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• Percutaneous aortic valve replacement with self-expanding stents: haemodynamics in the focus
  Georg Lutter
  Published on: 23 November 2015

• Published on: 23 November 2015

  Percutaneous aortic valve replacement with self-expanding stents: haemodynamics in the focus

  • Georg Lutter, Christian-Albrechts-University of Kiel, School of Medicine, Kiel, Germany
  • Other Contributors:
    • Tim Attmann, Jochen Cremer, and Georg Lutter.

  Dear Editor,

  We would like to compliment Ferrari and associates on their recent study [1]. They convincingly prove the need for a less invasive technique of aortic valve replacement, firstly, due to the increasing number of older patients requiring aortic valve replacement and, secondly, due to the high one-month mortality rate among nonagenarians after open heart surgery.

  The authors evaluated the feas...

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  Dear Editor,

  We would like to compliment Ferrari and associates on their recent study [1]. They convincingly prove the need for a less invasive technique of aortic valve replacement, firstly, due to the increasing number of older patients requiring aortic valve replacement and, secondly, due to the high one-month mortality rate among nonagenarians after open heart surgery.

  The authors evaluated the feasibility of percutaneous aortic valve replacement with a self-expanding nitinol stent in beating pig hearts. The implanting procedure could be successfully performed in four of six animals via the left subclavian artery with an implantation catheter of 25 French. For the first time, this technology was tested in their experimental model under haemodynamic stress conditions.

  Besides these haemodynamic stress tests, the fact that the valved stents could be deployed intra-annular without obstructing the coronary orifices deserves merit. Our group’s experience demonstrated that it is very difficult to position a valved stent into porcine aortic anuli without occlusion of the coronary ostia by native leaflets when pushed against the aortic wall. We reported on endovascular aortic valve implantation to the descending and ascending aorta using self-expanding nitinol stents in 2002. In eleven of 14 pigs, valved stents were successfully implanted via an iliac or infra-renal approach (descending, n=6, supracoronary, n=3, subcoronary, n=2) and demonstrated low transvalvular gradients with good angio- and echocardiographic results. An implantation device of 22 French had been used [2].

  Unfortunately, our study has been inadvertently cited in the wrong context because it was the first-ever use of a self-expaning valved stent, not a balloon expandable. Therefore, the author’s statement that “all approaches to percutaneous valve replacement to date have used a balloon expandable stent” is not quite correct.

  The haemodynamic conditions during percutaneous valve implantation are very crucial. Ferrari and co-workers could not reveal “any relevant drop in blood pressure” in their healthy pigs. We would like to emphasize that even minor disturbances of the haemodynamics can lead to fatal complications in patients with end-stage aortic valve stenosis and cardiomyopathy. Therefore, heamodynamic parameters should be meticulously registered during valved stent deployment in future studies and the data should be presented in detail. These data are important to evaluate the necessity of circulatory support, e.g. a femoro-femoral bypass, during deployment [3].

  Another key concern in progressing from the experimental model to clinical applicability is mentioned by Doctor Ferrari and colleagues: calcification. They speculate that a stent may obstruct the left ventricular outflow tract in heavily calcified aortic stenosis, and suggest a preceding balloon valvoplasty in these patients before implantation of a self-expanding stent valve. We agree with the authors that calcification is the major obstacle to implanting a self-expanding valved stent in the aortic position. Not only because the expansion force of the stent is not great enough to dilate the stenotic valve structures resulting in an insufficient valve area, but also because of the well known dilemmas, not mentioned by the authors: embolic complications, impairment of coronary flow, paravalvular leakage, haemorrhaging, and smaller aortic valve area compared to after a surgical procedure.

  We would like to offer an alternate procedure, on which we are already working, for the solution of these problems: percutaneous aortic valve resection. In a preliminary study, the use and feasibility of a high -pressure water jet system as a new promising surgical method for the endovascular ablation of human calcified aortic valves has been successfully performed and evaluated [4]. Nevertheless, the realization of an ideal endoluminal aortic valve replacement process is challenging, and only sophisticated technical refinements of the tools will lead to success [2,3].

  The Jena-group’s article advances the transarterial aortic valve replacement procedure. At the same time, this study shows clearly the multiple limitations that are still present in this evolving field. Only two thirds of the implantations were successful in the Jena-study. Problems with the implantation device and the correct positioning occurred. Therefore, their and also our study indicate the necessity for further improvements of the: visualization method, resection tool (for prior percutaneous valve resection), application device, guidance of catheters and their miniaturisation [3,4].

  Certainly, open heart surgery is still and will remain the golden standard in aortic valve replacement for many years to come.

  References

  (1). Ferrari M, Figulla HR, Schlosser M, Tenner I, Frerichs I, Damm C, Guyenot V, Werner GS, Hellige G. Transarterial aortic valve replacement with a self-expanding stent in pigs. Heart. 2004;90:1326-31.

  (2). Lutter G, Kuklinski D, Berg G, von Samson P, Martin J, Handke M, Uhrmeister P, Beyersdorf F. Percutaneous aortic valve replacement: an experimental study. I. Studies on implantation. J Thorac Cardiovasc Surg. 2002;123:768-76.

  (3). Lutter G, Ardehali R, Cremer J, Bonhoeffer P. Percutaneous valve replacement: current state and future prospects. Ann Thorac Surg. 2004;78:2199-2206.

  (4). Quaden R, Attmann T, Puehler T, Boening A, Hagemann A, Cremer J, Lutter G. Percutaneous aortic valve replacement: studies on ablation. 3rd EACTS/ESTS Joint Meeting, September 12-15, 2004, Leipzig, Germany.

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  Conflict of Interest:
  None declared.

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