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 stimulati
2、on (exercise, 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 patho
3、physiologic process 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 oft
4、en accompany AF and is diagnosed 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 block
5、ing agents or techniques Many 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 t
6、he complicationsRadiofrequency 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 co
7、nversion rate is 60% Paroxysmal AF : 7 days 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 N
8、onpharmacologic methods of rhythm control include 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
9、 m id eC l a ss: na usea , vo m iti ngQ uinidine: 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 r
10、o-a rrhythmi a ,na usea , dizzy ness2b eta-b lockers S A nod 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 tit
11、i s,p ulm o na ry fi b rosi s, t hyroidd is o rde rs, p eriphe ralneu ropa 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
12、23AF with WPWthere is no p wave, indicating that it did not originate anywhere 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 Esca
13、pe BeatQRS is slightly different but still narrow, indicating that conduction through the ventricle is relatively normalRecognizing and Naming Beats & RhythmsVentricular Tachyarrhythmias GENERAL PRINCIPLES Ventricular tachyarrhythmias should be initially approached with the assumption that they will
14、 have a malignant course until proven otherwise Characterization of the arrhythmia involves 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
15、need for device or ablation-based therapyDefinition of Ventricular TachyarrhythmiasNonsustained 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 T
16、achycardia composed of ventricular complexes of a single QRS morphology that lasts longer 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 Po
17、lymorphic VT is usually associated with hemodynamic collapse or instabilityVF is associated 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
18、annuallyEtiologyVT associated with structural heart disease Active ischemia or history of infarct Nonischemic cardiomyopathy Infiltrative cardiomyopathies (sarcoid, hemochromatosis, amyloid) Adults with prior repair of congenital heart disease Arrhythmogenic right ventricular dysplasia or cardiomyop
19、athy Bundle branch reentry VTVT in the absence of structural heart disease Inherited ion channelopathies ( 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 c
20、ardiomyopathy, or it may be idiopathic (no known cause) Typical V-tach patient MI with complications & extensive 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 at
21、ria may “capture” the entire beat beat an atrial beat may “merge” with an ectopic ventricular beat (fusion beat)Fusion 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 be
22、at - note that the complex is narrow enough to suggest normal ventricular conduction. This indicates that an atrial impulse 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 EC
23、G is critical in the determination of appropriate acute and chronic therapyImmediate unsynchronized DC cardioversion is the primary therapy for pulseless VT and VFNonpharmacologic therapy ICDs Radiofrequency catheter ablation Medications VF that is resistant to external defibrillation requires the a
24、ddition of IV antiarrhythmic agents. IV amiodarone appears to be more effective in increasing survival of VF when used in conjunction with defibrillation Chronic antiarrhythmic drug therapy is indicated for the treatment of recurrent symptomatic ventricular arrhythmiasLAORAOBRADYARRHYTHMIAS Definiti
25、on Cardiac rhythms whose ventricular rate 60 bpmCauses of BradycardiaIntrinsicCongenital disease Idiopathic degeneration(aging)Infarction or ischemiaCardiomyopathyInfiltrative disease: sarcoidosis, amyloidosisCollagen vascular diseasesSurgical traumaInfectious diseaseExtrinsicAutonomically mediated
26、(Neurocardiogenic syncope Carotid sinus hypersensitivity) Increased vagal tone: coughing, vomiting, micturition, defecation, intubationDrugs: -blockers, calcium channel blockers, digoxin, antiarrhythmic agentsHypothyroidismHypothermiaNeurologic disorders: increased intracranial pressureElectrolyte i
27、mbalances: hyperkalemia, hypermagnesemiaHypercarbia/obstructive sleep apneaSepsisDIAGNOSISSTABLE: Is the patient hemodynamically unstable?SYMPTOMS: Does the patient have symptoms and do the symptoms correlate with the bradycardia?SHORT-TERM: Are the circumstances surrounding the arrhythmia reversibl
28、e or transient?SOURCE: Where in the conduction system is the dysfunction? Has the bradyarrhythmia been captured on electrocardiographic monitoring?SCHEDULE A PACEMAKER: Does the patient require a PPM? Sinus Bradycardia: HR 60 b/m Causes: Increased vagul tone, decreased sympathetic output, (endurance
29、 training) Hypothyroidism Heart Attack (common in inferior wall infarction) Vasovagul syncope (people passing out when they get their blood drawn) Depression Sick Sinus Syndrome: Failure of the hearts pacemaking capabilities Causes: Idiopathic (no cause can be found) Cardiomyopathy (disease and malf
30、ormation of the cardiac muscle) Implications and Associations Associated with Tachycardia / Bradycardia arrhythmias Is often followed by an ectopic “escape beat” or an ectopic “rhythm”actually a retrograde p-wave may sometimes be seen on the right hand side of beats that originate in the ventricles,
31、 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 indicates 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
