patient suffered from COPD and another patient from silicosis. Mean calculated logistic EuroScore of the study population was 6.22 ± 1.83% (range 4.52–9.28%) and all patients were in NYHA functional class III.


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  		Table 1 Preoperative patient characteristics
 
3.2 Surgical results
Valve implantation was achieved in all patients. Implanted valve sizes ranged from 21 to 27 mm. Procedural and postoperative characteristics are shown in Table 2 . Mean valve deployment time was 148 ± 173 s (range 10–420 s) and in two cases valve position was corrected due to malpositioning leading to an extended implantation time. Mean aortic cross-clamp time was 56.5 ± 24.5 min. Up to three stay sutures were placed, avoiding torsion or malpositioning. In the first case, stay sutures were placed commissurally leading to supraannular positioning of the valve. In the other five patients, stay sutures were placed at the lowest point of the annulus (nadir) resulting in optimal position. In one case (patient #5), the valve was exchanged intraoperatively (25 mm vs 23 mm) due to inappropriate sizing. In this case, high-grade transvalvular insufficiency was identified in the post extra-corporeal-circulation echocardiography leading to a second aortic-clamp time. There were no intraoperative deaths or major intraoperative complications. No reoperations due to major bleedings were necessary. One patient developed renal failure due to preoperative renal disease and needed short-term dialysis.


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  		Table 2 Intra- and postoperative procedural characteristics
 
3.3 Hemodynamic valve performance and follow-up
Prosthesis function and hemodynamic performance was assessed intraoperatively and at 6- and 12-month follow-up. Echocardiographic data are shown in Figs. 2 and 3 . Intraoperative aortic valve area (AVA) increased significantly compared with preoperative values (3.2 ± 0.4 cm2 vs 0.75 ± 0.1 cm2). AVA was 2.2 ± 0.5 cm2 at 12 months follow-up compared with 3.2 ± 0.4 cm2 intraoperatively (p = 0.002). At 12-month follow-up the 3F prosthesis showed good hemodynamic performance and mean pressure gradients remained unchanged during follow-up (5.8 ± 1.3 mmHg, 6.7 ± 2.5 mmHg and 6.8 ± 3.5 mmHg).


Figure 2
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  		Fig. 2. Aortic valve area (cm2) during follow-up (mean ± SD): (*) vs preoperative, ({dagger}) vs intraoperative calculated by Student's t-test.

 

Figure 3
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  		Fig. 3. Mean pressure gradients (mmHg) during follow-up (mean ± SD): (*) vs preoperative calculated by Student's t-test.

 
In two cases, paravalvular leakage could be observed (Table 3 ). One of these patients (patient #1) showed severe paravalvular leakage (PVL) during short-term follow-up, but the patient first refused reoperation. At 8 months after 3F-Enable implantation a reoperation was inescapable due to severe PVL and decline of physical strain. The prosthesis was replaced with an Elan aortic root prosthesis (AorTech, Bellshill, Scotland, UK) and an additional repair of the mitral and tricuspid valve was necessary. Another patient showed PVL during the follow-up period (grade 2 at 6 months), but decreased at 12 months (grade 1). Remaining patients are alive and asymptomatic at 12 months follow-up. Only one patient showed mild PVL at 12 months, and only one grade 1 transvalvular insufficiency at 12-month follow-up could be observed. One patient (patient #5) died 10 months after surgery due to preoperative unknown bronchial cancer. The NYHA functional class showed significant improvement during follow-up. At 12-month follow-up all patients were in NYHA class I (Fig. 4 ).


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  		Table 3 Echocardiographic findings
 

Figure 4
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  		Fig. 4. NYHA functional class during follow-up.

 

   4. Discussion
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
Appendix A
 References
 
The present study demonstrates our first clinical experience with the 3F-Enable aortic bioprosthesis in patients with severe aortic stenosis and proves the feasibility of sutureless valve implantation. The 3F-Enable equine valve is a new sutureless valve, constituting a step towards minimally invasive and time-saving techniques [12].

A flexible nitinol-based stent-frame design eliminates the need for additional structural features that are seen in traditional valves and thus results in increased valvular and supravalvular diameters lowering transvalvular pressure gradients. Furthermore, the 3F-Enable aortic valve requires no suture lines that are needed to be placed in conventional valve implantation. Nevertheless, we used two or three stay sutures to provide additional safety. This concept may lead to an increased speed of insertion; thus making implantation easier for the surgeon. In our series, mean valve implantation time was 148 ± 173 s (range 10 up to 420 s) suggesting an easy and time-saving method. In two cases, prolonged implantation time was found (300 and 420 s) due to repeated repositioning. In these two cases, valve expanding was extended and was assisted manually. A possible enhancement could be a protocol addition of intraprocedural balloon-inflation to assure faster and exact stent-expansion. This quick and easy method may lead to reduced extracorporeal circulation (ECC) time and thus, to reduced myocardial ischemia. The average time for aortic cross-clamping in our study was 56 ± 24 min (range 30 up to 97 min), which includes making and closing the aortotomy, excising the stenotic valve and placing the new prosthesis. Despite the fact that implantation time was quite short, our aortic cross-clamp time was 56 ± 24 min. Linneweber et al., who implanted the stentless 3F bioprosthesis in 35 patients, using a continuous running suture line, reported a mean ACC time of 57 ± 15 min [13]. Compared with the current literature, our ACC time was rather on average with 56 ± 24 min. In the present feasibility study, the aortic cross-clamp time was still longer than expected [14]. However, this new technology offers the potential capacity of a shorter valve-implantation time as compared to conventional AVR.

In the present study, the AVA increased up to 3.18 ± 0.41 cm2 (anatomical aortic valve area, calculated by planimetry) and decreased during follow-up to 2.5 ± 0.3 cm2 at 6 months and to 2.2 ± 0.5 cm2 at 12 months, respectively. This is explicable due to different echocardiographic measurements using the continuity equation, giving the effective orifice area. Additionally, echo measurements were performed under different hemodynamics (intra- and postoperative). There were no significant differences in the 6- and 12-month AVAs. Comparing AVAs with transapically implanted valves, we found higher aortic valve areas in our study. Ye et al. [6] found a mean aortic valve area of 1.6 ± 0.6 cm2 in their first seven patients undergoing transapical aortic valve implantation. This could be explained by the design of the 3F-valve, which eliminates additional structures, and thus increasing valvular diameter.

Regarding the valve-related complications of the present study, in one out of six patients, severe transvalvular leakage was observed during intraoperative TEE. This valve was exchanged intraoperatively (25 mm vs 23 mm) due to valve oversizing, leading to an increased mean aortic cross-clamp time.

No major adverse events or deaths have been found intraoperatively. We found hemodynamic parameters comparable to conventional aortic valves [15,16]. Low mean pressure gradients were observed in the short-term follow-up and remained unchanged during investigation (5.8 ± 1.3 mmHg, 6.7 ± 2.5 mmHg and 6.8 ± 3.5 mmHg). To our knowledge to date, only one animal study reports about implantations of a sutureless custom-made stented aortic valve. Although valve deployment took less than 1 min, the surgical procedure resulted in major complications in all cases: migration, paravalvular leakage, coronary ostia obstruction and mitral regurgitation [5,17]. In the present study, two patients were detected during follow-up with paravalvular leakage. One patient (patient #1) therefore required a reoperation; a full root replacement was necessary due to aortic wear caused by valve tab attachment. The second patient (patient #4) showed paravalvular leakage grade 2 at 6 months, but decreased to grade 1 at 12 months. Both PVLs may have occurred due to insufficient valve expansion caused by low radial forces of the nitinol-based stent.

The problem of PVL was already described by Magovern et al. An attempt to solve this problem was to add a thin silicone cuff around the outer circumference to prevent further PVL [18,19], however additional ballooning during procedure may also improve valve deployment and prevent further PVLs. The company (ATS Medical, Minneapolis, Minnesota, USA) already addressed this problem by further valve design enhancements: (1) the valve cuff has been expanded and (2) improved in flange design.

In none of our patients was valve migration due to insufficient fixation observed. This, we believe, is of major importance and therefore this concept of sutureless valve implantation might be considered as an additional tool in conventional aortic heart valve implantation, although further procedural and device enhancements are essential to prevent the problem of PVL. Comparing the sutureless technique with transcatheter valve implantation techniques, the sutureless technique has two major benefits: the first advantage of the sutureless technique is that the excision of the calcified valve is possible under safe conditions using the heart–lung-machine, whereas the pathology remains in-situ by the use of transcatheter aortic valve implantation, both transapical and transfemoral. Moreover, another potential advantage is that a shortened implantation time may lead to reduced aortic cross-clamping-time with the use of sutureless valve implantation technique.

In conclusion, this initial trial with the new 3F-Enable sutureless valve showed basic feasibility of this concept, but the common problem of paravalvular leakage still remains. The valve hemodynamic findings were satisfactory and comparable to conventional heart valves. This approach may not only reduce operation and ischemic times but also allow the resection of severely calcified aortic stenosis under direct vision of the surgeon, which is not addressed in all present endovascular valve techniques. The creation of an anatomic exact circular annulus in which the valve will be implanted would be an advantage. Further studies are necessary and the durability of this new valve has to be investigated in the long-term, but primarily, refinements of the design/construction of the 3F valve are necessary before going on with clinical studies.


   Appendix A
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
 Appendix A
References
 
Conference discussion

Dr A. Haverich (Hannover, Germany): Now, in these six patients, there were three patients who had an annulus diameter of 27 mm and one of 25, and this is somewhat unusual in the average population of aortic valve stenosis that we see. In addition, the extracorporeal circulation time was 87 min as a mean and the cross-clamp time was 56 min as a mean, and this is well double of what we see in a comparable sutureless valve being implanted in a recent study, and I wonder if the authors would comment on the implant times and extracorporeal and cross-clamp times as well.

Against the background of at least 30% paravalvular leakage and a 16% reoperation rate, I wonder whether the authors would also comment on the patient selection, again, taking into consideration the size of the aortic annulus.

And my third question would be if the authors would see for the sutureless valve an indication sui generis, especially in the very old patients with a very calcific aortic valve and some calcific aortic root where this type of valve might actually be advantageous to other suture type of valves.

And my last question would be, does this group continue to implant this valve, and if so, under which protocol?

Dr Wendt: First I want to answer the question concerning the ACC and CPB time. I think this was our learning curve, and our average aortic cross-clamp time was 56 min. So in one patient, like I told you, the valve had to be changed intraoperatively. So if we exclude this patient, the cross-clamp time will decrease to 40 min approximately. And in addition, this was a new technique and a feasibility study, so a lot of communication between the company, the anesthetist, and our partners from the other departments was necessary intraoperatively. I hope this could explain our prolonged CPB and ACC time.

Coming to the second question, three patients had a 27 mm annulus and one patient a 25 mm annulus – this is indeed unusual. But I think you should oversize these valves in order to prevent paravalvular leakage. In one patient we did this oversizing with a 25 mm valve, but under direct intraoperative echo, we found that this valve was insufficient, so it was explanted and changed to 23 mm.

And the last question?

Dr Haverich: It is our feeling from the study that we performed right now with sutureless valves that there might be an indication sui generis for this valve in severely calcified aortic roots where it is maybe much easier to implant this valve as opposed to a sutured valve.

Dr Wendt: That's right, but I think it will be a problem in a severely calcified annulus. Like we saw in patient number one: The valve was so heavily calcified and there was a high amount of calcium. These bulky parts could explain an insufficient expansion of the nitinol stent due to insufficient recoil forces creating a non-circular layer. This could cause severe paravalvular leakage. So in my opinion, this feasibility study is a step towards minimal invasive surgery but to get optimal results with this new technique, the perfect resection of the pathology, performed conventionally or endoscopically is essential, both in open-heart surgery and in the transapical/transfemoral approach.

Dr P. Kappetein (Rotterdam, The Netherlands): My concern is that when you have to reoperate such a patient you have to replace the ascending aorta in case of failure of the valve prosthesis. This is the same concern as one could have with the percutaneous Core Valve prosthesis. I thought that you mentioned that you had to reoperate the patient that had this paravalvular insufficiency.

Dr Wendt: Yes, that's right, perhaps you must replace the ascending aorta when you reoperate on a patient with previous Core Valve implantation.

Dr Kappetein: So while we don’t know the durability of this valve, there is the concern that when the valve fails within a few years one has to replace the valve and the ascending aorta in these patients.

Dr Wendt: Yes, this could happen, because there are no long-term results.


   Footnotes
 
{star} Presented at the 21st Annual Meeting of the European Association for Cardio-thoracic Surgery, Geneva, Switzerland, September 16–19, 2007.

{star}{star} The study was granted by 3F Therapeutics (Lake Forrest, CA, USA) and ATS Medical (Minneapolis, Minnesota, USA). None of the investigators or patients received payments to participate in this study.


   References
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
 Appendix A
 References
 

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