1、Cardiac ArrhythmiasJun JiangDepartment of CardiologyMechanisms of ArrhythmogenesisTACHYARRHYTHMIAS Definition Cardiac rhythms whose ventricular rate exceeds 100 beats per minute(bpm).Classification Narrow-Complex Tachyarrhythmia(QRS 100 b/m Causes:Withdrawal of vagul tone&Sympathetic stimulation(exe
2、rcise,pain,or fight)Fever&inflammation Hypovolemia Anemai Hypoxia Heart Failure or Cardiogenic Shock(both represent hypoperfusion states)Heart Attack(myocardial infarction or extension of infarction)Drugs(alcohol,nicotine,caffeine)Therapy targeted at treatment of underlying pathophysiologic process
3、Supraventricular Tachyarrhythmias Paroxysmal supraventricular tachycardi(PSVT)Prevalence and incidence of PSVT are 2.25 per 1,000 AVNRT(60%)AVRT(30%)Atrial fibrillation AF is the most common narrow-complex tachycardia seen in the inpatient setting Atrial flutter AFl can often accompany AF and is dia
4、gnosed one-tenth as often as AF but is twice as prevalent as the PSVTs Atrial tachycardia far less common Junctional tachycardia Sinoatrial nodal reentrant tachycardia(SANRT)TREATMENTAcute treatment of symptomatic SVT should follow the ACLS protocol as beforeAV nodal blocking agents or techniques Ma
5、ny SVTs can be terminated AF,AFl,and some atrial tachycardias will persist with a slowing of the ventricular rateCorrection of electrolyte abnormalities(K+and Mg+)Underlying etiologyChronic treatment should be aimed at either prevention of recurrence or prevention of the complicationsRadiofrequency
6、ablation(RFA)Success rates from 85%to 95%Compared to antiarrhythmic therapy,RFA improves quality of life and is more cost-effective in the long term15AVNRT Pin lead I,II,V1-V3AVRTWPW-A 4WPW-BAtrial Fibrillation Classification First occurrence.The spontaneous conversion rate is 60%Paroxysmal AF:7 day
7、s and usually 7 days in duration or require cardioversion Permanent AF Medical management Rate control of AF diltiazem,verapamil-adrenergic blockers digoxin Prevention of thromboembolic events Rhythm control Pharmacologic control Electrical cardioversion Nonpharmacologic methods of rhythm control in
8、clude catheter or surgical ablationClassification of Anti-arrhythmicsC l a ssA cti o nExa m p l esS i d e Effects1 AFa st so d ium chan nel bloc ker va ri esd ep o la riza ti o n a nd a ction p o tentiald ura ti o nQ uinidine,p ro ca ina m id e,d is op yra m id eC l a ss:na usea,vo m iti ngQ uinidin
9、e:hem o lyti ca nemi a,t hro m bo cy to pe nia,ti nnitusProc aina mi d e:lup us1 BLido ca ine,M ex il etineLido ca ine:d izziness,co nfusi o n,seizures,co m aM ex il etine:trem o r,a taxi a,ras h1 CFl eca i nide,Prop afen o neFl eca i nide:p ro-a rrhythmi a,na usea,dizzy ness2b eta-b lockers S A nod
10、 e&A V no d eco nd uctio nProp ra no l o l,m etop ro lolC l a ss:C H F,bro ncho spa sm,b ra dy ca rd ia,hy po tension3Pro l o ng a cti o n p oten ti a l b y b lockingK+cha nnelsA m i o d a ro ne,sota l o lA m i o d a ro ne:hepa titi s,p ulm o na ry fi b rosi s,t hyroidd is o rde rs,p eriphe ralneu r
11、opa thySo talol:b ro ncho sp a sm4calcium cha nnel bloc kers A V no d eco nd uctio nV era p a m il,d ilit ia zemC l a ss:AV b lo ck,hyp o tensi o n,b ra d ycard i a,co nstipa ti o nStroke Risk in Patients With Nonvalvular AF 23AF with WPWthere is no p wave,indicating that it did not originate anywhe
12、re in the atria,but since the QRS complex is still thin and normal looking,we can conclude that the beat originated somewhere near the AV junction.The beat is therefore called a junctional or a“nodal”beatJunctional Escape BeatQRS is slightly different but still narrow,indicating that conduction thro
13、ugh the ventricle is relatively normalRecognizing and Naming Beats&RhythmsVentricular Tachyarrhythmias GENERAL PRINCIPLES Ventricular tachyarrhythmias should be initially approached with the assumption that they will have a malignant course until proven otherwise Characterization of the arrhythmia i
14、nvolves hemodynamic stability Duration Morphology the presence or lack of underlying structural heart disease Ultimately,this characterization will aid in determining the patients risk for sudden cardiac arrest and need for device or ablation-based therapyDefinition of Ventricular TachyarrhythmiasNo
15、nsustained VT Three or more consecutive ventricular complexes(100 bpm)that terminates spontaneously within 30 seconds without significant hemodynamic consequences or need for interventionSustained monomorphic VT Tachycardia composed of ventricular complexes of a single QRS morphology that lasts long
16、er than 30 seconds or requires cardioversion due to hemodynamic compromise.Polymorphic VT is characterized by an ever-changing QRS morphology TdP is typically preceded by a prolonged QT interval in sinus rhythm Polymorphic VT is usually associated with hemodynamic collapse or instabilityVF is associ
17、ated with disorganized mechanical contraction,hemodynamic collapse,and sudden deathSCD is defined as the death that occurs within 1 hour of the onset of symptoms In the United States,350,000 cases of SCD occur annuallyEtiologyVT associated with structural heart disease Active ischemia or history of
18、infarct Nonischemic cardiomyopathy Infiltrative cardiomyopathies(sarcoid,hemochromatosis,amyloid)Adults with prior repair of congenital heart disease Arrhythmogenic right ventricular dysplasia or cardiomyopathy Bundle branch reentry VTVT in the absence of structural heart disease Inherited ion chann
19、elopathies(Brugada,long QT syndromes)Catecholaminergic polymorphic VT Idiopathic VT(VOT)Brugada criteria Recognizing and Naming Beats&RhythmsNotes on V-tach:Causes of V-tach Prior MI,CAD,dilated cardiomyopathy,or it may be idiopathic(no known cause)Typical V-tach patient MI with complications&extens
20、ive necrosis,EF40%,d wall motion,v-aneurysm)V-tach complexes are likely to be similar and the rhythm regular Irregular V-Tach rhythms may be due to to:breakthrough of atrial conduction atria may“capture”the entire beat beat an atrial beat may“merge”with an ectopic ventricular beat(fusion beat)Fusion
21、 beat-note p-wave in front of PVC and the PVC is narrower than the other PVCs this indicates the beat is a product of both the sinus node and an ectopic ventricular focusCapture beat-note that the complex is narrow enough to suggest normal ventricular conduction.This indicates that an atrial impulse
22、 has made it through and conduction through the ventricles is relatively normal.TREATMENTDifferentiation of SVT with aberrancy from VT on the basis of analysis of the surface ECG is critical in the determination of appropriate acute and chronic therapyImmediate unsynchronized DC cardioversion is the
23、 primary therapy for pulseless VT and VFNonpharmacologic therapy ICDs Radiofrequency catheter ablation Medications VF that is resistant to external defibrillation requires the addition of IV antiarrhythmic agents.IV amiodarone appears to be more effective in increasing survival of VF when used in co
24、njunction with defibrillation Chronic antiarrhythmic drug therapy is indicated for the treatment of recurrent symptomatic ventricular arrhythmiasLAORAOBRADYARRHYTHMIAS Definition Cardiac rhythms whose ventricular rate 60 bpmCauses of BradycardiaIntrinsicCongenital disease Idiopathic degeneration(agi
25、ng)Infarction or ischemiaCardiomyopathyInfiltrative disease:sarcoidosis,amyloidosisCollagen vascular diseasesSurgical traumaInfectious diseaseExtrinsicAutonomically mediated(Neurocardiogenic syncope Carotid sinus hypersensitivity)Increased vagal tone:coughing,vomiting,micturition,defecation,intubati
26、onDrugs:-blockers,calcium channel blockers,digoxin,antiarrhythmic agentsHypothyroidismHypothermiaNeurologic disorders:increased intracranial pressureElectrolyte imbalances:hyperkalemia,hypermagnesemiaHypercarbia/obstructive sleep apneaSepsisDIAGNOSISSTABLE:Is the patient hemodynamically unstable?SYM
27、PTOMS:Does the patient have symptoms and do the symptoms correlate with the bradycardia?SHORT-TERM:Are the circumstances surrounding the arrhythmia reversible or transient?SOURCE:Where in the conduction system is the dysfunction?Has the bradyarrhythmia been captured on electrocardiographic monitorin
28、g?SCHEDULE A PACEMAKER:Does the patient require a PPM?Sinus Bradycardia:HR 60 b/m Causes:Increased vagul tone,decreased sympathetic output,(endurance training)Hypothyroidism Heart Attack(common in inferior wall infarction)Vasovagul syncope(people passing out when they get their blood drawn)Depressio
29、n Sick Sinus Syndrome:Failure of the hearts pacemaking capabilities Causes:Idiopathic(no cause can be found)Cardiomyopathy(disease and malformation of the cardiac muscle)Implications and Associations Associated with Tachycardia/Bradycardia arrhythmias Is often followed by an ectopic“escape beat”or a
30、n ectopic“rhythm”actually a retrograde p-wave may sometimes be seen on the right hand side of beats that originate in the ventricles,indicating that depolarization has spread back up through the atria from the ventriclesQRS is wide and much different(bizarre)looking than the normal beats.This indica
31、tes that the beat originated somewhere in the ventricles and consequently,conduction through the ventricles did not take place through normal pathways.It is therefore called a“ventricular”beatVentricular Escape Beatthere is no p wave,indicating that the beat did not originate anywhere in the atriaRecognizing and Naming Beats&RhythmsTHANKS
