United States Patent 15
`Pickard
`
`[54] APPARATUS AND METHOD FOR TESTING
`PROSTHETIC HEART VALVES
`
`[76]
`
`Inventor: Murphy L. Pickard, 3250 Pierce St.,
`Wheatridge, Colo. 80030
`[21] Appl. No.: 830,854
`
`[22] Filed:
`
`Feb. 19, 1986
`
`(S1] Unt. C14ee eceesessssceeseeseesseeeessees G01M 19/00
`[52] US. Ch. oeeesccesecssessessssesssseeesaceas 73/37; 73/168;
`73/865.6
`[58] Field of Search................. 73/37, 168, 812, 865.6
`[56]
`References Cited
`U.S. PATENT DOCUMENTS
`
`5/1983 Swanson ........secessscseseesssseasees 73/37
`4,381,663
`« 73/37
`4,450,710 5/1984 Nettekoven
`
`4,546,642 10/1984 Swanson ........
`. 73/37
`
`4,598,579 7/1986 Cummingset al. ........eccseee 73/37
`
`FOREIGN PATENT DOCUMENTS
`
`6/1975 ULS.S.R. vcccescsccstevessescerconees 73/37
`445432
`9/1979 U.S.S.R.
`..
`73/432 SD
`685294
`728864 4/1980 ULS.S.R. vc ccescsssessescerereens 73/168
`
`OTHER PUBLICATIONS
`
`Pickard, M.L. et al., Computer Managedin Vitro Testing
`- of Ventricular Assist Devices, In Trans. Am. Soc. Artif.
`Intern. Organs, vol. XXV, pp. 192-196, 1979.
`Primary Examiner—Stewart J. Levy
`
`[11] Patent Number:
`
`[45] Date of Patent:
`
`4,682,491
`Jul. 28, 1987
`
`Assistant Examiner—Joseph W. Roskos
`Attorney, Agent, or Firm—Timothy J. Martin
`
`[57]
`
`ABSTRACT
`
`An apparatus and method for testing prosthetic heart
`valves prior to implant in the human body provides a
`test chamber having a flow channel therethrough and a
`passageway which receives a mounting fixture for a
`heart valve. The test chamberis used in a mock circula-
`tory loop with the flow channel beingin the loop. Pref-
`erably, the test chamber has a transverse passageway
`that intersects the flow channel, and the mounting fix-
`ture advances completely through the test chamber
`from an insertion location to a disconnect
`location
`while a dynamic seal
`is maintained. Two such test
`chambers may be used in a mock loop, and the loopis
`configured with an intake chamberfluidly interconnect-
`ing one side of each test chamber, and a restriction
`chamber fluidly interconnecting the other sides of the
`test chambers. The restriction chamberis variable, and
`pressure compensation is provided between eachoftest
`chambers and the restriction chamber. A pumpcycli-
`cally drives a fluid through the loop, and flow meters
`and pressure sensors monitor the test. A data processor
`monitors and processes the flow data and controls the
`pumpto create a desired flow waveform. The test can
`also be visually and optically monitored.
`42 Claims, 8 Drawing Figures
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`PAGE 1 OF 16
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`WATERS TECHNOLOGIES CORPORATION
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`EXHIBIT 1010
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`WATERS TECHNOLOGIES CORPORATION
`EXHIBIT 1010
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`U.S. Patent
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`COMPUTER
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`U.S. Patent
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`4,682,491
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`APPARATUS AND METHOD FOR TESTING
`PROSTHETIC HEART VALVES
`
`BACKGROUNDOF THE INVENTION
`The present
`invention relates to an apparatus and
`methodfortesting prosthetic heart valves under condi-
`tions simulating the circulatory system under which the
`valves are to be used. Accordingly, the present inven-
`tion 1s particularly useful for mimicking the human
`circulatory system so that a heart valve may be placed
`therein, tested and observed for determining the suit-
`ability of the heart valve for actual implantation into the
`body. Thus, the present invention concerns the con-
`struction of a circulatory loop or defining a flow chan-
`nel which loop includes various meansfortesting para-
`metric values of the heart valve as well as including
`novel and non-obvious test chambers which actual
`mount the heart valve for advancementand orientation
`in the flow channel.
`In recent years, the knowledge and skill of surgeons
`has dramatically increased in the cardiovascular field so
`that heart surgery has become somewhat common-
`place. Statistically, one of the more commoncorrective
`surgical procedures in the pulmonary field replaces
`damaged or deteriorated auricle or ventricle valves in
`the human heart. As a result, the medical community
`demands an increased supply of prosthetic valves for
`surgical
`implantation. Accordingly,
`there is a corre-
`sponding need to ensure the reiliability of prosthetic
`valves before actual implantation, especially since the
`operation, while common,is nonetheless delicate and
`stressful on the patient. Accordingly, there is value in
`knowing the suitability and integrity of a prosthetic
`valve prior to the start of such surgery.
`In the past, most techniques for testing heart valves
`have been directed to durability or fatigue testing of a
`single valve to see if the design of the valve suits its
`intended use. Such durability testing apparatus has been
`described in U.S. Pat. No. 4,381,663 issued 3 May 1983,
`andU.S. Pat. No. 4,546,642 issued 15 Oct. 1985, both of
`which were issued to Swanson. However, with in-
`creased demand for heart valves, manufacturers desire
`to test each heart valve for reliability and integrity
`rather than simple durability. The productionlinetest-
`ing of prosthetic heart valves thus requires a machine
`capable ofcreating a proper physiological environment
`and then acquiring parametric data on the performance
`of the valve under test. In such a machine it must be
`possible to quickly andeasily insert valves into the flow
`channel, test the valve and then removethe valve.
`In the past, most circulatory simulating systems have
`includedstationary heart valve supporting structures so
`that use of these devices require aninitial draining of the
`system, the removal of the heart valve support, the
`positioning of the heart valve support in the mounting
`fixture and the reassembly of the flow channel with the
`heart valve in place after which the flow channel is
`charged with fluid. Understandably, with a complex
`flow channel, this procedure is extremely time consum-
`ing andis thus difficult to implement for production line
`testing. Indeed, prior art apparatus of the type just de-
`scribed often requires a period ofup to thirty minutes to
`test a heart valve. Another dangerresides in this tech-
`nique, though,since biological heart valves must always
`be maintained in a moistened condition since the best
`available valves are constructed of organictissue. Due
`to the time involved in draining and recharging the
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`2
`the heart valve
`there exists the danger that
`system,
`might become desiccated. If this occurs during draining
`the system,
`it
`is therefore possible that a valve that
`actually tested good subsequently becomes degenerate
`due to the drying outofthe tissue during the draining of
`the system.
`In order to eliminate the need for draining, disassem-
`bling, reconstructing and recharging the flow channel
`of prior art devices, one prior art test chamber has been
`developed as described in U.S. Pat. No. 4,450,710 issued
`29 May 1984 to Nettekoven.In this device, a test cham-
`ber is provided for insertion into a flow channel with
`the mounting structure for the prosthetic heart valve
`comprising a shuttle into which oneor twoheart valves
`may be mounted. The shuttle means advances and re-
`tracts the heart valve into and out of the fluid flow
`while maintaining a dynamic seal between the shuttle
`carriage and the walls of the test chamber. Whilethis
`patent differs from previous techniques, there still re-
`mains the possibility that a heart valve may become
`desiccated when it is not in position within the flow
`channel.
`Another need resulting from the increased demand
`for prosthetic heart valves is the maintenance ofpro-
`duction line testing of each valve for archival purposes.
`The value of having a permanentrecord of parametric
`test data as well as visual data for each approved valve
`is readily apparent when considering the increased pro-
`pensity for malpractice and productsliability claims. By
`production line testing of each prosthetic valve and the
`maintenance of an archival record thereof, manufactur-
`ers will later be able to demonstrate the integrity of a
`valve implanted in the human body, should such need
`arise. Further, an advantage of the present apparatus
`and methodnot heretofore available is the customizing
`of the testing procedure to correspond to a specific
`individual's circulatory system, should various parame-
`ter of the patient’s pulmonary system be known, such
`that a specific valve can be tested, in vitro, in a manner
`that simulates the circulatory environment of the spe-
`cific patient who will receive the valve. Thus, a valve
`maybe tested under very close operating conditions on
`an individualized basis rather than under generalized
`test procedures.
`
`SUMMARYOF THE INVENTION
`
`It is therefore an object of the present invention to
`provide a new and useful apparatus and method for
`testing heart valves in a simulated circulatory environ-
`ment.
`it is another object of the present invention to pro-
`vide a method and apparatus for maintaining archival
`records of productiontesting of a heart valve, with this
`archival record containing both visual and parametric
`data on the performanceof the valve on the test.
`It is another object of the present invention to pro-
`vide a method and apparatusfor testing of a prosthetic
`heart valve underindividualized test conditions simulat-
`ing a specific human circulatory environment
`into
`which the valve maybe placed.
`It is a still further object of the present invention to
`provide an apparatus and methodforcallibrating flow
`and pressure sensors within a simulated circulatory
`system so that the system may be automatically adjusted
`by computerized techniques which can lead to non-sub-
`jective standardized action ofvalve testing.
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`3
`It is yet another object of the present invention to
`provide a test chamberused in an apparatusfor simulat-
`ing the circulatory environment whereby a prosthetic
`heart valve may always be maintained in substantial
`contact with moisturizing fluid while it
`is advanced
`throughthe circulatory loop’s flow channel and which
`allows a valve in the channel to be rotated so that differ-
`ent parametric values can betested.
`Accordingly,
`the apparatus according to the pre-
`ferred embodimentof the presentinvention is primarily
`formed as a circulatory loop that simulates a circulatory
`system of the human body. This circulatory loop in-
`cludes an intake chamber that receives a saline fluid
`through a fluid inlet under the cyclical action of a
`pump, the stroke of which acts as a heart beat. The
`intake chamberhas first and second orifices that are in
`fluid communication, respectively, with first and sec-
`ond test chambers. Each test chamber defines a test
`portion of the flow channel of the simulated circulatory
`system and each includes a mounting fixture and is
`received therein which fixtures has a cavity adapted to
`secure a prosthetic heart valve. Each mounting fixture
`is movable in the test chamberto selectively move the
`mounted heart valve from a passive position out of the
`flow channeland into the test position interposed in the
`flow channel while maintaining a dynamic seal through
`the test chamber. A restriction chamber defines a re-
`strictive portion of the flow channel and hasa pair of
`oppositely positioned restriction chamberflow orifices
`and means, such as a variable cross-section valve, inter-
`positioned in the flow channelfor selectively varying
`the resistance of the flow of the fluid through the re-
`striction chamber. According to the above, the pump
`and test chambers operate as one-half of the human
`heart with the restriction chamber mimicking the capil-
`lary system.
`Each test chamberis in fluid communication with a
`respective restriction chamberfloworifice by a conduit
`means that conducts fluid between restriction chamber
`flow orifice and the test chamberin a direction depend-
`ing on the positioning of a prosthetic valve. Since the
`pump and test chamber may pump morefluid into this
`circulatory loop on a given pumpstroke than the vol-
`ume of fluid which may be passed bythe restriction
`chamber, fluid pressure compensation chambers are
`provided as part of the conduit means. A fluid pressure
`compensation chamberis associated with each conduit
`between the respective chamber and the restriction
`chamberand each includes a fluid compensation reser-
`voir having oneresilient side wall defined by a dia-
`phram that expandsto receive excess fluid. Excess fluid
`pressure is compensated by meansofair pressure on an
`opposite side of the diaphram sothat the fluid compen-
`sation chambers act as the veins and arteries of the
`human body. Suitable flow measuring elements are
`provided to measure the velocity and volumeoffluid
`flow through the conduits.
`In the preferred embodimentof the present invention,
`a novel
`test chamber is employed wherein the test
`chambers each has a flow channel region extending
`between a first test chamberorifice and a second test
`chamberorifice, one of which acts as an intake for the
`test chamber and the other of which as an outlet for
`fluid in the test chamber. The test chamber is adapted
`for insertion into the flow channel and has a passageway
`extending transversely therethrough which intersects
`the flow channel region. In the valve mounting fixture
`is sized for close-fitting, mated engagement in the pas-
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`sagewayso that it may slide through the passageway in
`a sealed relationship with respect to the longitudinal
`axis of the passageway. The mountingfixture thus may
`be inserted on an entry opening of the passageway on
`one side of the test chamberand is slidably advanced
`completely through the passageway and is removed
`from the passagewayin an exit opening on the opposite
`side of the test chamber. The mounting chamber in-
`cludes a cavity extending therethrough which may be
`inserted into the flow channel and includes structure for
`mounting and supporting a heart valve to be tested.
`Preferably, the passageway is circular in cross-section
`with the mounting fixture being formed as a cylinder
`that may be selectively rotated to change the operative
`position of the prosthetic heart valve. A fluid reservoir
`is located on the entry side of the passageway so that a
`mounting fixture may be immersedin fluid contained in
`the reservoir thereby precharging the cavities around
`the heart valve prior to insertion into the passageway so
`that undesired air pockets are not introduced into the
`flow channel when the heart valve is moved into posi-
`tion. Flow shaping members and securring elements are
`provided within the cavity of the mounting element to
`secure the heart valve therein.
`In order to monitor the flow channel, various sensors
`are providedin addition to the flow meter noted above.
`In the preferred embodiment, a pair of pressure sensors
`are provided for each test chamber so that a pressure
`sensor is located on each side of the heart valve. These
`pressure sensors electronically monitor the pressure of
`the fluid in the flow channel to provide archivaldata. In
`addition, these signals may used to automatically con-
`trol the balancing air pressure for the diaphram of the
`pressure compensation chambers. Automatic monitors
`mayalso be used within the test chamber to monitor the
`position of the mounting element so that proper regis-
`tration of the heart valve within the flow channel may
`be automatically attained. Similarly, a step motor may
`be used to drive the position of the restriction means in
`the restriction chamber, and an electronic monitor may
`output the position of the restriction element for auto-
`matic processing. To this end, a computer may beinter-
`faced with the various sensors and pressure regulating
`devices to automatically control the simulated circuit
`loop described above.
`In order to record archival data, the flow channel on
`either side of the test chamberis preferably linear and is
`provided at opposite ends with view ports having lenses
`to permit visual observation of the opening and closing
`of the heart valve prothesis in actual operating condi-
`tions. Video cameras may be employed so that the vi-
`sual observation may take place on visual monitors with
`this visual data being recorded on tape for archival
`purposes. To this end, also, the computer may overlay
`textural parametric data onto the video tape with this
`tape being indexed with a serial number corresponding
`to the prosthetic vaive being tested.
`Additional advantages of the present apparatus are
`obtained by including a waveform generator and a
`servo amplifier driving a lead screw pump so that the
`stroke length, duty cycle and other parameters of the
`cycle may be controllably varied. To this end, individu-
`alized parametric data according to a specific individu-
`al’s circulatory system may be fed into the computer
`and waveform generator to generate the precise pump-
`ing action ofan individual’s heart. The waveform gen-
`erator, acting through the servo amp, can cause the
`pump to precisely mimick this pumping action. The
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`computer may then implement a feedback loop respon-
`applied bythefluid restriction element and controlling
`sive to the data measured from the various pressure and
`the waveform of the pump. The data process meansis
`flow sensors so that the circulatory loop fairly accu-
`loaded with data corresponding to the desired wave-
`rately simulates an individual’s circulatory environment
`form ofthe fluid flow through the channel and aninitial
`into which a selected prosthetic valve will be placed.
`pressure applied by the fluid restriction elementis set to
`To this end also, the preferred mounting elements for
`an initial pressure. The pumpis then activated through
`the vaives may be reversed in position and the paramet-
`the desired waveform according to its duty cycle. The
`Tic values changed, so that each valve performancefor
`flow rate offluid through the flow channel adjacent the
`bothinflow and outflow cardiac portions may be evalu-
`heart valve is measured to generate flow rate data, and
`ated.
`the pressure of the fluid upstream and downstream of
`Based on the foregoing, it should be appreciated that
`the heart valve is measured to generate channel pres-
`the broad form of the method according to the pre-
`sure data. The flow rate data and channelpressure data
`ferred embodiment includes the steps of providing at
`are input into the data processing means and used to
`least one test chamberin the flow channelin a simulated
`calculate the fluid flow and pressure waveform of the
`circulatory system whereby fluid may flow through the
`fluid through the flow channel. This actual fluid flow
`test chamber with the test chamber including a first
`and pressure waveform is then compared with the de-
`transport passageway completely therethrough which
`intersects the flow channel, and providingafirst mount-
`sired waveform to determine waveform error and the
`ing fixture having a first cavity sized to mounta heart
`resistance ofthe fluid restriction elementis adjusted by
`valve for orientation in the flow channel. The method
`the data processing meansto proprotionately reducethe
`then includes the step of mounting a heart valve in the
`waveform error by interrative processing of the flow
`cavity and advancing the mounting fixture through the
`rate and the channel pressure data to tune the fluid flow
`passageway from a passive position when the heart
`and pressure waveform on successive cycles of the
`valve is out of the flow channel through an entryway
`pumpuntil the fluid flow and pressure waveform mod-
`into the first passageway so that it may advancedinto a
`els the desired waveform within predefined errorrange.
`test position oriented in the flow channel after which it
`This method may include the step of adjusting the pres-
`may be further advanced to a disconnect location for
`sure applied by the pressure meansaspartofthe step of
`removal of the mounting fixture from the passageway.
`reducing the waveform error.
`The method includes the step of maintaining a dynamic
`Video recording apparatus may be used in this pre-
`seal between the test chamber and the mounting cham-
`ferred alternate method wherein the method includes
`ber during the slidable movementof the mounting way
`the step of monitoring the visual operation ofthe heart
`through the passageway.
`valve and recording the visual data corresponding to
`The preferred methodalso includes the steps of mea-
`the opening andclosing of the valve in order to provide
`suring the pressureoffluid in the flow channeloneither
`an archival record, and the method mayinclude the step
`side of the heart valve when the heartvalveis in the test
`of overlaying recorded visual data with the flow rate
`position and cyclically driving fluid through the flow
`data and the channel pressure data.
`channel and then measuring the flow rate offluid as the
`heart valve opensand closes. The position of the mount-
`These and other objects of the present invention will
`ing fixture in the first passageway may be automatically
`become morereadily appreciated and understood from
`monitored to indicate when the mountingfixture is in
`a consideration of the following detailed description of
`the passive, test and disconnect positions.
`the preferred embodiment when taken together with
`Preferrably, a pair of test chambers are provided and
`the accompanying drawings, in which:
`a second mountingfixture slides through a passageway
`in the second test chamberandis provided with a cavity
`that mounts a second heart valve. A plurality of test
`fixtures may be employed with each of the test cham-
`bers so that a stacked array of mountingfixtures may be
`used so that successive onesof the mountingfixtures are
`progressively advanced through its associated passage-
`way. The preferred method further includesthe step of
`maintaining each heart valve in a fluid environmentasit
`is passed from the passive to the disconnectposition.
`In the preferred form of the present invention, a com-
`puter interface and control system is provided so that
`the preferred method is directed toward a simulated
`circulatory system that has a flow channel containing a
`test fluid and which includes a selectably adjustable
`fluid restriction element in the flow channel, a compen-
`sation chamber which provides both an excess fluid
`compensation reservoir and which may be adjusted to
`selectively apply pressure to the fluid in the flow chan-
`nel, and that includes a pulsatile pump havinga select-
`able adjusted period, applitude and duty cycle for driv-
`ing the fluid in a selected waveform through the flow
`channel. Accordingly, another embodimentof the pre-
`ferred method includes the step of providing data pro-
`cessing means for automatically monitoring fluid condi-
`tions in the flow channel and adjusting the pressure
`
`FIG. 1 is a side view in elevation of the apparatus
`accordingto the preferred form of the present invention
`including a circulatory loop and support equipment
`therefor;
`FIG, 2 is a diagramatic view in block form of the
`preferred form of the present invention;
`FIG.3 is a top view and cross-section ofa circulatory
`loop according to the preferred embodiment of the
`present invention as is shownin FIG.1;
`FIG. 4 is a cross-sectional view of the test chamber
`and mounting element according to the preferred em-
`bodimentofthe present invention for advancing a pros-
`thetic heart valve into the flow channel;
`FIG.5 is an exploded view of the mounting element
`whichholdsthe prosthetic heart valve according to the
`preferred embodiment of the present invention;
`FIG.6 is a view in partial cross-section showing the
`restriction chamberusedin the circulatory loop of FIG.
`3;
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`BRIEF DESCRIPTION OF THE DRAWINGS
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`FIG. 7 is a cross-sectional view of a flow sensor
`chamberusedin the circulatory loop of FIG.3; and
`FIG. 8 is a view in cross-section of a compliance
`chamberused in the circulatory loop of FIG. 3.
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`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
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`4,682,491
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`The present invention is directed to an apparatus and
`method adapted for testing prosthetic heart valves.
`Preferredly, the present method accomplishes testing
`prosthetic valves in a mannersimulating the circulatory
`system into which the heart valve is to be used. Thus,
`the present
`invention seeks to provide a mechanical
`analog for the human circulatory system, including the
`heart, arteries, veins and capillaries so that a prosthetic
`valve may be tested and observed prior to use in the
`human body.
`Certain broad features of the invention are best
`shown by considering FIGS. 1 and 2 of the drawings
`together. FIG. 1 shows the mechanical features of the
`invention, while FIG. 2 shows a block diagram of the
`heart testing apparatus according to the embodiment of
`the present invention and which apparatus is used to
`implement the described methodofvalvetesting. Asis
`shownin FIG. 1, a table 12 supports testing apparatus
`10 is on structural uprights 14 fastened to platform 16
`which, in turn, may be positioned on a suitable support
`surface. Apparatus 10 includes a circulatory loop 18
`positioned on table 12. Circulatory loop 18 as will be
`described below, forms a flow path for a circulating
`fluid, such as saline solution, so that loop 18 mechani-
`cally models essential features of the humancirculatory
`system.
`In order to provide fluid for the system, fluid pump
`- 20 pumpsfluid from reservoir 22 through conduits 24
`and 26. Fluid is presented to circulatory loop 18
`through conduits 26 and 30 in fluid communication with
`- port 28 of loop 18. A valve 32 is provided to open and
`shut conduit 30. A bleed vaive 34,in the form of a quick
`- release coupling, opens and shuts vent port 36 to allow
`°' air to be bled from circulatory loop 18 asit is filled with
`fluid. Conduit 26 extends upwardly to also allow the
`filling offirst and second test chamberreservoirs 38 and
`~
`* 40 with fluid flow into the test chambers reservoirs
`“< being controlled by valves 42 and 44.
`Fluid is driven throughcirculatory loop 18 in a pulsa-
`tile or cyclical manner by meansof a piston pump 46. A
`monitor 48 sensesthe location of the piston in pump 46
`for purposesof controlling the volumetric displacement
`of pump 46. To this end, piston reservoir 50 is filled
`with fluid which communicates with circulatory loop
`18 through an intake opening 52 extending between
`reservoir 50 and circulatory loop 18. Piston pump 46 is
`mounted to a support 14 by brackets 54 and is powered
`by a power source through electrical cord 56. The
`pumpreservoir 50 is also secured to upright 14 by
`means of a strap bracket 58.
`Pressurized air is provided for pressure compensation
`in loop 18, as discussed more thoroughly below. To
`provide this air, air compressor 60 is connected to a
`power source through power cord 62 provides air
`through conduits 64 and 66 that are controlled by regu-
`lator guages 68 and 70, respectively.
`In order to monitor the operation of the prosthetic
`heart valves, various lens ports having suitable optical
`lenses, such as lenses 72 and 74, are provided for direct
`visual observation during the testing. In addition, re-
`movable mirrors 76 and 78 reflect light through open-
`ings 80 and 82 in table 12 so that video cameras, such as
`video cameras 84 and 88, maytransmit a visual signal to
`an associated video monitor, for example, video moni-
`tor 98 shown in FIG. 1. This video signal can also be
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`recorded, by a video recorder 92 and maintained as a
`permanent, archival
`record of the valve operation.
`Computer 102 is provided to control the system, allow
`any suitable data processing means is within the scope
`of this invention, and various electronic circuits are
`provided with power by power supply 104. Waveform
`generator 106 is used to define the power stroke of
`pump 46, described in greater detail below. Each of
`computer 102, power supply 104, and waveform gener-
`ator 106 are the type generally available through ordi-
`nary commercial channels.
`As noted above, the mechanical apparatus shown in
`FIG. 1, can be represented in diagramatic form,as is
`shown in FIG. 2. In FIG. 2, circulatory loop 18 is
`shownin greater detail. As shownin FIG.2, circulatory
`loop 18 includes an intake chamber 120 that receives
`fluid from pump 46 from intake opening 52. Intake
`chamber 120 hasa first orifice 122 and a secondorifice
`124. A first test chamber 126is in fluid communication
`with orifice 122, and a second test chamber 128 is in
`fluid communication with orifice 124. A restriction
`chamber 130is located in the flow channel 19 between
`test chambers 126 and 128 on an opposite flow side of
`intake chamber 120. Restriction chamber 130 hasa first
`restriction chamberflow orifice 132 is in fluid commu-
`nication with first test chamber 126 by conduit means
`formed by first flow module 134 and first compliance
`module 136. Likewise, restriction chamber 130 has a
`second restriction chamber flow orifice 138 that is in
`fluid communication with second valve chamber 128
`through a second conduit meansdefined by second flow
`module 140 and second compliance module 142.
`Asis shownin FIG.2,first test chamber 126 includes
`a pair of pressure sensors 144 and 146 that send signals
`through pressure amplifiers 154 to analog/digital con-
`verter 103 of computer 102. As is discussed below,
`pressure sensors 144 and 146 are on opposite sides of a
`heart valve to be tested in first test chamber 126. Simi-
`larly, second test chamber 128 includes pressure sensors
`148 and 150 which are located on opposite sides of a
`second heart valve to be tested, and pressure sensors
`148 and 150 send signals through pressure amplifier 156
`to analog/digital converter 103. Signals corresponding
`to fluid flow velocity are likewise transmitted to ana-
`log/digital converter 103 from first flow module 134
`and second flow module 140, and the amountofresis-
`tance in restriction chamber130 is received by analog/-
`digital converter 103 from resistance monitor 152.
`As discussed below, compensation modules 136 and
`142 operate on air pressure associated with a diaphram
`contacting fluid in the circulatory loop. In order to
`monitor the pressure, pressure amplifier 153 receives a
`pressure signal from pressure transducer 68 and presents
`the signal to analog/digital converter 103. Pressure amp
`155 receives a pressure signal from pressure transducer
`70 and presents this signal to analog/digital converter
`103 in order to monitor the air pressure on second com-
`pliance module 142. Finally, the existance of test posi-
`tions for prosthetic valves in first and second test cham-
`bers 126 and 128 are signalled to analog/digital con-
`verter by position sensors 158 and 160, respectively.
`Before turning to an explanation of the operation of
`this system as is shown in FIG.2,it is helpful to con-
`sider the structure of circulatory loop 18 as is shown in
`FIG.3, and the construction of the components ofcir-
`culatory loop 18 as is shown in FIGS.4-8.
`Turning first to FIG. 3, it is shown the circulatory
`loop 18 forms a closed-loop flow channel 19 that is
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`designed to simulate the human circulatory system.
`108 of the flow channel. First test chamber 126 prefera-
`Accordingly, intake chamber 120 receives fluid from
`bly has a square cross-section through which a cylindri-
`cylindrical pump 46 (shown in FIG. 1) with this fluid
`cal passagewayorbore 202is transversely formed, with
`being disbursed towardsfirst and secondintakeorifices
`bore 202 diametrically intersecting the longitudinal
`164 and 166. A first test chamber 126 is shownin fluid
`bore forming first test portion 208 that is also circular in
`communication with intake orifice 164, and includes a
`cross-section. Mounting fixture 204 is cylindrical
`in
`first mounting fixture 204 for positioning a first heart
`shape and is sized for close-fitting, mated insertion in
`valve 200 in the flow path ofcirculatory loop 18. First
`and passage through transverse bore 202. Mounting
`test chamber 126 includes a pair of pressure sensors 144
`fixture 204 has a diametric bore 206 that has a diameter
`