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1、 Cardiac ArrhythmiaINTRODUCTION Arrthythmia: abnormalities of cardiac rhythm and conduction Arrthythmias can be lethal (sudden cardiac death ) , symptomatic ( syncope , near syncope dizziness , or palpitations ) , or asymptomatic . Property of cardiac elctrophysiologyExcitabilityAutomaticityConducti
2、vityExcitability Electrical activity which takes place when myocardial cell is stimulated Electrical activity of single myocardial cell is called action potential(AP)Excitability Composition and features of APThere are five phase（0、1、2、3 、4）Electrophysiological phenomena during APRefractory periodAb
3、solute, Effective, RelativeConductivity Electrical impulse can conduct in myocardial tissue bidirectionally Normal conduction pathway： sinus nodeintranode bundle atrioventricula node and intraatrial bundleHis bundleright and left bundle branch(including left anterosuperior and posteroinferior)Purkin
4、je fibermyocardiumautomaticity Property of spontaneously discharging cells(spotaneous AP, diastolic depolarization) Automaticity increases from high to low as follows:Physiological status：SN、AVN、HIS、 Purkinjepathological：diseased myocardial and conductive tissue, etc.Property of normal rhythm Impuls
5、e from SN Heart rate is within 60100/min Regular rhythm，P interval0.12s PR interval is between 0.120.20s， QRS complex duration0.10s Frontal axis within -3090 It is considered as arrhythmia if any item above is not matchedClassification of cardiac arrhythmias Classified on property of electrical acti
6、vity Abnormality of impulse and conduction Classified on heart rate, rapid or slow Rapid or slow arrhythmias Classified on clinical manifestation, mild or sever Fatal or nonfatal High risk or low riskMechanisms of arrhythmogenesisReentry Conduction inconsistency of anatomy or physiology Single direc
7、tional conduction blocking Delayed conduction Initial blocking area recovers excitabilityMechanisms of arrhythmogenesisIncreased automaticity Endogenous or exogenous catecholamine increasing Abnormality of acid, electrolyte balance Ischemia, hypoxia Mechanical stretch drugs Disturbance of nerveMecha
8、nisms of arrhythmogenesisTriggered activity Depolarizing oscillations of membrane voltage induced by abnormal inward Na+ during earlier or later reporlarization, ie, After depolarizationEarly depolarizationDelayed depolarizationCategory of ArrthythmiaAbnormalities of impulses generating Abnormalitie
9、s of impulses conductionAbnormalities of impulses generatingSinus arrthythmias: sinus bradycardia, sinus tachycardia, sinus arrest, Abnormalities of impulses generatingEctopic rhythm: 1.Passive abnormalrhythm: escape beat, escape rhythm(atrial, AV junctional, ventricular) 2.Initiative ectopic rhythm
10、: premature beat(atrial, AV junctional, ventricular) paroxysmal tachycardia(atrial, AV junctional,ventricular) atrial flutter, atrial fibrillation ventricular flutter, ventricular fibrillationAbnormalities of impulses conduction1.physiologic 2.pathologic: sinoatrial block, intra- atrial block, atria
11、l ventricular block, bundle branch block, intraventricular block. 3.abnormal pathway conduction:preexcitation syndromeSinus Arrhythmia1.Normal sinus rhythm the P wave appear regularly, the P wave is upright in lead I, II, AVF, V4-V6 and negative in lead AVR, P-R interval exceed 120ms.2.Sinus Tachyca
12、rdia ECG Sinus Tachycardia is defined as a heart rate faster than 100 beats / min with sinus rhythm, frequency between 100-150bpm. P wave have a normal contour and appear before each QRS complex with a stable P-R interval . Sinus Tachycardia Causes: it occurs with fever , exercise , emotion , pain ,
13、anemia , heart failure , shock , thyrotoxicosis , or in response to many drugs . Alcohol ,tea, caffeine and alcohol withdrawal are common causes of sinus tachycardia.3.Sinus bradycardia ECG: sinus rhythm ECG, heart rate slower than 60 beats /min .Sinus bradycardia Causes: Physiological:young adults,
14、 atheletes, during sleep.Pathological: hypothermia, raised intracranial pressure, AMI affecting the SA node, drugs(e.g. beta- blockers), fibrosis of SA node.4.Sinus arrhythmia Sinus arrhythmia is characterized by a variation in sinus cycle length during which the maximum sinus cycle length minus min
15、imum sinus cycle length exceeds 120ms . Sinus arrhythmia is a cyclic increase in normal heart rate with inspiration and decrease with expiration . It results from reflex changes in vagal influence on the normal pacemaker5.Sinus arrest ECG: PP interval elongates abruptly, basically at sinus bradycard
16、ia, which is not common multiples of basic PP interval Escape beat or rhythm is common seen6.Sick sinus syndrome sssEtiology Intrinsic ：sinus node itself is involved, e.g. ischemia, regressive degeneration, infiltration of other cells or tissues Extrinsic ：high vagal tone, hyperkalemia, antiarrhythmicsmost frequent
