Herz
`
`© Urban & Vogel 2009
`
`History of Percutaneous Aortic Valve
`Prosthesis
`
`1 Department of Cardiol-
`ogy, Skejby University
`Hospital, Aarhus, Den-
`mark.
`
`Henning Rud Andersen1
`
`Abstract
`This review describes the development of percutane-
`ous transluminal catheter-mounted heart valves for
`permanent implantation. The time period from the
`first surgically implanted valve in 1952, through cathe-
`ter-mounted valves inserted for temporal relief, until
`
`the conception of the percutaneous transcatheter
`heart valve for permanent implantation is summar-
`ized. The process involved in the construction of the
`new valve is detailed in Figure 1, and the future of this
`new treatment modality is discussed.
`
`Geschichte der perkutanen Aortenklappenimplantation
`
`Zusammenfassung
`Diese Übersicht beschreibt die Entwicklung perkuta-
`ner transluminaler kathetermontierter Herzklappen
`zur permanenten Implantation. Der Zeitraum von der
`ersten chirurgisch eingepflanzten Klappe 1952, die
`mittels kathetermontierter Klappen zur temporären
`Entlastung eingesetzt wurde, bis zum Konzept der
`
`perkutanen Transkatheter-Herzklappe zur permanen-
`ten Implantation wird besprochen. Der mit der
`Konstruktion der neuen Klappe verbundene Prozess
`wird in Abbildung 1 detailliert dargestellt, und die Zu-
`kunft dieser neuen Behandlungsmodalität wird dis-
`kutiert.
`
`Key Words:
`Heart valve · Catheter ·
`Percutaneous · Im-
`plantation
`
`Herz 2009;34:343–6
`DOI 10.1007/
`s00059-009-3251-4
`
`Schlüsselwörter:
`Herzklappe · Katheter ·
`Perkutan · Implantation
`
`Introduction
`Implantation of an artificial heart valve as a treatment
`for valvular heart disease dates back to 1952, when
`Hufnagel performed the first implantation in a pa-
`tient with severe aortic insufficiency [1]. The artificial
`heart valve was implanted in the descending thoracic
`aorta, significantly reducing severe left ventricular re-
`gurgitation and improving hemodynamic function [2].
`This technique was used in a small series of opera-
`tions for aortic regurgitation [3, 4], and follow-up re-
`ports 24 years later revealed satisfactory results in
`some of the patients [5]. The development of extra-
`corporeal circulation made it possible for Harken et
`al. to perform the first subcoronary implantation in
`1960 [6]. Since then, implantation of prosthetic heart
`valves has been an open-heart surgical procedure. If,
`however, permanent implantation of heart valves
`could be accomplished without thoracotomy, it would
`be highly attractive, as it would not only significantly
`reduce surgical time and trauma, but the proce-
`dure-associated morbidity of the patient would be
`smaller. In recent years, interventional cardiology has
`introduced percutaneous implantation of many dif-
`ferent cardiac devices, but it was not until recently
`that percutaneous transluminal catheter-mounted
`heart valves were implanted into a human [7].
`
`Herz 34 · 2009 · Nr. 5 © Urban & Vogel
`
`Catheter-Mounted Heart Valves for
`Temporary Treatment
`In 1965, Davies described a catheter-mounted valve for
`temporary relief of aortic insufficiency and tested it in
`dogs [8]. A cone-shaped valve in the form of a parachute
`with wires was mounted on the tip of a 5-F catheter. The
`catheter was inserted via the femoral artery into the de-
`scending aorta and the extending catheter was fixed to
`the skin of the leg. The valve collapsed during antegrade
`blood flow, and, during diastole, it unfolded due to ret-
`rograde blood flow and pressure gradient. The para-
`chute wires prevented the valve from inverting during
`diastole. The catheter-mounted valve was designed for
`temporary relief of symptoms in patients with severe
`aortic insufficiency, and to render the patient fit for de-
`finitive surgery days or weeks later. The catheter was not
`designed for permanent implantation.
`In 1971, Moulopoulos et al. described three dif-
`ferent catheter-mounted aortic valves for insertion in
`the ascending aorta [9]. The devices were tested in vi-
`tro in a mock circulation system, and in vivo in dogs.
`One of the valves had an umbrella design and two
`were based on a balloon system.
`The umbrella-shaped polyurethane valve was
`2–3 cm in length and 1–2 cm in diameter and mounted
`at the tip of a polyethylene catheter. The diameter of
`NORRED EXHIBIT 2088 - Page 1
`Medtronic, Inc., Medtronic Vascular, Inc.,
`343
`& Medtronic Corevalve, LLC
`v. Troy R. Norred, M.D.
`Case IPR2014-00110
`
`

`
`Andersen HR. History of Percutaneous Aortic Valve Prosthesis
`
`Figure 1. Photograph of
`the Andersen stent
`valve built for percuta-
`neous transluminal
`catheter implantation.
`The stent valve was
`constructed in 1989 and
`consisted of two folded
`metal rings and a por-
`cine aortic valve mount-
`ed inside the stent.
`Abbildung 1. Photogra-
`phie der Andersen-
`Stentklappe zur
`perkutanen translumi-
`nalen Katheterimplan-
`tation. Die Stentklappe
`wurde 1989 konstruiert
`und bestand aus zwei
`gefalteten Metallringen
`und einer Schweineaor-
`tenklappe, die inner-
`halb des Stents ange-
`bracht wurde.
`
`344
`
`the open umbrella was planned to be larger than that
`of the aorta. During systole, the forward flow closed
`the umbrella. During diastole, the backward flow
`opened the umbrella, which touched the aortic wall.
`The umbrella was designed to be long enough so the
`open valve would touch the aortic wall over a large
`area and would not be inverted by the diastolic pres-
`sure gradient. This therefore precluded the need for
`parachute wires to prevent inversion of the valve.
`The two balloon systems were designed with a spher-
`ical balloon 1 cm in diameter made of polyurethane
`and tied at the end of a 40 cm long polyethylene cath-
`eter. The balloons could be inflated during diastole
`and deflated during systole. When inflated, the bal-
`loon occluded the aorta in order to prevent diastolic
`backflow. When deflated, it collapsed in order to al-
`low a free systolic flow. The catheters were connected
`to two different external pump systems which syn-
`chronized inflation and deflation in relation to dias-
`tole and systole. None of these three catheters was
`designed for permanent implantation.
`5 years later, in 1976, Phillips et al. described a
`catheter-tip-mounted aortic valve for temporary
`treatment of aortic insufficiency and tested it in dogs
`[10]. This design employed a mixture of the concepts
`described by Davies [8] and Moulopoulos et al. [9]. It
`was a catheter mounted with a polyurethane cusp de-
`signed to act as a temporarily inserted prosthetic aor-
`tic valve in the ascending aorta. The cusp should col-
`lapse during systole and unfold during diastole. It was
`mounted 1 cm from the end of a polyurethane cathe-
`ter 4 mm in diameter and 60 cm in length. The cusp
`had an umbrella design, but also one parachute wire
`to prevent the valve from inverting during diastole.
`The extending catheter was fixed to the skin.
`In 1977, Boretos & Poirier also described a cath-
`eter for temporary relief of aortic insufficiency [11].
`
`This catheter was also designed for extending out of
`the patient to be fixed against the surface of the body.
`The valve was mounted at the tip of a catheter, shaped
`as a cone with a broad circular basis pointing in the
`direction of the left ventricle, and with the flexible
`valves of the cone extending downstream. It allowed
`central flow through the cone during systole and clo-
`sure of the flexible valves during diastole, which was
`the result of both regurgitated flow and the diastolic
`pressure gradient.
`Several years later, in 1992, Matsubara et al. de-
`scribed a balloon catheter with check valves for ex-
`perimental relief of aortic regurgitation and tested it
`in a dog model [12]. A latex balloon was mounted
`near the end of a catheter and inflated to occlude the
`aorta. Holes on the proximal and distal sides of the
`balloon were connected to each other inside the cath-
`eter, allowing the passage of blood from the two dis-
`tal holes to the two proximal holes during the systolic
`phase. Two latex valves were mounted on the two
`proximal holes of the catheter to prevent regurgita-
`tion during diastole.
`The result of close to 30 years of design and test-
`ing of catheter-mounted valves for short-term inser-
`tion into the aorta designed for temporary relief of
`aortic insufficiency undoubtedly made experimental
`progress. However, despite the technical develop-
`ment these catheters never went into clinical use.
`None of these catheter-mounted valves was applica-
`ble for permanent implantation.
`
`The Conception of a Percutaneous
`Transluminal Catheter-Mounted Heart
`Valve for Permanent Implantation
`In February 1989, the idea of a percutaneous heart
`valve for permanent implantation was conceived by
`Andersen (Figure 1) [13]. The idea behind its concep-
`tion was to develop a new technology and treatment
`to be used by interventional cardiologists in a cardiac
`catheterization laboratory. Andersen defined three
`requirements for the new technology. The implanta-
`tion should be on a closed chest, a beating heart and a
`closed heart. Furthermore, no catheter should be left
`inside the heart or the vessel after implantation of the
`valve. The valve should be for permanent implanta-
`tion. The first valve was implanted on May 1, 1989 in
`the descending thoracic aorta of a pig (Figure 2). The
`first subcoronary implantation was performed in No-
`vember 1989 in a pig.
`
`The New Concept for Implantation
`of Artificial Heart Valves
`The idea was to mount a foldable biological cardiac
`valve inside a balloon-expandable metallic stent.
`
`NORRED EXHIBIT 2088 - Page 2
`Herz 34 · 2009 · Nr. 5 © Urban & Vogel
`
`

`
`Andersen HR. History of Percutaneous Aortic Valve Prosthesis
`
`Implantation of such a device (stent + valve = the stent
`valve) would enable implantation of artificial heart
`valves by the transluminal catheter technique without
`using thoracotomy or extracorporeal circulation. We
`constructed and hand-built the stent valve, sheets and
`catheters. The metal stent was constructed from two
`0.55-mm surgical stainless steel wires of the kind nor-
`mally used to close the sternum after thoracotomy.
`Each wire was folded into 15 loops, 8 mm high each
`(Figure 1). Three of the loops were 14 mm high, de-
`signed for fixation of the commissural points of a por-
`cine aortic valve. Each folded wire was bent into a cir-
`cle (diameter, 22 mm) which was closed end-to-end by
`soldering. The two circles were then stacked upon each
`other and fixed together with sutures. The ability of
`the metal stent to be compressed manually around a
`30-mm balloon was tested. Then, the ability of the bal-
`loon to expand the metal stent to 30 mm diameter,
`with the expanded stent having a sufficient stiffness to
`prevent recoil when it was implanted in vitro in an ex-
`planted pig aorta, was also tested. The choice of
`0.55-mm surgical stainless wires was determined after
`several “trial and error” tests with different wire thick-
`ness, stiffness and number of loops. The foldable valve
`was a porcine aortic valve taken from a pig heart
`bought from a local butcher. The valve was carefully
`dissected and cleaned manually, mounted inside the
`stent and then fixed with sutures (Figure 1). The stent
`valve was neither sterilized nor heparinized, nor was it
`treated with any drug or chemical agent. Thus, the
`stent valve was viable only for short-term use (hours)
`to prove the concept of catheter-based implantation of
`artificial heart valves. The proof of concept was docu-
`mented in pigs and in in vitro models [13, 14].
`
`Progression of Development from 1989
`until First Human Implantation in 2000
`The new technology did not gain much attention for
`several years. It was obvious that much more refine-
`ment and testing were necessary before implantation
`in humans could even be considered. Thus, such de-
`velopment required engineering, research, refine-
`ment and investment which could only be done by a
`company who believed in the concept. The interest,
`however, from industry involved in interventional
`cardiology was minimal. Academic research groups
`around the world continued to investigate the tech-
`nology. New biological valves were tested in animals
`[15–19], and mechanical valves, both cage-ball valves
`and disk valve prostheses, were also developed and
`tested [20, 21]. Then, in 2000, Bonhoeffer et al. per-
`formed the first human implantation in the pulmo-
`nary position [7]. This landmark achievement was
`followed by implantation in the aortic position in
`2002 by Cribier et al. [22]. Afterwards, the interest in
`
`Herz 34 · 2009 · Nr. 5 © Urban & Vogel
`
`Figure 2. The first An-
`dersen stent valve im-
`planted on May 1, 1989.
`Abbildung 2. Die erste
`Andersen-Stentklappe,
`implantiert am
`01.05.1989.
`
`this technology among cardiologists and industry sky-
`rocketed.
`
`The Future of Percutaneous Transluminal
`Catheter-Mounted Heart Valve
`Implantation
`The first pulmonary implantation in 2000 and the first
`aortic implantations in 2002 used a balloon-expand-
`able stent valve similar to the Andersen stent valve
`[13]. Later, self-expandable aortic valves were devel-
`oped [23]. Within the last 2–3 years, implantation of
`both balloon- and self-expandable stent valves has
`become routine treatment in Europe for selected pa-
`tients with aortic stenosis. The new treatment modal-
`ity has already been used in several thousand patients.
`Initially, the implantations were done only from the
`femoral vein or the femoral artery [7, 22, 24]. Recent-
`ly, a new transapical catheter technique for aortic
`valve implantation in humans has been developed
`and is now used very frequently [25, 26]. It allows
`treatment of patients with narrowed femoral arteries
`without the need for atrial septal puncture followed
`by antegrade implantation from the right atrium
`through the left atrium and the left ventricle – a dif-
`ficult and complex procedure. New technical modifi-
`cations of the initial concept are being developed,
`and in 2009 more than 20 companies around the world
`are involved in research and further development of
`the concept [27]. In addition, there have been recent
`mitral valve implantations that have been performed
`in animals (unpublished data). The percutaneous
`transluminal implantation technology is still very
`young and immature, but intense research and devel-
`opment will continue to bring it forward with high
`speed. This new technique has the potential to be the
`new major treatment breakthrough in interventional
`cardiology. Only time will tell.
`
`Disclosure: The autor declares that he has no financial or per-
`sonal relations to other parties whose interests could have af-
`fected the content of this article in any way, either positively or
`negatively.
`
`345
`NORRED EXHIBIT 2088 - Page 3
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`

`
`Andersen HR. History of Percutaneous Aortic Valve Prosthesis
`
`1.
`
`3.
`
`4.
`
`7.
`
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`
`Address for
`Correspondence
`Henning Rud Andersen,
`MD, PhD
`Associate Professor of
`Cardiology
`Department of Cardiology
`Skejby University Hospital
`8200 Aarhus N
`Denmark
`Phone (+45) 89496111,
`Fax -89496025
`e-mail: henning.rud.
`andersen@dadlnet.dk
`
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