1、,Cardiac Arrhythmia,INTRODUCTION,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 elctrophysiology,Excitability Automaticity Cond
2、uctivity,Excitability,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 AP There are five phase(0、1、2、3、4) Electrophysiological phenomena during AP Refractory
3、period Absolute, Effective, Relative,Conductivity,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 posteroinfer
4、ior)Purkinje fibermyocardium,automaticity,Property of spontaneously discharging cells(spotaneous AP, diastolic depolarization) Automaticity increases from high to low as follows: Physiological status:SN、AVN、HIS、Purkinje pathological:diseased myocardial and conductive tissue, etc.,Property of normal
5、rhythm,Impulse 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 matched,Classification of cardiac arrhythmias,Classified on property of el
6、ectrical activity 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 risk,Mechanisms of arrhythmogenesis,Reentry Conduction inconsistency of anatomy or physiolo
7、gy Single directional conduction blocking Delayed conduction Initial blocking area recovers excitability,Mechanisms of arrhythmogenesis,Increased automaticity Endogenous or exogenous catecholamine increasing Abnormality of acid, electrolyte balance Ischemia, hypoxia Mechanical stretch drugs Disturba
8、nce of nerve,Mechanisms of arrhythmogenesis,Triggered activity Depolarizing oscillations of membrane voltage induced by abnormal inward Na+ during earlier or later reporlarization, ie, After depolarization Early depolarization Delayed depolarization,Category of Arrthythmia,Abnormalities of impulses
9、generating Abnormalities of impulses conduction,Abnormalities of impulses generating,Sinus arrthythmias: sinus bradycardia, sinus tachycardia, sinus arrest,Abnormalities of impulses generating,Ectopic rhythm: 1.Passive abnormalrhythm: escape beat, escape rhythm(atrial, AV junctional, ventricular) 2.
10、Initiative ectopic rhythm: premature beat(atrial, AV junctional, ventricular) paroxysmal tachycardia(atrial, AV junctional,ventricular) atrial flutter, atrial fibrillation ventricular flutter, ventricular fibrillation,Abnormalities of impulses conduction,1.physiologic 2.pathologic: sinoatrial block,
11、 intra-atrial block, atrial ventricular block, bundle branch block, intraventricular block. 3.abnormal pathway conduction:preexcitation syndrome,Sinus Arrhythmia,1.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
12、exceed 120ms.,.,2.Sinus Tachycardia,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 feve
13、r , exercise , emotion , pain ,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,Ca
14、uses: Physiological:young adults, 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 max
15、imum sinus cycle length minus minimum 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 pacemaker,5.Sinus arrest,ECG: PP interval elongates abru
16、ptly, basically at sinus bradycardia, which is not common multiples of basic PP interval Escape beat or rhythm is common seen,6.Sick sinus syndrome sss,Etiology Intrinsic :sinus node itself is involved, e.g. ischemia, regressive degeneration, infiltration of other cells or tissues Extrinsic :high va
17、gal tone, hyperkalemia, antiarrhythmics most frequent etiology are regressive degeneration and CHD,Sick Sinus Syndrome,ECG: persistent marked sinus bradycardia(50bpm); sinus arrest , sinoatrial block; sinoatrial block and atrialventricular block exist at the same time; No escape beats appear after sinus arrest bradycardia-tachycardia syndrome(sinus bradycardia, atrial tachycardia, atrial flutter, atrial fibrillation alternatively),