ARRHYTHMIA (General) Prof. Hua Fu Cardiovascular Department West China Hospital, Sichuan University

Outline Arrhythmia is any of a group of conditions in which the electrical activity of the heart is irregular or is faster or slower than normal. The heartbeat may be too fast (over 100 beats per minute) or too slow (less than 60 beats per minute), and may be regular or irregular. A heart beat that is too fast is called tachycardia and a heart beat that is too slow is called bradycardia. Although many arrhythmias are not life-threatening, some can cause cardiac arrest. 四川大学华西医院 2018/11/22

Definition The Origin, Rate, Rhythm, Conduct velocity and sequence of heart activation are abnormally 四川大学华西医院 2018/11/22

Arrythmia related Cardioanatomy 心肌大部分由普通心肌纤维组成，小部分为特殊分化的心肌纤维，后者组成心脏的起搏传导系统。 心脏的起搏传导系统包括窦房结、结间束、房室结、房室束（希司束）、左右束支及其分支以及浦顷野纤维网。窦房结位于右心房上腔静脉入口处，是控制心脏正常活动的起搏点。房室结位于房间隔底部、卵圆窝下、三尖瓣内瓣叶与冠状窦开口之间，向前延续成房室束。房室束又称希司束，近端为主干或穿入部分，穿过中心纤维体，沿室间隔膜向前直至隔的肌顶部分（分支部分）。先分出左束支后分支，再分出左束支前分支，本身延续成右束支，构成三支系统。穿入部分经过中心纤维体时，位于二尖瓣与三尖瓣环之间，分支部分则至室间隔膜部、肌肉部和主动脉瓣邻近。左束支后分支粗短、较早呈扇形分支；左束支前分支和右束支细长，分支晚，两侧束支于心内膜下走向心尖分支再分支，细支相互吻合成网，称为浦肯野纤维网，深入心室肌 窦房结与房室结间有边界不清的前、中、后三条结间束连接。结间束终末连接房室结的部分，与房室结、房室束主干合称房室交接处（亦称房室交界或房室连接处）。 心房肌与心室肌之间有纤维环，心房兴奋不能经心肌传至心室，房室结与房室束为正常房室间传导的唯一通路。 心脏传导系统的血供：窦房结、房室结和房室束主干大多由右冠状动脉供血，房室速 分支部分、左束支前分支和右束支血供来自左冠状动脉前降支，而左束支后分支则由左冠状动脉回旋支和右冠状动脉供血。 窦房结和房室结有丰富的副交感神经分布。前者来自右侧迷走神经、后者来自左侧迷走神经 The cardiac muscle majority is composed of the ordinary cardiac muscle textile fiber, the small part for the cardiac muscle textile fiber of special differentiation, latter composes the cardiac pacing-conduction system 四川大学华西医院 2018/11/22

Cardiac Conduction System SAN Internodal pathways AVN His bundle L./R. bundle branch Purkinje fibers 四川大学华西医院 2018/11/22

Pacing conduction system 四川大学华西医院 2018/11/22

Pathogenesis and Inducement of Arrhythmia Some physical condition Pathological heart disease Other system disease Electrolyte disturbance and acid-base imbalance Physical and chemical factors or toxicosis 四川大学华西医院 2018/11/22

Mechanism of Arrhythmia Abnormal heart pulse formation Sinus pulse Ectopic pulse Triggered activity Abnormal heart pulse conduction Reentry Conduct block 四川大学华西医院 2018/11/22

心肌细胞的动作电位 5 Phases Phase 0 Phase 1 Phase 2 Phase 3 Phase 4 快速或上升 钠离子内流入进入细胞进行除极 Phase 1 快速复极初期：钾离子外流 Phase 2 平台期: 持续的钠离子内流和缓慢钙离子内流和钾离子外流 Once the membrane reaches -40 to -45mV the charge falls quickly to the resting level. The cell membrane once again becomes polarized and the cycle begins again. (Ellenbogen, Kenneth A. & Wood, Mark A. Basic Concepts of Pacing. Cardiac Pacing & ICDs, 3rd Edition. Malden, MA: Blackwell Science, Inc., 2002: 48-49.) Also see: Fogoros, Richard N. Electrophysiologic Testing, 3rd Edition. Blackwell Science, Inc. 1999. Phase 3 快速复极末期: 钾离子外流 Phase 4 静息期

Abnormal heart pulse formation 触发机制 后电位产生于动作电位的第3相（早期）或第4相（晚期） 可触发心律失常 Abnormal heart pulse formation Like automaticity, triggered activity involves the leakage of positive ions into a cell, resulting in new action potentials. However, unlike automaticity, Triggered Activity is not consistently spontaneous. It may be either a single or repetitive firing of a myocardial cell, or group of cells, caused by re-excitation. Ion leakages that occur late in Phase 3 or early in Phase 4 (after cell recovery has begun) are called afterdepolarizations, or late potentials. Afterdepolarizations can be the ‘trigger’ that cause ventricular tachyarrhythmias. Automaticity Triggered activity 四川大学华西医院 2018/11/22

Automaticity Heart cells other than those of the SA node depolarize faster than SA node cells, and take control as the cardiac pacemaker. Factors that enhance automaticity include:  SANS,  PANS,  CO2,  O2,  H+,  stretch, hypokalemia and hypocalcaemia. Examples: Ectopic atrial tachycardia or multifocal tachycardia in patients with chronic lung disease OR ventricular ectopy after MI 四川大学华西医院 2018/11/22

Triggered activity… is like a domino effect where the arrhythmia is due to the preceding beat. Delayed after-depolarizations arise during the resting phase of the last beat and may be the cause of digitalis-induced arrhythmias. Early after-depolarizations arise during the plateau phase or the repolarization phase of the last beat and may be the cause of torsades de pointes (ex. Quinidine induced) 四川大学华西医院 2018/11/22

Abnormal heart pulse conduction: Reentry: most common 四川大学华西医院 2018/11/22

A unidirectional block in one of those pathways. Reentry Requires… Electrical Impulse Cardiac Conduction Tissue Fast Conduction Path Slow Recovery Slow Conduction Path Fast Recovery 2 distinct pathways that come together at beginning and end to form a loop. A unidirectional block in one of those pathways. Slow conduction in the unblocked pathway. 2018/11/22 四川大学华西医院

Cardiac Conduction Tissue The “Re-Entry” Mechanism of Ectopic Beats & Rhythms Electrical Impulse Cardiac Conduction Tissue Fast Conduction Path Slow Recovery Slow Conduction Path Fast Recovery Tissues with these type of circuits may exist: in microscopic size in the SA node, AV node, or any type of heart tissue in a “macroscopic” structure such as an accessory pathway in WPW 2018/11/22 四川大学华西医院

Cardiac Conduction Tissue The “Re-Entry” Mechanism of Ectopic Beats & Rhythms Premature Beat Impulse Cardiac Conduction Tissue Repolarizing Tissue (long refractory period) Fast Conduction Path Slow Recovery Slow Conduction Path Fast Recovery 1. An arrhythmia is triggered by a premature beat The beat cannot gain entry into the fast conducting pathway because of its long refractory period and therefore travels down the slow conducting pathway only 2018/11/22 四川大学华西医院

Cardiac Conduction Tissue The “Re-Entry” Mechanism of Ectopic Beats & Rhythms Cardiac Conduction Tissue Fast Conduction Path Slow Recovery Slow Conduction Path Fast Recovery 3. The wave of excitation from the premature beat arrives at the distal end of the fast conducting pathway, which has now recovered and therefore travels retrogradely (backwards) up the fast pathway 2018/11/22 四川大学华西医院

Cardiac Conduction Tissue The “Re-Entry” Mechanism of Ectopic Beats & Rhythms Cardiac Conduction Tissue Fast Conduction Path Slow Recovery Slow Conduction Path Fast Recovery 4. On arriving at the top of the fast pathway it finds the slow pathway has recovered and therefore the wave of excitation ‘re-enters’ the pathway and continues in a ‘circular’ movement. This creates the re-entry circuit 2018/11/22 四川大学华西医院

Re-entry Circuits as Ectopic Foci and Arrhythmia Generators Atrio-Ventricular Nodal Re-entry supraventricular tachycardia Ventricular Re-entry ventricular tachycardia Atrial Re-entry atrial tachycardia atrial fibrillation atrial flutter Atrio-Ventricular Re-entry Wolf Parkinson White supraventricular tachycardia 2018/11/22 四川大学华西医院

bRADYCARDIAS A slow rhythm (less than 60 beats/min) May be caused by a slowed signal from the SAN, a pause in the normal activity of the SAN, or by blocking of the electrical impulse on its way from the atria to the ventricles (AV block or heart block) May also be present in the normally functioning heart of endurance athletes or other well-conditioned persons bRADYCARDIAS 2018/11/22 四川大学华西医院

MECHANISM OF BRADYCARDIAS 窦房结自律性受损　如因炎症、缺血、坏死或纤 维化可致窦房结功能衰竭，起搏功能障碍，引起 窦性心动过缓，窦性停搏 传导阻滞 SAN及A病变，可引起S-A阻滞等 AVB是由于AVN或房室束的传导功能降低，SAN的兴奋 激动不能如期向下传导而引起，可分为生理性和病理性 两种 病理性常见于风湿性心肌炎、白喉及其他感染、冠 心病、洋地黄中毒等 生理性多系迷走神经兴奋性过高 四川大学华西医院 2018/11/22

Classification of Arrhythmia Atrial Junctional arrhythmia Ventricular Heart blocks Sudden arrhythmic death syndrome Classification of Arrhythmia Arrhythmia may be classified by rate (normal sinus rhythm, tachycardia, bradycardia) or mechanism (automaticity, reentry, junctional, fibrillation). It is also appropriate to classify by site of origin: 四川大学华西医院 2018/11/22

Diagnosis of Arrhythmia Medical History Physical Examination Laboratory Test 四川大学华西医院 2018/11/22

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ELECTROCARDIOGRAM “5” steps approach to arrhythmias Step1: Is there a “QRS” Step2: Is there a “P” Wave Step3: What is the relationship between the P waves and the QRS complexes? Step4: Calculate rate Step5: Miscellaneous 四川大学华西医院 2018/11/22

Step 1: Is there a “QRS” (No pulse) YES NO NARROW WIDE CHAOTIC FLAT LINE PEA Asystole VT VF 四川大学华西医院 2018/11/22

Step 2: Is there a “P” Wave YES NO RR Interval RATE MORPHOLOGY VARY CONSTANT Inverted 220 to 350 AF JUNCTIONAL JUNCTIONAL Atrial Flutter 四川大学华西医院 2018/11/22

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Step 3: What is the relationship between the P waves and the QRS complexes? 四川大学华西医院 2018/11/22

HEART BLOCK n“P” = n“QRS” ? PR interval PR interval No Yes Normal < 0.2 Normal > 0.2 Io AVB Constant ? Yes IIo AVB type 2 No RR interval Yes IIIoAVB Constant? No Type1 IIo 四川大学华西医院 2018/11/22

1st Degree block (AV Nodal Delay) 四川大学华西医院 2018/11/22

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Event Monitors Holter monitoring: Document symptomatic and asymptomatic arrhythmias over 24-48 hours. Can also evaluate treatment effectiveness in a-fib, pacemaker effectiveness and identify silent MIs. Trans-telephonic event recording: patient either wears monitor for several days or attaches it during symptomatic events and an ECG is recorded and transmitted for evaluation via telephone. Only 20% are positive, but still helpful. 四川大学华西医院 2018/11/22

Exercise testing Symptoms only appear or worsen with exercise. Also used to evaluate medication effectiveness (esp. flecanide & propafenone) You can assess SA node function with exercise testing. Mobitz 1 (Wenkebach) is blockage at the AV node, so catecholamines from exercise actually help! Mobitz 2 is blockage at bundle of His, so it worsens as catecholamines from exercise increase AV node conduction, thus prognosis is worse. *PVCs occur in 10% without and 60% of patients with CAD. *PVCs DO NOT predict severity of CAD (neither for nor against)! 四川大学华西医院 2018/11/22

Signal Averaged ECG Used only in people post MI to evaluate risk for v-fib or v-tach. Damage around the infarct is variable, so this measures late potentials (low-signal, delayed action potentials) as they pass through damaged areas. Positive predictive value is 25%-50% but negative predictive value is 90%-95%, thus if test is negative, patient is at low risk. 四川大学华西医院 2018/11/22

Electrophysiologic Testing… Catheters are placed in RA, AV node, Bundle of HIS, right ventricle, and coronary sinus (to monitor LA and LV). Used to evaluate cardiogenic syncope of unknown origin, symptomatic SVT, symptomatic WPW, and sustained v-tach. *Ablative therapy is beneficial in AV node reentry, WPW, atrial tachycardia, a-flutter, and some v-tach. Complication is 1% 四川大学华西医院 2018/11/22

Management Physical maneuvers, Medications, Electricity conversion, or Electro- or cryo-cautery. Management The method of cardiac rhythm management depends firstly on whether or not the affected person is stable or unstable 四川大学华西医院 2018/11/22

Therapy Principal Pathogenesis therapy Stop the arrhythmia immediately if the hemodynamic was unstable Individual therapy 四川大学华西医院 2018/11/22

Physical maneuvers (vagal maneuvers) A number of physical acts can increase parasympathetic nervous supply to the heart, resulting in blocking of electrical conduction through the AV node. This can slow down or stop a number of arrhythmias that originate above or at the AV node 四川大学华西医院 2018/11/22

Anti-arrhythmia Agents Anti-tachycardia agents Anti-bradycardia agents 四川大学华西医院 2018/11/22

Anti-tachycardia agents Modified Vaugham Williams classification I class: Natrium channel blocker II class: ß-receptor blocker III class: Potassium channel blocker IV class: Calcium channel blocker Others: Adenosine, Digital 四川大学华西医院 2018/11/22

心肌细胞的动作电位 5 Phases Phase 0 Phase 1 Phase 2 Phase 3 Phase 4 快速或上升 钠离子内流入进入细胞进行除极 Phase 1 快速复极初期：钾离子外流 Phase 2 平台期: 持续的钠离子内流和缓慢钙离子内流和钾离子外流 Once the membrane reaches -40 to -45mV the charge falls quickly to the resting level. The cell membrane once again becomes polarized and the cycle begins again. (Ellenbogen, Kenneth A. & Wood, Mark A. Basic Concepts of Pacing. Cardiac Pacing & ICDs, 3rd Edition. Malden, MA: Blackwell Science, Inc., 2002: 48-49.) Also see: Fogoros, Richard N. Electrophysiologic Testing, 3rd Edition. Blackwell Science, Inc. 1999. Phase 3 快速复极末期: 钾离子外流 Phase 4 静息期

Classification of AADs 类别 亚 类 电 生 理 效 应 代 表 制 剂 新 制 剂 传导速度 不应期 Ap时限 Ⅰ Ⅰa ↓ ↑ 多↑ 奎尼丁 Ajmaline、Pirmenol、Aprindin Ⅰb ↓/↑ 利多卡因 Maxiletine、Tocainide Ⅰc ＝ Encainide Propafenone、Flecainide、Lorcainide、Ethmozide Ⅱ 心得安 Ⅲ =↑ 胺碘酮 Sotabl Ⅳ 异搏定 硫氮唑酮 Bepridi 目前临床应用的抗心律失常药物已有50种以上，常按药物对心肌细胞动作电位的作用来分类（Vaugham Williams法） Ⅰ类药抑制0相除极，曾被称为膜抑制剂，按抑制程度强弱及对不应期和传导速度的不同影响，再分为Ⅰa、Ⅰb和Ⅰc亚类，分别以奎尼丁、利多卡因和恩卡尼作为代表性药物。Ⅱ类为肾上腺素能β受体阻滞剂；Ⅲ类延长动作电位时限和不应期，以胺碘酮为代表性药物；Ⅳ类为钙内流阻滞剂，以维拉帕米为代表性药物 其它药物包括： 洋地黄类(临床上称之为第五类)以及新斯的明、甲氧胺、氯化钾、硫酸镁、ATP等 抗缓慢心律失常的药物，包括：拟交感胺类、阿托品类、碱性药物等 2018/11/22 四川大学华西医院

Clinical usage: Ia class Guinidine Procainamide Disopyramide: Side effect: like M-cholinergic receptor blocker Clinical usage: Ia class Less use in clinic 四川大学华西医院 2018/11/22

Clinical usage: Ib class Lidocaine Mexiletine Clinical usage: Ib class Perfect to ventricular tachyarrhythmia 四川大学华西医院 2018/11/22

Clinical usage: Ic class Moricizine Propafenone Clinical usage: Ic class Can be used in ventricular and/or supra-ventricular tachycardia and extrasystole. 四川大学华西医院 2018/11/22

Clinical usage: II class Propranolol: Non-selective Metoprolol: Selective ß1-receptor blocker, Perfect to hypertension and coronary artery disease patients associated with tachyarrhythmia. Clinical usage: II class ß-receptor blocker 四川大学华西医院 2018/11/22

Clinical usage: III class Amioarone: Perfect to coronary artery disease and heart failure patients Sotalol: Has ß-blocker effect Bretylium Clinical usage: III class Potassium channel blocker, extend-spectrum anti- arrhythmia agent. 四川大学华西医院 2018/11/22

Clinical usage: IV class and Others Verapamil Diltiazem Others: Adenosine Clinical usage: IV class and Others be used in supraventricular tachycardia 四川大学华西医院 2018/11/22

Anti-bradycardia agents ß-adrenic receptor activator Isoprenaline Epinephrine M-cholinergic receptor blocker Atropine Non-specific activator Aminophylline 四川大学华西医院 2018/11/22

Proarrhythmia effect of antiarrhythmia agents Ia, Ic class: Prolong QT interval, will cause VT or VF in coronary artery disease and heart failure patients III class: Like Ia, Ic class agents II, IV class: Bradycardia 四川大学华西医院 2018/11/22

Non-drug therapy Cardioversion: For tachycardia especially hemodynamic unstable patient Radiofrequency catheter ablation (RFCA): For those tachycardia patients (SVT, VT, AF, AFL) Artificial cardiac pacing: For bradycardia, heart failure and malignant ventricular arrhythmia patients. 四川大学华西医院 2018/11/22

Q & A 四川大学华西医院 2018/11/22