PacingConcepts心臟起搏基礎(chǔ)

基本起搏概念目的簡介不一樣起搏模式及NBG編碼理解起搏環(huán)路構(gòu)成部分理解電壓、電流及阻抗之間的關(guān)系理解低阻抗、高阻抗狀況及也許原因?qū)Φ呐袛鄪Z獲閾值計算安全余量理解起搏器的感知及感知敏捷度概念起搏模式單腔起搏系統(tǒng)一根電極心房心室(更普遍)一般用于房顫患者(VVIpacemaker)或竇房結(jié)功能良好且無房室傳導阻滯(AAIpacemaker)AAIPacemakerVVIPacemaker雙腔起搏系統(tǒng)植入兩根電極一根植入在心房

一根植入在心室提供房室同步及心房心室按需起搏DDDPacemaker雙腔起搏系統(tǒng)RVLeadattheApexRALeadinAppendage三腔起搏系統(tǒng)植入三根電極:右房右室左室(經(jīng)冠狀靜脈)一般稱之為CRTP同步起搏兩個心室使之再同步DDDBiVPacemakerNBG編碼IIIIIIIVV起搏心腔感知心腔感知后反應頻率支持多位點起搏O

=NoneA

=AtriumV

=VentricleD

=Dual(A+V)S

=Single(AorV)O

=NoneA

=AtriumV

=VentricleD

=Dual(A+V)S

=Single(AorV)O

=NoneT

=TriggeredI

=InhibitedD

=Dual(T+I)O

=NoneR

=RatemodulationO

=NoneA

=AtriumV

=VentricleD

=Dual(A+V)Examplesofpacingmodeswhicharetypicallyprogrammed:DDD

DDDRVVIDDIRVVIRAAIR知識點檢查Whattypeofpacemakeristhis起搏系統(tǒng)的構(gòu)成植入式起搏器回路可植入式脈沖發(fā)生器(IPG):電池電路連接頭電極陰極

陽極人體組織IPGLeadsAnodeCathode鋰碘電池2.8VBOL壽命與阻抗及輸出有關(guān)6-CircuitryBattery脈沖發(fā)生器電極是絕緣導線從脈沖發(fā)生器傳遞電脈沖至心臟感知心臟除極信號Lead電極極性單極電極直徑更細體表心電圖上信號顯示更大也許導致囊袋刺激Bipolarleads不易發(fā)生過感知(i.e.,myopotentials,EMI,etc.)UnipolarleadBipolarcoaxialleadTotip(cathode)Fromring(anode)Al-Ahmad,Amin,et.al.().PacemakersandImplantableCardioverterDefibrillators:AnExpert'sManualMinneapolis:CardiotextPublishing.(pg.20-21).單級起搏系統(tǒng)電極頭端只有一種電極極性（陰極）起搏器外殼為陽極Whenpacing,theimpulse:Flowsthroughthetipelectrode(cathode)StimulatestheheartReturnsthroughbodyfluidandtissuetotheIPGcan(anode)Cathode-Anode+Anode雙極起搏系統(tǒng)一根電極既有陰極又有陽極Thepacingimpulse:FlowsthroughthetipelectrodelocatedattheendoftheleadwireStimulatestheheartReturnstotheringelectrode,theanode,abovetheleadtipCathodeAnode+Cathode-經(jīng)靜脈起搏電極被動固定(叉齒狀)叉齒固定在心尖部肌小梁上或心耳部梳狀肌上積極固定(螺旋狀)螺旋伸出擰在心肌上可以固定在心腔內(nèi)任何地方使用內(nèi)置的工具將螺旋頭旋出心外膜起搏電極電極直接固定在心臟表面常用于小兒患者及不可經(jīng)靜脈植入電極的患者固定方式包括:刺入旋入縫合式電極的絕緣材料硅樹脂絕緣層電極

惰性生物兼容性穩(wěn)定聚亞安酯絕緣層電極生物兼容性抗斯強度大摩擦系數(shù)小導線直徑小NewerbipolarleadinsulationSiliconePolyurethaneHayes,DavidL.,et.al.().Cardiacpacing,defibrillationandresynchronization:aclinicalapproach.NewJersey:Wiley-BlackwellPublishing.(pg.127).

知識點檢查在雙極起搏模式中哪里是陽極CABDTipElectrodeRingElectrodeDeviceBodyTissue起搏器中的電學概念電壓在起搏系統(tǒng)中,電壓是:以伏特來衡量(V)用字母“V”表達由起搏器電池提供一般表達脈沖振幅Note:Theterms“amplitude”and“voltage”areoftenusedinterchangeablyinpacing.初始隨訪匯報Note:Allclinic,physician,andpatientnamesanddatainthisdocumentarefictitious電壓電流在起搏系統(tǒng)中，電流是:以安培衡量(mA)以字母“I”表達Note:Oneampereisaunitofelectricalcurrentproducedby1voltactingthrougharesistanceof1ohm.1Ampere=1000milliamps電流阻抗在起搏系統(tǒng)中，阻抗是:以歐姆來衡量(W)以字母“R”表達對電流所有阻力的計量LeadconductorresistanceTheresistancetocurrentflowfromtheelectrodetothemyocardiumPolarizationimpedance(theaccumulationofchargesofoppositepolarityinthemyocardiumattheelectrode-tissueinterface)初始隨訪匯報Note:Allclinic,physician,andpatientnamesanddatainthisdocumentarefictitious阻抗30阻抗變化影響起搏器的

功能和電池的壽命高阻抗減少電池的電力消耗并延長電池的壽命，但也許影響起搏功能，甚至無奪獲低阻抗增長電池的電力消耗并縮短電池的壽命起搏系統(tǒng)阻抗值在300至1,000W之間高阻抗導線的阻抗值不小于1,000歐姆Summary

Voltage,Current,andImpedanceVoltage:Theforcemovingthecurrent(V)InpacemakersitisafunctionofthebatterychemistryCurrent:Theactualcontinuingvolumeofflowofelectricity(I)Thisflowofelectronscausesthemyocardialcellstodepolarize(to“beat”)Impedance:Thesumofallresistancetocurrentflow(R)Impedanceisafunctionofthecharacteristicsoftheconductor(wire),theelectrode(tip),andthemyocardium(tissue).歐姆定律描述電壓、電流、阻抗之間的關(guān)系。V=IXRI=V/RR=V/IVIRVRIVRIRVI===XOhm’slawtellsus:Iftheimpedance(R)remainsconstant,andthevoltagedecreases,thecurrentdecreasesIfthevoltageisconstant,andtheimpedancedecreases,thecurrentincreasesV=IxRWhyisthisimportanttoclinicalmanagementofpacemakersTherelationshipbetweenvoltage,current,andimpedanceprovidestherationalefordecisionswemakeduringevaluationofpacingsystemsandreprogramming.Propermanagementofelectricalcharacteristicsisimportantforpatientsafetyanddevicelongevity.知識點檢查心房電極傳送的電流是多少測試起搏環(huán)路電極阻抗范圍電極阻抗在使用.一般,>30%的阻抗變化需要關(guān)注.TypicalImpedancerange=200to1,000Ohms.**Impedanceishigherforspeciallydesignedhighimpedanceleads.Hayes,DavidL.,et.al.().Cardiacpacinganddefibrillation:aclinicalapproach.NewYork:BlackwellPublishing.(pg.398).電極阻抗

電學模擬

正常電阻–frictioncausedbythehoseandnozzleSimilartoapacemakerleadwithaninsulationbreachwhichresultsinlowresistanceandhighcurrentdrain;maycauseprematurebatterydepletion.

高電阻

–aknotresultsinlowtotalcurrentflow

低電阻

–

leaksinthehosereducetheresistanceSimilartoapacemakerleadwithaleadconductorbreak-impedancewillbehighwithlittleornocurrentreachingthemyocardium.知識點檢查當電極導線斷裂時你認為會發(fā)生呢什么A.阻抗下降B.電流下降C.阻抗上升D.BothBandCLeadwirefractureIncreasedresistance高阻抗原因

電極斷裂電極斷裂會導致高阻抗阻抗坑也許高于3,000W其他高阻抗發(fā)生原因:電極與起搏器未連接好(usuallyanacuteproblem).CaseStudy:ClinicVisit85yearoldmalewithh/opacemakerimplantin1996.Generatorchangein.Followupvisitsinclinichavebeennormal.Henowcomesintoyourofficecomplainingoflight-headednessandfatigue.Youinterrogatehispacemakerandfindtheventricularleadimpedanceis1,867ohmsanditwasusuallytrendingaround700ohms.Canyouidentifyaproblem1stRib-ClavicleCrush

(leadfracture)ChestXRayLeadFractureLeadCrushNowthatyouknowwhattheproblemis,HowdoyoufixitSolutionsforLeadCrushUnipolarconfigurationiftheinnerconductorisstillintactLeadreplacement知識點檢查電極絕緣層發(fā)生破損時你認為也許發(fā)生什么狀況阻抗下降也許導致失奪獲電流增長電池壽命延長低阻抗原因

絕緣層破損絕緣層破損也許導致阻抗下降阻抗值也許低于300WCurrentwillfollowthepathofLEASTresistance起搏閾值在心臟不應期之外可以持續(xù)奪獲心臟的最小電壓。Ventricularpacemaker60ppmCaptureNon-CaptureEffectofLeadDesignonCapture導線成熟過程

導線成熟后周圍會被心肌纖維包裹。閾值會升高Ellenbogen,KennethA.andMarkA.Wood.().CardiacPacingandICDs.Massachusetts:BlackwellPublishing.(pg.342).激素洗脫電極激素洗脫電極減少心肌局部水腫緩和急性期閾值上升電極能保持持續(xù)的低閾值Siliconerubberplug

containingsteroidTinesfor

stable

fixationPorous,platinizedtipforsteroidelution類固醇對刺激閾值的影響PulseWidth=0.5msec036ImplantTime(Weeks)織物電極平滑金屬電極12345類固醇洗脫電極01245789101112VoltsReferences:PacingReferenceGuide,BakkenEducationCenter,1995,UC199601047aEN.CardiacPacing,2ndEdition,EditedbyKennethA.Ellenbogen.1996.影響閾值的原因起搏回路的完整性絕緣層破損電極斷裂電極規(guī)格

電極擺放位置藥物電解質(zhì)Hayes,CardiacPacingandDefibrillation,心肌奪獲奪獲與下列參數(shù)有關(guān):脈沖振幅—電刺激的電壓（V）電壓必須要到達足夠的強度使心臟除極(i.e.,to“capture”theheart)輸出電壓必須要給一種足夠的安全余量脈沖寬度—刺激電流的持續(xù)時間（ms）脈寬必須足夠長使除極過程擴散到周圍心肌組織不一樣起搏能量比較

Amplitude5.0V0.25ms1.0ms0.5ms5.0VoltAmplitudeatDifferentPulseWidths時間強度曲線舉例安全余量= 2x電壓閾值

OR 3x脈寬閾值程控輸出能量首要目的:保證患者的安全及起搏的有效性次要目的:延長電池壽命一般程控輸出電壓<2.5V,但必須保證足夠的安全余量。電壓值假如不小于起搏器的電池電壓(一般為2.8V)需要通過倍壓器,會大大增長電能的損耗，減少電池壽命。感知感知就是起搏器能“看見”心臟自身除極信號的能力

起搏器通過測量陽極和陰極之間的心肌細胞的電位變化來感知心臟除極活動0.5mVsignal2.0mVsignal可接受的感知范圍(mV)1

急性期慢性期Atrium>1.5>1.0Ventricle>7.0>5.0感知1Curtis,AnneB.().FundamentalsofCardiacPacing.Massachusetts:JonesandBartlettPublishers.(pg.98).感知敏捷度Amplitude(mV)Time5.02.51.25更低的敏捷度=高敏捷度數(shù)值A(chǔ)mplitude(mV)Time5.02.51.25更高的敏捷度=底敏捷度數(shù)值A(chǔ)mplitude(mV)Time5.02.51.25恰當?shù)拿艚荻仍O(shè)置Amplitude(mV)Time5.02.51.25VectorsandGradientsSenseThewaveofdepolarizationproducedbynormalconductioncreatesagradientacrossthecathodeandanode.Thischangingpolaritycreatesthesignal.Oncethissignalexceedstheprogrammedsensitivity–itissensedbythedevice.2.5mVChangingtheVectorSense2.