ARRHYTHMIAARRHYTHMIA Cardiological Department Cardiological Department

Li HongboLi Hongbo

Anatomy of the conducting system

ELECTROPHYSIOLOGIC ELECTROPHYSIOLOGIC PRINCIPLESPRINCIPLES

•Automaticity:Automaticity: • the property of a cardiac cell has depolathe property of a cardiac cell has depola

rization spontaneous during phase 4 of trization spontaneous during phase 4 of the action potential. normally observed ihe action potential. normally observed in the sinus node; the specialized fibers n the sinus node; the specialized fibers of the His-Purkinje system; some specialof the His-Purkinje system; some specialized atrial fibers .ized atrial fibers .

ELECTROPHYSIOLOGIC ELECTROPHYSIOLOGIC PRINCIPLESPRINCIPLES

ExcitabilityExcitability Refractoriness-the period of recovery Refractoriness-the period of recovery

that cells can be reexcited by a stimulthat cells can be reexcited by a stimulus after being discharged.us after being discharged.

Absolute refractory periodAbsolute refractory period Effective refractory periodEffective refractory period Relative refractory periodRelative refractory period

ELECTROPHYSIOLOGIC ELECTROPHYSIOLOGIC PRINCIPLESPRINCIPLES

• ConductivityConductivity• the cardiac conducting system included the cardiac conducting system included

sinus node; interatria; atrioventricular nsinus node; interatria; atrioventricular node; right and left bundle branch; purkinode; right and left bundle branch; purkinje system. je system.

• The conduction speed is fastest through The conduction speed is fastest through purkinje system and is slowest through tpurkinje system and is slowest through the atrioventricular node. he atrioventricular node.

Classification of Classification of arrhythmiaarrhythmia

• Pathogenesis of arrhythmia Pathogenesis of arrhythmia * Disturbances of impulse formationDisturbances of impulse formation1.1. Sinus nodal disturbance Sinus nodal disturbance 2.2. Ectopic rhythmEctopic rhythm * Disturbances of impulse conductioDisturbances of impulse conductio

nn1.1. physiological physiological 2.2. pathologicalpathological

Classification of arrhythmiaClassification of arrhythmia

•Heart rate of arrhythmiaHeart rate of arrhythmia* Bradyarrhythmias Bradyarrhythmias * TachyarrhythmiasTachyarrhythmias

Sinus Nodal Sinus Nodal disturbancedisturbance

Normal sinus rhythmNormal sinus rhythm

• The normal sinus rhythm is defined as siThe normal sinus rhythm is defined as sinus rhythm with a heart rate between 60 nus rhythm with a heart rate between 60 and 100 beats/min.and 100 beats/min.

• The P wave is negative in lead aVR and pThe P wave is negative in lead aVR and positive in lead II ositive in lead II

Sinus tachycardiaSinus tachycardia

• With a heart rate exceeding 100 beats/min , With a heart rate exceeding 100 beats/min , Generally is between 100 and 180 beats/minGenerally is between 100 and 180 beats/min

• Sinus tachycardia is an arrhythmia, but not Sinus tachycardia is an arrhythmia, but not necessarily an abnormal rhythm. necessarily an abnormal rhythm.

• The following conditions can develop sinus tThe following conditions can develop sinus tachycardia: Such as exercise, anxiety, fever, achycardia: Such as exercise, anxiety, fever, hyperthyroidism, anemia, myocarditis and shyperthyroidism, anemia, myocarditis and some drugs. ome drugs.

SinusSinus BradycardiaBradycardia• ECG characteristics: sinus rhythm is present aECG characteristics: sinus rhythm is present a

nd the heart rate is less than 60 beats/min nd the heart rate is less than 60 beats/min • As a normal variant many normal and older pAs a normal variant many normal and older p

eople have sinus bradycardiaeople have sinus bradycardia• Sinus bradycardia commonly occurs in the folSinus bradycardia commonly occurs in the fol

lowing conditions: trained athletes, during sllowing conditions: trained athletes, during sleep, Hypothyriodism, drugs or sick sinus syndeep, Hypothyriodism, drugs or sick sinus syndromerome

• Most people with sinus bradycardia have no sMost people with sinus bradycardia have no symptoms. If the patient has chronic sinus braymptoms. If the patient has chronic sinus bradycardia cause symptoms, an electronic pacedycardia cause symptoms, an electronic pacemaker may be needed. maker may be needed.

Sinus ArrhythmiaSinus Arrhythmia• The definition of sinus arrhythmia is The definition of sinus arrhythmia is

sinus rhythm with an irregular rate. sinus rhythm with an irregular rate. • The maximum sinus cycle length The maximum sinus cycle length

minus the minimum sinus cycle minus the minimum sinus cycle length exceeds 0.12 seclength exceeds 0.12 sec

• The most common cause of sinus The most common cause of sinus arrhythmia is respiration arrhythmia is respiration

• This arrhythmia is a normal finding This arrhythmia is a normal finding in children and teenagers.in children and teenagers.

Sinus Arrest or Sinus Sinus Arrest or Sinus PausePause• Sinus arrest or pause is recognized by a Sinus arrest or pause is recognized by a

pause in the sinus rhythm. pause in the sinus rhythm. • The P-P interval of the pause does not The P-P interval of the pause does not

equal a multiple of the basic P-P intervequal a multiple of the basic P-P interval. al.

• Sinus arrest or pause will lead to cardiaSinus arrest or pause will lead to cardiac arrest with asystole unless the sinus nc arrest with asystole unless the sinus node regains function or some other pacode regains function or some other pacemaker (escape pacemaker) takes over.emaker (escape pacemaker) takes over.

Sinus Arrest or Sinus PauseSinus Arrest or Sinus Pause

• Sinus arrest can be caused by hypoxia, Sinus arrest can be caused by hypoxia, myocardial ischemia, hyperkalemia, digimyocardial ischemia, hyperkalemia, digitalis toxicity, and some drugs.talis toxicity, and some drugs.

• In elderly people the sinus node may unIn elderly people the sinus node may undergo degenerative changes and fail to fdergo degenerative changes and fail to function effectively. unction effectively.

Sick Sinus Syndrome(1)Sick Sinus Syndrome(1)• Sick sinus syndrome is a term that is aSick sinus syndrome is a term that is a

pplied to a syndrome encompassing a pplied to a syndrome encompassing a number of sinus nodal abnormalities number of sinus nodal abnormalities

• SSS encompasses both disordered SA SSS encompasses both disordered SA node automaticity and SA conduction.node automaticity and SA conduction.

• With marked sinus bradycardia, sinus With marked sinus bradycardia, sinus arrest, sinus exit block or junctional esarrest, sinus exit block or junctional escape rhythmscape rhythms

• Bradycardia-tachycardia syndrome Bradycardia-tachycardia syndrome

Sick Sinus Syndrome Sick Sinus Syndrome (2)(2)

•EKG Recognition:EKG Recognition: Inappropriate sinus bradycardia; sinus arrestInappropriate sinus bradycardia; sinus arrest Bradycardia -tachycardia syndrome (sinBradycardia -tachycardia syndrome (sin

us bradyarrhythmia and nonsinus tachyarrhytus bradyarrhythmia and nonsinus tachyarrhythmia).hmia).

AF or Afi with a slow ventricular rate response iAF or Afi with a slow ventricular rate response in the absences of drugsn the absences of drugs

Escape rhythm in the setting of persistent sinuEscape rhythm in the setting of persistent sinus arrest or exit block s arrest or exit block

Premature beatPremature beat Extrasystole Extrasystole

• The term “ectopy” , “ectopic pacemakeThe term “ectopy” , “ectopic pacemaker”, “ectopic beat” are used to describe nor”, “ectopic beat” are used to describe non sinus beats. n sinus beats.

• Ectopic beats can be premature:Ectopic beats can be premature: premature atrial contractions (PACs) premature atrial contractions (PACs) premature AV junctional contractions (PJCs)premature AV junctional contractions (PJCs) premature ventricular contractions (PVCs) premature ventricular contractions (PVCs)

Some definition about the prematurSome definition about the premature beatse beats

• Coupling interval: refers to the interval Coupling interval: refers to the interval between the premature beat and the prbetween the premature beat and the preceding normal beat.eceding normal beat.

• Compensatory pause: Compensatory pCompensatory pause: Compensatory pause indicates that the interval betweeause indicates that the interval between the normal QRS complexes immediatn the normal QRS complexes immediately before and immediately after the prely before and immediately after the premature beat.emature beat.

A fully compensatory pause is exactly twA fully compensatory pause is exactly twice the basic R-R interval. ice the basic R-R interval.

Premature atrial contractions Premature atrial contractions (PACs)(PACs)

• Premature beats arising from somewhPremature beats arising from somewhere in either the left or the right atrium ere in either the left or the right atrium but not in the sinus node. but not in the sinus node.

• The atria are depolarized from an ectoThe atria are depolarized from an ectopic site. pic site.

• The ventricular depolarization is generThe ventricular depolarization is generally not affected by PACs. ally not affected by PACs.

Premature atrial contractions Premature atrial contractions (PACs)(PACs)• PACs have the following major features: PACs have the following major features: 1. The beat is premature1. The beat is premature2. The PAC is often preceded by a visible P wa2. The PAC is often preceded by a visible P wa

ve. Occasionally the P wave may be “burieve. Occasionally the P wave may be “buried” in the T wave of the preceding beat. Thid” in the T wave of the preceding beat. This P wave has different shape and/or differens P wave has different shape and/or different PR interval from the P wave seen with the t PR interval from the P wave seen with the normal sinus beats. .normal sinus beats. .

3. With noncompensatory pause.3. With noncompensatory pause.4. The QRS complex is normal. Occasionally, P4. The QRS complex is normal. Occasionally, P

ACs will result in aberrant ventricular conduACs will result in aberrant ventricular conduction so the QRS is wider than normal. ction so the QRS is wider than normal.

B: a blocked PAC

Premature junctional contractionPremature junctional contractions (PJCs)s (PJCs) • Premature beats arising from AV junctionPremature beats arising from AV junction• The direction of atrial depolarization is frThe direction of atrial depolarization is fr

om bottom to top, just opposite to directiom bottom to top, just opposite to direction of normal sinus rhythm.on of normal sinus rhythm.

• The P wave is upright in lead aVR and doThe P wave is upright in lead aVR and downward in lead II wnward in lead II

• QRS complex is normal.QRS complex is normal.• Fully compensatory pause Fully compensatory pause

P wave is upright in lead aVR and downward in lead II

P wave will before, after, or buried in the QRS complex.

P-R interval is less than 0.12’,

R-P interval is less than 0.20’

Premature ventricular contractioPremature ventricular contractions (PVCs)ns (PVCs) • Premature beats arising in either the right or the left Premature beats arising in either the right or the left

ventricle ventricle • The EKG characteristics of PVCs:The EKG characteristics of PVCs:1.1. Aberrant in appearance. Aberrant in appearance. QRS complex is abnormally wide, usually 0.12 sec or QRS complex is abnormally wide, usually 0.12 sec or

more. more. T wave and the QRS complex usually point in opposite T wave and the QRS complex usually point in opposite

directions.directions.2. Have fully compensatory pause. 2. Have fully compensatory pause. 3. Interpolated PVC: A PVC falls between two normal bea3. Interpolated PVC: A PVC falls between two normal bea

ts ts

Different forms of PVCs in different leads

Difference between PVC and PAC

Interpolated PVC

Ectopic TachycardiaEctopic Tachycardia

• A run of three or more consecutive preA run of three or more consecutive premature beatsmature beats

1.1. paroxysmal atrial tachycardia paroxysmal atrial tachycardia 2.2. paroxysmal AV junctional tachycardia paroxysmal AV junctional tachycardia • Both of them are called supraventriculBoth of them are called supraventricul

ar tachycardiaar tachycardia 3. paroxysmal ventricular tachycardia 3. paroxysmal ventricular tachycardia

Paroxysmal supraventricular tachParoxysmal supraventricular tachycardia (PSVT)ycardia (PSVT)

• Including paroxysmal atrial and AIncluding paroxysmal atrial and AV junctional tachycardia V junctional tachycardia

• Mechanism:Mechanism:1.1. ReentrantReentrant2.2. AutomaticAutomatic

Paroxysmal supraventricular tachParoxysmal supraventricular tachycardia (PSVT)ycardia (PSVT)• EKG characteristics EKG characteristics 1.1. The heart rate is between 150 and 240 The heart rate is between 150 and 240

beats/minbeats/min2.2. Extremely regularExtremely regular3.3. P waves may or may not be visible. P waves may or may not be visible.

When seen, they are different from the P When seen, they are different from the P waves with normal sinus rhythm.waves with normal sinus rhythm.

4.4. The QRS complexes are normalThe QRS complexes are normal A wide QRS complex will be seen if the A wide QRS complex will be seen if the

patient has an underlying bundle branch patient has an underlying bundle branch block or if the PSVT induces a “rate -block or if the PSVT induces a “rate -related” bundle branch block.related” bundle branch block.

Paroxysmal ventricular tachycardParoxysmal ventricular tachycardia (PVT)ia (PVT)• A run of three or more consecutive PVCsA run of three or more consecutive PVCs• May occur as a single isolated burst, recMay occur as a single isolated burst, rec

urrent, or may persist for a long runurrent, or may persist for a long run

Paroxysmal ventricular tachycardParoxysmal ventricular tachycardia (PVT)ia (PVT)• EKG characteristics EKG characteristics 1.1. The heart rate is generally between 14The heart rate is generally between 14

0-200 beats/min0-200 beats/min2.2. The QRS complex is abnormally wide, The QRS complex is abnormally wide,

usually 0.12 sec or more.usually 0.12 sec or more.3.3. AV dissociationAV dissociation4.4. Fusion beats, Sinus capture beats Fusion beats, Sinus capture beats

Nonparoxysmal TachycardiaNonparoxysmal Tachycardia • Accelerated rhythm: Including atrial, AV juAccelerated rhythm: Including atrial, AV ju

nctional, ventricularnctional, ventricular• The heart rate is faster than normal sinus The heart rate is faster than normal sinus

rhythm and slower than paroxysmal tachrhythm and slower than paroxysmal tachycardia ycardia

• Accelerated AV junctional rhythm: 70-130 beats/minAccelerated AV junctional rhythm: 70-130 beats/min• Accelerated ventricular rhythm: 60-100 beats/minAccelerated ventricular rhythm: 60-100 beats/min

Torsades de pointesTorsades de pointes

• A special form of ventricular tachycardia A special form of ventricular tachycardia • QRS complexes appear to rotate cyclicalQRS complexes appear to rotate cyclical

ly, pointing downward for several beats ly, pointing downward for several beats and then twisting and pointing upward iand then twisting and pointing upward in the same lead n the same lead

Flutter and FibrillationFlutter and Fibrillation

• The rate of flutter and fibrillation is fasteThe rate of flutter and fibrillation is faster than tachycardia, may arise from atria r than tachycardia, may arise from atria or ventricles or ventricles

Atrial flutter (AF)Atrial flutter (AF)• EKG characteristicsEKG characteristics1.1. no true P waves no true P waves 2.2. flutter waves have a sawtooth shape flutter waves have a sawtooth shape 3.3. Atrial rate is between 250-350 beats/minAtrial rate is between 250-350 beats/min4.4. AV conduction at 2:1, 4:1 or 3:1 fashionAV conduction at 2:1, 4:1 or 3:1 fashion5.5. Ventricular rate is about 150 beats/min, 100 Ventricular rate is about 150 beats/min, 100

beats/min, or 75 beats/minbeats/min, or 75 beats/min6.6. Most patients with atrial flutter the ventriculMost patients with atrial flutter the ventricul

ar rate is regular ar rate is regular

Atrial fibrillation (Af)Atrial fibrillation (Af)

• The most commonly arrhythmiasThe most commonly arrhythmias• Atrial rate is between 350-600 times/minAtrial rate is between 350-600 times/min• Two EKG characteristics of Af:Two EKG characteristics of Af:1.1. No P waves, with irregular, wavy baselinNo P waves, with irregular, wavy baselin

e produced by the rapid f wavese produced by the rapid f waves2.2. The ventricular rate is usually quite irregThe ventricular rate is usually quite irreg

ular ular

Atrial fibrillation (Af)Atrial fibrillation (Af)• The f waves are coarse or fineThe f waves are coarse or fine• In patients with a normal AV junctioIn patients with a normal AV junctio

n, the ventricular rate is between 11n, the ventricular rate is between 110 to 180 beats/min0 to 180 beats/min

• AF may paroxysmal, persistent or peAF may paroxysmal, persistent or permanentrmanent

• Fibrosis and dilation of the atria maFibrosis and dilation of the atria may relate to the onset of AF y relate to the onset of AF

Difference between atrial flutter atrial fibrillation

Ventricular Flutter and Ventricular Flutter and FibrillationFibrillation

• These arrhythmia are severely and fatallyThese arrhythmia are severely and fatally• No distinct QRS complexes, ST segments, No distinct QRS complexes, ST segments,

and T wavesand T waves• Ventricular flutter: Ventricular flutter: sine wave sine wave 150 to 300 /min (uaually about 200)150 to 300 /min (uaually about 200) regularregular• Ventricular fibrillationVentricular fibrillation irregular undulations of varying contour airregular undulations of varying contour a

nd amplitude nd amplitude