33

Mechanical heart valve prostheses:identification and evaluation (erratum)

Jagdish Butanya,*, Manmeet S. Ahluwaliaa, Craig Munroea, Cristina Fayeta, Christina Ahna,Patrick Blita, Charis Keprona, Roberto J. Cusimanob,c, Richard L. Leaska

aDepartment of Pathology E4-322, Toronto General Hospital, Toronto, ON, Canada M5G 2C4bCardiovascular Surgery, Toronto General Hospital, Toronto, ON, Canada M5G 2C4

cUniversity of Toronto, Toronto, ON, Canada M5G 2C4

Received 31 July 2002; received in revised form 20 August 2002; accepted 20 August 2002

Abstract

Mechanical heart value prostheses have been in use since the 1950s. Many prostheses have been used for a while and then discontinued.Today, there are a large number and variety of prostheses in use and an even larger variety that are in place in patients. These may beexplanted at any time for a number of reasons. It is essential for the practicing pathologist to be able to identify the prosthesis and be aware ofsome of its reported complications and modes of failure. This article, and a second one on bioprosthetic heart valves, is designed as a readyreference guide to heart valve prostheses, their important identifying features, their common complications, and modes of failure. It shouldhelp in the accurate identification of explanted prosthetic valves and more definitive reports. This accuracy of identification as well astracking of abnormalities noted will, we hope, permit the identification of new failure modes and the recording of causes of failure of new (oreven modified) prosthetic heart valves. D 2003 Elsevier Inc. All rights reserved.

Keywords: Heart valves; Prosthetic mechanical heart valve

1. Introduction

Prosthetic heart valves have been in use for over 40 years.The first heart valve substitute was actually placed in thedescending thoracic aorta by Hufnagel (Hufnagel valve) in1952 [1]. With the availability of cardiopulmonary bypass,the first orthotropic heart valve replacements were performedin 1960 [2,3]. Today, patients with significant valvularlesions, stenotic or regurgitant, are routinely managed bythe replacement (or repair) of the diseased valve. Heart valveprostheses are generically classified as mechanical heartvalves (MHVs), which have only synthetic or nonbiologicalcomponents and bioprosthesis (or tissue valves), which aremade, at least in part, of biological components [4].

Worldwide, the number of prosthetic heart valvesimplanted is around 250,000 and is increasing at the rateof 5–7% per year [5]. Of all valves implanted, 60,000–

75,000 are implanted in the United States of America.Worldwide, approximately 55% of implanted prostheticheart valves are mechanical and 45% biological. In de-veloped countries, percentages are reversed with biologicalvalves holding 55% of the market. The use of MHVs isincreasing at the rate of 3–5% per year, while bioprosthesisimplants are increasing at 8–11% per year [5].

All MHV prostheses have a similar basic structure withthree essential components: (1) the occluder, (2) the housingand (3) the sewing ring. The occluder is usually one or morerigid moveable parts which may be a ball (as in the Starr-Edwards valves), a disc (free floating as in the Bjork-Shileyvalves) or a hinged leaflet, which may be circular or semi-circular. The housing may include a cage-like structure thathelps the occluder to move by guiding and restricting itsmovement and a valve base or body, which is a ring made ofmetal (alloy) or a graphite coated with pyrolytic carbon, andsupports the cage/struts and provides the ‘‘seat’’ for theoccluder. The occluder fits in the housing, which hasthe fabric-sewing cuff attached to it, to allow implantationof the device. Most contemporary MHV prostheses have

1054-8807/02/$ – see front matter D 2003 Elsevier Inc. All rights reserved.doi:10.1016/S1054-8807(02)00105-4

* Corresponding author. Tel.: +1-416-340-3003; fax: +1-416-340-4213.E-mail address: [email protected] (J. Butany).

Cardiovascular Pathology 12 (2003) 322–344

pyrolytic carbon as a major component, while some havemetal components also. The sewing cuff is made withsynthetic fabrics, with or without a ‘‘filler’’ between thelayers of the fabric. Other refinements of this basic structuremay be seen.

MHV prostheses can be divided into two kinds based ontheir flow pattern, those with lateral flow such as the ball incage valves and those with more central flow such as thetilting disc and bileaflet valves.

Prosthetic heart valves of every kind work on the simpleprinciple of passive movement, wherein closure depends onthe pressure gradients and changes of blood flow in the heart.The competency of valve substitutes is generally related tothe structure of the prosthesis and, more specifically, the waythe prosthesis occluder is seated. Most MHV prostheses havea minimal degree of incompetence built in (1–5%) to allow‘‘backwash’’ of the components to inhibit thrombosis.

The features of an ideal heart valve were enunciated byHarken et al. [3] in 1962 and have since been modified [6].To this day, these criteria are not fulfilled by any oneprosthetic heart valve.

Prostheses are frequently associated with complicationsthat impact significantly on the patient’s prognosis after heartvalve replacement surgery [7]. Prosthetic heart valves areincreasingly seen and will continue to be seen by surgicalpathologists when they are removed at reoperation or when apatient who has had one or more valves replaced comes toautopsy. There are many excellent reviews available on thepathology of heart valve prostheses and many more will beavailable in the future about the current generation of pros-theses [8,9]. This paper and another on bioprostheses, whichwill follow in a subsequent issue of this journal, are meant toprovide the pathologist with a ready reference to contempor-ary prosthetic heart valves, in an effort to help identify themand to familiarize themselves with major known complica-tions associated with particular devices. A few of these valveshave been used for many years and a good body of literature isavailable about them. Many others have been in use forrelatively short periods and definitive information about themis not yet available. The detailed examination of theseprostheses by skilled pathologists will have an immenseimpact on the accumulation of a body of information aboutthese devices. This will help in deciding the value ofindividual types of devices and to compare different deviceswith each other.

Heart valve prostheses have many common complica-tions. These include prosthesis-related complications such asdevice failure, whether design- or materials-related. Compli-cations may also be related to the host, including infectionsand tissue overgrowth. The lifelong use of anticoagulants ismandatory for all patients with MHV prostheses. This treat-ment is associated with its own set of complications, such ashemorrhage. Many of these complications necessitate urgentremoval of the device and its replacement. A workingknowledge about each device is clearly essential whenexamining these explanted devices.

Numerous heart valve substitutes have been designedover the last 50 years. Many of these are no longer in use. Inthis paper, we have described heart valve prostheses that arecurrently being implanted in North America and, as well,the rest of the world. We have also described some that,though discontinued, continue to be explanted, and hencewill be seen by pathologists for many years to come. Wehave excluded many that have been discontinued long ago,whose implant numbers were small and are highly unlikelyto be seen today. Explanted prostheses if not easily iden-tified should be referred to a pathologist with an interest inprosthetic heart valves, for detailed analyses. We havedivided MHVs by occluder types and then described them(where necessary) alphabetically (by manufacturers names).The authors do not have any bias whatsoever for or againstany manufacturer or for that matter any particular prostheticheart valve.

2. Ball in cage

2.1. The Starr-Edwards prosthesis

Model: Starr-Edwards 1260 (other Starr-Edwards mech-anical prostheses include model 1000, 1200, 2300, 2310,2320, 2400, 6000, 6120, 6300, 6310, 6320 and 6400).

Type: Caged ball.Technical information: Manufactured and sold by

Edwards Lifesciences (formerly Baxter Healthcare). TheStarr-Edwards ball in cage model was the first commer-cially available mechanical prosthetic heart valve; intro-duced clinically in September of 1960 [10]. The aorticmodel 1260 was first implanted in 1968 and is still in usein some countries (Fig. 1A). A four-strut (mitral model6400) with a hollow metal ball and the struts covered bycloth was used for some time (Fig. 1B). The mitral model6120 is also in current use. This model has a four-strut cage(Fig. 1C,D) as opposed to the three-strut cage of model1260. All other Starr-Edwards caged ball models have beendiscontinued [11].

Size range and available dimensions: Model 1260:21–31 mm. Orifice diameters: 13–19 mm [11].

Physical characteristics: The caged ball constructiongives the valve its characteristic lateral flow mechanismdue to the centrally seated occluding poppet.

Poppet material: Silicone rubber (silastic) with 2%barium sulfate by weight for radiologic identification [11].

Housing and cage material: Stellite (R) alloy no. 21;three monocast struts (model 6120— four struts), whichjoin at the apical region [11].

Sewing ring material: Knitted, porous Teflon (TM) andpolypropylene cloth [11].

Radiographic characteristics: Radiopaque closed cageprofile with four struts, no projecting feet, tapered strutjunction 11 (Fig. 1C,D). Other Starr-Edwards caged ballmodels differ slightly in design.

J. Butany et al. / Cardiovascular Pathology 12 (2003) 322–344 323

salaminia

salaminia

salaminia

Potential complications: Early models of the Starr-Edwards prostheses were reported to show poppet damage(cracks) and occasionally embolization [10]. Thrombusformation and pannus growth may occur at the base of thestruts and the apex of the closed cage, the latter potentiallyleading to orifice stenosis and improper poppet seating withresulting valvular incompetence [12]. Hemodynamic injuryto the aortic intima with subsequent thrombosis and fibrousplaque formation to the endothelial lining can also occur,especially at the proximal end of the ascending aorta [12].Paravalvular leaks do occur, as does infective endocarditis[13,14]. In valves made prior to 1966, the silastic poppetoften imbibed lipid and the dimension of the poppetincreased in comparison to the original specifications,leading to a change in color and occasionally to ballvariance. This leads to decreased valve excursion, increasedvalvular regurgitation [15] and, in some cases, even suddendeath [16]. Related to the high profile of this prosthesis, thevalve struts can get ‘‘trapped’’ in scar tissue on the left

ventricular free wall or on the inter ventricular septum.(Most of these problems have largely been eliminated, butmay still occasionally be seen.)

Additional comments: Although chronologically a veryold valve, the Starr-Edwards caged ball prostheses was formany years the gold standard against which other valves werecompared. These valves have a longer history of clinicalusage than any other heart valve prosthesis [17]. Pathologistsmay still observe these valves upon explantation.

FDA approval: Only models 1260 and 6120 are currentlyapproved in North America.

3. Single leaflet/tilting disc

3.1. The AorTech Ultracor mechanical valve

Model: AorTech Ultracor U19A–U29A (aortic) andU23M–U33M (mitral).

Fig. 1.

J. Butany et al. / Cardiovascular Pathology 12 (2003) 322–344324

Type: Single leaflet/tilting disc valve.Technical information: AorTech Europe (Strathclyde,

UK) markets the Ultracor valve. This prosthesis obtainedthe CE mark in 1995 and in its first 4 years of implantation,approximately 14,000 valves have been implanted world-wide [18].

Size range and available dimensions: The AorTechUltracor model is available with sewing cuff diametersranging from 19 to 29 and 23 to 33 mm for the aortic andmitral sites, respectively.

Physical characteristics: This design features a tita-nium housing machined from a single block to eliminatewelds. A single strut and a centrally located pivot axisare designed to increase laminar blood flow (Fig. 2). Themaximum opening angle for the valve is 73! and 68! forthe aortic and mitral positions, respectively. The sewingring is fabricated of knitted Teflon to promote rapidcontrolled ingrowth and minimize the risk of paravalvularleak [19].

Radiographic characteristics: Improved radiographicimaging is obtained from a plano-convex disc with aPyrolite carbon coating on a tungsten-impregnated graphitesubstrate [18].

Special features: This valve is designed to facilitateimplantation procedures and also allows for in siturotation of the housing for maximum hemodynamiccapabilities. In situ operation of the prosthesis is reportedto be fairly quiet [19].

Potential complications: No structural failures wereobserved in two different studies on the Ultracor prosthesis[18,19], which evaluated a total of 540 patients. However,other common MHV complications were reported. For theUltracor valve, freedom from thromboembolism at 5 yearswas reported as being 90% [19] and, according to a differentreport, 99% and 88% for the aortic and mitral positions,respectively [18]. Thrombosis, on the other hand, proved tobe sparse in the Ultracor clinical datum. One study reports a

freedom from thrombosis at 5 years of 99% for the mitralposition and 100% for both the aortic and double valvereplacements (DVRs) [18]. Another study consisting of94 patients observed no thrombosed valves during a 5-yearfollow-up period [19]. Li et al. [18] reported a freedom fromhemorrhage at 5 years of 91% (AVR) and 94% (MVR),while Sin et al. [19] reported a 5-year freedom of 89%. Inaddition, there exists an elevated risk of endocarditis withprosthetic heart valve replacement. Actuarial 5-year free-dom from endocarditis has been reported at 96% [19] and,from another source, 99% (AVR) and 97% (MVR) [18] forthe Ultracor valve.

However, the current literature on the Ultracor valveis limited and further reports are needed to confirmthese findings.

FDA approval: The Ultracor valve has obtainedthe CE mark of approval but has not yet applied forFDA approval.

3.2. The Bjork-Shiley single leaflet prosthesis

Model: Bjork-Shiley tilting standard disc and convexo-concave (CC) disc.

Type: Single leaflet, tilting disc.Technical information: Manufactured and marketed by

Shiley This valve was introduced in 1969 with a Delrin(white) disc. The Delrin disc was replaced by a pyrolyticcarbon coated graphite disc in 1971 and, in 1975, a markerring was added to the disc. In 1975, the disk was modified toa spherical shape to reduce eddy flow. In 1975, the CCmodel was introduced to reduce the incidence of valvethrombosis in the minor orifice. In 1979, Pfizer purchasedthe rights to the Bjork-Shiley valves. This valve was takenoff the North American market in 1986 due to a series ofcases of strut fracture leading to disc dislodgement. In 1992,Sorin Biomedica Cardio bought the rights to the Bjork-Shiley valves (except the convexoconcave (CC) model).

Size range and available dimensions: Sewing ring sizes:17–33 (aortic), 17–33 mm for supra-annular (mitral) andsub-annular (mitral), and 17–31 mm for the intra-annularposition (mitral) with orifice diameters being 12–24 mm forboth aortic and mitral valves.

Physical characteristics: The tilting disc (single leaflet)gave the valve its characteristic near central flow (Fig. 3A).In the CC model, the pyrolitic carbon coated disc is held inplace by the large inflow and small outflow struts, which fitsinto the central depression of the disc (Fig. 3B).

Poppet material: Pyrolytic carbon, Delrin (pre 1972).Housing and strut material: Haynes 25 (R) alloy.Sewing ring material: Teflon.Radiographic characteristics: The range of motion is

60! between the open and the closed position. A thinradiopaque ring is seen within the disc of valves sold post1975 (Fig. 3C,D).

Potential complications: Thrombus on the metal struts,orifice and prosthesis-tissue interface. Death (before they

Fig. 2.


could be operated upon) has been reported in approximately50% of patients with thrombosis of the tilting disc [10].Perivalvular leak, not related to calcification, is reportedparticularly with the aortic site valves and is apparentlygreater in the 19-mm size [20]. Thrombus and tissueovergrowth along the perimeter of the minor outflow regioncan further reduce the flow in this region [21]. Pannus onthe sewing ring with extension onto the metal housing canlead to valve dysfunction and predisposition to thrombosis[20,22]. The incidence of infective endocarditis is similar tothat of all other MHVs.

Additional comments: The CC model was introduced toreduce thrombosis originating in the small orifice. Itdecreased the stagnation zone behind the disc and decreasedemboli from 4.2% to 1.2% per year after mitral valvereplacement (MVR) [23]. It was removed from the marketin 1986 after reports of a series of outlet strut fracturesleading to embolization of the disc. Close follow-up isrecommended for all patients. Prophylactic removal isrecommended in some patients with this series of valves,especially those with valve sizes greater than 29 mm. Veryfew if any more such cases have been reported in recent

years. Other factors considered are valve implant position,weld date, welder identity, valve shop order, body surfacearea and current age of patient [24,25].

FDA approval: Not approved by FDA (since 1986).

3.3. The Bjork-Shiley monostrut valve

Model: Bjork-Shiley tilting disc with single outflowstrut (monostrut).

Type: Single leaflet, tilting disc.Technical information: Shiley first manufactured the

Bjork-Shiley monostrut in 1981. Sorin Biomedica Cardiobought it in 1992 from Pfizer and then sold it to AllianceMedical Technologies.

Size range and available dimensions: This valve wasavailable in sewing ring sizes 17–33 mm with orificediameters of 12–24 mm (aortic and mitral valves).

Physical characteristics: The valve used a thin waferdisk to pivot into open and closed position. The hingeplacement permitted a near central flow. The inlet strutwas C-shaped. The single outlet strut fit into the centraldepression of the disc and held it in place.

Fig. 3.


Poppet material: Graphite coated with pyrolytic carbon.Housing material: Haynes 25.Sewing ring material: Teflon or carbon-coated Dacron.Radiographic characteristics: The disc had a radiopaque

rim. The housing, inlet strut (c-shaped) and outlet strut(single) are all radiopaque (Fig. 4B,C).

Special features: The Bjork-Shiley Monostrut valve wasmachined from one piece of Haynes 25 alloy, eliminatingthe need for a weld and hence eliminating the possibility ofstrut fracture and disc embolization [26]. The valve had aCC disc made of pyrolytic carbon that opens to 70! tooptimize performance across the valve.

Potential complications: Thrombus can form on themetal orifice, struts and valve-tissue interface. The incid-ence of thromboembolism is comparable to that of othermechanical valves. Pannus forming over the valve-sewingring can extend onto the valve housing and lead to valvestenosis or incompetence by restricting disc movement[27]. The risk of infective endocarditis is similar to othermechanical valves.

Additional comments: The monostrut valve has a low rateof valve-related complications, a durable design, excellenthemodynamics and functional results [28]. A review of our

own series of mechanical valves shows that this monostrutprosthesis has the lowest incidence of complications (per-sonal experience-JB).

FDA: Approved in 1997 (AllianceMedical Technologies).This valve is no longer manufactured.

3.4. The Omniscience valve

Model: Omnicarbon (R) (OC) and Omniscience (R) (OS).Type: Monoleaflet/pivoting disc (aortic, mitral).Technical information: Manufactured and sold by Med-

ical CV (Inver Grove Heights, MN), the OC valve evolvedin design from the OS valve. The OS and OC valves havebeen available on the international markets since 1978 and1984, respectively.

Size range and available dimensions: The OS valve hasorifice diameters of 14.4–24.0 (aortic), 14.4–26.0 (mitral)and corresponding annulus diameters of 19–31 mm (aorticand mitral). The OC has annulus diameters of 19–33 mm(aortic and mitral) and corresponding orifice diameters of14–24 mm (aortic and mitral).

Physical characteristics:Omniscience

Fig. 4.


Disc: Pyrolytic carbon with smooth proximal anddistal surfaces.

Housing: Nickel-free titanium (machined from one block).Sewing ring: Seamless PTFE knit fabric (polytetra-

fluoroethylene).The OS (Fig. 5A) was followed by the OC

(Fig. 5B), which features a housing of pyrolytic carbon[29]. The pivots were shortened to provide a lowerprofile [30].

OmnicarbonDisc: Pyrolytic carbon with smooth proximal and

distal surfaces.Housing: Smooth pyrolytic carbon.Sewing ring: Teflon.Radiographic characteristics: The housing and disc are

both radiopaque.Special features: Both valves have two guards to guide a

curvilinear disc. Maximum opening angle is 80! and closedangle is 12!.

Potential complications: As with other mechanical valves,the OS andOC have associated risks and complications. Afterisolated aortic valve replacement (AVR) with the OC, 10-yearfreedom from various complications was the following:thromboembolism 94.8%/patient year (pty), valvar throm-bosis 95.0%/pty, anticoagulant-related hemorrhage 93.6%/pty, prosthetic valve endocarditis 93.0%/pty and reoperation90.6%/pty (n= 882.7 pty) [30]. After 12 years of AVR andMVR with the OS, respective freedom from various compli-cations was: thromboembolism 85.5 ± 5.0%/pty and 85.2 ±6.5%/pty, hemorrhage 92.3 ± 3.0%/pty and 91.4 ± 3.5%/pty,endocarditis 96.2 ± 2.1%/pty and 98.8 ± 1.2%/pty, perival-vular leak 95.0 ± 3.0%/pty and 97.6 ± 1.7%/pty, and pan-nus interference 98.7 ± 1.3%/pty and 96.5 ± 3.4%/pty(n = 1475 pty) [31]. A 1995 review paper by Akins in Boston,USA [32] reports incidence of anticoagulant-related compli-cations for the OS as lowest compared to four other mech-anical valves but includes a caveat due to the small number ofpatient follow-up years. In the same review, the OS was

reported to have the highest linearized rate of thromboemb-olism, nonstructural dysfunction and valve endocarditis.

FDA approval: The OS and OC valves were FDAapproved for clinical use in 1978 and 2001, respectively.

3.5. The Medtronic-Hall prosthesis

Model: Medtronic-Hall A7700 (aortic) and M7700(mitral).

Type: Single leaflet/pivoting disc (aortic, mitral).Technical information: The Medtronic-Hall valve is

manufactured and sold by Medtronic Inc. (Minneapolis,USA) and has been available since 1977 [11].

Size range and available dimensions: The Medtronic-Hall valve is available with sewing ring diameters of 20–29 (aortic), 23–31 (mitral), and corresponding orificediameters of 16–24 (aortic) and 18–24 mm (mitral),respectively [11].

Physical characteristics: This valve ‘‘encourages’’ cent-ral flow through a large orifice-to-annulus ratio and lowtransvalvular gradients (Fig. 6A,B). Normal opening anglesare 70! for the mitral and 75! for the aortic position. Thevalve’s closed angle is 0!.

Poppet: Pyrolytic carbon.Housing material: Titanium (machined from a single

block).Sewing ring material: Knitted PTFE standard, knitted

PET for the EZ FIT sewing ring option.Radiographic characteristics: The housing and disc are

radiopaque and radiolucent, respectively (Fig. 6C,D).Potential complications: No mechanical failures have

been reported at 9 (n = 502 prostheses) and 20 years(n = 1776 procedures) [33,34]. This design has excellenthemodynamics, good durability and low thrombogenicity[33,34]. Nitter-Hauge et al. [35] have found that theincidence of thromboembolism can be kept down toapproximately 1% per patient-year if anticoagulant treat-ment is carefully monitored. Overall incidence of

Fig. 5.


obstructive valve thrombosis was reported at 0.04% peryear in another study [34]. Anticoagulant-related hemor-rhage was negatively correlated with intensity of anti-

coagulation [35] and was most frequent in the earlypostoperative stage [34]. Preoperative patient statusand postoperative care are major factors affecting the

Fig. 6.

Fig. 7.


risk of infective endocarditis [34]. At 15 years, 99.7%/pty of aortic valves (AV), 99%/pty of mitral valves(MV), 98%/pty of DVRs were free of reoperation forperivalvular leaks (n = 1766) [34]. In the same study, at10 and 15 years, freedom from all valve-related compli-cations was 72%/pty and 60%/pty for AV, 61%/pty and50%/pty for MV and 61%/pty and 52%/pty for DVR,respectively [34].

Additional comments: The cage is free of welds andbends and the rotating central disc allows for uniform wear[11]. The sizes 20–22 mm Medtronic-Hall valves aredeemed especially appropriate for patients with a smallaortic annulus [36]. Recent studies have shown the eccentricdesign of the Medtronic-Hall valve to reduce turbulence andmaximize hemodynamic performance when oriented toalign with the eccentric flow in the native annulus. This

has been shown to give superior results to that possible withsymmetrical bileaflet designs [37].

FDA approval: The Medtronic-Hall A7700 and M7700valves, including the EZ FIT option are currently approvedfor clinical use in North America.

3.6. The Sorin Allcarbon tilting disc valve

Model: Sorin Allcarbon, Monocast and Carbocast tilt-ing disc.

Type: Single leaflet tilting disc valve.Technical information: Monocast was the first tilting

disc valve, made by Sorin, and used clinically in 1977.Sewing ring was coated with a carbon film in Carbocast(1986). In addition, Allcarbon (1988) has a Carbofilm(TM)-coated housing.

Fig. 8.


Size range and available dimensions: The valve is avail-able in sewing ring sizes 19–31 (aortic) and 19–33 mm(mitral) with orifice diameters of 14–24 mm for both aorticand mitral valves.

Physical characteristics: The housing is made of Stellite25 (Haynes 25, Alacrite XSM), a chrome-cobalt alloy, withdroplet shaped struts, using a microcasting process to elim-inate any welds. The graphite substrate of the disc is coatedwith pyrolytic carbon. The sewing ring is coated with a thinfilm of turbostatic carbon (Fig. 7A).

Poppet material: Pyrolytic carbon over a graphitesubstrate.

Cage material: Haynes (R) HS25 (Stellite 25, AlacriteXSM (R)).

Sewing ring material: Teflon.Radiographic characteristics: The disc has a tantalum

wire that is radiopaque. The range of motion is 60! fromopen to closed position.

Special features: The inflow and outflow portions of thesewing ring are coated with Carbofilm to improve hemocom-patibility and reduce the risk of tissue overgrowth (Fig. 7A).The central portion, intended for contact with tissue annulus,does not have this coating. According to the manufacturer,this feature is intended to promote tissue growth. The strutsare droplet shaped to provide an optimal hydrodynamiccontour to reduce turbulence and thrombogenicity.

Potential complications: Thrombus can form on thefabric, struts and interface of valve and tissue. The incidenceof thromboembolism is low and comparable to other mech-anical prosthesis [38]. Pannus grows on the sewing cuff(valve-tissue interface) and can lead to stenosis of the valve[39]. Periprosthetic leak is the most common cause of non-structural dysfunction seen [40]. The risk of infection issimilar to other mechanical valves.

Additional comments: CE Mark for sale in Europe. TheSorin tilting disc valve was also available as a Monostrutmodel (Monostrut X) (Fig. 7B).

FDA approval: Not approved.

4. Bileaflet

4.1. The advancing the standard (ATS) open pivotbileaflet valve

Model: ATS open pivot bileaflet valve standard series andATS open pivot bileaflet AP (advanced performance) series.

Type: Bileaflet valve; aortic and mitral positions.Technical information: Manufactured and sold by ATS

Medical; the standard series is designed for intra-annularplacement; the AP series is designed for the supra-annularposition [41].

Size range and available dimensions: Standard series(Fig. 8A,C)—aortic: 19–31 mm, mitral: 19–33 mm [42].AP series (Fig. 8D)—aortic: 16–28 mm, mitral: 16–20 mm[42].

Physical characteristics: The open pivot valves (standardand AP series) have central flow.

Orifice ring: Pyrolytic carbon [43].Leaflets: Pyrolytic carbon over graphite substrate impreg-

nated with 20% tungsten by weight [41].Sewing ring material: Double velour Dacron to promote

controlled tissue ingrowth [43], with Teflon insert toincrease materials pliability [41]. The rotation ring is madeof titanium [43].

Radiographic characteristics: The leaflets have increasedvisibility due to high tungsten content of the discs substrate.The titanium rotation ring is also radiopaque [43]. The flattitanium ring profile of the ATS valve (Fig. 8B) is similar tothat of some Carbomedics models (Fig. 14I,J).

Special features: In contrast to other bileaflet prostheses(Fig. 9B), the pivot area is not ‘‘cavitied’’ in the ATS models(Fig. 9A) [32]. The ATS design features a reverse geometry atthe hinge points creating four semi-spheres that project intothe blood stream. ATS Medical claims this design promotesbetter washing and decreased stasis, thus, decreasing the inci-dence of thrombus and thromboembolism. Additional fea-tures include a reputedly decreased valvular noise level whenclosing, low profile structure and pre-mounted design [41].

Potential complications: The ATS open pivot bileafletvalve has an incidence of complications similar to that ofother bileaflet valves [43,44]. In-vitro studies indicate that the

Fig. 9.


ATS bileaflet valve does not open to the full 85! it wasmanufactured to attain, which may explain why the samestudies report that the valve closes extremely quickly [45].This failure to open fully may also explain the reducedclosing noise reputed to be a feature of this valve. Thelong-term effects of the suboptimal opening are not fullyunderstood [45].

Overall, at this early follow-up stage, the ATS open pivotbileaflet valve has shown decreased levels of thrombosis andhemolysis when compared to some earlier model valves.There have been no structural changes reported, and reducedtransvalvular gradients have been measured [44].

FDA approval: The first clinical trial of the ATS valvewas in May of 1992, and the valve received FDA approvalin October 2000 [44].

4.2. The Edwards bileaflet valves

Models: Edwards-Duromedics valve (discontinued)(AKA TEKNA).

Type: Bileaflet valve.

Technical information: Introduced by Hemex Scientific in1982 and subsequently acquired by Baxter Healthcare [46].In 1988, Baxter Healthcare voluntarily withdrew the valve(Fig. 10A) from the market citing 12 leaflet escapes out of atotal of 20,000 implants [47]. In June of 1990, the valve wasreintroduced to the market as the revised Edwards-Duro-medics, and later still as the Edwards Tekna valve. Thesevalves are no longer on the market.

4.3. Edwards Mira (R) valve

The present Edwards Bileaflet valve is the Mira (R)Valve (Fig. 10B). The mechanical components of the Miravalve are manufactured by Sorin Biomedica (Italy). It differsfrom the Sorin bileaflet Bicarbon in that the sewing ring issofter and ‘‘waffled,’’ and has a Silicone insert. This makesthe cuff similar to the Starr-Edwards valve. This sewing cuffis meant to increase the ease of implantation.

Size range and available dimensions:Model 3160 in aorticposition: 19–27 mm. Model 9210 in mitral: 25–33 mm [48].

Physical characteristics: Central blood flow.

Fig. 10.


Orifice ring: Pyrolytic carbon with a stiffener ringcomposed of Stellite [48].

Leaflets: Pyrolytic carbon over graphite substrate impreg-nated with tungsten [48].

Sewing ring material: Dacron, with or without Biolitecoating [48].

Radiographic characteristics: The stiffener ring is com-pletely radiopaque. Leaflets are somewhat visible due to thetungsten-impregnated substrate (Fig. 10C,D). Characteristiccurved leaflets can be seen on X-ray, but are more visible incertain orientations [48].

Special features: Special features include curved leaf-lets that provide three equivalent orifice areas, rotationalability once implanted and a self irrigating hinge mech-anism where the leaflets join the body of the valve [49].

Potential complications: The main complication with theoriginal series (Duromedics) of valves was leaflet escape. ByDecember 1995, 46 cases of leaflet escape had been reported,which correlated to an estimated linearized rate of 0.029%/pty [46]. After removing the valve from the market, Baxter’scorporate investigations implicated five reasons for leafletescape: (1) clustered microporosity (2) cavitation bubbles, (3)dimensional tolerances, (4) insufficient compliance of thesewing ring and (5) surgical mishandling [49]. Of thesecomplications, Baudet et al. [49] cited surgical mishandlingas being the most significant for leaflet escape. This was incontrast to Mastroroberto et al. [46] and Hemmer et al. [47]who implicated cavitation as the most common cause ofleaflet fracture. Leaflet escape notwithstanding, this valveshows excellent hydrodynamic performance [49]. Regardlessof the etiology, when the valve was reintroduced in 1993, thecompanymade several improvements to the design to attemptto avoid these complications. Of these, the most notableinclude an improvement to the shock absorber in the sewingring and a more sophisticated quality control procedure formaking pyrolytic material [50]. Even with the informationpresent regarding failure of some of the Edwards-Duromed-ics valves, the recommendation cannot be given to haveprophylactic re-replacement of the prosthesis [50]. Thisconclusion was reached by taking into account both the datacollected and the operative mortality of valve replacement,especially in the mitral position [50]. This is in contrast tocertain diameters and dates of production of the Bjork-Shiley CC prosthesis [50].

FDA approval: The Edwards-Duromedics and the Teknavalves have been withdrawn from the market.

The MIRA valve (Fig. 10B) received its European CEmark in 1998, was licensed in Canada in 2000 and is inFDA clinical trials in the United States.

4.4. The On-X and Conform-X valves by MCRI

Models: TheOn-X aortic, mitral and theConform-X valve.Type: Bileaflet valve.Technical information: Manufactured and sold by the

Medical Carbon Research Institute (MCRI). All series of

the valve (Fig. 11A–F) are designed for supra-annularsewing ring placement with intra-annular housing place-ment [51].

Size range and available dimensions: Aortic: 19–29 mm,mitral: 23–33 mm [51]. The On-X Conform-X valve(Fig. 11F) has a flexible cuff that conforms to the dimen-sions of annulus. This cuff allows one valve size to be usedfor all annulus sizes between 25 and 33 mm [51].

Physical characteristics: Central blood flow (Fig. 11A,B).The pyrolytic carbon used by MCRI is not alloyed withsilicon, as it is in other valves that utilize pyrolyticcarbon. MCRI calls this new, purer pyrolytic carbon On-X carbon. The On-X carbon is meant to reduce thrombo-genicity while increasing the strength and durability of thematerial [51].

Orifice ring: On-X carbon.Leaflets: On-X carbon over a graphite substrate with 20%

tungsten by weight.Sewing ring material: Polytetrafluoroethylene (PTFE)

[51]. The sewing ring is attached to the valve using atitanium-retaining band (Fig. 10A–C).

Radiographic characteristics: The leaflet substrate isimpregnated with tungsten to aid X-ray visibility. Thetitanium-retaining band to which the sewing ring is attachedis also radiopaque (Fig. 11C–E). The aortic valve has tworings (Fig. 11D).

Special features: The On-X valves feature a uniquecarbon design that is reported to have better mechanicalproperties than the original pyrolytic carbon [52]. Othersalient features include the butterfly-like hinge configura-tion, flared and elongated orifice inlets and thin leaflets topromote more effective hemodynamics [53]. The elongatedorifice reduces the total angle that the leaflets must travel,thus the regurgitant closing volume is effectively minimizedand the leaflet impact velocity at closure is diminished [51].The intra-annular flare design and leaflet guards (Fig. 11A,B)provide a physical barrier to protect against tissue encroach-ment [51].

Potential complications: Because the On-X valve is stillvery new (especially in the North American market), littledocumentation of potential complications is available.Short-term studies on the valve seem positive, and comparefavorably to other bileaflet valves [52]. Walther et al. [52]have reported some problems with valve sizing due to theelongated housing and the flared inlet. This may becomemore critical for the inexperienced surgeon.

FDA approval: On-X clinical trials began in September1996 in Germany. The valve received FDA premarketapproval for the aortic prosthesis in May 2001 and for themitral and Conform-X valves in March of 2002 [51].

4.5. The Sorin Bicarbon mechanical valve

Model: Sorin Bicarbon ART19LN to ART31LN/ART19LNF to ART31LNF (aortic), MTR19LS toMTR33LS/MTR19LNF to MTR33LNF (mitral).


Type: Bileaflet mechanical valve.Technical information: The Bicarbon valve is manufac-

tured and distributed by Sorin Biomedica Cardio (Saluggia,Italy). This prosthesis has been available on the Europeanmarket since 1990 [54].

Size range and available dimensions: The standardSorin Bicarbon model is available with sewing cuff

diameters ranging from 19 to 31 mm and 19 to 33 mmfor the aortic and mitral sites, respectively. The SorinBicarbon Fitline valve, which features a reduced sewingcuff to facilitate implantation, is also available in thesesame dimensions.

Physical characteristics: This prosthesis design featurestwo curved pyrolytic carbon covered leaflets intended to

Fig. 11.


enable laminar blood flow (Fig. 12A,B). The hinge mech-anism consists of a rolling pivot design to minimize wear andthe housing is of a titanium alloy (Ti6Al4V) coated withCarbofilm to ensure low thrombogenicity. The sewing cuff,made of a double-velour PET and PTFE fabric, is also coatedwith a thin layer of Carbofilm.

Radiographic characteristics: The Sorin Bicarbon valvehas an 80! opening angle (55). The leaflets and housing areradiopaque (Fig. 12C).

Special features: This valve utilizes an ‘‘aerofoil’’leaflet design that is meant to minimize turbulence andstagnation. The curved leaflets also allow for three hydro-dynamically equivalent streamlines, which further enhancethe hemodynamics of the valve [56]. In addition, the hingemechanism is designed to allow a small degree of back-flow near the hinges to increase backwash of this area andreduce the risk of thrombosis, even when the valve is inthe closed position [56].

Potential complications: Through its 12 years ofimplantation, there have been no reports of mechanical

failure [57]. However, studies have reported wear behaviorin relation to the Carbofilm coating on the valve housing inthe hinge areas [54,58,59]. This wear has not been signific-ant enough to cause dysfunction.

The Bicarbon valve appears to have a low degree ofthrombogenicity. One report suggests that this prosthesis hasan actuarial freedom from thrombosis at seven years of99 ± 1% (aortic), 97 ± 3% (mitral) and 98 ± 1% (aortic andmitral) (60), while another report claims an overall five yearfreedom from thrombosis of 99.2 ± 0.3% [57].

Bleeding complications proved to be slightly moreimportant; Bortolotti et al. [60] report a freedom frombleeding at 7 years of 91 ± 3% (AV), 86 ± 7% (MV) and82 ± 13% (DV), while Borman et al. [57] report a freedom at5 years of 95.5 ± 1.0%. Mecozzi et al. [61] believe that thedesign, specifically the curved profile of the leaflets,account for the lower severity of hemolysis than in theCarbomedics prostheses.

Infective endocarditis remains an important complicationin this, as in other MHVs. Freedom from endocarditis at

Fig. 12.


seven years has been reported as 99 ± 1% (AV), 99 ± 1%(MV) and 95 ± 1% (DV) [60], while another study reports aslightly higher incidence of endocarditis with freedom fromendocarditis at 5 years of 90.9 ± 4.6% [57].

Freedom from all valve-related complications at 7 yearshas been reported at 80 ± 5% (AV), 73 ± 1% (MV) and

34 ± 18% (DV) [60] and the linearized incidence of valve-related complications at 8.02%/pty (MV) [55].

Additional comments: Sorin Biomedica has a new Bicar-bon Slimline valve designed for supra-annular placement.This valve differs from the standard model in that it has asmaller sewing cuff, allowing implantation of a larger valve

Fig. 13.


in a given annulus. This new design reportedly minimizespressure gradients and increases the effective orifice area(EOA), thus improving overall hemodynamics.

FDA approval: The Sorin Bicarbon valve is not yetFDA approved. It is currently under clinical investigationin the USA and marketed elsewhere with European CEmark approval.

4.6. The St. Jude Medical (SJM) bileaflet mechanical valve

Models: SJM standard mechanical valve. Also, SJMExpanded series, SJM Hemodynamic Plus (HP) series,SJM Masters series, SJM Regent Valve and SJM Mastersseries with Silzone (SZ) coating (see Section 4.7).

Type: Bileaflet; aortic, mitral and tricuspid.Technical information: Manufactured and sold by SJM

Regent Valves (St. Paul, MN, USA). The SJM standardbileaflet valve (Fig. 13A–C) was introduced clinically in1977 [11], while the Expanded series was introduced inMarch 1996 (USA), the HP series in 1996 (Fig. 13G), theMasters series (Fig. 13E) in 1995 (USA), the Regent valve

(Fig. 13D) in February 1999 (March 2002 in the US) andthe SJM Silzone (Fig. 13F) was introduced in 1997 inCanada and Europe and in the USA in August 1998.

Size range and available dimensions: SJM bileafletvalves (Fig. 13A,B), SJM regent valves (Fig. 13D) andthe HP series (Fig. 13G) are available with mountingdiameters of 17–31 (aortic), 17–31 (mitral) and corres-ponding orifice diameters of 14.7–26 mm (aortic andmitral) [11]. Overall open height is 8.4–12.2 mm for allaortic and mitral SJM bileaflet valves [62].

Physical characteristics: In vitro studies show that flowthrough all SJM mechanical valves is symmetric and rel-atively nonturbulent [11]. In vivo mean pressure gradientsrange from 3.0 to 5.2 mm Hg in the aortic position and from1.4 to 7.0 mm Hg in the mitral position [63]. Regurgitantvolume ranges from 7.6 to 10.6 cm3/stroke for aortic valvesand 4.3 to 6.4 cm3/stroke for mitral valves [63].

The valve housing and leaflets are constructed of graph-ite coated with pyrolytic carbon. In addition, the leafletsubstrates are impregnated with tungsten (5–10 wt.%) toensure adequate radio-opacity (Fig. 13C) [11]. Leaflet hinge

Fig. 13. (continued )


configuration is a butterfly-like depression and pivot guardsare upright. The sewing cuff is made of polyester PET orPTFE [62]. Design differences between the various valveseries are outlined below.

Expanded series: 10% more sewing cuff material formitral valves and 25% more for aortic valves, with nochange to either mounting or orifice diameters.

HP series: Supraannular sewing cuff with intraannularcarbon rim (Fig. 13G). HP series eliminates sewing cuffmaterial in the annulus and increases geometric flow area byup to 26% [62]. HP series valves open fully to an angle of85!, hence with a large effective orifice area, lower meanpressure gradients, and hemodynamic performance consid-ered equivalent to that of the next larger size of standardcuffed valve [64,65].

Masters series: The main design difference of this seriesis the addition of a controlled torque rotation mechanismand additional suture markers, both of which facilitateimplantation [62]. Aortic models are available with stand-ard, expanded or HP sewing cuffs while the mitral modelsare available with the standard or expanded sewing cuff(Fig. 13E). In addition, Masters series HP valves areavailable with either the standard HP cuff or with a FlexCuffsewing ring. The FlexCuff ring is flanged and more pliablethan other SJM sewing cuffs.

Regent valve: This series has the same design as theMasters series with two exceptions: the carbon rim is shiftedto the supraannular position along with the sewing cuff, andthe rotation mechanism is housed completely within thecarbon rim (Fig. 13D). Hemodynamically, this series has anapproximate one-size increment (improvement) over HPseries valves. Regent valves are available with either thestandard or the FlexCuff sewing ring.

Radiographic characteristics: The valve housing is madeof pyrolytic carbon and is radiolucent in the standard model.The leaflets are visible in the fully open position asradiopaque lines. A radio-opaque lip-shaped inner designwith sharply defined midline lucent stripes corresponding tothe valve leaflets is seen in Fig. 13C [11]. The rotationmechanism of the Masters series valve, like the Silzonemodel, appears as an opaque double ring (Fig. 13H,I). Thisallows the surgeon to change the orientation of leaflets afterimplantation [62].

Potential complications: A loss of structural integrity hasbeen reported for a small number of SJM mechanical valves(approximately 15–20 out of 9514), including one incidentof post-operative leaflet dislodgment [32]. The most com-mon nonstructural complication of the SJM mechanicalvalve is thromboembolism with a reported rate of 2.0 eventsper pty for aortic valves (n = 17,242 pty) and 2.5/pty formitral valves (n= 17,696 pty) [32]. Rates of anticoagula-tion-related complications in patients with SJM valves werereported as 2.2/pty (n = 14,845) for aortic valves and 1.7/pty(n = 16,679) for mitral valves [32]. Obstruction of mech-anical valves due to thrombus or pannus formation is a rarebut life-threatening complication that should not be disre-

garded when dealing with bileaflet valves. The rate ofpannus formation on SJM mechanical valves has beenquoted as 0.03–0.14%, and pannus is more likely to beseen on valves in the mitral or tricuspid position (n = 18,523pty). Acute prosthesis thrombosis is mostly a complicationof inadequate anticoagulation, more specifically poorpatient compliance, but has been related to pannus forma-tion [66]. Infective endocarditis is a risk for all types ofprosthetic valves, and rates for SJM mechanical valves arereported as 0.2–0.4 cases per patient year [32].

Additional comments: The SJM standard bileaflet pros-thesis is the ‘‘gold standard’’ against which most othermechanical valves are compared. It is the most frequentlyimplanted MHV prosthesis worldwide.

FDA approval: All SJM mechanical valves discussedabove, except the SJM SZ valve (see below), are currentlyapproved for clinical use in North America and the EU. TheSJM SZ bileaflet mechanical valve was voluntarily with-drawn from the market in January of 2000.

4.7. SJM bileaflet mechanical valve with Silzone coating

Model: SJM Masters series with Silzone (SZ) coating.Type: Bileaflet; aortic and mitral.Technical information: Manufactured and sold by SJM

(St. Paul, MN, USA). The SZ coating was first introduced inEurope (and Canada) in September 1997 and in the USA inMay 1998. SJM initiated a voluntary withdrawal of all SZvalves (and annuloplasty rings) in January 2000.

Size range and available dimensions: same as for thenon-SZ SJM Masters series valves (see above).

Physical characteristics: Basic valve design and flowcharacteristics are the same as those described for Mastersseries valves (see above) (Fig. 13F). Features of the SJMMasters series with SZ coating include:

Leaflet material: Pyrolytic carbon with graphite substrateimpregnated with tungsten, 5–10% by weight.

Cage material: Pyrolytic carbon over graphite substrate.Sewing ring material: PET polyester coated with

metallic silver by an ion beam-assisted vapor depositionprocess [67].

Radiographic characteristics: Same as for non-SZ Mas-ters series valves (see above) (Fig. 13H,I).

Potential complications: The potential complicationsassociated with SZ valves are as described for non-SZSJM valves (see above). In addition, the SZ valves wereassociated with a higher rate of major paravalvular (PV)leakage as compared with non-SZ valves. Major PV leak isdefined as PV leak that resulted in explant, required reop-eration or was implicated in a death [68,69]. It has beenhypothesized that this increased risk of PV leak may be dueto an inhibition of normal fibroblast response and incorp-oration of the fabric of the sewing cuff into host tissues insome patients [68]. In another study, freedom from PV leakat 12 and 24 months follow up was 98.5% ± 1.5% and 100%for the aortic and mitral valves, respectively [70]. One


observational study also reported a higher rate of emboliccomplications with SZ valves and concluded that the SZcoating is more thrombogenic [68,71]. Mortality rates havevaried between centers. Data from the AVERT study have so

far not shown any significant increase in mortality [68,69].A case of left atrial rhabdomyosarcoma was reported in apatient who had undergone a MVR with a Silzone-coatedSJM MHV 1 year earlier [72].

Fig. 14.


Additional comments: The SZ coating was introducedwith the hope that the silver layer would prevent bacterialcolonization of the valves and consequent prosthetic valveendocarditis. The SZ fabric was shown to reduce attachmentand colonization of microorganisms such as Staphylococcusaureus, S. epidermidis, Escherichia coli, Klebsiella pneumo-

niae and Candida albicans in cell-culture and animalstudies [67,73].

FDA approval: SJM initiated a voluntary withdrawal ofall valves (and other devices) with the SZ coating in Januaryof 2000 following reports of significantly higher rates of PVleak as compared to non-SZ SJM valves. FDA approval was

Fig. 14. (continued )


subsequently withdrawn and the SZ coating is no longer inclinical use.

4.8. The Sulzer CarboMedics valves

Models: (A) Standard (Fig. 14A); (B) ‘‘R’’ series reducedcuff aortic (Fig. 14B); (C) OptiForm Mitral (Fig. 14E); (D)Pediatric-small adult; (E) Top Hat supra-annular aortic(Fig. 14A–E).

Type: Bileaflet valves. Aortic (Models A, B, D and E)and mitral (Models A, C and D).

Technical information: The CarboMedics prosthetic heartvalve (CPHV) is manufactured by Sulzer CarboMedics,Austin, TX and was introduced in 1986. The leaflet pivotdesign is believed to allow thorough washing of the hingemechanism but incomplete ‘‘wiping’’ of the hinge surfaces.The mitral valve is implanted intra-annularly. The smallmitral-21 mm (model D) is designed for intra-annular orintra-atrial implant. The Top Hat is the first bileaflet mech-anical valve designed for truly supra-annular placement (74).Its small size and placement position makes it possible for thesurgeon to use a prosthesis that is one size larger than wouldbe permissible with an intra-annular valve [75]. This advant-age is especially important in patients with a small aortic root.A contraindication would be coronary ostia that are displaceddownwards. Based on its ‘‘one size-up’’ feature, this model isbelieved to provide a potential increase in valve flow areaalong with a reduction in pressure gradients [74].

Size range and available dimensions: Aortic valves: 19–31 mm, mitral valves: 23–33 mm. The ‘‘R’’ Series is true-sized to eliminate sizing conflicts and downsizing. Valvesizes are 19–29 mm with respective internal orifice diam-eters ranging from 18.8 to 29.0 mm. Pediatric-Small Adultaortic valve sizes range from 16 to 19 mm and mitral from16 to 21 mm.

Physical characteristics: All CPHVs are made of Pyrolite.Pyrolytic carbon-coated discs pivot inside a pyrolytic carbonhousing into which the valve hinges are recessed. The flowsurface of the Dacron sewing cuff is coated with BioliteCarbon (R) (black). A titanium ring surrounds the valvehousing and allows rotation of the valve for optimal orienta-tion after implantation. The two leaflets open to 78! from thehorizontal axis. The valve discs seat closer to the edge of thehousing. In the aortic position both discs of the CPHVs openuniformly and remain in the open position during systole[76]. The 21-mm Pediatric-Small Adult mitral valve has aunique cuff design made of polyester knit fabric.

Radiographic characteristics: The titanium ring surround-ing the valve housing and the leaflets are radiopaque(Fig. 14F,G). CPHVs have two main types of ring profiles.The Standard mitral and aortic models have a humped profile(seen as a slight hump at the inflow end on Fig. 14H). Theopening in the metal ring where the wire is inserted to securethe carbon housing is seen as a small dark gap on one side ofthe profile. The second ring profile is the flat profile. Thisprofile is used for the pediatric valves, the R-Series aortic

(Fig. 14I), the Optiform mitral (Fig. 14J) and the Orbis valve.The flat ring profile is also seen on the ATS valves.

Special features: The mitral valve has a soft pliantsewing cuff that conforms to the annulus and shields theleaflets and outflow area from interference by native mitraltissues. The aortic valve has a pliable ‘‘cork-shaped’’ sewingcuff that helps minimize perivalvular leaks. The ‘‘R’’ Serieshas a reduced outer diameter with no change in the internalorifice diameter, allowing the largest intra-annular valve(29 mm) in patients with narrow aortic annuli. This featureminimizes the need for annuloplasty. The OptiForm has asymmetrical compliant sewing cuff design that conforms tothe patient’s annulus and seals around the native annulus.This gives the surgeon a choice of valve placement byvarying needle entry and exit sites. The Pediatric-SmallAdult model has a smaller sewing cuff that allows implanta-tion of a 19-mm housing in a patient with a 16-mm tissueannulus. This provides the increase in blood flow andhemodynamic requirements as the patient grows and mayminimize the need for repeated valve replacement in thegrowing heart [77]. Its small size and supra-annular place-ment allows the surgeon to upsize the valve by 2–4 mm,minimizing the need for annulus enlargement procedures[78,79].

Potential complications: CPHVs have higher reportedstatic leak rates when compared to other valves such as theStarr-Edwards, Omniscience and Medtronic-Hall [76]. Sim-ilar mortality and linearized rates of possible complicationshave been reported by different studies with a comparablenumber of patient-years (pty). Early mortality rates reportedwere 5.0% (n = 4040 pty) [80] and 5.6% (n = 4765.0 pty)[81]. A study on a Japanese population revealed a lowerearly mortality rate of 1.2% (n = 2016 pty) [82]. Linearizedrates of complications reported by Fiane et al. [80] (n =4040 pty) and Dalrymple-Hay et al. [83] (n = 4342 pty) weremajor thromboembolism at 0.9%/pty and 2%/pty, valvethrombosis at 0.2%/pty and 0.14%/pty, and prosthetic valveendocarditis at 0.1%/pty and 0.18%/pty, respectively. Theincidence of paravalvular leak needing reoperation wasreported as 0.5%/pty by Fiane et al [80].

Additional comments: There is an additional CarboMed-ics bileaflet model, the Orbis Universal (R), that is not as yetapproved by the FDA. It is available in sizes 21–33 mm thatcan be adapted to either the mitral or aortic position. Thevalve’s subassembly is identical to other CPHVs with atitanium-reinforced ring. Its sewing ring is fabricated from aknitted polyester fabric.

FDA approval: 1993.Closing comments: In this paper, we have given details of

a select group ofMHVprostheses most of which are currentlybeing implanted, while some, though no longer in use, willcontinue to be explanted in significant numbers for years tocome. In an occasional valve model, a relatively smallnumber were implanted, however the cause of valve-failureand subsequent withdrawal from the market has not yet beenestablished. We hope that proper identification of these


prostheses and documentation of the findings from series ofprostheses will help elucidate their modes of failure.

Acknowledgments

We gratefully acknowledge Ms. Melissa Skarban for herhelp in preparing this manuscript. We thank ATS valves,Edwards Life Sciences, Medtronic Heart Valves Division,Sorin Biomedica and St. Jude Medical for assistance withtechnical information, illustrative material either in elec-tronic or hard copy photographs or the use of their websiteson which illustrative material and technical data wereavailable. We are particularly thankful to Ms. SandraSchlehuber and Prof. Martin Guenther who graciouslyallowed us to use illustrations from their collection entitledHerzklappen Museum Mechanisch and ATS for the use ofFig. 9 (A&B). JB is a financially compensated consultantfor St. Jude Medical. JB has, in the past, also been afinancially compensated consultant to Sulzer CarboMedics,Medtronic (Canada), and Medical Carbon Research In-stitute. MSA received a summer scholarship from theUniversity Health Network-Department of Pathology, whileCM, CF and PB received summer scholarships from theUHN-Dept. of Pathology and the University of Toronto.

References

[1] Hufnagel CA, Harvey WP, Rabil PJ, Mcdermott TF. Surgical correc-

tion of aortic insufficiency. Surgery 1954;673–83.

[2] Starr A, Edwards ML. Mitral replacement: clinical experience with aball valve prosthesis. Ann Surg 1961;726.

[3] Harken DF, Taylor WJ, LaFemme LE, et al. Aortic valve replacement

with a cage ball valve. Am J Cardiol 1962;9:292.

[4] Schoen FJ. Future directions in tissue heart valves: impact of recentinsights from biology and pathology. J Heart Valve Dis 1999;8: 350–8.

[5] Schoen FJ. Pathology of heart valve substitution with mechanical

and tissue prostheses. In: Silver MD, Gotlieb AI, Schoen FJ, editors.

Cardiovascular pathology. Philadelphia (PA): Churchill Livingstone,2001. pp. 629–77.

[6] Roberts WC. Choosing a substitute cardiac valve: type, size, surgeon.

Am J Cardiol 1976;38:633–44.[7] Hammermeister K, Sethi GK, Henderson WG, Grover FL, Oprian C,

Rahimtoola SH. Outcomes 15 years after valve replacement with a

mechanical versus a bioprosthetic valve: final report of the Veterans

Affairs randomized trial. J Am Coll Cardiol 2000;36:1152–8.[8] Schoen FJ. Cardiac valve prostheses: pathological and bioengineering

considerations. J Card Surg 1987;2:65–108.

[9] Silver MD, Butany J. Complications of mechanical heart valve pros-

theses. Cardiovasc Clin 1988;18:273–88.[10] Lefrak EA, Starr A. Cardiac valve prostheses. New York: Prentice

Hall, 1979.

[11] Morse D, Steiner RM, Fernandez J. Cardiac valve identification atlas

and guide. In: Dryden Morse RM, Sa JF, editors. Guide to prostheticcardiac valves. New York: Springer-Verlag, 1985. pp. 257–346.

[12] Yoganathan AP, Reamer HH, Corcoran WH, Harrison EC, Shulman

IA, Parnassus W. The Starr-Edwards aortic ball valve: flow charac-teristics, thrombus formation, and tissue overgrowth. Artif Organs

1981;5:6–17.

[13] Silver MD, Wilson GJ. Pathology of mechanical heart valve prostheses

and vascular grafts made of artificial materials. In: Silver MD, editor.Cardiovascular pathology. New York: Churchill Livingstone, 1991.

pp. 1489–545.

[14] Sakata K, Ishikawa S, Ohtaki A, Otani Y, Suzuki M, Kawashima O,

Morishita Y. Malfunctioning Starr-Edwards mitral valve 21 years afterinstallation. J Cardiovasc Surg (Torino) 1997;38:81–2.

[15] Machler HE, Schmidt CH, Neuner P, Iberer F, Anelli-Monti M, Dacar

D, Rigler B, Kraft-Kinz J. Twenty-four years’ implant duration of the

aortic Starr-Edwards silastic ball prosthesis: a valve of the past? Eur JCardio-thorac Surg 1993;7:114–6.

[16] Hylen JC, Kloster FE, Herr RH, Hull PQ, Ames AW, Starr A, Gris-

wold HE. Phonocardiographic diagnosis of aortic ball variance. Cir-culation 1968;38:90–102.

[17] American Edwards Laboratories Clinical Data report. 1983. Ref type:

Pamphlet.

[18] Li HH, Jeffrey RR, Davidson KG, Seifert D, Korfer R, GrunkemeierGL. The Ultracor tilting disc heart valve prosthesis: a seven-year

study. J Heart Valve Dis 1998;7:647–54.

[19] Sin YK, Campbell K, Pillai R. The Ultracor tilting disc heart valve

prosthesis in the aortic position: mid-term follow up. J Heart Valve Dis2000;9:688–92.

[20] Alvarez L, Escudero C, Figuera D, Castillo-Olivares JL. The Bjork-

Shiley valve prosthesis. Analysis of long-term evolution. J Thorac

Cardiovasc Surg 1978;104:1249–58.[21] Yoganathan AP, Corcoran WH, Harrison EC, Carl JR. The Bjork-

Shiley aortic prosthesis: flow characteristics, thrombus formation

and tissue overgrowth. Circulation 1978;58:70–6.[22] Cleveland JC, Lebenson IM, Dague JR. Early postoperative develop-

ment of aortic regurgitation related to pannus ingrowth causing in-

complete disc seating of a Bjork-Shiley prosthesis. Ann Thorac Surg

1982;33:496–8.[23] Bjork VO, Henze A. Ten years’ experience with the Bjork-Shiley

tilting disc valve. J Thorac Cardiovasc Surg 1979;78:331–42.

[24] Walker AM, Funch DP, Sulsky SI, Dreyer NA. Patient factors asso-

ciated with strut fracture in Bjork-Shiley 60 degrees convexo-concaveheart valves. Circulation 1995;92:3235–9.

[25] Schondube FA, Althoff W, Dorge HC, Voss M, Laufer JL, Chandler

JG, Messmer BJ. Prophylactic reoperation for strut fractures of theBjork-Shiley convexo-concave heart valve. J Heart Valve Dis 1994;

3:247–53.

[26] Bjork VO, Lindblom D. The Monostrut Bjork-Shiley heart valve.

J Am Coll Cardiol 1985;6:1142–8.[27] Alajmo F, Perna AM, Calamai G, Nigro R, Cassai M, Montesi G,

Braconi L, Borgioli A, Preziuso M, Palminiello A. [Mitral valve re-

placement with the Bjork-Shiley monostrut prosthesis: a 4-year clin-

ical experience]. G Ital Cardiol 1990;20:44–9.[28] Aris A, Padro JM, Camara ML, Lapiedra O, Caralps JM, Borras X,

Carreras F, Pons-Llado G. The Monostrut Bjork-Shiley valve. Seven

years’ experience. J Thorac Cardiovasc Surg 1992;103:1074–82.[29] DeWall RA, Qasim N, Carr L. Evolution of mechanical heart valves.

Ann Thorac Surg 2000;69:1612–21.

[30] Abe T, Kamata K, Kuwaki K, Komatsu K, Komatsu S. Ten years’

experience of aortic valve replacement with the omnicarbon valveprosthesis. Ann Thorac Surg 1996;61:1182–7.

[31] Teijeira FJ. Long-term experience with the omniscience cardiac valve.

J Heart Valve Dis 1998;7:540–7.

[32] Akins CW. Results with mechanical cardiac valvular prostheses. AnnThorac Surg 1995;60:1836–44.

[33] Beaudet RL, Nakhle G, Beaulieu CR, Doyle D, Gauvin C, Poirier NL.

Medtronic-Hall prosthesis: valve related deaths and complications.

Can J Cardiol 1988;4:376–80.[34] Butchart EG, Li HH, Payne N, Buchan K, Grunkemeier GL. Twenty

years’ experience with the Medtronic Hall valve. J Thorac Cardiovasc

Surg 2001;121:1090–100.[35] Nitter-Hauge S, Abdelnoor M, Svennevig JL. Fifteen-year experience

with the medtronic-hall valve prosthesis. A follow-up study of 1104

consecutive patients. Circulation 1996;94:II105–8.


[36] Brazao AJ, Prieto D, de Oliveira JF, Eugenio L, Antunes MJ. Aorticvalve replacement with small-sized disc prostheses (medtronic hall).

J Heart Valve Dis 1999;8:680–6.

[37] Laas J, Kleine P, Hasenkam MJ, Nygaard H. Orientation of tilting disc

and bileaflet aortic valve substitutes for optimal hemodynamics. AnnThorac Surg 1999;68:1096–9.

[38] Milano A, Bortolotti U, Mazzucco A, Mossuto E, Testolin L, Thiene

G, Gallucci V. Heart valve replacement with the Sorin tilting-disc

prosthesis. A 10-year experience. J Thorac Cardiovasc Surg1992;103: 267–75.

[39] Vitale N, Paparella D, Ranieri VM, Memmola C, Caruso G, Tunzi P,

de Luca L. Survival despite almost complete fibrous obstruction of aSorin tilting disc mitral prosthesis. Tex Heart Inst J 1996;23:167–9.

[40] Hurle A, Abad C, Feijoo J, Ray V, Ponce G. Long-term clinical

performance of Sorin tilting-disc mechanical prostheses in the mitral

and aortic position. J Cardiovasc Surg (Torino) 1997;38:507–12.[41] ATS Medical pamphlet. 1992. ATS Medical. Ref type: Pamphlet.

[42] ATS Medical website. 1998. ATS Medical website. Ref type: Elec-

tronic Citation.

[43] Van Nooten G, Caes F, Francois K, Missault L, Van Belleghem Y.Clinical experience with the first 100 ATS heart valve implants. Car-

diovasc Surg 1996;4:288–92.

[44] Ozeren M, DoGan OV, Dolgun A, Kocyldirim E, Karapinar K,

Yucel E. Clinical results of the ATS prosthetic valve in 240 implantsand review of the literature. J Heart Valve Dis 2001;10:628–35.

[45] Feng Z, Nakamura T, Fujimoto T, Umezu M. In vitro investigation of

opening behavior and hydrodynamics of bileaflet valves in the mitralposition. Artif Organs 2002;26:32–9.

[46] Mastroroberto P, Chello M, Bevacqua E, Cirillo F, Covino E. Duro-

medics original prosthesis: what do we really know about diagnosis

and mechanism of leaflet escape? Can J Cardiol 2002;16:1269–72.[47] Hemmer WB, Doss M, Hannekum A, Kapfer X. Leaflet escape in a

TEKNA and an original duromedics bileaflet valve. Ann Thorac Surg

2000;69:942–4.

[48] Morse D, Steiner R, Fernandez J. Cardiac valve identification atlas andguide. In: Morse D, Steiner RM, Fernandez J, editors. Guide to pros-

thetic heart valves. New York: Springer-Verlag, 1985. pp. 247–346.

[49] Baudet E, Roques X, McBride J, Panes F, Grimaud J-Ph. A 8-yearfollow-up of the Edwards-Duromedics bileaflet prosthesis. J Cardio-

vasc Surg 1995;36:437–42.

[50] Podesser BK, Khuenl-Brady G, Eigenbauer E, Roedler S, Schmied-

berger A, Wolner E, Moritz A. Long-term results of heart valve re-placement with the Edwards-Duromedics bileaflet prosthesis: a

prospective ten-year clinical follow-up. J Thorac Cardiovasc Surg

1998;115:1121–9.

[51] Medical Carbon Research Institute website. 2002. MCRI website. Reftype: Electronic Citation.

[52] Walther T, Falk V, Tigges R, Kruger M, Langebartels G, Diegeler A,

Autschbach R, Mohr FW. Comparison of On-X and SJM HP bileafletaortic valves. J Heart Valve Dis 2000;9:403–7.

[53] Laczkovics A, Heidt M, Oelert H, Laufer G, Greve H, Pomar JL,

Mohr FW, Haverich A, Birnbaum D, Regensburger D, Palatianos G,

Wolner E. Early clinical experience with the On-X prosthetic heartvalve. J Heart Valve Dis 2001;10:94–9.

[54] Arru P, Rinaldi S, Stacchino C, Vallana F. Wear assessment in bileaflet

heart valves. J Heart Valve Dis 1996;5(Suppl 1):S133–43.

[55] Camilleri LF, Bailly P, Legault BJ, Miguel B, D’Agrosa-Boiteux MC,de Riberolles CM. Mitral and mitro-aortic valve replacement with

Sorin Bicarbon valves compared with St. Jude Medical valves.

Cardiovasc Surg 2001;9:272–80.

[56] Vallana F, Rinaldi S, Galletti PM, Nguyen A, Piwnica A. Pivot designin bileaflet valves. ASAIO J 1992;38:M600–6.

[57] Borman JB, Brands WG, Camilleri L, Cotrufo M, Daenen W, Gandj-

bakhch I, Infantes C, Khayat A, Laborde F, Pellegrini A, Piwnica A,Reichart B, Sharony R, Walesby R, Warembourg H. Bicarbon

valve—European multicenter clinical evaluation. Eur J Cardiothorac

Surg 1997;13:685–93.

[58] Campbell A, Baldwin T, Peterson G, Bryant J, Ryder K. Pitfalls andoutcomes from accelerated wear testing of mechanical heart valves.

J Heart Valve Dis 1996;5(Suppl 1):S124–32.

[59] Hasenkam JM, Pasquino E, Stacchino C, Arru P, Vallana F, Paulsen

PK. Wear patterns in the Sorin Bicarbon mechanical heart valve: aclinical explant study. J Heart Valve Dis 1997;6:105–14.

[60] Bortolotti U, Milano A, D’Alfonso A, Piccin C, Mecozzi G, Magagna

P, Fabbri A, Mazzucco A. Evaluation of valve-related complications

in patients with Sorin Bicarbon prosthesis: a seven-year experience.J Heart Valve Dis 2001;10:795–801.

[61] Mecozzi G, Milano AD, De Carlo M, Sorrentino F, Pratali S, Nardi C,

Bortolotti U. Intravascular hemolysis in patients with new-generationprosthetic heart valves: a prospective study. J Thorac Cardiovasc Surg

2002;123:550–6.

[62] St. Jude Medical Products. St. Jude Medical. 2002. Ref type: Elec-

tronic Citation.[63] Rashtian MY, Stevenson DM, Allen DT, Yoganathan AP, Harrison

EC, Edmiston WA, Faughan P, Rahimtoola SH. Flow characteristics

of four commonly used mechanical heart valves. Am J Cardiol

1986;58: 743–52.[64] Feng Z, Nakamura T, Fujimoto T, Umezu M. In vitro investigation of

opening behavior and hydrodynamics of bileaflet valves in the mitral

position. Artif Organs 2002;26(1):32–9.

[65] Vitale N, Caldarera I, Muneretto C, Sinatra R, Scafuri A, Di Rosa E,Contini A, Tedesco N, Pierangeli A, Abbate M, Gherli T, Casarotto D,

Di Summa M, Marino B, Chiariello L, de Luca L. Clinical evaluation

of St. Jude Medical Hemodynamic Plus versus standard aortic valveprostheses: the Italian multicenter, prospective, randomized study.

J Thorac Cardiovasc Surg 2001;122:691–8.

[66] Rizzoli G, Guglielmi C, Toscano G, Pistorio V, Vendramin I, Bottio T,

Thiene G, Casarotto D. Reoperations for acute prosthetic thrombosisand pannus: an assessment of rates, relationship and risk. Eur J

Cardiothorac Surg 1999;16:74–80.

[67] Seipelt RG, Vazquez-Jimenez JF, Seipelt IM, Franke A, Chalabi K,

Schoendube FA, Messmer BJ. The St. Jude ‘‘Silzone’’ valve: mid-term results in treatment of active endocarditis. Ann Thorac Surg

2001;72: 758–62.

[68] Schaff HV, Carrel TP, Jamieson WR, Jones KW, Rufilanchas JJ, Cool-ey DA, Hetzer R, Stumpe F, Duveau D, Moseley P, van Boven WJ,

Grunkemeier GL, Kennard ED, Holubkov R. Paravalvular leak and

other events in silzone-coated mechanical heart valves: a report from

AVERT. Ann Thorac Surg 2002;73:785–92.[69] Butany J, Scully HE, Van Arsdell G. Leak, R. Prosthetic heart valves

with silver coated sewing cuff fabric: early morphologic features in

two patients. Can J Cardiol 2002;18(7).

[70] Houel R, Kirsch M, Hillion ML, Loisance D. Silzone-coated St. Judemedical valve: a safe valve. J Heart Valve Dis 2001;10:724–7.

[71] Ionescu AA, Fraser AG. High incidence of embolism after St. Jude

Silzone prosthetic valve implantation. Circulation 1999;100(18):I –524(Ref type: Abstract).

[72] Grubitzsch H, Wollert HG, Eckel L. Sarcoma associated with silver

coated mechanical heart valve prosthesis. Ann Thorac Surg 2001;72:

1739–40.[73] Tweden, KS, Cameron JD, Razzouk AJ, Holmberg WR, Kelly SJ.

Biocompatibility of silver-modified polyester for antimicrobial protec-

tion of prosthetic valves. J Heart Valve Dis 1997;6:553–61.

[74] cts.net website. Cardiothoracic Surgery website. 2002. Ref type: Elec-tronic Citation.

[75] de Brux JL, Subayi JB, Binuani P, Laporte J. Doppler-echocardio-

graphic assessment of the carbomedics supra-annular ‘‘Top-Hat’’ pros-

thetic heart valve in the aortic position. J Heart Valve Dis 1996;5(Suppl 3): S336–8.

[76] Akins CW. Results with mechanical cardiac valvular prostheses. Ann

Thorac Surg 1995;60:1836–44.[77] Sulzer Carbomedics Pediatric/Small Adult Prosthetic Heart Valves.

1997. Sulzer Carbomedics. Ref type: Pamphlet.

[78] Roedler S, Moritz A, Wutte M, Hoda R, Wolner E. The CarboMedics


‘‘top hat’’ supraannular prosthesis in the small aortic root. J Card Surg1995;10:198–204.

[79] Lundblad R, Hagen OM, Smith G, Kvernebo K. The CarboMedics

supraannular top hat valve improves prosthesis size in the aortic root.

J Heart Valve Dis 2001;10:196–201.[80] Fiane AE, Geiran OR, Svennevig JL. Up to eight years’ follow-up of

997 patients receiving the CarboMedics prosthetic heart valve. Ann

Thorac Surg 1998;66:443–8.

[81] Jamieson WR, Fradet GJ, Miyagishima RT, Henderson C, Brown-

lee RT, Zhang J, Germann E. CarboMedics mechanical pros-thesis: performance at eight years. J Heart Valve Dis 2000;9:

678–87.

[82] Soga Y, Okabayashi H, Nishina T, Enomoto S, Shimada I, Miyamoto

TA, Ban T. Up to 8-year follow-up of valve replacement with carbo-medics valve. Ann Thorac Surg 2002;73:474–9.

[83] Dalrymple-Hay MJ, Pearce RK, Dawkins S, Alexiou C, Haw MP,

Livesey SA, Monro JL. Mid-term results with 1,503 CarboMedics

mechanical valve implants. J Heart Valve Dis 2000;9:389–95.


33

Documents

Transcript of 33