1、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
2、membrane in an orderly manner.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
3、 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
4、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 circumstance
5、s.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
6、 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 a
7、n 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 Clini
8、cal 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
9、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
10、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 int
11、erval 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
12、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.Antid
13、romic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,emot
14、ional 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
15、 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 mene
16、uver 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 charac
17、teristics 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
18、,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,hyperthyroidis
19、m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:Electr
20、ical 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
21、 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 n
22、ormal 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 16
23、0 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
24、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 atr
25、ial 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 35
26、0 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
27、 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 com
28、plexPremature 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 t
29、rigeminy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 bea
30、t,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
31、,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 a
32、ngina 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 retr
33、ograde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
34、 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).Ventr
35、icular 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
36、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
37、 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 characteristi
38、cs 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
39、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”,
40、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
41、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 unconsci
42、ousness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 an
43、d 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
44、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
45、 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 fi
46、rst 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 g
47、radual 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
48、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
49、 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 ma
50、y 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 cont
