Sick sinus syndrome-2

SICK SINUS SYNDROMESICK SINUS SYNDROME

SARA BIRGEES MALIKSARA BIRGEES MALIK

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.

MECHANISMMECHANISM Normally, the sinuatrial node produces a steady pace of Normally, the sinuatrial node produces a steady pace of

regular electrical impulses. In sick sinus syndrome, these regular electrical impulses. In sick sinus syndrome, these signals are abnormally paced. A person with sick sinus signals are abnormally paced. A person with sick sinus syndrome may have heart rhythm that are too fast, too syndrome may have heart rhythm that are too fast, too slow, punctuated by long pause or an alternating slow, punctuated by long pause or an alternating

combination of all of these rhythm problemscombination 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, Electrical signals move too slowly through sinus node, causing abnormally slow heart rate.causing 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 The heart rate alternates between abnormally fast and slow rhythms, often with a long pause (asystole) between heart slow rhythms, often with a long pause (asystole) between heart beats.beats.

It may be brought on by use of drugs like digitalis, calcium It may be brought on by use of drugs like digitalis, calcium channel blockers, beta blockers and antiarrhythmics.channel blockers, beta blockers and antiarrhythmics.

Sick sinus syndrome usually occurs in people older than 50,in Sick sinus syndrome usually occurs in people older than 50,in whom the cause is often a non specific, scar like degeneration whom the cause is often a non specific, scar like degeneration of the heart’s conduction system like of the heart’s conduction system like amyloidosis,sarcoidosis,chagas disease and cardiomyopathiesamyloidosis,sarcoidosis,chagas disease and cardiomyopathies..

• In children, a common cause of sick sinus syndrome is In children, a common cause of sick sinus syndrome is heart heart surgery especially on heart chambers.surgery especially on heart chambers.• In coronary artery disease, high blood pressure, aortic In coronary artery disease, high blood pressure, aortic and and mitral valve diseases may be associated with sick sinus mitral valve diseases may be associated with sick sinus syndromesyndrome..

HEART BLOCKSHEART BLOCKS Interference with the conduction process of the heart causes Interference with the conduction process of the heart causes

the phenomena called heart block or atrioventricular block.the 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 First degree heart block or first degree atrioventricular block

is defined as prolongation of the PR interval on the ECG to is defined as prolongation of the PR interval on the ECG to more than 200msec.First degree heart block is considered more than 200msec.First degree heart block is considered “marked” when the PR exceeds 300msec.While the “marked” when the PR exceeds 300msec.While the

conduction is slowed, there are no missed beatsconduction is slowed, there are no missed beats..

MECHANISMMECHANISM

With first degree atrioventricular (AV) block every atrial With first degree atrioventricular (AV) block every atrial impulse is transmitted to the ventricles ,resulting in regular impulse is transmitted to the ventricles ,resulting in regular ventricular rate. This type of AV block can arise from delays ventricular rate. This type of AV block can arise from delays in the conduction system in the AV node itself, the His in the conduction system in the AV node itself, the His Purkinjie system or a combination of both. Overall, Purkinjie system or a combination of both. Overall, dysfunction at the AV node is much more common than dysfunction at the AV node is much more common than dysfunction at the His dysfunction at the His PurkinjiePurkinjie system. system.

If the QRS complex is of normal width and morphology on If the QRS complex is of normal width and morphology on the ECG than the conduction delay is almost always at the the ECG than the conduction delay is almost always at the level of the AV node.level of the AV node.

If however, the QRS demonstrates a bundle branch If however, the QRS demonstrates a bundle branch morphology than the level of the conduction delay is often morphology than the level of the conduction delay is often localized to His Purkinjie systemlocalized to His Purkinjie system

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 Drugs(esp.those drugs that increase the refractory time of the

AV node, there by slowing conduction).AV 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)

SECOND DEGREE HEART BLOCKSECOND DEGREE HEART BLOCK Second degree heart block implies intermittent conduction, some Second degree heart block implies intermittent conduction, some

impulses from the atria are conducted to ventricles whereas others impulses from the atria are conducted to ventricles whereas others are not.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

MOBITZ TYPE 1MOBITZ TYPE 1

In this condition, there is progressive lengthening of In this condition, there is progressive lengthening of successive PR intervals followed by a dropped beat (non successive PR intervals followed by a dropped beat (non conducted P). This is also known as wenckebach’s conducted P). This is also known as wenckebach’s phenomenon.phenomenon.

In this AV block, there is conduction defect in AV node and In this AV block, there is conduction defect in AV node and AV conduction time (PR interval) progressively lengthens AV conduction time (PR interval) progressively lengthens before blocked beat pulse is clinically irregular. before blocked beat pulse is clinically irregular.

Prognosis is good in first degree and in Mobitz type 1,since Prognosis is good in first degree and in Mobitz type 1,since reliable alternative pacemaker arise from AV junction reliable alternative pacemaker arise from AV junction below the block, if complete heart block develops.below the block, if complete heart block develops.

Site of block is AV node. QRS complex is normal in Site of block is AV node. QRS complex is normal in morphology because there is no delay in interventricular morphology because there is no delay in interventricular

depolarizationdepolarization..

MOBITZ TYPE 2MOBITZ TYPE 2 In this condition, the PR interval of the conducted impulses In this condition, the PR interval of the conducted impulses

remain constant but some P waves are not conducted (i.e remain constant but some P waves are not conducted (i.e more P waves than QRS complexes)more P waves than QRS complexes)

Site of block is infranodal in location and QRS complexes Site of block is infranodal in location and QRS complexes are wide. Mobitz type 2 AV block is abrupt and is not are wide. Mobitz type 2 AV block is abrupt and is not preceded by lengthening of AV conduction time. It is usually preceded by lengthening of AV conduction time. It is usually due to block within the bundle of His.due to block within the bundle of His.

Mobitz 2 block is almost always due to organic heart Mobitz 2 block is almost always due to organic heart disease, in case it proceeds to complete heart blockdisease, in case it proceeds to complete heart block. .

2:1 BLOCK2:1 BLOCK

It may represent as either type for type 2 AV block in which It may represent as either type for type 2 AV block in which there are two P waves to each QRS complex and therefore, there are two P waves to each QRS complex and therefore, called 2:1 block. called 2:1 block.

If PR interval is prolonged and QRS complex is narrow then If PR interval is prolonged and QRS complex is narrow then it is type1 second degree heart block. it is type1 second degree heart block.

If PR interval is normal then QRS complex is wide, it is If PR interval is normal then QRS complex is wide, it is called second degree AV blockcalled second degree AV block

THIRD DEGREE(COMPLETE) HEART THIRD DEGREE(COMPLETE) HEART BLOCKBLOCK

Third degree heart block is an advanced form of block. No Third degree heart block is an advanced form of block. No impulse from atria reaches the ventricles. Cardiac action is impulse from atria reaches the ventricles. Cardiac action is maintained by an escape rhythm. maintained by an 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

MECHANISMMECHANISM

Escape rhythm arising in the bundle of His produces narrow Escape rhythm arising in the bundle of His produces narrow QRS complex at the rate of 50-60beats/min.Escape rhythm QRS complex at the rate of 50-60beats/min.Escape rhythm arising below the His bundle produces broad complexes arising below the His bundle produces broad complexes and at rate of 15-40beats/min.and at rate of 15-40beats/min.

It is more advanced form of heart block due to lesion at the It is more advanced form of heart block due to lesion at the level of bundle of His or more often distally in Purkinjie level of bundle of His or more often distally in Purkinjie system and associated with bilateral bundle branch block. system and associated with bilateral bundle branch block. QRS complex is wide and ventricular rate is slower. QRS complex is wide and ventricular rate is slower. Transmission of atrial pulses through AV node is completely Transmission of atrial pulses through AV node is completely blocked and a ventricular rate, usually less than blocked and a ventricular rate, usually less than 45beats/min.45beats/min.

In chronic complete heart block, pulse is slow (30-40min) In chronic complete heart block, pulse is slow (30-40min) regular and does not vary with exerciseregular and does not vary with exercise

Stokes-Adams AttacksStokes-Adams Attacks

Episodes of ventricular asystole may occur during periods Episodes of ventricular asystole may occur during periods of transition from partial to complete heart block lasting of transition from partial to complete heart block lasting several seconds to minutes. These episodes may cause several seconds to minutes. These episodes may cause cardiac syncope called Stokes-Adams attacks.cardiac syncope called Stokes-Adams attacks.

These attacks often occur without warning, there is rapid These attacks often occur without warning, there is rapid loss of consciousness and pt. may fall.loss of consciousness and pt. may fall.

Convulsions may occur, if heart does not begin to beat Convulsions may occur, if heart does not begin to beat within about 10sec and death will result, if arrest is within about 10sec and death will result, if arrest is

prolongedprolonged..

BUNDLE BRANCH BLOCKS AND BUNDLE BRANCH BLOCKS AND HEMIBLOCKSHEMIBLOCKS

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 bundle of His, from which it is transmitted to the ventricles by the right and left which it is transmitted to the ventricles by the right and left bundle branches.bundle branches.

TYPES TYPES Left bundle branch block Left bundle branch block Right bundle branch blockRight bundle branch block

LEFT BUNDLE BRANCH BLOCKLEFT BUNDLE BRANCH BLOCK In LBBB, left bundle branch no longerIn LBBB, left bundle branch no longer conducts electricalconducts electrical activity. activity.

The electrical impulse thus entersThe electrical impulse thus enters right bundle branchright bundle branch block andblock and is is

carried to right ventricle. From there, itcarried to right ventricle. From there, it finally spreadsfinally spreads to leftto left ventricle.ventricle. The two ventricles no longer receive the electrical impulseThe two ventricles no longer receive the electrical impulse simultaneously. First, the Rt. ventriclesimultaneously. First, the Rt. 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).

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 Conduction system is composed of three

fasciclesfascicles:: Right Bundle Fascicle. Right Bundle Fascicle. Left Anterior Fascicle.Left Anterior Fascicle. Left Posterior Fascicle.Left Posterior Fascicle.

RIGHT BUNDLE BRANCH BLOCKRIGHT BUNDLE BRANCH BLOCK RBBB results from a defect in heart’s electrical conducting RBBB results from a defect in heart’s electrical conducting

system. There is a delay in or failure ofsystem. There is a delay in or failure of transmission of transmission of

electricalelectrical impulses down the right bundle of heart. As a impulses down the right bundle of heart. As a

result , theresult , the Rt. Ventricle depolarizes by meansRt. Ventricle depolarizes by means of of cell- to- cell- to-

cell conduction.cell conduction. TheseThese impulsesimpulses spread more slowly than spread more slowly than usual from inter ventricular septum to Rt. Ventricle.This usual from inter ventricular septum to Rt. Ventricle.This

delay in conduction resultsdelay in conduction results in characteristicin characteristic ECG pattern,ECG 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 the Rt. branch is delayed ,conduction down the Lt. branch is normal. As a result, the interventricular septum and Lt. normal. As a result, the interventricular septum and Lt. ventricle in normal fashion. ventricle in normal fashion.

TYPES TYPES There are two types. There are two types.

Complete RBBB. Complete RBBB. Incomplete RBBB.Incomplete RBBB.

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.

HEMIBLOCKHEMIBLOCK

DEFINITION:DEFINITION:

When there is blockage in anterior or posterior division of When there is blockage in anterior or posterior division of left bundle branch, it is called hemiblock.left 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 In bifascicular and trifascicular block there are more

chances to progress to complete heart block.chances to progress to complete heart block.

TRIFASCICULAR BLOCK:TRIFASCICULAR BLOCK: RBBB + Hemiblock + First degree heart block.RBBB + Hemiblock + First degree heart block.

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