Modern concepts from old ideas in manufacture of cardiac valve prostheses

Abstract

In reviewing the history of mechanical prosthetic valves, it appears evident how many improvements and technical advances have been obtained in this field. Looking to the past, it must also be underlined how some old concepts, which can be considered quite revolutionary for those years, clearly indicate the great skill and ingenuity of those who conceived them. Old ideas have been revitalized by modern concepts, and this is exemplified when considering the developments of bileaflet and sutureless prostheses.

Introduction

The history of cardiac prosthetic valves starts in September 1952 when Charles Hufnagel implanted, in Washington, DC, USA, the first cardiac prosthesis, a ball valve made of methyl metacrylate, into the descending aorta in a patient with aortic valve disease [1]. Unavailability at that time of the cardiopulmonary bypass machine forced this unusual application which, however, had very limited benefit for patients with either aortic stenosis or regurgitation [2]. Eight years later, in March 1960, Dwight Harken performed the first aortic valve replacement (AVR) with orthotopic implantation of a caged-ball prosthesis in the subcoronary position for aortic stenosis [3], while 1 day later, Nina Braunwald successfully replaced for the first time an incompetent mitral valve using a prosthesis made from 2 leaflets of polyurethane connected to the papillary muscles by strips of Teflon [4]. Mitral valve replacement (MVR) had already been attempted in July 1955 by Judson Chesterman in Sheffield, UK, with a prosthesis, made of Perspex®, an acrylic material, which worked on the principles of a car engine valve. The patient survived 14 h and died because of sudden prosthetic failure [5]. Therefore, Albert Starr is credited for the first successful MVR with a caged-ball prosthesis performed in September 1960 in a patient with mitral stenosis [6]. Such operations started the modern era of prosthetic valve replacement, and during the ensuing decades, a wide variety of mechanical prostheses became available with significant changes in materials, structural design, and shapes [2] (Fig. 1a–e).

Fig. 1.

Some of the most popular models of mechanical prostheses through the years. a Hufnagel. b Starr-Edwards caged-ball. c Kay-Shiley caged-disc. d Björk-Shiley tilting-disc. e St. Jude Medical bileaflet

The aim of this review is to recognize how some prosthetic models, currently still on the market or have been more recently conceived which are considered to be the product of modern ideas, nevertheless clearly derive from old concepts of the past.

Where does an idea come from?

In reviewing the history of mechanical prosthetic valves, it appears evident how many improvements and technical advances have been obtained in this field. Looking to the past, it must also be underlined how some old concepts, which can be considered quite revolutionary for those years, clearly indicate the great skill and ingenuity of those who conceived them. The Hufnagel principle was substantially derived from the patent of the bottle stopper dating back to 1858, later transferred to the Starr-Edwards caged-ball prosthesis which has been in clinical use for many years. It is however interesting to recall that the Hufnagel principle was revisited almost 40 years later by implanting a tilting-disc prosthesis in the descending thoracic aorta of patients with a failing aortic prosthesis considered otherwise too risky for a standard reoperation [7].

Another unique mechanical prosthesis was developed in Cape Town, South Africa, by Christiaan Barnard in 1962. It consisted of a double cone-shaped poppet resembling a toilet plunger from which the idea was taken. A modification of such design was adopted by others to reduce the high rate of thromboembolic complications obtaining a disc valve resembling a collar button [8].

The bileaflet prosthetic valve

In the search for the mechanical device with the best hemodynamic performance, modifications of prosthetic designs have gone from the caged ball to the bileaflet principles, passing through caged and tilting-disc models. Currently the only mechanical prostheses available on the market are those which incorporate the bileaflet mechanism. This concept was pioneered by Vincent Gott as late as 1963, by developing a central-hinging bileaflet valve with a polycarbonate housing and leaflets made of silicone rubber and Teflon fabric [9] (Fig. 2a). This device has demonstrated unexpected durability with apparently no reported cases of structural failures [10]. Later in 1968, Walton Lillehei developed an all titanium bileaflet prosthesis with improved hemodynamics in vitro owing to a central laminar flow (Fig. 2b). This prosthesis was implanted in mitral position only in one patient, who did not survive the operation [11]. These original prostheses were abandoned in favor of others, such as the caged-ball prostheses, which, paradoxically, created more intracardiac obstruction and less favorable hemodynamics with the potential for prosthesis-patient mismatch (PPM) especially after AVR [12, 13]. PPM is a potential complication with any type of prosthesis, both after AVR and MVR, depending on several factors, the most important being prosthesis size related to patient body surface area resulting in abnormally high transprosthetic gradients [14]. It has been demonstrated that occurrence of PPM following valve replacement is associated to lower early and long-term survival [14]. Contrary to a common belief, the Starr-Edwards caged-ball valve had an incidence of thromboembolic events similar to that of other mechanical devices and even longer durability [15, 16]; this valve has been subsequently replaced by lower profile bileaflet mechanical prostheses that are considered to have better hemodynamics [16].

Fig. 2.

a Gott-Daggett central-hinge bileaflet prosthesis. b Kalke-Lillehei prosthesis. c St. Jude Medical bileaflet prosthesis (Abbott Laboratories, Abbott Park, IL, USA)

In the continuous effort to provide a prosthesis with reduced resistance to flow, the bileaflet model has been consistently revised in more recent years, yielding various mechanical prostheses with excellent hemodynamic performances and particularly no reports of structural failures in the recent models (Fig. 1c). These devices are those at present predominantly employed worldwide as cardiac valve substitutes, while single-leaflet mechanical prostheses are still used in some developing countries. Indeed, after an initial skepticism, bileaflet prostheses are now considered extremely reliable with unsurpassed records of durability [17–19] (Fig. 2c).

Sutureless prosthetic valves

The introduction of sutureless prostheses dates back to 1962, just 2 years after the beginning of surgical AVR with the caged-ball prosthesis. Magovern and Cromie, with the aim of an easier implantation and reduction of the surgical risk, used a sutureless prosthesis for both AVR and MVR. The prosthesis consisted in a caged-ball device with a peculiar mechanism of fixation based on an inner ring containing 9 titanium pins and in an outer ring to which the valvular mechanism is attached (Fig. 3a). A special tool was used to hold the valve and by rotation allowed the pins to be ejected out and be driven into the aorta. Interestingly, the prosthetic basal ring was designed to conform to the shape of the sinuses of Valsalva. The mitral model was similar differing only in the shape of the ring to accommodate the mitral annulus [20]. Most likely because unfavorable results and high incidence of thromboembolic complications, the Magovern-Cromie prosthesis had limited clinical application; nevertheless, long-term results indicate that this device in some series has been associated with favorable late outcomes and low incidence of reoperations [21].

Fig. 3.

a Magovern-Cromie sutureless mechanical prosthesis. b Perceval® sutureless bioprosthesis (LivaNova, Saluggia, Italy). c Intuity rapid deployment pericardial valve (Edwards Lifesciences, Irvine, CA, USA)

The sutureless idea has been replicated in a modern way in a new generation of bioprosthetic valves which has been introduced as an alternative to conventional surgery to reduce the cardiopulmonary bypass time and enhance the minimally invasive approach [22] (Fig. 3b). Sutureless bioprosthesis has fulfilled the expectation of old pioneers of this concept and together with rapid deployment valves (Fig. 3c) have currently conquered the market; although the original concept has been transferred from mechanical to biological devices, the goal to perform valve replacement avoiding sutures and knots has been fulfilled.

Conclusions

Based on this brief review we can conclude that (1) mechanical prostheses have undergone many technological modifications and improvements through the years before reaching the reliability of current models; (2) experience gained and lessons learned from mistakes of the past have yielded the current extremely reliable and efficient models; and (3) recognizing the many milestones in prosthetic valve evolution, one cannot ignore that history sometimes repeats itself as once again demonstrated by the revival of old and seemingly unsuccessful concepts.

Funding

None.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethics Comm approval

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Informed consent

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Human and animal rights statements

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