Sick sinus syndrome-2

Rawalpindi Medical college

2. SICK SINUS SYNDROMESICK SINUS SYNDROME

SARA BIRGEES MALIKSARA BIRGEES MALIK

3. DEFINITIONDEFINITION
•Sick sinus syndrome describes Sick sinus syndrome describes
dysfunction of the intrinsic dysfunction of the intrinsic
pacemaker of heart, the pacemaker of heart, the
sinoatrial node. As a result, the sinoatrial node. As a result, the
cardiac rhythm becomes cardiac rhythm becomes
abnormal characterized by: abnormal characterized by:
Sinus bradycardia…slow Sinus bradycardia…slow
heart rate heart rate
Tachycardia…fast heart rateTachycardia…fast heart rate
Bradycardia-tachycardia…Bradycardia-tachycardia…
alternating slow and fast alternating slow and fast
heart rhythms.heart rhythms.

4. MECHANISMMECHANISM
Normally, the sinuatrial node produces a steady pace of regular Normally, the sinuatrial node produces a steady pace of regular
electrical impulses. In sick sinus syndrome, these signals are electrical impulses. In sick sinus syndrome, these signals are
abnormally paced. A person with sick sinus syndrome may have abnormally paced. A person with sick sinus syndrome may have
heart rhythm that are too fast, too slow, punctuated by long pause or heart rhythm that are too fast, too slow, punctuated by long pause or
an alternating combination of all of these rhythm problemsan alternating combination of all of these rhythm problems..
TYPES AND CAUSESTYPES AND CAUSES
Types of sick sinus syndrome and their causes include:Types of sick sinus syndrome and their causes include:
SINUS BLOCK: SINUS BLOCK:
Electrical signals move too slowly through sinus node, causing Electrical signals move too slowly through sinus node, causing
abnormally slow heart rate.abnormally slow heart rate.
SINUS ARREST: SINUS ARREST:
The sinus node activity pauses.The sinus node activity pauses.
TACHYCARDIA-BRADYCARDIA SYNDROME: TACHYCARDIA-BRADYCARDIA SYNDROME:
The heart rate alternates between abnormally fast and slow The heart rate alternates between abnormally fast and slow
rhythms, often with a long pause (asystole) between heart beats.rhythms, often with a long pause (asystole) between heart beats.

5. It may be brought on by use of drugs like digitalis, calcium channel It may be brought on by use of drugs like digitalis, calcium channel
blockers, beta blockers and antiarrhythmics.blockers, beta blockers and antiarrhythmics.
Sick sinus syndrome usually occurs in people older than 50,in whom Sick sinus syndrome usually occurs in people older than 50,in whom
the cause is often a non specific, scar like degeneration of the heart’s the cause is often a non specific, scar like degeneration of the heart’s
conduction system like amyloidosis,sarcoidosis,chagas disease and conduction system like amyloidosis,sarcoidosis,chagas disease and
cardiomyopathiescardiomyopathies..
• In children, a common cause of sick sinus syndrome is heart In children, a common cause of sick sinus syndrome is heart
surgery especially on heart chambers.surgery especially on heart chambers.
• In coronary artery disease, high blood pressure, aortic and In coronary artery disease, high blood pressure, aortic and
mitral valve diseases may be associated with sick sinus mitral valve diseases may be associated with sick sinus
syndromesyndrome..

6. HEART BLOCKSHEART BLOCKS
Interference with the conduction process of the heart causes the Interference with the conduction process of the heart causes the
phenomena called heart block or atrioventricular block.phenomena called heart block or atrioventricular block.
•Heart block is classified according to the level of impairment:Heart block is classified according to the level of impairment:
First Degree Heart BlockFirst Degree Heart Block
Second Degree Heart BlockSecond Degree Heart Block
Third Degree (complete) Heart BlockThird Degree (complete) Heart Block
FIRST DEGREE HEART BLOCK:FIRST DEGREE HEART BLOCK:
First degree heart block or first degree atrioventricular block is First degree heart block or first degree atrioventricular block is
defined as prolongation of the PR interval on the ECG to more than defined as prolongation of the PR interval on the ECG to more than
200msec.First degree heart block is considered “marked” when the 200msec.First degree heart block is considered “marked” when the
PR exceeds 300msec.While the conduction is slowed, there are no PR exceeds 300msec.While the conduction is slowed, there are no
missed beatsmissed beats..

7. MECHANISMMECHANISM
With first degree atrioventricular (AV) block every atrial impulse is With first degree atrioventricular (AV) block every atrial impulse is
transmitted to the ventricles ,resulting in regular ventricular rate. transmitted to the ventricles ,resulting in regular ventricular rate.
This type of AV block can arise from delays in the conduction This type of AV block can arise from delays in the conduction
system in the AV node itself, the His Purkinjie system or a system in the AV node itself, the His Purkinjie system or a
combination of both. Overall, dysfunction at the AV node is much combination of both. Overall, dysfunction at the AV node is much
more common than dysfunction at the His more common than dysfunction at the His PurkinjiePurkinjie system. system.
 If the QRS complex is of normal width and morphology on the ECG If the QRS complex is of normal width and morphology on the ECG
than the conduction delay is almost always at the level of the AV than the conduction delay is almost always at the level of the AV
node.node.
If however, the QRS demonstrates a bundle branch morphology If however, the QRS demonstrates a bundle branch morphology
than the level of the conduction delay is often localized to His than the level of the conduction delay is often localized to His
Purkinjie systemPurkinjie system

8. CAUSESCAUSES
Following are the most common causes of first degree Following are the most common causes of first degree
(atrioventricular block).(atrioventricular block).
Intrinsic AV nodal disease.Intrinsic AV nodal disease.
Enhanced vagal tone.Enhanced vagal tone.
Acute MI particularly acute inferior wall MI.Acute MI particularly acute inferior wall MI.
Myocarditis.Myocarditis.

Electrolyte disturbances (e.g hypokalemia, hypomagnesemiaElectrolyte disturbances (e.g hypokalemia, hypomagnesemia))
Drugs(esp.those drugs that increase the refractory time of the AV Drugs(esp.those drugs that increase the refractory time of the AV
node, there by slowing conduction).node, there by slowing conduction).
Drugs that most commonly causes first degree AV block include Drugs that most commonly causes first degree AV block include
following:following:
Class 1c antiarrhythmias (e.g Quinidine, procainamide, Class 1c antiarrhythmias (e.g Quinidine, procainamide,
disopyramide)disopyramide)
Class2c antiarrhythmias (e.g Flecainide, encainide)Class2c antiarrhythmias (e.g Flecainide, encainide)
Class3c antiarrhythmias (Beta blockers)Class3c antiarrhythmias (Beta blockers)

9. SECOND DEGREE HEART BLOCKSECOND DEGREE HEART BLOCK
Second degree heart block implies intermittent conduction, some impulses Second degree heart block implies intermittent conduction, some impulses
from the atria are conducted to ventricles whereas others are not.from the atria are conducted to ventricles whereas others are not.
CAUSES:CAUSES:
Inferior wall MI.Inferior wall MI.
Drugs like digitalis, beta blockers, calcium antagonists.Drugs like digitalis, beta blockers, calcium antagonists.
Hyperkalemia in well trained athelets during sleep.Hyperkalemia in well trained athelets during sleep.
MyocarditisMyocarditis
TYPES OF SECOND DEGREE HEART BLOCK:TYPES OF SECOND DEGREE HEART BLOCK:
There are three types of second degree heart block.There are three types of second degree heart block.
Mobitz type 1Mobitz type 1
Mobitz type 2Mobitz type 2
2:1 block2:1 block

10. MOBITZ TYPE 1MOBITZ TYPE 1
In this condition, there is progressive lengthening of successive PR In this condition, there is progressive lengthening of successive PR
intervals followed by a dropped beat (non conducted P). This is also intervals followed by a dropped beat (non conducted P). This is also
known as wenckebach’s phenomenon.known as wenckebach’s phenomenon.
In this AV block, there is conduction defect in AV node and AV In this AV block, there is conduction defect in AV node and AV
conduction time (PR interval) progressively lengthens before conduction time (PR interval) progressively lengthens before
blocked beat pulse is clinically irregular. blocked beat pulse is clinically irregular.
Prognosis is good in first degree and in Mobitz type 1,since reliable Prognosis is good in first degree and in Mobitz type 1,since reliable
alternative pacemaker arise from AV junction below the block, if alternative pacemaker arise from AV junction below the block, if
complete heart block develops.complete heart block develops.
Site of block is AV node. QRS complex is normal in morphology Site of block is AV node. QRS complex is normal in morphology
because there is no delay in interventricular depolarizationbecause there is no delay in interventricular depolarization..

11. MOBITZ TYPE 2MOBITZ TYPE 2
In this condition, the PR interval of the conducted impulses remain In this condition, the PR interval of the conducted impulses remain
constant but some P waves are not conducted (i.e more P waves constant but some P waves are not conducted (i.e more P waves
than QRS complexes)than QRS complexes)
Site of block is infranodal in location and QRS complexes are wide. Site of block is infranodal in location and QRS complexes are wide.
Mobitz type 2 AV block is abrupt and is not preceded by Mobitz type 2 AV block is abrupt and is not preceded by
lengthening of AV conduction time. It is usually due to block within lengthening of AV conduction time. It is usually due to block within
the bundle of His.the bundle of His.
Mobitz 2 block is almost always due to organic heart disease, in Mobitz 2 block is almost always due to organic heart disease, in
case it proceeds to complete heart blockcase it proceeds to complete heart block. .
2:1 BLOCK2:1 BLOCK
It may represent as either type for type 2 AV block in which there It may represent as either type for type 2 AV block in which there
are two P waves to each QRS complex and therefore, called 2:1 are two P waves to each QRS complex and therefore, called 2:1
block. block.
If PR interval is prolonged and QRS complex is narrow then it is If PR interval is prolonged and QRS complex is narrow then it is
type1 second degree heart block. type1 second degree heart block.
If PR interval is normal then QRS complex is wide, it is called If PR interval is normal then QRS complex is wide, it is called
second degree AV blocksecond degree AV block

12. THIRD DEGREE(COMPLETE) HEART THIRD DEGREE(COMPLETE) HEART
BLOCKBLOCK
Third degree heart block is an advanced form of block. No impulse Third degree heart block is an advanced form of block. No impulse
from atria reaches the ventricles. Cardiac action is maintained by an from atria reaches the ventricles. Cardiac action is maintained by an
escape rhythm. escape rhythm.
CAUSES:CAUSES:
CONGENITALCONGENITAL
ACQUIREDACQUIRED
Idiopathic fibrosisIdiopathic fibrosis
MI/IschemiaMI/Ischemia
INFECTIONS: Infective endocarditis, Chagas disease, Lyme’s INFECTIONS: Infective endocarditis, Chagas disease, Lyme’s
disease. disease.
INFILTRATION: Sarcoidosis, Amyloidosis, NeoplasiaINFILTRATION: Sarcoidosis, Amyloidosis, Neoplasia
DRUGS: Digioxin, Beta blockers, Amiodaron DRUGS: Digioxin, Beta blockers, Amiodaron
 TRAUMA: Cardiac surgery.TRAUMA: Cardiac surgery.
CONNECTIVE TISSUE DISEASE: SLE,RACONNECTIVE TISSUE DISEASE: SLE,RA

13. MECHANISMMECHANISM
Escape rhythm arising in the bundle of His produces narrow QRS Escape rhythm arising in the bundle of His produces narrow QRS
complex at the rate of 50-60beats/min.Escape rhythm arising below complex at the rate of 50-60beats/min.Escape rhythm arising below
the His bundle produces broad complexes and at rate of 15-the His bundle produces broad complexes and at rate of 15-
40beats/min.40beats/min.
It is more advanced form of heart block due to lesion at the level of It is more advanced form of heart block due to lesion at the level of
bundle of His or more often distally in Purkinjie system and bundle of His or more often distally in Purkinjie system and
associated with bilateral bundle branch block. QRS complex is wide associated with bilateral bundle branch block. QRS complex is wide
and ventricular rate is slower. Transmission of atrial pulses through and ventricular rate is slower. Transmission of atrial pulses through
AV node is completely blocked and a ventricular rate, usually less AV node is completely blocked and a ventricular rate, usually less
than 45beats/min.than 45beats/min.
In chronic complete heart block, pulse is slow (30-40min) regular In chronic complete heart block, pulse is slow (30-40min) regular
and does not vary with exerciseand does not vary with exercise

14. Stokes-Adams AttacksStokes-Adams Attacks
Episodes of ventricular asystole may occur during periods of Episodes of ventricular asystole may occur during periods of
transition from partial to complete heart block lasting several transition from partial to complete heart block lasting several
seconds to minutes. These episodes may cause cardiac syncope seconds to minutes. These episodes may cause cardiac syncope
called Stokes-Adams attacks.called Stokes-Adams attacks.
These attacks often occur without warning, there is rapid loss of These attacks often occur without warning, there is rapid loss of
consciousness and pt. may fall.consciousness and pt. may fall.
Convulsions may occur, if heart does not begin to beat within about Convulsions may occur, if heart does not begin to beat within about
10sec and death will result, if arrest is prolonged10sec and death will result, if arrest is prolonged..

15. BUNDLE BRANCH BLOCKS AND BUNDLE BRANCH BLOCKS AND
HEMIBLOCKSHEMIBLOCKS

16. BUNDLE BRANCH BLOCKBUNDLE BRANCH BLOCK

In normal heart, each electrical impulsesIn normal heart, each electrical impulses from the atria isfrom the atria is
conducted through the AV node to theconducted through the AV node to the bundle of His, from which it bundle of His, from which it
is transmitted to the ventricles by the right and left bundle branches.is transmitted to the ventricles by the right and left bundle branches.
 TYPES TYPES
Left bundle branch block Left bundle branch block
Right bundle branch blockRight bundle branch block

17. LEFT BUNDLE BRANCH BLOCKLEFT BUNDLE BRANCH BLOCK

In LBBB, left bundle branch no longerIn LBBB, left bundle branch no longer conducts electricalconducts electrical activity. The activity. The
electrical impulse thus enterselectrical impulse thus enters right bundle branchright bundle branch block andblock and is carried to is carried to
right ventricle. From there, itright ventricle. From there, it finally spreadsfinally spreads to leftto left ventricle.ventricle. The two The two
ventricles no longer receive the electrical impulseventricles no longer receive the electrical impulse simultaneously. First, the simultaneously. First, the
Rt. ventricleRt. ventricle receives thereceives the electricalelectrical impulse, then left.impulse, then left.
 CAUSESCAUSES
 Hypertrophy, dilatation or fibrosis LV myocardium.Hypertrophy, dilatation or fibrosis LV myocardium.
 Ischemic heart disease.Ischemic heart disease.
 Cardiomyopathies.Cardiomyopathies.
 Advanced valvular heart disease.Advanced valvular heart disease.
 Toxic, inflammatory changes.Toxic, inflammatory changes.
 Hyperkalemia.Hyperkalemia.
Digitalis toxicity. Digitalis toxicity.
Degenerative disease of conducting system (Lenegre disease).Degenerative disease of conducting system (Lenegre disease).

18. TYPES OF LBBBTYPES OF LBBB
•The LBBB can be divided into two fascicles:The LBBB can be divided into two fascicles:
Anterior Fascicles.Anterior Fascicles.
Posterior Fascicles.Posterior Fascicles.
 Conduction system is composed of three fasciclesConduction system is composed of three fascicles::
Right Bundle Fascicle. Right Bundle Fascicle.
Left Anterior Fascicle.Left Anterior Fascicle.
Left Posterior Fascicle.Left Posterior Fascicle.

19. RIGHT BUNDLE BRANCH BLOCKRIGHT BUNDLE BRANCH BLOCK
RBBB results from a defect in heart’s electrical conducting system. RBBB results from a defect in heart’s electrical conducting system.
There is a delay in or failure of There is a delay in or failure of transmission of electricaltransmission of electrical impulses impulses
down the right bundle of heart. As a result , thedown the right bundle of heart. As a result , the Rt. Ventricle Rt. Ventricle
depolarizes by meansdepolarizes by means of of cell- to- cell conduction.cell- to- cell conduction. TheseThese impulsesimpulses
spread more slowly than usual from inter ventricular septum to Rt. spread more slowly than usual from inter ventricular septum to Rt.
Ventricle.This delay in conduction resultsVentricle.This delay in conduction results in characteristicin characteristic ECG ECG
pattern,pattern, which is wide and notched QRS. Although conduction down which is wide and notched QRS. Although conduction down
the Rt. branch is delayed ,conduction down the Lt. branch is normal. the Rt. branch is delayed ,conduction down the Lt. branch is normal.
As a result, the interventricular septum and Lt. ventricle in normal As a result, the interventricular septum and Lt. ventricle in normal
fashion. fashion.
 TYPES TYPES
There are two types. There are two types.
Complete RBBB. Complete RBBB.
Incomplete RBBB.Incomplete RBBB.

20. CAUSES OF RBBBCAUSES OF RBBB
Following are the causes of RBBB.Following are the causes of RBBB.
After repair of VSD.After repair of VSD.

AfterAfter Rt.ventriculotomy.Rt.ventriculotomy.

Right Venticular hypertrophyRight Venticular hypertrophy..
Ebstein’s anomaly.Ebstein’s anomaly.

Large ASD or AV cushion defectLarge ASD or AV cushion defect..
Right ventricular dysplasia.Right ventricular dysplasia.
 Brugada syndrome.Brugada syndrome.

Congenital absence or atrophy of bundleCongenital absence or atrophy of bundle branch.branch.
After CABG and in transplanted heart.After CABG and in transplanted heart.

21. HEMIBLOCKHEMIBLOCK
DEFINITION:DEFINITION:
When there is blockage in anterior or posterior division of left When there is blockage in anterior or posterior division of left
bundle branch, it is called hemiblock.bundle branch, it is called hemiblock.
BIFASCICULAR BLOCK:BIFASCICULAR BLOCK:
RBBB plus left anterior or posterior hemiblock.RBBB plus left anterior or posterior hemiblock.
 In bifascicular and trifascicular block there are more chances to In bifascicular and trifascicular block there are more chances to
progress to complete heart block.progress to complete heart block.
TRIFASCICULAR BLOCK:TRIFASCICULAR BLOCK:
RBBB + Hemiblock + First degree heart block.RBBB + Hemiblock + First degree heart block.

22. THANK YOUTHANK YOU