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Properties of cardiac tissue 心脏组织的特性 Automaticity 自律性自律性:ability to initiate an impulse spontaneously and continuously.Excitability兴奋性兴奋性:ability to be electrically stimulated.Contractility收缩性收缩性:ability to respond mechanically to an impulse.Conductivity传导性传导性:ability to transmit an impulse along a membrane in an orderly manner.Conduction system:a brief review传导系统传导系统 P wave begins with the firing of the SA node and represents depolarization去极化去极化 of the fibers of the atria心房心房,resulting in atrial contraction心房收缩心房收缩.The QRS complex represents depolarization去极化去极化 of the ventricles心心室室,resulting in ventricular contraction心室收缩心室收缩.The T wave represents repolarization复极复极of the ventricles心室心室,or the time at which the ventricles return to the prestimulated state.Conduction system:a brief review Intervals波间隔波间隔between these waves reflects the lengths of time it takes for the impulses to travel from one area of the heart to the other.The PR interval represents the period during which the impulse spreads through the atria,AV node房室结房室结,bundle of His希氏束希氏束,and Purkinje浦肯野纤维浦肯野纤维.The QRS interval represents the time it takes for depolarization去去极化极化of both ventricles.The QT interval represents the time it takes for complete depolarization除极除极and repolarization复极复极of the ventricles.Dysrhythmia Dysrhythmia is an abnormal cardiac rhythm in terms of the frequency of the impulse频率,rhythm节律,origin site起源部位,conduction velocity传导速度and excitement order激动次序.Classification of Dysrhythmia 心律失常的分类心律失常的分类 Abnormal impulse formation 冲动形成异常冲动形成异常sinus dysrhythmia 窦性心律失常sinus tachycardia窦性心动过速窦性心动过速sinus bradycardia窦性心动过缓窦性心动过缓窦性心律不齐sinus arrest窦性停搏ectopic rhythm异位心律Passive ectopic rhythm被动性异位心律Escaped 逸博Escapedrhythm 逸博心律Active ectopic rhythm主动性异位心律期前收缩期前收缩Premature ContractionParoxysmal tachycardia阵发性阵发性心动过速心动过速atrial flutter房扑，房扑，atrial fibrillation房颤房颤ventricular flutter室扑，室扑，ventricular fibrillation室颤室颤 Abnormal impulse comduction 冲动传导异常冲动传导异常 Physiological:生理性：interference and separation of AV干扰和房室分离 pathological病理性：block of SA窦房传导阻滞 block of atrial pathway房内传导阻滞 block of atrioventricular pathway房室传导阻滞房室传导阻滞 Block of bundle branch束支或分支阻滞或室内阻滞 房室间传导途径异常：WPW 预激综合征Sinus tachycardia窦性心动过速 Clinical association:It associated with physiological stressors such as exercise,fever,pain,anxiety,hypotension,hypovolemia低血容量,anemia,hypoxemia低氧血症,hypoglycemia低血糖症,myocardial ischemia,CHF,and thyrotoxicosis甲状腺毒症.It also can be affected by drugs such as epinephrine,norepinephrine,caffeine,atropine阿托品,theophylline茶硷,nifedipine硝苯地平,hydralazine胼酞嗪(降压药)Sinus tachycardia窦性心动过速 Significance:The clinical significance of sinus tachycardia depends on patients tolerance of the increased HR.The patient may have symptoms of dizziness头头晕晕,hypotension低血压低血压may occur.Angina or an increase in infarct size may accompany persistent sinus tachycardia in the patient with MI心肌梗塞心肌梗塞.Treatment The treatment is determined by underlying causes.In certain setting,-blocker therapy is used to reduced HR and decrease myocardial oxygen consumption.Sinus tachycardiaECG characteristics HR is greater than 100 bpm,rhythm is regular.The P wave is normal,precedes each QRS complex,and has a normal contour and fixed interval.The PR interval is normal and the QRS complex has a normal contour.Sinus bradycardia 窦性心动过缓窦性心动过缓 Clinical association 临床联系临床联系:It occurs in response to hypothermia低体温,carotid sinus massage按压颈动脉窦按压颈动脉窦,increased intraocular pressure眼内压眼内压,increased vagal tone迷走神经紧张迷走神经紧张,and administration of parasympathomimetic拟副交感神经药drugs.Diseases states associated with sinus bradycardia are hypothyroidism 甲状腺机能减退,increased intracranial pressure颅内压,obstructive jaundice阻塞性黄疸 and inferior wall MI.Sinus bradycardia 窦性心动过缓窦性心动过缓 Significance意义意义:The clinical significance of sinus bradycardia depends on how the patients tolerates it hemodynamically.Hypotension with decreased CO may occur in some circumstances.Treatment治疗治疗:for the patient with symptoms,administration of atropine阿托品阿托品,and anticholinergic drug抗胆碱能药抗胆碱能药.Pacemaker therapy may be required.Sinus bradycardia窦性心动过缓窦性心动过缓ECG characteristics HR is less than 60 bpm,rhythm is regular.The P wave precedes each QRS complex.The PR interval is normal and the QRS complex has a normal contour and normal length.Premature Atrial Contraction(PAC)房性期前收缩房性期前收缩 A PAC is a contraction originating from an ectopic focus异位病灶异位病灶 in the atrium in a location other than the sinus node.It originates in the left or right atrium and travels across the atria by an abnormal pathway,creating a distorted P wave.At the AV node房室结房室结,it is stopped(nonconducted PAC),delayed(lengthened PR interval),or conducted normally.It moves through the AV node,and in most cases,it is conducted normally through the ventricles.Premature Atrial Contraction(PAC)房性期前收缩房性期前收缩 Clinical association In a normal heart,it can result from stress or the use of caffeine,tobacco or alcohol.It also can result from diseases states such as infection,inflammation,hyperthyroidism甲亢甲亢,COPD,heart diseases,valvular diseases.A PAC and also be caused by enlarged atria.Significance:a PAC may be prelude前奏前奏to supraventricular tachycardias室上性心动过速室上性心动过速.Treatment:depends on patients symptoms.Withdrawal of sources of stimulation such as caffeine may be warranted.Drugs such as digoxin,quinidine奎尼丁,procainamide普鲁卡因,flecainide氟卡尼,and-blockers can be used.Premature Atrial Contraction(PAC)房性期前收缩房性期前收缩ECG characteristics HR varies and rhythm is irregular.The P wave may be notched缺迹缺迹 or have negative deflection逆向逆向的偏转的偏转,or it may be hidden in the preceding T wave.QRS is usually normal,if the QRS interval is 0.10 second or longer,abnormal conduction through the ventricle is present.The PR interval may be shorter or longer than normal PR interval,but its within normal limit.Paroxysmalsupraventriculartachycardia(PSVT)阵发性室上性心动过速阵发性室上性心动过速PAVT is dysrhythmia originating in an ectopic focus anywhere above the bifurcation of the bundle of His希氏束希氏束分支分支.PSVT occurring via an accessory pathway旁路途径旁路途径is designated as orthodromic顺向顺向or antidromic逆逆向性向性 tachycardia.Paroxysmalsupraventriculartachycardia(PSVT)阵发性室上性心动过速阵发性室上性心动过速 Orthodromic顺向顺向refers to anterograde顺时顺时,or forward 向前向前conduction through the AV node and retrograde逆行逆行,backward 向后向后conduction,through the accessory pathway.Antidromic逆逆向向refers to the opposite:anterograde conduction顺时传导顺时传导through the accessory path 旁路途径旁路途径 and retrograde conduction 逆行传导逆行传导through the AV node.Paroxysmal supraventricular tachycardia(PSVT)阵发性室上性心动过速阵发性室上性心动过速 Clinical association In the normal heart,PSVT is associated with overexertion,emotional stress,changes of position,deep inspiration,and stimulation and stimulants such as caffeine and tobacco.In a diseases state,PSVT is associated with rheumatic heart disease,Wolff-Parkinson-White(WPW)预激综合症预激综合症(conduction via accessory pathways),digitailis intoxication,coronary artery disease or cor pulmonary.Paroxysmal supraventricular tachycardia(PSVT)阵发性室上性心动过速阵发性室上性心动过速 Significance:a prolonged episode and HR greater than 180 bpm may precipitate a decreased CO with hypotension and myocardial ischemia.Treatment:vagalstimulation迷走神经刺激迷走神经刺激:carotid massage按按摩颈动脉窦摩颈动脉窦or the Valsalva meneuver Valsalva动作动作 pharmacologic therapy:adenosine腺苷腺苷,verapamil异搏定异搏定,diltiazem地尔硫卓地尔硫卓,digitalis洋地黄洋地黄 and propranolol心得安心得安.However,dititalis洋地黄洋地黄and calcium channel blockers can cause hemodynamic collapse in WPW syndrome.Paroxysmal supraventricular tachycardia(PSVT)阵发性室上性心动过速阵发性室上性心动过速ECG characteristics HR is 150to250 bpm and rhythmisregular.The P wave is often hidden in the preceding T wave and has an abnormal contour.The PR interval may be prolonged,shortened or normal QRS complex may have a normal or abnormal contour.Atrial flutter 心房扑动 Atrial flutter is identified by recurring,regular,sawtooth-shape flutter waves锯齿形扑波锯齿形扑波.Atrial flutter is relatively rare dysrhythmia.Clinical association:It rarely occurs in a normal heart.In disease states,it is associated with CAD,hypertension,mitral valve disorders,pulmonary embolus肺栓塞肺栓塞,cor pulmoale肺心肺心病病,cardiomyopathy心肌病心肌病,hyperthyroidism甲甲亢亢 and the use of drugs such as digitalis,quinidine奎尼丁,and epinephrine.Atrial flutter心房扑动 Significance:high ventricular rates associated with atrial flutter can decrease CO and cause serious consequence such as heart failure,especially in the patient with underlying heart disease.Treatment:Electrical cardioversion心脏电复律心脏电复律may be used to convert the atrial flutter to sinus rhythm in an emergency situation.Drugs used include verapamil 异搏定异搏定,digoxin洋地洋地黄黄 quinidine奎尼丁奎尼丁,procainamide普鲁卡因普鲁卡因 and-blockers.Atrial flutter心房扑动ECG characteristics Atrial rate is 250 to 330 bpm.The ventricular rate varies according ot the conduction ratio.In 2:1 conduction,the ventricular rate is typically found to be apporximately 150 bpm.Atrial rhythm is regular,and ventricular rhythm is usually regular.The P wave is represented by sawtooth waves锯齿波锯齿波or F waves.The PR interval is available.QRS complex is normal in contour.Atrial fibrillation心房颤动 Atrial fibrillation is characterized by a total disorganization of atrial electrical activity电生理电生理活动活动without effective atrial contraction心房收缩心房收缩.Ventricular response心室反应心室反应is irregular,and if the patient is untreated,the ventricular rate will be 100 to 160 bpm.The dysrhythmia may be chronic or intermitten.Clinical association:it usually occurs in the patient with underlying heart disease;it also associated with thyrotoxicosis甲状腺毒症甲状腺毒症,alcoholism,infection,gastroenteritis and stress.Atrial fibrillation心房颤动 Significance:It often result in a decrease in CO due to ineffective atrial contractions and a rapid ventricular response.Thrombi血栓血栓may form in the atria as a result of ineffective atrial system may occur as a complication with subsequent development of a stroke.Treatment In emergeny situation,cardioversion心脏电复心脏电复律may be used to convert atrial fibrillation to normal sinus rhythm.Medication used include digoxin洋地黄洋地黄,verapamil 异异搏定搏定,quinidine奎尼丁奎尼丁,procainamide普鲁卡普鲁卡diltiazem地尔硫卓地尔硫卓,and-blockers,flecainide氟卡尼,propafenone 普罗帕酮普罗帕酮 and sotalol施太可盐酸索施太可盐酸索他洛尔他洛尔.Atrial fibrillation心房颤动ECG characteristics Atrial rate may be as high as 350 to 600 bpm.The ventricular rate varies from as low as 50 to as high as 180 bpm.Atrial rhythm is chaotic混乱,and ventricular rhythm is irregular.The P wave shows fibrillatory waves房颤波房颤波(f wave),but no definite P waves can be observed.The PR interval is not measurable.QRS complex usually has a normal contour.Premature ventricular contractions室性期前收缩 Premature ventricular contractions:is a contraction originating in a ectopic focus异位节律异位节律in the ventricles.The QRS wave is usually wider than 0.12 seconds.The T wave is generally large and opposite in direction to the major deflection of the QRS complexPremature ventricular contractions(PVC)室性期前收缩室性期前收缩PVC are initiated from different foci病灶appear different in contour不同轮廓from each other and are call multifocal PVCs多灶性期前收缩.When every other beat is PVC,it is called ventricular bigeminy心室二联律.When every third beat is PVC,it is called ventricular trigeminy心室三联律.Premature ventricular contractions(PVC)室性期前收缩室性期前收缩Two consecutive PVCs are called couplets成对室性期前收缩成对室性期前收缩.Three consecutive PVCs are called triplets.Ventricular tachycardia室性心动过速室性心动过速occurs when there are three or more consecutive PVCs.When a PVC falls on the T wave of preceding beat,the R on T phenomenon R波落在波落在T波上现象波上现象 occurs and is considered to be dangerous because it may precipitate ventricular tachycardia室室性心动过速性心动过速or ventricular fibrillation心室颤动心室颤动.Premature ventricular contractions(PVC)室性期前收缩室性期前收缩 Clinical association:Is associated with stimulation such as caffeine,alcohol,aminophyline氨茶碱,epinephrine and digoxin.They are also associated with hypokelemia低钾血症低钾血症,hypoxia缺氧缺氧,fever,exercise,and emotional stress.Disease states associated with PVC includes MI,CHF and CAD.Significance:In heart diseases,depending on frequency,PVCs may reduce the CO and precipitate angina and heart failure.Treatment:FortreatingPVCs,lidocaine利多卡因利多卡因is the drug of choice.Procainamide普鲁卡因普鲁卡因 is the second drug of choice if lidocaine is ineffective.Premature ventricular contractions(PVC)室性期前收缩室性期前收缩ECG characteristics HR varies.Rhythm is irregular because of premature beat.A retrograde逆行逆行P wave is possible,and P wave is rarely visible because is usually lost in the QRS complex of PVC.The PR interval is not measurable.QRS complex is wide and distorted in shape,more than 0.01 second.Ventricular tachycardia 室性心动过速The ECG diagnosis of ventricular tachycardia is made when a run of three or more PVCs occurs.The QRS is distorted歪曲歪曲in appearance with a duration exceeding 0.12 second and with the ST-T direction pointing to the major QRS deflection.Ventricular tachycardia may be sustained持续性(lasting longer than 30 seconds)or nonsustained 非持续性(lasting 30 seconds or less).Ventricular tachycardia Clinical association:Is associated with acute MI,CAD,significant electrolyte imbalances,cardiomyopathy心肌病,long QT syndrome and coronary reperfusion after thrombolytic therapy溶栓治疗后冠状动脉再灌注.Is also can be observed in the patient who has not heart diseases.Significance:The appearance of ventriculartachycardia is an ominous不祥sign.It may cause a severe decreased in CO.The result may be pulmonary edema肺水肿肺水肿,shock休克休克,and insufficient blood flow to the brain大脑大脑血流量不足血流量不足.Ventricular fibrillation心室颤动心室颤动may develop.Ventricular tachycardia Treatment:If the patient is hemodynamically stable,treatment consists of administration of lidocaine利多卡因利多卡因bolus,Procainamide普鲁卡因 is the second drug of choice if lidocaine is ineffective.If the patient is unconscious or hemodynamically unstable,immediate cardioversion心脏电复律is the recommended treatment.Ventricular tachycardiaECG characteristics Ventricular rate is 110 to 250 bmp.Rhythm may be regular or irregular.The P wave may be dissociated from脱离QRS complex,or it may be buried in QRS complexes or T waves.The PR interval is not measurable.QRS complex is prolonged for more than 0.10 seconds and the QRS complex is distorted.Ventricular fibrillation心室颤动Ventricular fibrillation is a severe derangement of the heart rhythm characterized on the ECG by irregular undulations 波动波动of varying contour and amplitude.This represents the firing of multiple ectopic foci异位病灶异位病灶in the ventricle.Mechanically the ventricle is simply“quivering颤抖颤抖”,and no effective contraction or CO occurs.Ventricular fibrillation心室颤动 Clinical association:It occurs in acute MI and myocardial ischemia and in chronic diseases such as CAD and cardiomyopathy心肌病心肌病.It may occur during cardiac pacing心脏起搏心脏起搏or cardiac catheterization procedures心导管检查心导管检查as a result of catheter stimulation of the ventricle.It may also occur with coronary reperfusion冠状动冠状动脉重新灌注脉重新灌注after thrombolytic therapy溶栓治疗溶栓治疗.Other clinical associations are accidental electrical shock,hyperkalemia高钾血症高钾血症and hypoxemia低氧血症低氧血症.Ventricular fibrillation心室颤动Significance:It results in unconsciousness昏迷昏迷,absence of pulse,apnea呼吸困难呼吸困难,and seizure癫痫癫痫.If left untreated,the patient with this condition will die.Treatment:Immediate initiation of cardiopulmonary resuscitation心肺复苏心肺复苏(CPR)and initiation of advanced cardiac life support(ACLS)measures高级心脏生命支持高级心脏生命支持with use of defibrillation and definitive drug therapy.Ventricular fibrillation心室颤动ECG characteristicsHR is not measurable.Rhythm irregular and chaotic.The P is not visible.The PR interval and the QRS interval are not measurable.First degree AV block I度房室传导阻滞First degree AV block is a type of AV block in which every impulse in conducted to the ventricles but the duration of AV conduction is prolonged.This is manifested by PR interval greater than 0.20 second.After the impulse moves through the AV node,it is usually conducted normally through the ventricle.First degree AV block I度房室传导阻滞Clinical association:it is associated with MI,chronic ischemia heart diseases,rheumatic fever风湿热风湿热,hyperthyroidism甲亢甲亢,vagal simulation and drugs such as digitalis,-blocker,flecainide 氟卡尼,and IV verapamil 异搏定异搏定.Significance:first degree AV block may be a precursor of high degrees of AV block.Treatment:there is no treatment for the first degree AV block.First degree AV block I度房室传导阻滞ECG characteristics Atrial rate is normal,and rhythm is regular.The P wave is normal.The PR interval is prolonged for more than 0.20second.QRS complex usually has a normal contour.Second degree AV block,Type I I型 二度房室传导阻滞 Type I AV block includes a gradual lengthening of the PR interval,and a QRS complex is droped.Type I AV block most commonly occurs in the AV node,but it can also occur in the His-Purkinje System.Clinical association:type I AV block may result from use of drugs such as digoxin or-blocker.It may also be associated with ischemia cardiac disease and other diseases that can slow AV conduction.Second degree AV block,Type I I型 二度房室传导阻滞Significance:is usually a result of myocardial ischemia in an inferior MI.It is almost transient and is usually well tolerated,however,it may be a warning signal预警信号预警信号of impending significant AV conduction disturbance.Treatment:if the patient is symptomatic,atropine阿托品阿托品is used to increased HR or a temporary pacemaker临时起搏器临时起搏器may be needed,especially if the patient has an acute MI.Second degree AV block,Type I I型 I I度房室传导阻滞ECG characteristics Atrial rate is normal,and ventricular rate may be slower as a result of dropped QRS complexs.Ventricular rhythm is irregular.The P wave has a normal contour.The PR interval is progressively lengthens before the nonconducted P wave occurs PR间期逐步延长，间期逐步延长，直至下一个直至下一个P波受阻不能下传波受阻不能下传至心室，至心室，and a QRS complex is dropped.QRS complex has a normal contour.Second degree AV block,Type II I I型 二度房室传导阻滞 Type II AV block:A P wave is nonconducted,and this almost always occurs when a bundle branch block is present束支传导阻滞束支传导阻滞.Type II AV block almost always occurs in the His-Purkinje system浦肯野系统浦肯野系统.Second-degree block is a more serous type of block in which a certain number of impulse from the sinus node are not conducted to the ventricles.This occurs in ratios of 2:1 or 3:1,and so on then there are two P waves to one QRS complex,three P waves to one QRS complex.Second degree AV block,Type II I I型 二度房室传导阻滞 Clinical association:Type II AV block is associated with rheumatic风湿性风湿性and atherosclerotic粥样硬化性粥样硬化性heart disease,acute anterior MI,digitalis toxicity.Significance:It often progresses to third degree AV block and is associated with a poor prognosis.It is an indication for therapy with a permanent pacemaker.The reduced HR may result in decreased CO with subsequent hypotension and myocardial ischemia.Second degree AV block,Type II I I型 二度房室传导阻滞Treatment:Temporary treatment before insertion of a permanent pacemaker involves the use of a temporary pacemaker.Drugs such as atropine阿托品阿托品,epinephrine or dopamine多巴胺多巴胺can be tired as temporary measures to increase HR until pacemaker therapy is available.Second degree AV block,Type II I I型 二度房室传导阻滞ECG characteristics Atrial rate is normal,and ventricular rate depends on the intrinsic rate and the degree of AV block.Sinus rhythm is regular,but ventricular rhythm may irregular.The P wave has a normal contour.The PR interval may be normal or prolonged but remains fixed on conducted beats.QRS complex widens more than 0.12 second because of bundle branch block.Third-degree AV block三度房室传导阻滞Third-degree AV block:is complete heart block,constitutes one form of AV dissociation房室分离房室分离in which no impulse from the atria are conducted to the ventricles.The atria are stimulated and contract independently of the ventricles.The ventricle rhythm is an escape rhythm,and focus may be above or below the bifuration of the His bundle 希氏束希氏束.Third-degree AV block I I I度房室传导阻滞 Clinical association:is associated with fibrosis 纤维化纤维化 or calcification 钙化钙化 of the cardiac conduction system,CAD,myocarditis,cardiomyopathy心肌炎心肌炎,open heart surgery and some systemic diseases such as amyloidos
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