REVIEW ARTICLE 285

Lessons can be learned from the history of heart valve prostheses

The evolution of surgical valves

Marco Russo a , Maurizio Taramasso a , Andrea Guidotti a , Alberto Pozzoli a , Fabian Nietilspach a ,
­L udwig K. von Segesser b , Francesco Maisano a
a
University Heart Center, Universitätsspital Zürich, University of Zurich, Switzerland; b Cardio-Vascular Research Department of Surgery and
­A nesthesiology, CHUV, Lausanne, Switzerland

implanted an heterotopic valvular heart prosthesis in

Summary the descending aorta of a patient with aortic valve re-
gurgitation. This represented the first step in a long
The treatment of heart valve diseases started in 1914 with closed heart pro- journey that lasted more than 50 years and is not fin-
cedures. In 1952, the first valvular heart prosthesis was implatanted in the ished yet. It is inspiring that most modern-generation
heterotopic position. In almost one century, cardiovascular surgery has pro- surgical valves have some features already researched
gressively evolved in several steps that represented correct answers to up- in the early days of surgical evolution, such as
coming clinical challenges. In this ­review we retrace the history of heart ­sutureless implantation, plastic leaflets and the beat-
valve prostheses, from the first steps to the present. ing heart approach.
Several key concepts as “operative mortality”, “durability”, “thromboembolic Heart valve innovation has been one of the most
events”, “less-invasiveness” guide our long journey and help us to explain ­important factors influencing the evolution of cardio-
the mechanisms of this evolution. vascular medicine. Denton Cooley often said “­Apply,
Simplify, Modify”. This philosophy inspired genera-
Key words: mechanical heart valves; biological heart valves; transcatheter heart valve implantation;
valve durability; less invasiveness tions of cardiac physicians and describes well what
happened in the evolution of heart valve prostheses.
Continuous and passionate research into new
­materials, technologies and techniques to overcome
the infinite challenges of replacing a natural structure
with an artificial implant.
Introduction
Heart valve innovation is also a good example of team-
a r tic le

On 7 September 1896, a 22-year-old man was stabbed in work, between physicians and engineers. Albert Starr,
Peer

the heart and collapsed. Two days later Dr Ludwig a surgeon from Colombia University and Lowell
re
v ie we Rehn, from Frankfurt, performed the first reported ­Edwards, an engineer close to retirement, met in 1957
d

heart surgery operation, suturing the wound in the and created the first commercial mechanical valve
heart through a left thoracotomy approach [1]. Since prosthesis with a long history of successful implants:
that time, many changes have occurred and cardiovas- the Starr-Edwards balloon cage prosthesis. A multi­
cular surgery has evolved exponentially since its be- disciplinary team composed of a cardiac surgeon, Dr
ginning in 1953, when, John Gibbon performed the first Nicoloff, an industrial engineer, Dr Posis, and an entre-
closure of an atrial septal defect with use of a heart- preneur, Manuel Villafana, together developed, in 1976,
lung machine. But the history of surgical valve treat- the first bileaflet prosthesis [4].
ment starts even earlier. Before the availability of the The early days of prosthetic valve development pro-
heart-lung machine, valve surgery was performed via vided much information that is still of value today.
a closed approach, on the beating heart. What can we learn from the good, the bad and the ugly
The first “closed heart procedure” was performed in experiences of the pioneers of valve innovation?
1914 when Theodor Tuffier treated an aortic valve ste-
nosis by digitally opening the valve through the aortic
wall [2]. In 1923, Elliot Carr Cutler, in conjunction with
his cardiology colleague, Samuel Levine, performed a
closed transventricular mitral commissurotomy. Abbreviation list:
Digital commissurotomy was introduced in 1948 by SVD = structural valve deterioration
EOA = effective orifice area
Bailey in Philadelphia and Harken in Boston and for
PPM = patient-prosthesis mismatch
many years was the treatment of choice for patients
TAVI = transcatheter aortic valve implantation
with mitral valve stenosis. The first valve prosthesis THV = transcatheter heart valve
was a “sutureless valve”: Charles Hufnagel [3], in 1952, TMVI = transcatheter mitral valve implantation

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Review article 286

We would like to give an overview of the history and of 40 years would have been expected. Recently this
­evolution of heart valves, focusing not only on the hypothesis was confirmed [10].
technical features of each prosthesis, but also on the The haemodynamic performance of the heart prosthe-
trends and mechanisms that influenced this continu- sis should be as close as possible to the native “perfect”
ous development. We have divided the paper in sec- valve, with low resistance to the forward flow and
tions that ­each describe the evolution of a subtype of ­allowing only trivial regurgitant backflow once the
heart valve, from mechanical and biological surgical ­occluder closes [11]. Paravalvular leakage and the risk of
prostheses to the transcatheter valves, and explain the endocarditis were immediately detected: they were
reasons that ­determined the emergence of the “next- the indications for r­eoperation in the two surviving
step valve”. With this purpose, we are not going to patients of Harken’s initial series. Valve noise was rec-
mention all the devices, but take example of the major ognised as an important problem and was solved early,
ones to understand the trend of evolution. for instance by replacing the methacrylate ball in the
Hufnagel prosthesis with a nylon one coated with a
­silicone rubber. Initial preclinical studies with me-
First steps in heart valve surgery
chanical valves showed the high level of anticoagula-
The evolution of heart valves began in the late 1940s, tion needed to avoid valve occlusion and an elevated
when, Charles Hufnagel designed a methacrylate risk of thromboembolic events was also described.
chamber containing a methacrylate ball that was All these aspects were already clear in the first decades
­implanted in the descending aorta of a patient with of heart valve surgery and they have steadily guided
aortic regurgitation. More that 200 patients were the evolution of heart valve prostheses. These “old con-
treated after 1952 [5]. The opportunity to work with an cepts” will be the “key words” adopted in this review, to
open heart permitted Dwight Harken, in 1960, for the explain the prostheses’ evolution.
first time to implant, in an annular position, a “double-
caged ball” prosthesis called the Harken-Soroff [6, 7]. In
Mechanical heart valves:
the same year, Nina Braunwald started her experience
past, present and future
with mitral valve replacement using a flexible poly­
urethane mitral prosthesis with attached Teflon chor- The poor haemodynamic performances of the “ball-
dae tendinae [8] and Albert Starr performed the first cage” valves indicated a need for the development of a
mitral valve replacement with the Starr-Edwards ball- second generation of mechanical prostheses. In fact,
valve. This valve was inspired by an old bottle stopper the central ball occluder caused lateralisation of
and was developed as a ball valve with a single meth- ­forward flow and therefore high turbulence; moreover,
acrylate cage and a Silastic ball inside, as occluder. the high profile and the large sewing ring produced a
The first results of this procedure were published in restricted effective orifice area (EOA), and limited effi-
1961 in an enthusiastic and innovative manuscript, cacy in the mitral position, with the risk of outflow
which is still inspirational today. A careful reading of tract obstruction [11, 12].
the original paper of Albert Starr and Lowell Edwards The need for the central flow, reproducing a more
reveals challenges and questions that are still valid to- physio­logical pattern, led, at the end of the 1960s, to
day, and that affected the evolution of the last genera- the development of tilting-disk prostheses. The Björk-
tion of surgical valves, endovascular implantable tran- Shiley valve was the first tilting-disc prosthesis to be
scatheter valves [9]. The authors were confronted with widely implanted: it was designed with a central disk
the (still) difficult choice between the more physio­ hold in place by two struts [13]. The open valve had two
logical option of valve repair and the more reproduci- orifices, with the turbulent flow limited to the area
ble and reliable option of valve replacement. near to the occluder. The flow r­ esistance was related to
A high operative mortality represented the first limit- the disc design and to the d
­ egree of the opening angle,
ing factor, mostly related to the complexity of opera- and for this reason the disc was progressively modified
tion and perioperative care. A lower profile valve that into a convexo-concave shape that could slide about
enabled easier and faster implantation appeared to be 2 mm during its movement, increasing the EOA. These
mandatory from the first. This was one of the first minor engineering modifications, with the aim to
steps in the evolution of heart valve design: Starr mod- achieve a better haemodynamic profile, led unexpect-
ified the Harken valve by removing the second cage to edly to a higher incidence of leaflet blockade and
simplify implantation. The issue of durability was ­embolisation due to the excessive “leverage-loading”
raised as long ago as 1961. The Starr-Edwards valve was on the outflow strut [13]. This brought about the end of
tested in vitro and, according to the results, a durability production of this prosthesis. The history of the Björk-

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Review article 287

Shiley is a paradigmatic example of how delicate the human practice [18]. New materials could be less
evolution of mechanical heart valves was. thrombogenic and patient selection could be redefined
Hoping to improve haemodynamics, Kalke and ­Lillehei accordingly, but there is not yet sufficient evidence to
developed the first prototype of a rigid bileaflet valve, change the standard anticoagulation management.
but very limited clinical use was reported. In 1977, the As a matter of fact, today most patients prefer to re-
St. Jude Medical (SJM) bileaflet prosthesis was intro- ceive a tissue valve, to avoid anticoagulation, and the
duced and implanted by Nicoloff and associates [14]. age threshold is continually reduced in guidelines,
This design produces three flow areas through the ranging between 60 and 65 years.
valve orifice, with a more uniform and laminar central
flow. Better haemodynamics was associated with less
Reducing anticoagulation-related events:
blood stagnation and the lower profile allowed easier
the advent of biological valves
implantation. Recently, the valve has been redesigned
as the SJM Regent valve. The sewing ring and the exter- The evolution of biological tissue valves is a mix of
nal profile were modified to further increase the effec- ­biochemistry, mechanical engineering and biology. A
tive orifice area, especially in the smaller aortic pros- tissue valve provides some clear advantages in terms
theses [15]. of biocompatibility, with concerns related to its dura-
After more than 50 years of evolution, mechanical bility.
valve replacement represents an optimal treatment for The history of tissue valves originated from evidence
patients with heart valve disease. Mortality decreased of the haemodynamic and biological advantages of ca-
progressively and no differences in term of prognosis daveric homografts, first implanted in the aortic posi-
have been described when comparing mechanical tion by Donald Ross in 1962 [19]. His effort was largely
with biological valves [16–17]. Figure 1 shows the evolu- based on the premise that “our entire physical makeup
tion of mechanical heart valve prostheses. and body structures represent the end result of mil-
But what can we expect in the current era from this old lions of years of evolutionary development” [20], and
tool? Could innovation in valvular heart therapies the assumption that no prosthetic valve can replicate
­alter the role of mechanical valves? Could mechanical such perfection.
valves benefit from new anticoagulation strategies? Since homograft cadaveric valves were difficult to col-
Studies in animals showed that dabigatran was effec- lect and preserve, the next step was to use xenografts –
tive in preventing valve thrombosis and was associ- valves collected from animals. The first generation of
ated with reduced mortality after mitral valve surgery. biological valves was substantially consisted of por-
These encouraging data have not yet translated into cine valves, the valves most similar to human ones.
Several new issues were debated. How can these xeno-
grafts be preserved and how made immunologically
inactive? What is the haemodynamics of non-human
valves and their durability after implantation?
Tissue valve engineering began with the use of forma-
lin to sterilise and fix the fresh xenograft tissue. This
technique was complicated by collagen breakdown,
with risk of early cusp calcification and occurrence of
fibrosis with a big shortfall in expected valve dura­
bility. Remembering the origin, Carpentier wrote some
years later: “It became obvious that the future of tissue
valves would depend upon the development of meth-
ods of preparation capable of preventing inflamma-
tory cell reaction, and penetration into the tissue” [21].
Therefore, he suggested the use of glutaraldehyde for
the chemical treatment of porcine valves [22]. Creating
cross-links in collagen molecules, this treatment pro-
tected the leaflets from denaturation and made the tis-
sue immunological inactive due to a
­ ntigen modifica-
tion. Anticalcification treatment changed the history
Figure 1: Mechanical heart valve evolution. From Hufnagel heart valve to the the current of tissue valves, increasing the expected durability.
bileaflet prostheses. Moreover, in 1966 Carpentier began to mount the

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Review article 288

whole porcine valve into a stent, obtaining a proper made” prosthesis, to optimise the anatomical configu-
three dimensional space relationship between the leaf- ration and avoid the fixed geometry of an animal
lets and simplifying the implantation technique. From valve. Bovine pericardium treated with glutaraldehyde
the haemodynamic standpoint, a central flow was was mounted on Delirin flexible stent, in order to
achieved but further analyses revealed an important achieve a synchronous opening of the three leaflets
pressure drop attributed to several factors, such as the (Ionescu-Shiley valve). In vitro haemodynamic studies
restriction of leaflet opening caused by the stent, the showed more symmetrical opening than with the por-
stiffness of the fixed geometry imposed by the pig’s cine ones. Despite the first enthusiasm, after 5 years of
anatomy and the presence of artificial commissures. follow-up the first cases of structural valve deteriora-
The roles played by haemodynamic factors, mechani- tion (SVD) were detected. Analysis of the explanted
cal stress and biological response in structural valve valves revealed that the leaflets were torn by move-
failure led to a growing interest in alternative strate- ments within the stent. The mode of failure was very
gies and new materials to improve outcomes [12]. unfortunate, and led to sudden severe aortic regurgita-
tion, o
­ ccasionally fatal. The technique of suturing the
pericardium onto the stent was modified, such that it
Increasing the durability and improving
was sewn in the outermost part, in order to reduce im-
haemodynamics: from porcine to peri­
pingement. Moreover, different types of stent were in-
cardial
troduced; these were more flexible and thinner, with
As postulated by Carpentier, an understanding of the stress reduction in the commissural site, and allowed
chemical properties of biological tissue led to continu- supra-anular implantation so that larger prostheses
ous and intensive research into the creation of a bio- could be used [23].
prosthesis that would provide longer freedom from To improve durability, after 1980 most prostheses were
structural deterioration. developed by treating the leaflets with zero- or low-
Bovine pericardium was identified as a promising pressure fixation. The goal of these methods was to
­alternative tissue source for producing artificial leaf- maintain a more normal morphology of the leaflets.
lets, because of its histological and physical character- Several antimineralisation methods were invented by
istics in terms of thickness, pliability, abundance and different companies to obtain durable leaflets, and
wide availability [23]. In 1971, Ionescu in Leeds started characterised the continuous evolution of bio­logical
the production and implantation of pericardial heart valves [6].
valves. The concept was to create a completely “man- Figure 2 summarises schematically biological prosthe-
ses for the mitral and aortic positions.

Patient-prosthesis mismatch: how to

manage it by use of different prostheses
Firstly reported by Rahimtoola in 1978, patient-pros-
thesis mismatch (PPM) represents an important issue
in current practice [24]. Patients with valves with an
EOA too small for their body size develop PPM and are
at higher risk of postoperative mortality, reduced mass
regression and limited functional benefit.
The negative impact of PPM on patient prognosis after
aortic valve replacement has been reported in several
studies showing an increased risk of mortality and
SVD [25]. As previously mentioned, a totally supra-anu-
lar valve implantation technique was proposed: the
third generation of bioprostheses (St. Jude Trifecta,
Sorin Mitroflow, Carpentier-Edwards Perimount
Magna) were designed to achieve a larger EOA through
modification of the stent architecture, but here surgi-
Figure 2: Biological heart valves evolution. In the first line mitral prostheses, porcine
cal technique plays a major role. Surgeons should be
(Carpentier Edwards Porcine) and pericardial (Hancock II and Epic). In the second line aware of the consequences of implantation of a valve
3rd generation of aortic prostheses. too small for the patient, and avoid it.

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Review article 289

Various alternative solutions have been suggested to A route to less invasiveness:

overcome to the issue of PPM. Stentless valves were in- the role of sutureless aortic valves
troduced by Tirone David in 1988. They are xenograft,
both porcine and pericardial, without any stent or sew- During the 1990s, minimally invasive cardiac surgery
ing cuff, and represent the extreme of the continuous was rapidly developing [27]. This concept brings at least
reduction in valvular stent dimensions. Providing a two benefits: a reduction in surgical access in order to
large valve orifice and improved haemodynamics, they minimise surgical trauma and wound complication
could theoretically induce a greater reduction of ven- and a reduction in cross-clamp and cardiopulmonary
tricular mass and avoid PPM. These promising results bypass time. Moreover, several datasets showed that
are balanced by a more difficult and time-consuming the prevalence of frail patients with heart valve dis-
implantation, which requires specific skills in aortic ease, and aortic stenosis in particular, was progres-
root surgery. sively increasing [28].
Initial experience with stentless prostheses revealed a Three valves were introduced: the Livanova Perceval S,
high rate of perioperative aortic regurgitation due to a the Edwards Intuity and the Enable 3F (fig. 3). The aim
discrepancy between the valve annulus and the native was to reduce surgical time by avoiding the use of su-
sino-tubular junction. Complete root replacement was tures to fix the valve to the annulus as a result of a new
thus encouraged and new prostheses were developed, stent configuration, which can expand and thus an-
such as the complete porcine root (fig. 3). The great en- chor the valve in the right position [29]. The stent char-
thusiasm for these valves culminated in the late 1990s, acteristics depend on the properties of nitinol, which
and faded because no superiority over stented valves has memory of shape and becomes flexible according
was detected in long-term studies [26]. The stentless to the temperature. Although several studies showed
technology made a big contribution to the next wave optimal results with sutureless valve implantation
of valve technology evolution. Both sutureless and ­instead of an increased risk of complete atrioventricu-
trans­catheter valves were designed on the foundation lar block and residual paravalvular leaks, the use of 3F
of stentless bioprostheses, and furthermore, several has been discontinued owing to late valve migration.
new antimineralisation strategies and the use of Haemodynamic features were comparable to those of
equine pericardium (3F aortic bioprosthesis) were de- stentless prostheses, but long-term durability is still
veloped during the evolution of stentless valves. unknown [30].
Although sutureless aortic valves were initially in-
tended for intermediate-high risk patients, the rapid
­development of transcatheter valve technologies pro-
foundly affected the course of their evolution. Their
current role is still to be clarified, but several condi-
tions, such as small aortic root, multiple valve surgery,
or use as a facilitating tool in minimal invasive aortic
valve surgery could represent fields of application.

The last step of the evolution: transcathe-

ter valve procedures bring surgery back
to the time of “closed-heart” procedures
Transcatheter valve interventions are the most ad-
vanced development in cardiac surgery and were ini-
tially introduced as the ideal solution to the new epide-
miological scenario of a large number of untreated
elderly and high-risk patients with aortic stenosis.
Transcatheter valves take advantage of decades of
valve e
­ volution to deliver surgical grade interventions
involving ­miniaturised instruments (catheter-based
devices) by an endovascular approach, without the
need of cardiopulmonary bypass and cardioplegia [31].
Percutaneous mitral valve commissurotomy was the
Figure 3: Stentless and sutureless aortic prostheses. first surgical treatment converted into a transcatheter

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Review article 290

procedure. Its development is a model in the field. Ini- without any damage to the leaflet. Two types of stents
tially, balloon valvuloplasty was restricted to high-risk were developed: the stainless steel baloon-expandable
and inoperable patients; more recently, balloon valvu- stent and the self-expanding nitinol ones (fig. 4).
loplasty became the gold standard treatment for all Since the beginning of this technology several issues
comers, and surgery is performed only in patients with have been identified as potential limiting factors: para-
anatomical contraindications to transcatheter treat- valvular leakage, a high rate of vascular complications,
ment. The first implantation of a transcatheter valve risk of neurological events and complete atrioventricu-
into a human was performed in 2000, when Bonhoef- lar block.
fer implanted a pulmonary transcatheter valve [32]. The Cribier-Edwards (previously PVT) balloon-expand-
Two years later, this approach was translated to the able valve (Edwards Lifesciences) was the first tran-
aortic position by Cribier, with worldwide clinical reso- scatheter aortic prosthesis (2002). It consisted initially
nance [33]. of equine pericardium and a stainless-steel frame. In
When read together, the first report of mechanical order to improve sealing, a polyethylene terephthalate
heart valve implantation by Starr [9] and the Cribier’s fabric skirt was introduced; this modification repre-
first transcatheter aortic valve implantation (TAVI) re- sented the first Edwards SAPIEN model (2006) [34].
port [33] have many similarities. Just as Starr treated ­Owing to the high profile of the delivery system, sev-
end-stage patients, so TAVI was introduced as a “last eral patients were treated via a transapical approach.
­resort” solution. The same enthusiasm and the same The SAPIEN XT (2009) valve was then designed with a
passion of a cardiac surgeon in 1960 and a cardiologist lower-profile tubular cobalt-chromium stent that
about 40 years later characterise the two papers. This made it possible to downsize it to reduce peripheral
parallel demonstrates how the evolution represents a ­access complications and increase the use of the trans-
continuous cycle of different solutions to treatment of femoral approach. The last development of the SAPIEN
the same pathology, with continuously new technolo- valve is the SAPIEN 3 (2013), in which an additional
gies. Each step is a fundamental contribution to know­ outer skirt was added to increase sealing and an
ledge and fosters further developments. Many prob- ­expandable 14/16 F sheet was designed to minimise
lems in this process can be avoided by reading and femoral invasiveness. All the valves were treated with
digesting the history of previous mistakes. an anticalcification process involving glutaraldehyde
The development of percutaneous heart valves fixation and phospholipid extraction, and a new “mild-
brought together the evolution of bio-valves, stents heat” treatment that removes unstable glutaraldehyde
and delivery catheter design. In order to permit endo- molecules was introduced.
vascular releasing, the prosthesis should be crimped, The prototype of self-expandable valves is represented
with a decrease in dimensions of more than three folds by the Medtronic Corevalve (2005). This consists of
peri­cardial leaflets mounted on a nitinol frame. The
first-generation leaflets were made of bovine peri­
cardium, but a switch to porcine pericardium, together
with the use of a more flared outflow design, allowed
the development of a lower profile device. The evolu-
tion of the Corevalve resulted in the EVOLUT R. Several
improvements made this device repositionable,
resheathable and recapturable, and the height and
­diameter of the delivery system were reduced. Re-
cently the Evolut PRO device was approved by the US
Food and Drug Administration. New features include
an outer wrap that adds surface area contact between
the valve and the native aortic annulus to improve
valve sealing.
Innovation profoundly changed the clinical use of
TAVI. In contrast to the early stages, when its use was
limited to high risk and inoperable patients, inter­
mediate-risk patients are currently treated since re-
cent data showed that TAVI is a non-inferior, and some-
time superior, alternative to surgery in the short term.
Figure 4: Transcatheter aortic valve implantation devices currently in use. The design of TAVI valves gives them optimal haemo-

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Review article 291

dynamic results [35], which might support the clinical How the “new” valves are changing
superiority, particularly in patients at risk of PPM. the “old” valves
The transcatheter approach is also used in the treat-
ment of atrioventricular valve diseases, most of all in “Valve-in-valve” procedures have been recently intro-
repair procedures. Recently, transcatheter mitral valve duced and rapidly became the treatment of choice, in
implantation (TMVI) became an option for patients order to avoid surgical reoperation, for patients who
with degenerated bioprosthesis or with recurrence of experienced the limited durability of bioprostheses.
mitral regurgitation after ring annuloplasty. Although The anatomical characteristics and the size of the pre-
TMVI presents a number of challenges as a result of the viously implanted valve represent the major limiting
native anatomy, its feasibility in high-risk patients factors for the implantation of a TAVI valve in valve.
with functional and degenerative valve disease has This new therapeutic scenario created a new need for
been recently reported [36]. ­bioprosthesis design to provide a more efficient “re-
Several devices (fig. 5) have been introduced, but the valving” procedure in the future and provide patients
procedure is still technically demanding and the and surgeons an ad-hoc platform from which to ex-
­patient’s anatomy is still a controversial issue for feasi- pand indications for tissue valves in the aortic posi-
bility. Risk of left ventricular outflow tract obstruction, tion, and possibly also in the mitral position, to a popu-
optimal fixation to the native mitral annulus and lation younger than 60 years of age.
­access nowadays represent the greatest challenges in The INSPIRIS valve (Edwards Lifescience) was devel-
TMVI procedures [37]. oped as a new class of surgical valves. The Cobalt-chro-
Whether to repair or replace the mitral valve was for a mium stent has an area of possible expansion that
long time a matter of debate in the surgical context. gives the valve the capability to be enlarged in the case
Similarly, we could expect that, once a reliable replace- of a future valve-in-valve procedure. Moreover, the bo-
ment device becomes available, most operators would vine pericardial tissue is transformed by means of a
abandon repair. However, with time and experience, novel integrity preservation technology that elimi-
valve repair could come back as an option to limit the nates free aldehyde molecules while protecting and
drawbacks of a permanent implant in the mitral posi- preserving the tissue [38]. The COMMENCE Trial to
tion (Starr and Edwards said the same in the 1960s, a evaluate the results of this promising technology, also
prediction which turned out to be true today for sur- the in mitral and pulmonary positions, is ongoing.
gery).

Beyond the present: tissue-engineered

heart valves
All the devices described exhibit a lack in remodelling
and growth capability. This concept has led to the
­development of innovative valve substitutes called re-
generative valves or tissue-engineered valves (TEHVs).
This novel approach is based on various tissue engi-
neering technologies that provide an alternative
crimp­able valve replacement device thought to be a
­definitive solution, also for younger and paediatric
­patients [39].
A TEHV would be a living organ, capable of responding
and growing like the native valve. The immune re-
sponse plays a special role in regulating remodelling
after implantation. This technology aims to become
the most advanced means to improve valve durability
[40].
Experience with TEHVs is still preclinical and, even if
transcatheter implantation is successfully performed
in animal models, the way the device could interact
with a calcified annulus must be clarified, before it can
be translated into clinical practice [39, 40].
Figure 5: Transcatheter mitral valve implantation prostheses.

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Review article 292

What can we expect from new-era view from “operator-related” to “patient-related”. The
­prostheses and new-era physicians? concept of “heart team” was introduced in order to
­define which patient could benefit from a particular
The long process of evolution of heart valves demon- treatment. Cardiac surgeons, cardiologists, anaesthesi-
strates how innovation induces changes in practice ologists, imaging physicians and dedicated nurses,
and contributes to better patient treatment. Different started to work in cooperation to build a new environ-
subcategories of patient and new challenges have been ment of cardiovascular medicine, focused on patient-
overcome during almost one century of cardiovascu- centred care. Creating new competences and new
lar interventions. And the story is not finished yet ­evidence nowadays represents the main goal of our
(fig. 6). profession. In this ever evolving landscape, looking
The latest evolution of transcatheter therapies has back into history will pave the way to the future.
­induced a revolution in clinical practice, moving the

Figure 6: Evolutionary steps in heart valve technology. Images courtesy of Prof. von Segesser [4].

Disclosure statement
F. Nietlispach is a consultant for Abbott and Edwards Lifesciences.
Correspondence: F. Maisano is consultant surgeon for Abbott, Medtronic and St. Jude.
Francesco Maisano MD, FESC The other authors have no conflict of interest to declare.
University Heart Center
Rämistrasse 100 References
CH-8091 Zürich The full list of references is included in the online version of the
francesco.maisano[at]usz.ch ­article at www.cardiovasmed.ch.

CARDIOVASCULAR MEDICINE – KARDIOVASKULÄRE MEDIZIN – MÉDECINE CARDIOVASCULAIRE  2017;20(12):285–292

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