Proceedings−23rdAnnualConfbrence−rEEE侶MBSOct．25−28，200l，Istanbul，TURKEY

EFFECTOFSEGMENTEDPOIXURETIIANECOATINGONTHROMBUS
REGULATED WITH PULSATILE SHEAR FLOW

ShigehiroHashimotol，MembermEE，YoshinoriMurashigel，AtsushiYamanakal，HajimeOtani2，HirqiiImamura2，AkiraFukntome3
I

DepartmentofElectronics，InformationandCommunicationEngineerlng，OsakaInstituteofTechnology，5−16−1，Ohmiya，Asahi−ku，Osaka，535−8585Japan2

E−mail：hasimoto＠elc．oit．ac．jp

DepartmentofThoracicandCardiovascularSurgery，KansaiMedicalUniversity，
10−15，Fumizono−Cho，Moriguchi，Osaka，570−8506，Japan

3zeonMedicalInc・，1−2−1，Yakoh，Kawasaki−ku，Kawasaki，210−8507Japan
Abstract−The efrbct of segmented polytlrethaTLe COating on（Fig．1）．Theapexangle（2B）ofconvexconeisl15degrele・thrombus fbrmation was quantitatively studiedllnder shear
Unifbrm shear rate（G（1／s））is applied between theneldi］1VLtro．TheCouette−tyPeOfshearrateWaSaPpliedtothe COnCaVeandconvexcones．
Canime blood between 仙e concaYe and tIte co爪YeX eOneS．

Variation was made about materials of cones：
Polymethyl−metllaCrylate，pOlyvlnylcl1loride，8nd polyYinylChloride coated with segmented polyllrethane．The study
Sbows tllat the clo相ng time extends on tlle ＄egmented
polyllrethaneespeciallyatthehighershearrates，althoughthe
ClotratioisinthesameleYelasthatofwitho11tCOating．This
Clotting time extension shot）ld regulate thrombus formation
underpnlsatileshear†Iow．

whereNisangularvelocity（rad／s）oftheconcavecone，Pisangle（rad）betweentheconcaveandconvex

Kqv Fybrds−Bio−nuid mechanics，pulsatile shear now，blood，

PrOpOrtiontotherotatlngSPeedofconcavecone・thrombll＄，Clottingtime，pOtyllrethanecoating
I．INTRODUCTION

G＝Nr几＝（Nysin（B））／（yP）＝（Nsin（B））rP （1）．

betweentheapexandtheshearlngPOlnt・Theshearrateis
constantregardless ofthe distance（r）斤omrotating axes・

Shear rateis contro11ed betweenlOO andlOOOl／sin
Variationwasmadeinmaterialoftheconcaveandconvex
cones；POlymethyトmethacrylate，POlyvlnyl chloride，
polyvlnylchloride coated with segmented polyurethane・Combinationwasselectedsothatbothmaterialsofconcaveand convex cones arethe same．The cones coatedwith
vesselwalls．It consists ofplatelets and coagulants．It
segmentedpolyurethanewerefbrthesingleuse，becausethe
The clotplaysanimportant role to repalrruPtured bloodinterruPtS，Ontheotherhand，bloodnow，Whenitplugsthesurfaceconditionmightchangea命erexposuretoblood・
blood now path・Especially，in artincialvessels，Clot

fbrmation has to be delicately regulated between keeping
stableconnectiontonaturalvesselsandinhibitingformationof plugs. Many factors control the dynamic balance
between the fbrmation and removalof clots．Previous
StudiesshowthatsegmentedpolyurethaneCOatlngdecreases
Clotfbrmationto soe eXtent［1］・Themechanismto
preventclotfbrmationlSunderdiscussion，becausethee舵ct

changes with flow condition.
GeneralclottestsinvitrDareOnClottingtimeinatesttube［2］．Clotformationin now condition should be tested
underquantitativelycontrolledshearneld【3］・Inthepresentstudy，boththeclottingtimeandthecIotting
ratio have simultaneously been measured with concave
COnVeXCouettenowsysteminvitTV・
ⅠⅠ．METHODOLOGY

TheCouettetypeofshearratewasappliedtotheblood
between the concave and convex cones．The parts ofconcaveandconvexconesaredemountable，andtheaxisof
rotationisquicklyadjustedwithtaperedcorLneCtlngCylinderllN
Fig．l．Concaveandconvexcones・

0＿7803−7211−5／01＄10．00⑥2001IEEE

Proceedings−23rdAnnualConference−IEEE偲MBSOct．25−28，2001，Istanbul，TURKEY

One milliliter blood was drained without anticoagulants
丘omthejugularvein ofthe mongreldogweighed15kg．

1

lmmediatelyafter drainage，the blood sample was sheared
between the concave and convex cones at25degrees C，
While the viscous torque between two cones was●

0．8？Ontinuously measured（Fig・2）lThe viscou戸tOrquelnCreaSeS With clot fbrmation． ARer severalmlnuteS Of⊂〉■0・6

Stable torque traclngS，rOtation of the concave cone was
StOPpedandclotsweremacroscoplCallyobserved．

〕●h⊂〉 己0・4

ⅠⅠⅠ，RESUIJS●．●l0．2

Fig．2exemplines torque traclngS．The viscous torque

● ● ●
●

●500

1000

0increases with clot fbrmationfrom T to T ．The clottlng
time（t）was measured at torque tracings，andis shownin

0relationto shearratesinFigs4，6，8．Thesenguresshow

1500

Shearrate［1／s】

thattheclottlngtimedecreaseswiththe shearratebothon
POlymethyl−methacrylate and on polyvlnylchloride．The

tendencylS remarkable on polyvlnylchloride：from six toFig．3 Clotratiovs．shearrateon

twominutes（Fig．6）．

polymethylmethacrylate

Theclotratio（R）wascalculatedfromTandT一（2）．
R＝1−T／T■（2）

Theclotratioiszero，Whenthetorquedoesnotincrease（Tl＝Onpolyvlnylchloridecoatedwithsegmentedpolyurethane，ontheotherhand，theclottlngtimekeepsthesamelevelof
sixminutesevenathighershearrates（Fig．8），althoughtheT）・ItbecomesO・5，Whenthetor9ueincreasestodoubled clotratiodecreaseswiththeshearrate（Fig．7）・

Value（Tl＝2T）．Itapproachesunlty，thegreaterthetorquebecomes（T ＞＞T）．

IV．DrscussION

Figs．3，5，7showtheclotratioasafunctionoftheshear
rate．The clot ratio decreaseswith the shear rate，andit

becomessmallerthanO−5attheshearrateshigherthan4001／s（Figs・3，5）．

Segmented polyurethane，Whichis usedin the presentstudy，hasbeenappliedto coattheinnersurfaceinbLood

pumpsin artincialhearts・Its efftct to prevent clot
fbrmationhasbeenreportedinprevious studies［1］・The
morphologyofclotfbrmedonthesurface，however，depends
onbloodflowconditions．

Themostoftestmethods fbr anti−COagulate propertyof︹凸6▲411≡lニ主≡ぎ⁝＝ltl●
0500

1000

Shearrate［1／s］

Fig・4Clottingtimevs・Shearrate
よだ ・l岬 ー，▲−トー トー−−トT−

Fig．2 Torquetracings●㌧

onplymethylmethacrylate

1500

Proceeding＄−23rdAnnualCon危rence一正E打EMBSO比25−28，2001，Istanbul，TUMY

10．8
●

60●

● ●

400叫︸qh﹈blU

0 焉0・6l■・●■

0 60．4

●

●●

0．2

●●●●
‡●
0O

600

01000

1000

600

1500

Sbearrate【1／81Sllearrate【1／8】

r、Fig．7Clotratiov8．Shearrateon
polyurethaneFig．6Clotratiovs．shearrateon
pdyvhyl￠uOridetimeinthe shear丘eld．Atthelowershearrates，theclot
ratioincreases，Whiletheclottingtimeextends．

Theclottlngtimeextendsonsegmcntedpolyurethanc．Its
extensionisremarkableathighershearrates．Theclotratio
OnPObvinylchloridecoatedwithsegmentedpolymethane，Ontheotherhand，isinthesamelevclasthatonpolyvinyl
Chloddewithoutcoadng．
Segmented polyurethane coathg should be e蝕ctive to

8

Otherhand，Showsthatclotratiodoesnotrelatetoclotting

7−月む月忘月一葛tU

toanti・COagulation prope吋 Thc present study，On the01

COnSideredthattheextenslOnOfclo仕ingtimerelate＄directly

21materialsmeasurethcc？agulationtime［2］・lthasbeeTI64

20

PreVentClotfbrmationespeciallyinpulsatilc幻ow［3］，When

the blood is washed out periodically before formation of
Clotsintheextendedclo仕ingtimc．hthesteadynow，On0600

1000

1500

Sbearrate【1／s】

Fig．8Clottingtimevs．8hearrate086

the otherhand，Segmented polymethane coating maynot
haveenoughe飽cttopreventclotformationatthelower
shearratcs．Thematerial，Whichextendstheclottingtlme，hastheconsiderablee飴cttopreventthrombusfbrmationin

4

thepulsatilepumpsorinthearterialprostheses，butnotin
thevenousprostheses．

2

7叫jむ臼叫忘美玉OIU

1

OnpOlyurethane

V二CoNCLUSION
0500

1000

Sbe群ra鴨【1／8】Fig．6Clottingtinev8．8h飽rrate

OnpOlyvhylcuoride

Theclottingtimewasevaluatedseparately危omtheclot
ratioundershear鮎IdsinviETV．Thestudyshowsthattheclottingtimeextendsonthesegmentedpolymethanecoatlngespeciallyatthehighershearrates，althoughtheclotratiois
inthesamelevelasthatofwithoutcoatlng．Thisclottlng
time extcnsion regulates thrombus fbrmation under theProceedings−23rdAnnualConftrence−IEEE／EMBSOct．25−28，2001，Istanbul，TURKEY

pulsatileshearnow．

POlymerS．II．Processing technology／product property
COrrelations ofhemocompatible avcothane elastomers，

AcKNOWLEDGMENT

This work was supportedin part by a Grant−in・Aid fbr

ScientihcResearchfromtheJapaneseMinistryofEducation，
Science，SportsandCulture．
REFERヱNCES∫cf．花cカ〝ロメ．A殉珊L fkcピ∫∫，Pmc．J〃J・C叩／，pp・770−808，1979．

［2］R．Ⅰ．Lee，and P．D．White，‖A clinicalstudy ofthe
COagulationtimeofblood，‖Am・JMed・Sci・，VOl・145，
pp．495−503，1913・【3］S．Hashimoto，‖Clot growth under periodicallyfluctuatlng Shear rate， Biorheology，VOl・31，PP・
521−532，1994．

［1］E．Nylas，andR．S．Ward，Jr， Productionofbiomedical