心脏电生理及射频消融基础

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1、Cardiac vein stenosisPTCA with 3.5 mm balloonFinal resultModified Seldinger technique for percutaneous catheter sheath introductionSinus Node SAJunctionAtrium(P wave)Non-visible process on the EKGNon-visible process on the EKGAV node“Slowzone”IVCLead IISUMMARYMechanisms of SVTAtrial TachycardiaAVNRT

2、AVRTFPSPPQRS TBundle branch blocksLook at the QRS morphology in V1 and V6“Typical isthmus dependent atrial flutter”is due to a macro reentrant circuit around the tricuspid valve This rhythm can be stopped by pacing and cured with ablation Embolic risk may be less than in fibrillation,but same recomm

3、endations applyElectrophysiology II Supraventricular ArrhythmiasAtrial FlutterVentricular rate 150 bpm“Saw tooth”p wavesAtrial FlutterElectrophysiology II Supraventricular ArrhythmiasAtrioventricular Nodal Reentrant Tachycardia(AV Node Reentry or AVNRT)Most common cause of paroxysmal SVT in the youn

4、g adult Occurs over a small reentrant circuit located near the AV node The circuit consists of a fast and slow pathway connected by a common top and bottom pathwayElectrophysiology II Supraventricular ArrhythmiasAV Node Reentry TachycardiaRate of 145 bpm(Short RP tachycardia)Electrophysiology II Sup

5、raventricular ArrhythmiasRetrograde p wavesRP=60 msecEctopic Atrial Tachycardia(Long RP tachycardia)Uncommon cause of paroxysmal SVT in the young adult(0.21 would be classified as first degree block.Usually this block is above His bundle Second degree-some P waves are not followed by QRS.Often has a

6、 regular sequence,i.e.,2:1 or 3:2.The first number is the number of P waves present and the second is the number of QRSs.What is this?Mobitz I(Wenckebach)the PR progressively lengthens with one P wave for every QRS until a beat is dropped.Usually the block is above His bundle.This is common in coron

7、ary patients and is caused by increased vagal tone and usually eventually disappears with no problems Mobitz II the PR is constant but with occasional dropped beats.This is a more serious arrhythmia because the injury is probably in fast conducting tissue below the His bundle which is not under vaga

8、l control.This is unambiguously Mobitz IIIt is a dangerous arrhythmia because the heart may suddenly start beating very slowly or even stop.Complete heart block.Since there is no conduction down the AV node pathway atria and ventricles beat regularly but at different rates.Slow ventricular rateUsual

9、ly treated with pacemakerMay be temporary or intermittent.Can be induced by drugs that cause increased vagotoniaWPW:Normally conducting cardiac muscle bridges the gap between atria and ventricles.The accessory pathway activates the ventricle before normal activation via the AV node.The PR interval i

10、s 100b/min1.Normal P waves2.Normal or shortened PR interval3.QRS and T vectors are normal4.ST segments are normal5.RR interval short 15mm1500/100=15Fig 3Normal sinus rhythmSinus tachycardiaSinus bradycardiaSinus Bradycardia 25mm1500/60=25Premature ventricular contraction(PVC)1.Arises from ectopic fo

11、cus in ventricles2.Early QRS not preceded by a P wave(see fig 4)3.Will have an unusual QRS shapea)odd vectorb)prolonged QRS duration Premature ventricular contraction(PVC)1.Arises from ectopic focus in ventricles2.Early QRS not preceded by a P wave(see fig 4)3.Will have an unusual QRS shapea)odd vec

12、torb)prolonged QRS duration 4.A compensatory pauseMultifocal PVCs.Two separate foci are originating PVCsIrritable ventricleIF all PVC are identical it is from one ectopic site(Unifocal).Premature atrial contraction(PAC)1.Arises from an ectopic focus in the atria.2.Will have an identifiable P wave bu

13、t the shape of the P wave may be altered3.May have a normal QRS 4.May have a compensatory pauseThe QRS may be altered if some of the ventricle is still in its refractory period.The compensatory pause is lacking because the SA node was reset.The rhythm has been shifted.Atrial fibrillation1.Irregularl

14、y irregular2.No P wavesThe AV node keeps the ventricular rate lowMay be treated with drugs to depress AV conduction and slow the ventricular rhythm:Beta blockers,calcium channel blockersCommon:will occur in about 1/3 of the populationNot a serious arrhythmia unless in WPWElectrical reentry can cause

15、 fibrillations and tachycardias.Ventricular tachycardia(Fig 9)1.Regularly occurring rhythm originating from a regular ventricular ectopic focus.2.QRS morphology is usually like a PVCBecause the cardiac output is very low it usually produces myocardial ischemia and often progresses to ventricular fib

16、rillation Ventricular fibrillation(VF)1.Thought to be a reentrant excitation of the ventricles;premature impulse may arise during vulnerable period2.Irregular baseline with no identifiable waves3.No cardiac output.Usually the cause of sudden death4.May be the result of ischemia,lightning strike,elec

17、trocution,chest trauma,or drugs5.Requires CPR and electrical difibrillation.Patients do not spontaneously recover.Extended phase two cause long QT syndrome.Q-T interval is rate-dependent and is an index of the duration of phase 2 in the ventricular AP12 x 40=480 ms12 blocksLong QT syndrome1.Prolonge

18、d duration of phase 2 causes an early afterdepolarization.That can trigger an early action potential causing a reentrant tachycardia 2.Patients may experience attacks of VT with torsades de pointes-a waxing and waning of the QRS morphology(as if circling around a point).3.Long QT is induced by some

19、drugs and can be due to genetic abnormalities in some potassium and calcium channels.At present 5 separate genetic defects have been identified which cause long QT 14 STEPS TO ASSURE A SUCCESSFUL READING AND UNDERSTANDING OF AN UNKNOWN ECG1.Is the ventricular rhythm regular?2.Are there P waves?3.Is

20、the atrial rhythm regular?4.Is there one P wave for each QRS?5.What are the atrial and ventricular rates?6.What is the P-R interval?7.Is the P-R interval constant?8.Are there extra or premature beats?9.What is the QRS duration?10.Does the QRS morphology indicate presence of a conduction defect?11.Wh

21、at is the mean electrical QRS axis?12.What is the mean electrical P wave axis?13.Is there S-T segment deviation?14.Are there pathologic Q waves?Fig 12 a summary of heart blocks.a summary of other arrhythmiasAV NodalReentryAV ReciprocatingTachycardiaSinus Nodal ReentryIntra-atrial ReentryAutomatic AtrialTachycardiaCoarse FibrillationFine FibrillationScheidt S,Erlebacher JA,Netter FH.Basic Electrocardiography ECG.Ciba-Geigy:First Printing,1986,p23.