Conduction DisturbancesConduction Disturbances

Waseem Jaffrani,MDWaseem Jaffrani,MD Department of CardiologyDepartment of Cardiology Tulane University School of Tulane University School of

Medicine Medicine

Overview of the PresentationOverview of the Presentation

Sino Atrial Exit BlockSino Atrial Exit Block AV BlocksAV Blocks Bundle Branch BlockBundle Branch Block Fascicular BlockFascicular Block Indications For Permanent Indications For Permanent

Pacemaker ImplantationPacemaker Implantation

Sino Atrial Exit BlockSino Atrial Exit Block

• Implies that there is delay or failure of a Implies that there is delay or failure of a normally generated sinus impulse to exit the normally generated sinus impulse to exit the nodal region.nodal region.

• First degree SA blockFirst degree SA block

• Second degree SA blockSecond degree SA block1.Type 1 (Mobitz 1)1.Type 1 (Mobitz 1)2.Type 2 (Mobitz 2)2.Type 2 (Mobitz 2)

• Third degree SA blockThird degree SA block

First Degree Sino AtrialFirst Degree Sino Atrial Exit Block Exit Block

Implies that the conduction time Implies that the conduction time where each impulse leaving the node where each impulse leaving the node is prolongedis prolonged

This problem cannot be observed on This problem cannot be observed on surface EKGsurface EKG

Electro physiology study needed to Electro physiology study needed to measure the sino atrial conduction measure the sino atrial conduction time time

Second Degree Sino Atrial Second Degree Sino Atrial Exit BlockExit Block

Type I (SA Wenckebach) Type I (SA Wenckebach) 1.PP intervals gradually shorten until a pause 1.PP intervals gradually shorten until a pause occurs (i.e., the blocked sinus impulse fails to occurs (i.e., the blocked sinus impulse fails to reach the atria) reach the atria)

2.The pause duration is 2.The pause duration is less thanless than the two the two preceding PP intervals preceding PP intervals

3.The PP interval following the pause is 3.The PP interval following the pause is greater greater thanthan the PP interval just before the pause the PP interval just before the pause

Second DegreeSecond DegreeType II SA BlockType II SA Block

PP intervals fairly constant (unless PP intervals fairly constant (unless sinus arrhythmia present) until sinus arrhythmia present) until conduction failure occurs. conduction failure occurs.

The pause is approximately The pause is approximately twicetwice the the basic PP interval basic PP interval

Third Degree Or Complete Sino Third Degree Or Complete Sino Atrial Exit BlockAtrial Exit Block

Cannot be distinguished from a Cannot be distinguished from a prolonged sinus pause or arrestprolonged sinus pause or arrest

Can be identified from direct Can be identified from direct recording of sinus node pacemaker recording of sinus node pacemaker activity during an EP studyactivity during an EP study

AV Blocks: AV Blocks: Divided in to incomplete and Divided in to incomplete and

complete blockcomplete block Incomplete AV block includesIncomplete AV block includes

a. first-degree AV blocka. first-degree AV block

b. second degree AV blockb. second degree AV block

c. advanced AV blockc. advanced AV block

Complete AV block,also known as third Complete AV block,also known as third degree AV blockdegree AV block

Location of the BlockLocation of the Block

Proximal to, in, or distal to the His bundle Proximal to, in, or distal to the His bundle in thein theatrium or AV node atrium or AV node

All degrees of AV block may be All degrees of AV block may be intermittent or persistentintermittent or persistent

First Degree AV BlockFirst Degree AV Block

PR interval is prolonged 0.21- PR interval is prolonged 0.21- 0.40 seconds, but no R-R interval 0.40 seconds, but no R-R interval changechange

Second-Degree AV BlockSecond-Degree AV Block

There is intermittent failure of the There is intermittent failure of the supraventricular impulse to be conducted supraventricular impulse to be conducted to the ventriclesto the ventricles

Some of the P waves are not followed by a Some of the P waves are not followed by a QRS complex.The conduction ratio (P/QRS QRS complex.The conduction ratio (P/QRS ratio) may be set at 2:1,3:1,3:2,4:3,and so ratio) may be set at 2:1,3:1,3:2,4:3,and so forthforth

Types Of Second-Degree AVTypes Of Second-Degree AVBlock:I and IIBlock:I and II

Type I also is called Wenckebach Type I also is called Wenckebach

phenomenon or Mobitz type I and phenomenon or Mobitz type I and represents the more common typerepresents the more common type

Type II is also called Mobitz type II Type II is also called Mobitz type II

Type I Second-Degree AV Type I Second-Degree AV Block: Wenckebach Block: Wenckebach

PhenomenonPhenomenon ECG findings ECG findings

1.Progressive lengthening of the PR 1.Progressive lengthening of the PR interval until a P wave is blockedinterval until a P wave is blocked

2.Progressive shortening of the RR 2.Progressive shortening of the RR interval until a P wave is blockedinterval until a P wave is blocked

3.RR interval containing the blocked 3.RR interval containing the blocked P wave is shorter than the sum of P wave is shorter than the sum of two PP intervalstwo PP intervals

Type II Second-Degree AVType II Second-Degree AVBlock:Block:

Mobitz Type IIMobitz Type II ECG findings ECG findings

1.Intermittent blocked P waves1.Intermittent blocked P waves2.PR intervals may be normal or 2.PR intervals may be normal or prolonged,but they remain constantprolonged,but they remain constant3.When the AV conduction ratio is 2:1,it is 3.When the AV conduction ratio is 2:1,it is often impossible to determine whether the often impossible to determine whether the second-degree AV block is type I or IIsecond-degree AV block is type I or II4. A long rhythm strip may help4. A long rhythm strip may help

High-Grade or Advanced AV High-Grade or Advanced AV BlockBlock

When the AV conduction ratio is 3:1 or When the AV conduction ratio is 3:1 or higher,the rhythm is called advanced AV higher,the rhythm is called advanced AV blockedblocked

A comparison of the PR intervals of the A comparison of the PR intervals of the occasional captured complexes may occasional captured complexes may provide a clue provide a clue

If the PR interval varies and its duration is If the PR interval varies and its duration is inversely related to the interval between inversely related to the interval between the P wave and its preceding R wave (RP), the P wave and its preceding R wave (RP), type I block is likely type I block is likely

A constant PR interval in all captured A constant PR interval in all captured complexes suggests type II block complexes suggests type II block

Complete (Third-Degree) AV BlockComplete (Third-Degree) AV Block

There is complete failure of the There is complete failure of the supraventricular impulses to reach the supraventricular impulses to reach the ventriclesventricles

The atrial and ventricular activities are The atrial and ventricular activities are independent of each otherindependent of each other

ECG FindingsECG Findings

In patients with sinus rhythm and In patients with sinus rhythm and complete AV block, the PP and RR complete AV block, the PP and RR intervals are regular, but the P waves intervals are regular, but the P waves bear no constant relation to the QRS bear no constant relation to the QRS complexes complexes

Bundle Branch BlockBundle Branch Block

• Left Bundle Branch BlockLeft Bundle Branch Block1.Complete LBBB1.Complete LBBB2.Incomplete LBBB2.Incomplete LBBB

• Rigt Bundle Branch BlockRigt Bundle Branch Block1.Complete RBBB1.Complete RBBB2.Incomplete RBBB2.Incomplete RBBB

Left Bundle Branch BlockLeft Bundle Branch BlockElectrocardiographic CriteriaElectrocardiographic Criteria

1.The QRS duration is >/- 120 ms1.The QRS duration is >/- 120 ms

2.Leads V5,V6 and AVL show broad and 2.Leads V5,V6 and AVL show broad and notched or slurred R wavesnotched or slurred R waves

3.With the possible exception of lead AVL, 3.With the possible exception of lead AVL, the Q wave is absent in left-sided leadsthe Q wave is absent in left-sided leads

4.Reciprocal changes in V1 and V24.Reciprocal changes in V1 and V2

5.Left axis deviation may be present5.Left axis deviation may be present

Causes Of LBBBCauses Of LBBB

Hypertrophy, dilatation or fibrosis of the Hypertrophy, dilatation or fibrosis of the left ventricular myocardium left ventricular myocardium

Ischemic heart disease Ischemic heart disease

CardiomyopathiesCardiomyopathies

Advanced valvular heart diseaseAdvanced valvular heart disease Toxic, inflammatory changes Toxic, inflammatory changes

Hyperkalemia Hyperkalemia Digitalis toxicityDigitalis toxicity Degenerative disease of the conducting Degenerative disease of the conducting

system (Lenegre disease) system (Lenegre disease)

Prevalence Of LBBBPrevalence Of LBBB

At age 50 is 0.4%, and at age 80 it At age 50 is 0.4%, and at age 80 it is 6.7%is 6.7% In most subjects with LBBB,regional wall In most subjects with LBBB,regional wall

motion abnormalities (akinetic or motion abnormalities (akinetic or dyskinetic segments in the septum, dyskinetic segments in the septum, anterior wall or at the apex) are present anterior wall or at the apex) are present even in the absence of CAD or even in the absence of CAD or cardiomyopathycardiomyopathy

Incomplete Left Bundle Branch Incomplete Left Bundle Branch BlockBlock

Criteria for incomplete LBBB includeCriteria for incomplete LBBB include

1.QRS duration > 100 ms but < 120 1.QRS duration > 100 ms but < 120 msms

2.Absence of a Q wave in leads V5,V6 2.Absence of a Q wave in leads V5,V6 and I and I

Right Bundle Branch BlockRight Bundle Branch Block

The diagnostic criteria includeThe diagnostic criteria include

1.QRS duration is >/- 120 ms1.QRS duration is >/- 120 ms

2.An rsr’,rsR’ or rSR’ pattern in lead V1 2.An rsr’,rsR’ or rSR’ pattern in lead V1 or V2 and occasionally a wide and or V2 and occasionally a wide and notched R wave.notched R wave.

3.Reciprocal changes in V5,V6,I and 3.Reciprocal changes in V5,V6,I and AVL AVL

Causes of RBBBCauses of RBBB

1.After repair of the VSD 1.After repair of the VSD

2.After right ventriculotomy2.After right ventriculotomy

3.Right ventricular hypertrophy3.Right ventricular hypertrophy

4.Increase incidence of RBBB among 4.Increase incidence of RBBB among population at high altitudepopulation at high altitude

5.Ebstein’s anomaly5.Ebstein’s anomaly

6.Large ASD (secundum type) or AV cushion 6.Large ASD (secundum type) or AV cushion defectdefect

7.Brugada Syndrome7.Brugada Syndrome

RBBB in the General PopulationRBBB in the General Population

The incidence increased with ageThe incidence increased with age

1.Below age 30 the incidence is 1.3 1.Below age 30 the incidence is 1.3 per 1000per 1000

2.Between 30 and 44 it ranges from 2.Between 30 and 44 it ranges from 2.0 to 2.9 per 10002.0 to 2.9 per 1000

Incomplete RBBBIncomplete RBBB

Criteria for incomplete RBBB are the Criteria for incomplete RBBB are the same as for complete RBBB except same as for complete RBBB except that the QRS duration is < 120 msthat the QRS duration is < 120 ms

Causes of Incomplete RBBBCauses of Incomplete RBBB

1.Atrial septal defect (RAD in secundum or 1.Atrial septal defect (RAD in secundum or sinus venosus type, LAD with ostium sinus venosus type, LAD with ostium primum type) primum type)

2.Ebstein’s anomaly2.Ebstein’s anomaly

3.Right ventricular dysplasia3.Right ventricular dysplasia

4.Congenital absence or atrophy of the 4.Congenital absence or atrophy of the bundle branchbundle branch

5.After CABG and in transplanted hearts5.After CABG and in transplanted hearts

6.Brugada Syndrome6.Brugada Syndrome

Fascicular BlocksFascicular Blocks

The left bundle branch divides into The left bundle branch divides into two fasciclestwo fascicles

1.Superior and anterior1.Superior and anterior

2.Inferior and posterior2.Inferior and posterior

Types Of Fascicular BlockTypes Of Fascicular Block

Left anterior fascicular blockLeft anterior fascicular block Left posterior fascicular blockLeft posterior fascicular block Bifascicular BlockBifascicular Block Trifascicular BlockTrifascicular Block

Left Anterior Fascicular Block Left Anterior Fascicular Block Left axis deviation , usually -45 to -90 degrees Left axis deviation , usually -45 to -90 degrees

QRS duration usually <0.12s unless coexisting QRS duration usually <0.12s unless coexisting RBBB RBBB

Poor R wave progression in leads V1-V3 and Poor R wave progression in leads V1-V3 and deeper S waves in leads V5 and V6deeper S waves in leads V5 and V6

There is RS pattern with R wave in lead II > lead IIIThere is RS pattern with R wave in lead II > lead III S wave in lead III > lead IIS wave in lead III > lead II

QR pattern in lead I and AVL,with small Q waveQR pattern in lead I and AVL,with small Q wave No other causes of left axis deviationNo other causes of left axis deviation

Causes of Left Anterior Causes of Left Anterior Fascicular BlockFascicular Block

1.Acute Myocardial Infarction1.Acute Myocardial Infarction

2.Hypertensive heart disease2.Hypertensive heart disease

3.Degenerative disease of the 3.Degenerative disease of the conducting systemconducting system

4.Myocardial fibrosis4.Myocardial fibrosis

Left Posterior Fascicular BlockLeft Posterior Fascicular Block

Diagnostic Criteria includeDiagnostic Criteria include

1.QRS duration 100- <120 ms1.QRS duration 100- <120 ms

2.No ST segment or T wave changes2.No ST segment or T wave changes

3.Right axis deviation (100 degree)3.Right axis deviation (100 degree)

4.QR pattern in inferior leads (II,III,AVF) 4.QR pattern in inferior leads (II,III,AVF) small q wavesmall q wave

5.RS patter in lead lead I and AVL(small R 5.RS patter in lead lead I and AVL(small R with deep S)with deep S)

6.No other causes of right axis deviation6.No other causes of right axis deviation

Bifascicular Bundle Branch Bifascicular Bundle Branch BlockBlock

RBBB with either left anterior or left RBBB with either left anterior or left posterior fascicular blockposterior fascicular block

Diagnostic criteriaDiagnostic criteria

1.Prolongation of the QRS duration to 0.12 1.Prolongation of the QRS duration to 0.12 second or longersecond or longer

2.RSR’ pattern in lead V1,with the R’ being 2.RSR’ pattern in lead V1,with the R’ being broad and slurredbroad and slurred

3.Wide,slurred S wave in leads I,V5 and V63.Wide,slurred S wave in leads I,V5 and V6

4.Left axis or right axis deviation 4.Left axis or right axis deviation

Causes of Bifascicular BlockCauses of Bifascicular Block

1.Coronary artery disease1.Coronary artery disease2.Degenerative disease of the conducting 2.Degenerative disease of the conducting

systemsystem3.Aortic stenosis3.Aortic stenosis4.Hypertensive heart disease 4.Hypertensive heart disease 5.Myocardial fibrosis5.Myocardial fibrosis6.Infiltrative process6.Infiltrative process7.Tetralogy of Fallot7.Tetralogy of Fallot8.After cardiac transplantation8.After cardiac transplantation

Trifascicular BlockTrifascicular Block

The combination of RBBB, LAFB and The combination of RBBB, LAFB and long PR interval long PR interval

Implies that conduction is delayed in Implies that conduction is delayed in the third fasciclethe third fascicle

Indications For Implantation of Indications For Implantation of Permanent Pacing in Acquired AV Permanent Pacing in Acquired AV

BlockBlock Class IClass I1.Third-degree AV block associated with1.Third-degree AV block associated witha.Bradycardia with symptoms (C)a.Bradycardia with symptoms (C)b.Arrhythmias and other medical conditions that b.Arrhythmias and other medical conditions that

require drugs that result in symptomatic require drugs that result in symptomatic bradycardia(C)bradycardia(C)

c.Asystole>/-3.0 seconds or any escape c.Asystole>/-3.0 seconds or any escape rate<40bpm awake, symptom free Pt (B,C)rate<40bpm awake, symptom free Pt (B,C)

d.After catheter ablation of the AV junction (B,C) d.After catheter ablation of the AV junction (B,C) e.Neuromuscular diseases with AV block (Myotonic e.Neuromuscular diseases with AV block (Myotonic

muscular dystrophy)muscular dystrophy)2.Second-degree AV block with symptomatic 2.Second-degree AV block with symptomatic

bradycardiabradycardia

Class IIaClass IIa

Asymptomatic third-degree AV block Asymptomatic third-degree AV block with average awake ventricular rates of with average awake ventricular rates of 40 bpm or faster (B,C)40 bpm or faster (B,C)

Asymptomatic type II second-degree AV Asymptomatic type II second-degree AV block block (B)(B)

First-degree AV block with symptoms First-degree AV block with symptoms suggestive of pacemaker syndrome and suggestive of pacemaker syndrome and documented alleviation of symptoms documented alleviation of symptoms with temporary AV pacing with temporary AV pacing (B)(B)

Class IIbClass IIb

Marked first-degree AV block (>0.30 Marked first-degree AV block (>0.30 second) in patients with LV dysfunction second) in patients with LV dysfunction and symptoms of congestive heart and symptoms of congestive heart failure in whom a shorter AV interval failure in whom a shorter AV interval results in hemodynamic improvement, results in hemodynamic improvement, presumably by decreasing left atrial presumably by decreasing left atrial filling pressure filling pressure (C)(C)

Class IIIClass III

Asymptomatic first-degree AV block Asymptomatic first-degree AV block (B)(B)

Asymptomatic type I second-degree Asymptomatic type I second-degree AV block at the supra-His (AV node) AV block at the supra-His (AV node) level or not known to be intra- or level or not known to be intra- or infra-Hisian infra-Hisian (B, C)(B, C)

AV block expected to resolve and AV block expected to resolve and unlikely to recur (eg,drug toxicity, unlikely to recur (eg,drug toxicity, Lyme disease) Lyme disease) (B)(B)

Indications for Permanent Indications for Permanent Pacing in Chronic Bifascicular Pacing in Chronic Bifascicular

and Trifascicular Blockand Trifascicular Block1.Class I1.Class I Intermittent third-degree AV block. Intermittent third-degree AV block. (B)(B) Type II second-degree AV block. Type II second-degree AV block. (B)(B)2.Class IIa2.Class IIa Syncope not proved to be due to AV block when Syncope not proved to be due to AV block when

other likely causes have been excluded, other likely causes have been excluded, specifically ventricular tachycardia (VT). specifically ventricular tachycardia (VT). (B)(B)

3.Class III3.Class III Fascicular block without AV block or symptoms. Fascicular block without AV block or symptoms.

(B)(B) Fascicular block with first-degree AV block Fascicular block with first-degree AV block

without symptoms. without symptoms. (B)(B)

Indications for Permanent Pacing Indications for Permanent Pacing After The Acute Phase Of After The Acute Phase Of

Myocardial InfarctionMyocardial Infarction Class IClass I Persistent second-degree AV block with bilateral Persistent second-degree AV block with bilateral

bundle branch block or third-degree AV block bundle branch block or third-degree AV block within or below the His-Purkinje system after within or below the His-Purkinje system after AMI. AMI. (B)(B)

Transient advanced (second- or third-degree) Transient advanced (second- or third-degree) infranodal AV block with bundle branch block. infranodal AV block with bundle branch block. (B)(B)

Persistent and symptomatic second- or third-Persistent and symptomatic second- or third-degree AV block. degree AV block. (C)(C)

Indications Of Permanent Pacing Indications Of Permanent Pacing After the Acute Phase Of After the Acute Phase Of

Myocardial Infarction Myocardial Infarction (Continuation)(Continuation)

Class IIb Class IIb Persistent second- or third-degree AV block at the AV Persistent second- or third-degree AV block at the AV

node level. node level. (B)(B) Class III Class III

Transient AV block in the absence of intraventricular Transient AV block in the absence of intraventricular conduction defects. conduction defects. (B)(B)

Transient AV block in the presence of isolated left Transient AV block in the presence of isolated left anterior fascicular block. anterior fascicular block. (B)(B)

Acquired left anterior fascicular block in the absence Acquired left anterior fascicular block in the absence of AV block. of AV block. (B)(B)

Persistent first-degree AV block in the presence of Persistent first-degree AV block in the presence of bundle branch blockbundle branch block that is old or age indeterminate. that is old or age indeterminate. (B)(B)