mechanical circulatory support: state of the art and...

Mechanical circulatory support: state of theart and future perspectivesDR Wheeldon

World Heart Corporation, Ottawa, Ontario, Canada

Mechanical circulatory support (MCS) has been viewed,until recently, as a rescue therapy to be applied when allelse fails. Not surprisingly, this has resulted in subopti-mal outcomes. Fortunately, the perseverance of a fewdedicated groups has produced improved outcomes andthe concept of MCS as an elective therapy is now steadilygaining acceptance. This is particularly true in thepostcardiotomy setting, where a large number of newoptions are now available. The recently completedREMATCH study has demonstrated the feasibility andefficacy of permanent MCS as a therapy for end-stageheart failure, despite a high rate of device complications.Donor availability is decreasing and biological solutionswill not be available for many years. New generation

implantable rotary pumps, a fully implantable left ven-tricular assist device and a total artificial heart are allundergoing clinical evaluation, and several new excitingdesigns are in preclinical evaluation. A new paradigm forthe treatment of terminal heart failure is emerging, wherean unpredictable and expensive medically manageddeath in an intensive care unit setting is being exchangedfor a more predictable high-cost, front-loaded therapywith management from the outpatient clinic. The perfu-sionist community has much to contribute to this emer-ging life support field, not only in the perioperativeperiod, but also in providing ongoing technical supportto hospital staff, recipients and their families. Perfusion(2003) 18, 159¡/169.

Background

Congestive heart failure is a major public healthissue in the developed world and a rapidly increas-ing health problem in the developing world.Although mortality from cardiovascular disease,particularly secondary coronary disease, has de-clined significantly since the 1950s, the impact ofheart failure continues to increase. This trend isrelated to an ageing population and, ironically, byadvances in emergency and interventional thera-pies, which now rescue patients from previouslyfatal acute events.

The statistics are impressive, showing cardiovas-cular disease to be easily the number one cause ofdeath in the US, responsible for twice as manydeaths as cancer and eclipsing the next sevenleading causes combined. The US prevalence issome 4.8 million cases per year and, with 400 000new cases annually, heart failure is the primary orcontributing cause in 260 000 deaths per year. At anannual cost approaching $40 billion in the US, heartfailure is the single most expensive health careproblem.1 Despite advances in medical therapy,this is a progressive disease, resulting in increasing

disability, more frequent hospitalizations and pre-mature death. The mortality of patients with ad-vanced New York Heart Association (NYHA) classIII¡/IV exceeds 50% at two years, and for end-stageclass IV patients, refractory to oral medications anddependent on intravenous inotropic agents, ap-proaches 70% at six months.2 Similar epidemiolo-gical and economic data apply to Europe as awhole.3

Heart transplantation provides the only currentlyavailable effective therapy,4 with a five-year survivalof approximately 65%. However, the paucity ofdonors means that less than 5% of patients whocould benefit actually receive a donor heart.5

So, is there a magic cure just around the corner?The answer is a resounding ‘no’. While gene-basedtherapies and cell and tissue transplants offer apossible solution for the future, these treatments aremany years away from clinical reality.

Mechanical circulatory support (MCS) has beenviewed, until recently, as a rescue therapy to beapplied when all else fails. Not surprisingly, this hasresulted in suboptimal outcomes. Fortunately, theperseverance of a few dedicated groups has pro-duced improved outcomes and the concept of MCSas an elective therapy is now steadily gainingacceptance. The recently completed REMATCHstudy6 has demonstrated the feasibility and efficacyof permanent MCS as a therapy for end-stage heart

Address for correspondence: Dereck Wheeldon, PhD, 8 JohnstoneRoad, Stanpit, Christchurch, Dorset BH23 3NG, UK.E-mail: [email protected]

Perfusion 2003; 18: 159 ¡/169

# Arnold 2003 10.1191/0267659103pf674oa

failure, despite a high rate of device complications.New generation implantable rotary pumps, a fullyimplantable left ventricular assist device (LVAD)and a total artificial heart (TAH) are all undergoingclinical evaluation and several new exciting designsare in preclinical evaluation. There are also anincreasing number of devices aimed at acute supportand a few devices designed to prevent or slowventricular remodelling.

A new paradigm for the treatment of terminalheart failure is emerging, where an unpredictableand expensive medically managed cardiac death inan intensive care unit (ICU) setting is being ex-changed for a more predictable high-cost, front-loaded therapy with management from the out-patient clinic.

The mechanical options

There are a number of ways in which MCS devicescan be classified. However, the system outlined inFigure 1 provides a scheme in which devices areclassified according to their intended use. Class Idevices are intended for very short-term use (hoursto days) and are used when early functional recov-ery is expected and minimal intervention is desir-able. Class II devices are used when an intermediatesupport time is expected (days to weeks), but

functional recovery is expected to take longer. ClassIII devices are intended for extended use (months toyears). There are three main subcategories of ex-tended use; as a therapeutic bridge to recovery (BTR)or as a means to provide a chronic boost to nativefunction and, therefore, provide a better exerciseresponse and, hence, improved quality of life (QOL).The bridge to transplant (BTT) category has beenwhere most of the current first generation deviceshave been tried, tested and evolved as the transplantwaiting lists around the world grow longer andaverage waiting times increase from a few weeks tonow nearly nine months. The final category hasbeen variously described as a destination, long-termalternative to transplantation, permanent and defi-nitive (DT) MCS therapy.7 This application is aimedat patients who are thought to have no prospect ofeither transplantation or of native ventricular recov-ery and who will be reliant on a device (notnecessarily the same device) for the rest of theirlives. Other potential candidates are those who,while fulfilling the transplant criteria, are likely tohave poor post-transplant outcomes or those whoare likely to be difficult to match because of bodyhabitus, blood group or antibody status.8 Class IIIbincludes all devices that do not have direct bloodcontact and is further subdivided into active andpassive devices.

Figure 1 This �gure illustrates one scheme for the classi�cation of MCS devices, based on the intended application. Class I devices areintended for hours to days, Class II for weeks to months and Class III for months to years. Class III devices are further divided into thosethat have a direct blood interface (IIIa) and those that do not (IIIb). Class IIIb devices are further divided into active and passive devices.

Mechanical circulatory supportDR Wheeldon

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Class I devices

These pump systems include intra-aortic balloonpumps, catheter-mounted pumps, external pumpsand the pump/gas exchanger systems comprisingextracorporeal life support systems (ECLS). Thecatheter mounted pumps come in two genericvarieties in which the pumping mechanism iseither mounted within the implanted section ofthe catheter or mounted externally, connected to acoaxial or other specialized catheter system.

Impella CardioSystems AG (Aachen, Germany) ismarketing two devices (Figure 2); the left-sidedpump (Recover100) is a 9 Fg catheter-mounted 6.4mm axial pump that can be introduced, via thefemoral artery, into the left ventricular cavity. Bloodis pumped from the left ventricle into the descend-ing aorta at flows up to 5.0 L/min. The rightventricular assist device (RVAD; Recover600) com-prises the same axial pump mounted in a cagedesigned to be implanted into the right atrium. Apolytetrafluoroethylene (PTFE) 8-mm graft connectsthe output to the pulmonary artery and the pumpscan deliver up to 6.0 L/min. Both pumps aredesigned for up to seven days use.

A-Med Systems (Sacramento, CA, USA) markettwo pump-catheter systems that employ a smallexternally mounted centrifugal pump connected tocoaxial catheter systems. The left ventricular system

(pLVAD) is inserted percutaneously over a guide-wire in the femoral artery into the left ventricle andis able to aspirate blood into the aorta at flows up to4.0 L/min. Distal limb perfusion is accomplishedwith a 20 Fg shunt catheter. The right ventricularsystem is inserted via the internal jugular vein andplaced so that the take-up ports are in the rightatrium and the distal delivery port in the mainpulmonary artery. Blood is pumped at up to 4 L/minand both systems are intended for use up to threedays.

A number of manufacturers market centrifugalpumps that are mainly used for cardiopulmonarybypass (CPB) applications, including Biomedicus,Terumo, Sarns, Bard, Jostra and Nikkiso.

The TandemHeart Pump (Cardiodynamics, Pitts-burgh, PA, USA) is a small centrifugal pump con-nected to an uptake cannula introduced via thefemoral vein trans-septally into the left atrium witha return into the femoral artery.

The DeltaStream Pump (Medos AG, Aachen,Germany) is a diagonal flow pump that is beingdeveloped for a number of applications, rangingfrom CPB to paracorporeal MCS. The pump has anoption for pulsatile operation. Cancion CardiacRecovery System (Orqis Medical Corporation, LakeForest, CA, USA) is a magnetically levitated cen-trifugal pump with inflow from the left femoralartery and outflow through the right femoral artery

Figure 2 Impella market two Class I integrated microaxial pump systems designed for short-term support. The left sided Recover100 isintroduced by way of the femoral artery and placed so that blood is aspirated out of the left ventricle into the aorta. The Recover600 isused for temporary support of the failing right ventricle. Anticoaglation is provided by a local purge system and both pumps are approvedfor use up to seven days. (Courtesy of Impella Cardiotechnik AG, Aachen, Germany.)


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into the descending aorta. It is used to providetemporary unloading of the left ventricle and circu-latory boost for patients suffering from acute decom-pensated heart failure. Table 1 summarizes the majorcharacteristics of this group of devices.

Class II devices

These pumps usually comprise pump systems thatare mounted in the paracorporeal position; thepumps are attached to the outside of the body andconnected to the circulation via large percutaneouscannulae. The pumps may be of a rotary or sac/diaphragm design. Patients are usually able to bemobilized, supported by relatively large consoles.Some systems now have a portable driver option,which may even allow discharge home. Thesesystems are characterized by having more versatilitythan other classes of pumps, in that a variety ofcannulation options (Figure 3) are available andboth uni- and biventricular support are possible fora wide range of patient sizes. The pneumaticallyactivated pumps use alternate negative and positivepressure to fill and eject blood from sac-lined, rigidpump housings. Inflow and outflow valves areeither of a standard mechanical design or trileafletpolymeric construction. Control is usually semi-automatic and triggered in a fill-to-empty mode.Anticoagulation is required. Some designs have a

selection of pump and cannula sizes, making pae-diatric support an option. Disadvantages for chronicuse include the use of pneumatic power (size ofdrivers), large percutaneous drivelines and the useof relatively restrictive inflow and outflow cannulae.

The Abiomed BVS 5000 (Abiomed Inc., Danvers,MA, USA) is an extracorporeal, dual chamber,pneumatically powered pulsatile pump. Blood isdrained into the upper 100 mL atrial chamber undergravity. The lower ventricle is ejected according tothe filling conditions, using a closed circuit auto-matic control console. The resistances of the longextracorporeal lines are offset, to some extent, bythis arrangement, which allows continuous flowfrom the heart. The system can provide both uni-or biventricular support.

The Berlin Heart (Mediport, Berlin, Germany) is afamily of pneumatically actuated pulsatile ventri-cles and cannulae. There are five sizes of ventricles,ranging from 12 to 80 mL stroke volumes, allowing alarge size range of patients, from neonates to adults,to be supported. A choice of valve types is available:mechanical disk or trileaflet polymeric. The ventri-cles are heparin-bonded polyurethane. A portabledriver (EXCOR) is available.

The Medos VAD (Medos, Aachen, Germany) issimilar to the Berlin Heart, but uses different cannulaeand does not yet have a portable driver option.

The Thoratec VAD (Thoratec, Pleasanton, CA,USA) comprises a single size (65 mL stroke volume)

Table 1 Class I devices are used for short-term (hours to days) applications; some have specialized catheter/cannulae systems but mostcan be connected to whatever access the surgeon requires

Device Power Pump type Support Inflow Patient size Ambulation

A-MED pLVAD Electricalcable drive

Centrifugal LVAD LV Paed/adult No

A-MED pRVAD Electricalcable drive

Centrifugal RVAD RA/RV Paed/adult No

Impella Recover100 Electricalpump/motor

Axial LVAD LV Paed/adult No

Impella Recover600 Electricalpump/motor

Axial RVAD RA/RV Paed/adult No

Biopump Electrical Centrifugal BiVAD Atrial Paed/adult NoCapiox PumpSarns DelphinBard IsoflowJostra RotaflowNikkiso

Cardiodynamics Tandem Electrical Centrifugal LVAD Transeptal left atrium Adult No

MEDOS Deltastream Electricalpump/motor

Diagonal BiVAD Atrial Paed/adult No

Orqis Medical Cancion Electricalcable drive

Centrifugal LVAD Femoral arteries,descending aorta

Adult No


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ventricle and a range of cannulae to facilitate anumber of cannulation options (Figure 4). Despite asingle ventricle size, patients as small as 17 kg havebeen supported. An implantable version of theventricle (IVAD) is undergoing clinical trials. Aportable driver option is available.

Table 2 summarizes the major characteristics ofthis group of devices.

Class III devices

There are two broad divisions in this group ofdevices, all of which are designed for extendedsupport times; those that have direct blood contact(IIIa) and those which do not (IIIb). The IIIa systemsare either fully or partially implanted and most areelectrically powered, allowing for maximum patientmobility and autonomy (Table 3).

In the BTR/QOL application, sac/diaphragmpumps can be used in combination with portabledrivers, but if chronic support is required, this is notan optimal solution. For BTT applications, the

paracorporeal pneumatically operated pumps, theimplanted electrical sac pumps and the implantedrotary pumps all offer potential solutions. However,for the DT application it is imperative to have animplantable system.

Electrical sac pumpsThe wearable Novacor (World Heart Corporation,Ottawa, Canada) and the HeartMate XVE (ThoratecCorporation, Pleasanton, CA, USA) are the onlycommercially approved and currently availablelong-term systems, although three rotary pumps(MicroMed DeBakey, Jarvik 2000 and HeartMateII), several other rotary designs, one fully implan-table LVAS and one TAH are also currently under-going trials for this application.

The Novacor system was originally designed as atotally implantable system, but has only evolved asfar as the current wearable system (Figure 4). Thepump-drive unit is implanted in a pocket createdbelow the diaphragm and unloads the left ventriclevia an apical cannula, returning blood to theascending aorta. A percutaneous driveline, contain-

Figure 3 Class II devices are intended for medium-term support and have the advantage of maximum versatility with respect to patientsize and cannulation options. Option A shows an LVAD application with input from the left atrial appendage and return to the ascendingaorta. Option B shows a biventricular application in which the RVAD input is from the right atrium with returns to the main pulmonaryartery. The LVAD input is from the LV apex with a return to the ascending aorta. Option C is also a biventricular application but the leftinput is from the roof of the left atrium (intra atrial groove) in this case. (Courtesy of Thoratec Corp., Pleasanton, CA, USA.)


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ing power and control leads, is tunnelled subcuta-neously to exit near the right iliac crest. The pumpincorporates a dual pusher plate, sac-type bloodpump with a 70-mL stroke volume and a smoothpolyurethane blood contact surface. Modular por-cine-valved conduits provide directional flow con-trol. Actuation of the pusher plates is accomplishedby way of a decoupled solenoid actuator and twotitanium beam springs connected to the pusherplates. This results in a simple mechanism thatdevelops no reactionary forces and results in highdurability and reliability.9 The wearable controllerprovides for a number of control options, which canbe fine-tuned to the requirements of the recipient,and allows complete autonomous operation. Porta-ble power packs provide for up to seven hours oftether-free operation.

The HeartMate10 is similar to the Novacor, butdiffers in that pump actuation is achieved by way of

a rotary motor driving a cam-operated single pusherplate, delivering a stroke volume of 80 mL. Theother major difference is in the blood contact sur-face, which is textured to encourage the develop-ment of an adherent pseudoneointimal lining. Boththese systems allow recipients to return home and tolead near normal lives in the community.

The LionHeart11 (Arrow International, Reading,PA, USA) is the first fully implantable LVAD. Theblood pump is based on the Pierce-Donachy designwith the addition of a mechanical actuator, compris-ing an electric motor driving a roller/screw mechan-ism, controlled by Hall effect sensors. The pumpfills passively and the maximum output is 8 L/minwith a dynamic stroke volume of 64 mL. Theimplanted components include the pump driveunit, controller/power pack, a transcutaneous en-ergy transfer system (TETS) and a volume compen-sator with refill port. The TETS system is placed in

Figure 4 The Novacor electrical implanted LVAS was designed, from the outset, as a permanent solution to end-stage heart disease. Thepump is implanted below the diaphragm and drains the left ventricle by way of a valved apical conduit. Blood is returned to theascending aorta. Power and control lines are connected via a vented percutaneous driveline. The patient wears an electronic controllerand two power packs, which allow up to seven hours of tether-free operation. (Courtesy of World Heart, Ottawa, Canada.)

Table 2 Class II devices are used for intermediate support times (weeks to months); most are used in the paracorporeal position, attachedto the outside of the torso

Device Power Pump type Support Inflow Patient size Ambulation

Abiomed BVS 5000 Pneumatic Sac BiVAD Atrial Paed/adult NoMediport Berlin Heart Pneumatic Sac BiVAD Atrial/ventricle Infant/adult YesMEDOS VAD Pneumatic Sac BiVAD Atrial/ventricle Infant/adult YesThoratec VAD Pneumatic Sac BiVAD Atrial/ventricle Adult Yes


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the right chest wall and the volume compensator inthe left chest wall (Figure 5). The internal powerpack provides approximately 30 minutes completetether-free operation, allowing MCS patients thechance to swim for the first time.

Rotary pumpsRotary pumps come in three generic forms, axial,diagonal and centrifugal. Hydraulic efficiency isbest in the centrifugal designs, but a smaller sizecan be accomplished with the axial designs for thesame outputs. Diagonal designs give mixed benefitsand disadvantages. Blood pump design is, therefore,a matter of compromise to meet the application.12

Two other features of rotary pumps are important inMCS applications; bearings and pump control. Firstgeneration rotary pumps all have various forms ofmechanical journal bearings and this producesproblems of local heating, stasis around the bearingand limited durability. Second generation pumpsemploy various forms of magnetic or hydraulicbearings, or a combination of both. Control issuesare more difficult to solve since the intrinsic func-tion of rotary pumps is to be flow boosters. Thismeans that they have relatively flat pressure/volumecurves and are relatively afterload sensitive. Themajor impact of these characteristics is the difficultyin avoiding high negative pressures on the inputside and having a system that responds in aphysiological way to changes in flow demand. Otherareas of concern revolve around the physiologicalconsequences of chronic nonpulsatile flow and thesafety concerns regarding retrograde shunts in theevent of a pump stoppage, since these devices haveno valves. However, the advantages are small size,simplicity and relatively low cost.

The DeBakey VAD13 (MicroMed Technology Inc.,Houston, TX, USA) is a 95 g, 30 mm diameter axialpump and the first to be used clinically. The pumpcan produce a flow of 6 L/min against a 100 torrpressure at 10 000 rpm. Pump flow is monitored

using an ultrasonic flow probe on the outflow graft.Control is by physician-set pump speed.

The Jarvik 200014 (Jarvik Heart Inc, New York,USA) is the smallest of the current axial pumps witha 25 mm diameter and a weight of 90 g. Designed forintraventricular placement through an apical attach-ment cuff, the pump is implanted through a leftthoracotomy as an apioaortic pumped shunt to thedescending aorta (Figure 6). The pump is designedto be operated as a true assist system, and the aim isto set the pump output so as to allow the aortic valveto continue to open with each heartbeat. Control isby the recipient who is allowed to change pumpspeed within a window determined by the physi-cian. Several patients have now been supported formore than two years and one patient, implanted forDT therapy, is doing well after more than three yearsof support.

The HeartMate II15 (Thoratec Corporation, Plea-santon, CA, USA) is similar to the other two axialpumps, but larger; 176 g and 40 mm in diameter(Figure 6). This pump can deliver flows of up to 10L/min against a pressure of 120 torr at 13 000 rpm.Pump speed is controlled by the physician.

INCOR16 (Mediport, Berlin, Germany) is a magne-tically suspended axial pump, 200 g in weight and13 cm in diameter. The pump can deliver flows ofup to 7 L/min against a pressure of 100 torr at 10 000rpm. Pump speed is controlled by the physician.

SynCardia TAH17 (SynCardia, Tuscon, AZ, USA)has had a variety of names over the years: Jarvik 7,CardioWest, and now SynCardia. This is a biven-tricular replacement device (BVRD) even though themore common nomenclature is TAH. The 70 mLpneumatically actuated ventricles are attached viaDacron cuffs to the atria at the level of the atrial-ventricular valves. Power and control are via a largeconsole by way of percutaneous drivelines. TheBVRD approach would seem to be able to conferthe advantages of high flow with low preloadsimmediately after implantation, which may benefitearly secondary organ recovery. The BVRD is also

Table 3 Class III devices are for extended applications (months to years)

Device Power Pump type Valves Implatable Support Patient size Console Durability

Thoratec HeartMate Elec Sac Porcine Partial LVAD Í/45 kg Wearable B/2 yearsWorldHeart Novacor Elec Sac Porcine Partial LVAD Í/45 kg Wearable Í/4 yearsThoratec IVAD Pneu Sac Mech Disk Partial BiVAD Í/40 kg Portable ?Arrow LionHeart Elec sac Mech Disk Fully LVAD Í/70 kg Wearable 2 ¡/3 yearsMicroMed DeBakey Elec Axial None Partial LVAD Í/35 kg Wearable ?Jarvik 2000 Elec Axial None Partial LVAD Í/35 kg Wearable ?Berlin Heart INCOR Elec Axial None Partial LVAD Í/35 kg Wearable ?SynCardia Pneu Sac Mech Disk Partial BVRD Í/70 kg Hospital 2 ¡/3 yearsAbioCor Elec Sac Polymeric Fully BVRD Í/75 kg Wearable B/2 years

IIIa devices all have direct blood contact and are used for three major applications: for recovery or for boosted output, as a BTT or fordefinitive (permanent) support. IIIb devices all have no direct blood contact and are not covered in this table.


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Figure 5 The Arrow LionHeart is the �rst fully implantable pulsatile LVAD. This provides the advantages of removing the need for apercutaneous driveline, greatly reducing the infection risk and allowing the recipient the possibility of being completely untethered, forperiods of up to 40 minutes. However, the design also requires the implantation of a large amount of equipment, making it only suitablefor larger patients. TETS¾/transcutaneous energy transfer system. (Courtesy of Arrow International, Reading, PA, USA.)

Figure 6 The Jarvik 2000 Flowmaker is the smallest of the implantable axial pumps. This design requires no in�ow cannula as it isplaced within the ventricular cavity. Arterial return can be to the descending aorta, as illustrated, or to the ascending aorta. Two drivelineoptions are available; a transcutaneous small (4.3 mm) �exible cable or a connection to a behind-the-ear pedestal, based on implantablecochlea technology. (Courtesy Jarvik Heart Inc., New York, USA.) The Berlin Heart INCOR is a second generation axial pump whichemploys a magnetically suspended impeller, so making for an enhanced potential durability. (Courtesy Mediport, Berlin, Germany.)


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the device of choice in patients with morphologicalmyocardial damage, intractable dysrhythmias orfixed high pulmonary vascular resistance.

AbioCor TAH18 (Abiomed Inc., Danvers, MA,USA) is the first electrically powered BVRD that isfully implantable with an associated controller/power pack, volume compensator and TETS (Figure7). The ventricles are actuated by a compact uni-directional centrifugal hydraulic pump, mountedbetween the two ventricles, capable of producingblood flows in excess of 10 L/min. A cylindricalrotary valve alternately directs the hydraulic fluid tothe right and left ventricle. Balance between left andright blood flow is achieved using a hydraulicbalancing chamber attached to the left inflow portand to the right pumping chamber, by way of ashunt. This allows regulation of the right outputaccording to left input pressure. Unidirectionalblood flow is achieved using four trileaflet poly-meric valves.

Future perspectives

A greater variety of simple, inexpensive Class Idevices means that acute cardiogenic shock cannow be more easily and inexpensively treated,

where the overall survival has been less than25%.19 Postcardiotomy failure remains at approxi-mately 3%, so that a significant number of patientscould benefit from effective therapy. Current Class IIdevices are likely to be superceded by the smallrotary pumps when these have been optimized,since they offer the prospect of easier implantation,less critical management and lower cost. In Class IIIadevices, the field is moving towards fully implan-table devices, which will give a reduced incidenceof infection complications and an overall greaterquality of life. First generation devices with percu-taneous drivelines have infection rates in the 40%range, the small rotary pumps with small flexibledrivelines have an incidence of less than 10% andthe fully implantable systems a rate of less than 5%.However, most current devices, with the exceptionof Novacor, are not demonstrating the multiyeardurability that will be required of a permanentdevice. This will be overcome by better engineeringand by new designs, such as the HeartSaver VAD(World Heart, Ottawa, Canada), where the existingelectromagnetic technology, used so successfully inthe Novacor, is being adapted to power a newcompact design requiring no contact surfaces andno volume compensator (Figure 8). This devicecould be produced at less than 50% of the cost of

Figure 7 The AbioCor Total Arti�cial Heart is the �rst fully implantable BVRD. The heart is placed orthotopically and the TETS,controller and rechargeable battery pack are implanted within the abdominal space. This device is under clinical investigation in the USand Europe. (Courtesy Abiomed Inc., Danvers, MA, USA.)


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the current device. The current applications for BTTwill probably continue for patients requiring ino-tropic support, as recent literature suggests thatpostbridge outcomes are superior to inotropebridged patients,20 and for the high risk transplantcandidates. The application of therapeutic BTR is afascinating one and evidence is steadily growingthat this approach should work for significantnumbers of patients.21

The development of the Class IIIb devices is alsoof interest, since these nonblood-contacting devicessimplify many of the management challenges of theother systems and can be used adjunctively at thetime of conventional surgery.22

Costs

There has been much concern over how society willpay for the widespread use of DT MCS devices,given that the overall demand is variously estimatedat between 30 000 and 200 000 patients per year inthe US alone. However, cost data from REMATCH23

showed that the median overall cost was some$250 000 (including $65 000 for the device), whichcompares with the current US cost of cardiactransplantation ($205 000), liver transplantation

($250 000) and medical care for NYHA III¡/IV pa-tients ($500 000).24 In REMATCH, it was also clearthat the high rates of infection (40%)25 and devicefailures (35% at two years)6 were responsible for asignificant proportion of the costs. The smallerdrivelines in the rotary devices and the lack ofdrivelines in the fully implantable devices havedemonstrated that the potential to reduce thiscomplication down to less than 5% is achievable.The durability and reliability of the first generationNovacor device (1.4% pump exchanges, for anyreason, and 26 patients supported for more thantwo years with the longest ongoing patient sup-ported for more than five years) also demonstratesthat designing in these characteristics is entirelyfeasible. The perception that MCS therapy is extra-ordinarily expensive is also not borne out bypublished data, either in absolute terms or in termsof cost benefit.26

Conclusions

MCS therapy stands on the brink of a new era. Anumber of simpler and less expensive options areavailable for acute applications and much has beenlearned about patient selection and management

Figure 8 The WorldHeart HeartSaver VAD is a second generation fully implantable, pulsatile LVAS design, currently undergoingdevelopment trials. The use of an electromagneticallydriven pusher plate results in no contact surfaces and therefore little wear. Controlis extremely accurate and simple. A dual chamber design removes the need for a volume compensator. The system has backwardcompatibility with the current Novacor LVAS. (Courtesy World Heart, Ottawa, Canada.)


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from the first generation devices. With continuedimprovements in design and function, MCS systemswill soon provide a practical off-the-shelf, sched-uled, permanent therapeutic alternative for the end-stage heart failure patient with the promise of returnto an essentially normal life.

Will extended MCS continue to be a luxury itemon the health care budget or will it become acommodity? The evidence points to the latter, butthe appropriate strategy for each patient group willneed to be worked out from an evidence base.

Certainly, the current practice of multiple sequentialexpensive interventions on the same patient willneed to be rationalized. What about the health careprofessionals working in the changing world ofcardiac repair and replacement? The author believesthat MCS therapy offers a new dimension to heartreplacement therapy, which perfusionists shouldembrace with all the enthusiasm and passionbrought to bear over the last 50 years and whichhas made cardiac surgery one of the most successfulbranches of modern medicine.

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